Month: December 2024

Research in Mechanical Engineering

Mixed Mode Fracture Characterization of Hydrogel-3D Printed Polymer Adhesively Bonded Systems 

By Nicholas Sardinha

Introduction 

Hydrogels are soft polymer networks with an interstitial liquid, usually water, and they have many applications ranging from tissue engineering, water purification [1], and even anti- biofouling. However, for hydrogels to be more useful for anti-biofouling, their adhesion to different surfaces must be investigated. Many marine vessels have hulls made of different metals such as steel and aluminum, but with the rise of additive manufacturing came the increase in the use of 3D-printed polymers as hull materials. This research attempted to study the adhesive bonding of hydrogel and 3D-printed acrylonitrile butadiene styrene (ABS). The specific method chosen to evaluate the fracture toughness was the J-integral method, used on a mixed mode bending fixture described in the methodology section of this report and based on the work of Zhao Y, Seah LK, Chai GB [2]. Mixed mode bending applies opening mode-I and shearing mode-II to the double cantilever beam (DCB) specimen. However, this type of test has never been conducted with two materials with such a large difference in elastic moduli, with hydrogel having a Young’s modulus in the 10 kPa – 2 MPa range and ABS in the 2-4 GPa range. This causes the ABS to experience much less deformation than the hydrogel at the same load. That is the primary reason why the traditional peel test was not used, as hydrogel experiences significant deformation, which absorbs energy. This leads to the peel test not accurately measuring fracture toughness of softer materials, since that additional energy absorption is not properly accounted for in fracture toughness calculations. 

Methodology 

Specimen Production 

Table 1: Hydrogel Composition 

Number of Samples  Total Solution (ml)  DI Water (ml)  AAm (g)  DAC (ml)  MBAA 

(mg) 

 KA (mg) 
1  25  14.8  8.9  10.2  23.2  13.7 
3  75  44.4  26.7  30.6  69.6  41.1 

The specimens used in this research were fabricated using a unique in situ fabrication method. Firstly, a hydrogel precursor solution was made using the five main components: deionized water (DI Water), Acrylamide (AAm) monomer, Acryloyloxyethyltrimethyl ammonium chloride (DAC) cationic monomer, N,N’-Methylenebisacrylamide (MBAA) crosslinker, and α-Ketoglutaric acid (KA) photoinitiator. From Table 1 the weight percentage of AAm and DAC are 25.24 wt.% and 32.69 wt.%, respectively. This process produces a clear hydrogel precursor solution that can be used for the fabrication of test specimens. 

The second half of each specimen is a 3D-printed ABS T-shape, which was produced using a Stratasys uPrint 3D printer and ABS P430. After the ABS T-shape finished printing, a 10 mm long pre-crack film was glued to the top surface, as shown in the red area of Figure 1(a). 

 For the control samples, the rest of the 3D-printed surface was left unaltered, and the ABS T- shape was placed into a silicone mold. This silicone mold was designed with two connected cavities: one for the ABS and the other for the hydrogel precursor solution. The side for the precursor solution had an opening that was sealed using a strip of photocopier film and two glass microscope slides. The purpose of using transparent materials to seal that side of the mold is to ensure that the 365 nm ultraviolet light can pass through and photocure the hydrogel. After many experiments, a 4-hour photocuring time was chosen and used for all samples. Since the mold had an opening on the top for the hydrogel precursor solution to be poured in, a sheet of plastic wrap was applied around the entire mold to prevent moisture from entering or exiting during curing. Photocopier film was also used to line the inside of the mold to ensure that the surface of the hydrogel would be smoother. 

After the samples finished curing, they were removed from the mold, and excess hydrogel was cut away with a razor blade so that the edge of the hydrogel aligned with the edge of the ABS. Once this was completed, a 20× 100 mm2 strip of photocopier film was superglued to the backside of the hydrogel. Next, a 100 mm long strip of paper with millimeter markings was applied to the side of the ABS to help measure the pre-crack length. To ensure that the pre- crack area did not have any adhesion, the crack was slightly opened by hand, and the end of the pre-crack was marked on the side of the ABS with a black marker. 

Photooxidation 

The photooxidation process refers to the exposure of the ABS surface to chlorine dioxide (ClO2) gas and 365 nm ultraviolet light. To produce ClO2, 100 mg of sodium chlorite (NaClO2) was added to 14 ml of DI water inside a small dish. This small dish was then transferred into a larger glass reaction vessel. Any ABS samples to be photooxidized were then placed in the reaction vessel close to the small dish. The entire reaction vessel was then placed in the fume hood. Then using an adjustable pipette, 100 µl of 37% hydrochloric acid (HCl) was added to the solution, which starts producing chlorine dioxide gas. After that, the reaction vessel was sealed using plastic wrap and a clear flat plastic sheet to contain all the produced gas. Then the ultraviolet light was placed on top of the reaction vessel, and a timer was started as soon as the light was switched on. After the desired time was completed, the ABS samples were transferred into another container, where they could be used immediately for either contact angle measurements or for fabrication of mixed mode bending specimens. All remaining reacted solution was then transferred into a designated waste container specifically for that solution. 

Mixed Mode Bending Fixture 

Figure 1:(a) Hydrogel/ABS adhesive system and (b) T-Shape drawing with dimensions in millimeters. 

 

Figure 1(a) shows the ABS/hydrogel adhesive systems, and Figure 1(b) shows the dimensions of the T-shape part of either portion. The double T-shape specimens were placed into a mixed-mode bending fixture as shown below in Figure 2. This fixture was loaded under compression with a load P, where force and displacement measurements were recorded using a Shimadzu AGS-X universal testing machine (UTM) with a 50N load cell. A Celestron handheld digital microscope was used to capture the crack initiation. The loads at locations A, B, C, and D were determined using statics, and the angles measured at these four locations were used in determining the fracture toughness. Due to the significant difference in elastic moduli between the hydrogel and ABS, θB & θD are extremely small and approximated as zero. 

 

Figure 2: Mixed mode bending loading configuration of the adhesive system. 

 

The lever length c can be adjusted to change the mode mixity, and for these experiments a length of 30.61 mm was used. The horizontal distance between points B and C called length L in Figure 2 cannot be adjusted and was set to 45 mm. Prior to each set of tests, the load 50 N load cell was calibrated. 

To secure the prepped samples into the fixture, superglue was applied to the top surface of the hydrogel to meet the grip, and the grips were tightened down. The lower grips on the ABS side did not require superglue, since the ABS did not deform during testing. Once the specimen was in the fixture, the pivot was slowly lowered until it contacted the surface, then a vertical line was drawn onto the hydrogel to measure the angle at point C. Both the force and displacement were then zeroed. A loading rate of 4 mm per minute was used based on previous mixed mode tests. The recording on the digital microscope and the UTM were started at the same time and two screenshots were taken, one at the start of the experiment and one at fracture initiation. 

These screenshots were then imported into MATLAB, where a code was used to analyze the angles of 3 different points. The first screenshot was analyzed to measure the initial angle of the vertical line at point C, and the second screenshot was analyzed to measure the angle of the fixture, the angle at A, and the angle at C (this is shown below in Figure 3). The time of fracture initiation was also recorded from this video and was used to get the load and displacement at fracture initiation. With the P, θA, & θC, the fracture toughness can be calculated using the following formula:

= 100( sin() + sin() − sin() + sin() ) 

The average fracture toughness and 95% confidence interval were plotted using Excel. The force vs displacement was also plotted using MATLAB and the Excel spreadsheets produced by the UTM. After the completion of each test, the hydrogel was separated from the ABS and the ABS surface was cleaned using deionized water for future use. This procedure was repeated until four consistent tests were performed. 

Figure 3: Example of Angle Measurements at Fracture Initiation. 

 

Water Contact Angle Measurement 

Water contact angle measurements were taken using a Ramé-Hart Model 90 goniometer. The goniometer was calibrated using the included calibration sphere and the water contact angle software package. The surface to be tested was placed on the test platform with the backlight turned on and leveled using the included adjustment knobs. After that, a droplet of deionized water was dropped on the surface using the included syringe, and the contact angle was recorded. This was repeated in four separate locations on the ABS surface on two different specimens. This procedure was repeated for the three different conditions which were untreated, 15-minute photooxidation, and 30-minute photooxidation. The average and 95% confidence interval were then plotted in Excel. 

Results 

Figure 4: Water Contact Angle for Untreated, 15 Minute Photooxidation, and 30 Minute Photooxidation. 

 

The water contact angle measurements from Figure 4 showed a significant difference between untreated samples and samples that have had the photooxidation procedure done on them. The average contact angle decreased from 76.23° to 42.06°. This was an expected result as the photooxidation process modifies the ABS surface with more reactive groups, meaning the surface should become more hydrophilic, which it did. It also showed that increasing the photooxidation treatment time from 15 minutes to 30 minutes did not have much of an effect. This is important information as it led to one of the challenges experienced later on in the process. 

 

Figure 5: Control Load vs Displacement. 

 

The load versus displacement graph in Figure 5 shows the same trend for all specimens. There is an initial shallower slope section that quickly transitions into a linear portion until the peak load is achieved, and then the load quickly drops off as the crack grows along the interface. All four specimens achieved peak load values within 1 N of each other. 

Figure 6: Control Fracture Initiation Toughness. 

 

The average fracture toughness for the untreated control samples was 31.1 J/m2 as seen in Figure 6. There are no other conditions to compare to the control which is explained in the discussion section of this report. 

Discussion 

Many challenges were faced during this research that limited the scope of this project. Due to the novelty of bonding hydrogel and ABS plastic, a unique hydrogel precursor solution had to be created and iterated on. Initially, the hydrogel used had half of the concentration of AAm and DAC, which caused the hydrogel to be very soft, excessively deform, and ultimately lead to inconclusive tests. This challenge was eventually overcome by doubling the concentration of AAm and DAC, along with increasing the MBAA cross-linker concentration. 

This led to very successful control experiments. However, after the control tests concluded, photooxidation tests started. Based on the contact angle results, a 10-minute photooxidation procedure was selected. As expected, the photooxidation had a major effect on the adhesive bond between the surfaces; it had such a large effect that the hydrogel consistently failed prior to the interfacial bond. Corrective measures were attempted, such as decreasing the concentration of the NaClO2 and HCL solution by half and the exposure time down to 3 minutes. This still resulted in the same challenges as previous tests, namely crack propagation into the hydrogel. 

The second-largest challenge was determining the proper method to measure θC. The methods used by other researchers who used the same fixture did not work as expected due to the ABS acting as a rigid body and causing the hydrogel to indent rather than bend. This indentation issue was compounded by the fact that the hydrogel used in these experiments was prone to warping. Many different solutions were proposed to combat those problems, but ultimately, applying a backing layer to the hydrogel and drawing a vertical line at point C was chosen, as described in the methodology section of this report. 

Conclusion / Future Work 

There are many more aspects of this research topic that can be further investigated, the most pressing being the degree to which the photooxidation process increases the fracture toughness. This would require the control samples to be redone using a hydrogel stronger than an interfacial bond to prevent cracks from propagating into the hydrogel. Once the hydrogel is strong enough to withstand the photo-oxidized tests, other test configurations can be tested, such as modifying the surface geometry or roughness. Following that, another future step for this research is using digital image correlation (DIC) to determine the mode mixity of these mix mode tests. The lever length used for these tests was chosen because, with the same material for top and bottom T-shapes, it produces equal parts mode I & II loading conditions. However, since the top and bottom are not the same material, the mixity is not the same. With the help of DIC, the strain fields near the crack tip can be analyzed to determine the true mode mixity. Overall, this research has built up some knowledge of hydrogel and ABS adhesively bonded systems. Even though it did not achieve all of its goals from its onset, it still provides a solid foundation that can be built upon by future researchers. 

References 

Yahia LH, Chirani N, Gritsch L, et al. History and Applications of Hydrogels. J Biomedical Sci. 2015, 4:2. http://dx.doi.org/10.4172/2254-609X.100013. 

 Y. Zhao, L. K. Seah, G. B. Chai, Measurement of interlaminar fracture properties of composites using the J-integral method, J. Reinf. Plast. Compos. 35 (2016) 1143-1154. https://doi.org/10.1177/0731684416642031. 

 

Research in English

Evolving Feminism in The Hunger Games Series

By Ellie Cook

My project analyzes the differences in feminine gender performance between Katniss Everdeen, the protagonist of the original The Hunger Games trilogy by Suzanne Collins, and Lucy Gray Baird, the protagonist of the prequel novel The Ballad of Songbirds and Snakes. It analyzes the two characters from an intersectional perspective and argues for the importance of cultural, economic, social, etc. contexts when accounting for differences in gender performance, as these factors are all intertwined with gender norms. From the basis of their contrasting gender performance, the paper then delves into agency as a theme and how each character’s relative agency impacts their feminine representation. These differences in gender performance and agency show a different archetype for a young adult feminine heroine over ten years after the original trilogy’s publication. 

From the end of May to mid-July, I completed the background reading to prepare for writing my paper. I read critical theory such as Judith Butler’s Gender Trouble, Undoing Gender, and Who’s Afraid of Gender? as well as Butler Matters: Judith Butler’s Impact on Feminist and Queer Studies by Warren J. Blumenfeld and Margaret Sönser Breen. I also read scholarship about The Hunger Games series that focused on gender and feminism. Some of these texts include: “You Love Me. Real’: Gender in the Hunger Games Trilogy” by Bienvenue Bray and “I Hunt. He bakes.’: Constructing and Deconstructing Gender Identity in Suzanne Collins’s The Hunger Games Trilogy” by Rakchuda Thibordee. I also read books that gave a general overview of the young adult dystopian genre, such as Female Rebellion in Young Adult Dystopian Fiction by Sarah K. Day, et al. and Contemporary Dystopian Fiction for Young Adults: Brave New Teenagers by Carrie Hintz, et al. Using these texts, I completed an annotated biography.

I met with my Apex mentor, Professor Caroline Gelmi, in mid-June, mid-July, and mid-August to check my progress. From mid-July to the end of August, I completed the first draft of my paper. I will continue to work on it with Professor Gelmi throughout the Fall 2024 semester and will finish my final draft at the end of the semester.  

I am grateful to Professor Gelmi for her feedback and mentorship and to OUR for supporting this project through a summer research grant.

Research in Chemistry and Biochemistry

Microwave Mediated Synthesis of Quinazolinone Natural products of  Peganum harmala for Medicinal Chemistry Applications 

By Amelie Duval
Introduction

In the pharmaceutical field, quinazolinones have become an important pharmacophoric scaffold due to their presence in natural compounds with a wide range of medicinal chemistry applications. Among these, Peharmaline A (1), a natural alkaloid with b-Caroline and tricyclic pyrroloquinazolinone cores (Figure 1) that exhibits various biological activities, including antimalarial, anticancer, anti-inflammatory, and antibacterial activities has garnered significant interest of synthetic and medicinal chemists in recent years. In addition, quinazolinones possess stability and change adaptability that makes it easy to prepare, which is prime for scientific investigations. Peharmaline A is found in Peganum harmala L., a species coming from the family of medicinally important Zygophyllaceae. In Chinese traditional medicine, P. harmala L. seed extract is widely used to treat malignancies of the digestive system and malaria. 

(±}-Peharmaline A (1} 

Figure 1: (±)-Peharmaline A precursors 

Objective of the Proposal 

We proposed to develop a novel approach to synthesize Peharmaline A utilizing the deoxyvasicinone and 5-methoxytryptamine, and extend the same to access a library of analogues of peharmaline to further study their biomedicinal potential. 

Methodology – for the Synthesis of (±)-Peharmaline A and Its Analogues 

According to our retrosynthetic plan shown in Scheme 1, we have proposed a total synthetic route to achieve (±)-Peharmaline A 1 in a three-step process: through Pictet-Spengler reaction with the use of 5- methoxytryptamine 3 and deoxyvasicinone methyl oxalate intermediate 2, which itself can be made by of the acylation reaction of deoxyvasicinone 4 with methyl oxalyl chloride 5. It required us to develop a short and effective synthesis for deoxyvasicinone itself through adapting and modifying the reported synthesis into a practical large–scale under microwave irradiation chemistry one-pot synthesis. Starting from commercially available isatoic anhydride 6 and pyrrolidinone 7, they would serve as the building blocks and will result in (±)-Peharmaline in just three steps. It would also provide a divergent approach towards the (±)-Peharmaline A analogues in a modular fashion. 

Scheme 1: Retrosynthetic plan of synthesizing (±)-Peharmaline A 

Results and Discussions 

Scheme 1 describes our efforts toward the development of a total synthetic approach to the synthesis of (±) -Peharmaline A. After a lot of careful experimentation with stoichiometry and heating (temperatures and time intervals), we finally optimized the synthesis of deoxyvasicinone to work on 1Og scale. It required thorough mixing of 1:1.25 equals of isatoic anhydride 5 and the pyrrolidinone 6 and heating of three minutes at medium power household MW (with one-minute intervals). Once the reaction was completed, it was allowed to cool to room temperature, and any remaining starting materials were removed under reduced pressure. The next step was acylation of the deoxyvasicinone 4. The acylation reaction conditions needed a lot of optimizations. We started with the available chemical in the lab i.e., ethyl oxalyl chloride 6 instead of methyl oxalyl chloride, which will lead to Methyl (±)-Peharmaline A, while we awaited the other chemical to arrive from the vendor. 

After a great deal of experimentation to optimize the temperature conditions, the equivalence of acylation reaction, and the solvent environment, we found out that 3 eq of ethyl oxalyl chloride and 2 eq of Et3N base in anhydrous DCM was needed to complete the reaction with deoxyvasicinone, resulting in  32.6 % of yield. Further, it was confirmed that the initially maintained O °C temperature needs to be increased after the complete addition (1 h) of ethyl oxalyl chloride to overnight refluxing to 48 h for the completion of the reaction to obtain a green clean solid product. The addition of both ethyl oxalyl chloride and Et3N base was separated into two portions, with the first half equivalent being added in at OoC initially, and the second half equivalent being added after 24 hours of refluxing in the same method before placing the reaction back to reflux for an additional 24 h. The acylated deoxyvasicinone 2 was obtained in enol form and it was confirmed by NMR and X-ray crystallography. 7 The methyl oxalyl chloride had arrived from the vendor and was tested with the same chemical and temperature environment, and experiments are still on-going to examine the identity and quality of the product. Additional tests are being conducted with deoxyvasicinone with benzoyl chloride and oxalyl chloride to determine if analogues can be developed to further the research with the final (±)-Peharmaline A and other quinazolinone products. 

Scheme 2: Synthesis approach of (±)-Peharmaline A analogue 

 

The next step in the sequence was the Pictet-Spengler reaction. We decided to establish it first with the commercially available tryptamine instead of the expensive 5-methoxy tryptamine (required to be synthesized in the lab later). Accordingly, we combined the tryptamine base 3.85b with acylated deoxyvasicinone 2 under refluxing conditions. After a lot of experimentation trials, our efforts towards the Pictet-Spengler reaction conditions were successful. It ensued in the presence of a catalytic amount of acid that could facilitate the reaction forward to the formation of (±)-Peharmaline A analogue when there was no water present in the sample. As we ran these optimization reactions on a mg scale, we obtained the product through preparative TLC thus far. We need to further optimize them on a larger scale and obtain the pure compound. 

 

Scheme 3: Pictet-Spengler reaction for the final assembly 

 

Figure 2 shows the changes in the 1H NMR peaks along the path of (±)-Peharmaline A analogue (8) (C) formation from the deoxyvasicinone 4 (A). 

Figure 2: Comparison of (±)-Peharmaline A analogue synthesis process A) 1H NMR of Deoxyvasicinone 4 in CDCl3 synthesized through MW irradiation chemistry. B) 1H NMR of enol form of acylated deoxyvasicinone 2 in CDCl3) 1H NMR of Peharmaline A analogue 8 in CDCl3 synthesized in TFMS acid/DCM solution. 

Conclusions and Future Directions

In summary, we have established the groundwork needed for the synthesis of peharmaline A and its analogues. Scheme 4 deliniates our approach of making a library of (±)-Peharmaline A analogues by employing different tryptamines and tyrosines–based primary arylethanamines in Pictet-Spengler reaction by applying our optimized reaction conditions (anh. DCM/TFMSA/reflux-24 h) towards appending the b-Carboline ring to the deoxyvasicinone ring. As can be seen, it is a modular and divergent approach to making (±)-Peharmaline A analogues via employing different acid chlorides as well, as seen in Scheme 5. We propose to carry it out when the grad student that I was associated with returns in the next winter and summer breaks. 

 

Scheme 4: Future study: Scoping Pictet-Spengler towards (±)-Peharmaline A analogues 

Scheme 5: Other modifications for Diversity Oriented Synthesis of Peharmaline A 

Acknowledgments

Support from the UMassD OUR is greatly appreciated. Many thanks to Fazmina Anver and Dr. Rasapalli for their teaching and mentoring in the lab. 

References

Kulkarni, A. S.; Dash, A.; Shingare, R. D.; Chand, J.; Manhas, D.; Singh, A.; Nandi, U.; Goswami, A.; Srinivasa Reddy, D. Identification of New Modulator of DNA Repairing Pathways Based on Natural Product   (±)-Peharmaline   A.   Bioorg.   Med.   Chem.   2023,   91,   117365. https://doi.org/1O.1O16/j.bmc.2O23.117365. 

Piemontesi, C.; Wang, Q.; Zhu, J. Enantioselective Synthesis of (+)-Peganumine A. J. Am. Chem. Soc. 2016, 138 (35), 11148-11151. https://doi.org/1O.1O21/jacs.6bO7846. 

K.-B. Wang, S.-G. Li, X.-Y. Huang, et al. (±)-Peharmaline A: a pair of rare B-carboline-vasicinone hybrid alkaloid enantiomers from Peganum harmalaEur J Org Chem, 2O17 (2O17), pp. 1876-1879, 1O.1OO2/ejoc.2O17OO137 

Anver, F; Rasapalli, S. Thesis: Synthetic Studies Towards Biologically Active Heterocyclic Alkaloids and Their Analogues a dissertation in Chemistry and Biochemistry 

Alsibaee, A. M., Al-Yousef, H. M., & Al-Salem, H. S. (2O23). Quinazolinones, the Winning Horse in Drug Discovery. Molecules (Basel, Switzerland), 28(3), 978. https://doi.org/1O.339O/molecules28O3O978 

Cao, R.; Peng, W.; Wang, Z.; Xu, A. B-Carboline Alkaloids: Biochemical and Pharmacological Functions. Curr. Med. Chem. 2007, 14, 479-5OO. https://doi.org/1O.2174/O929867O777994O998. 

Alshehry, R; Rasapalli, S. Synthetic studies toward biologically active quinazolinones : a dissertation in Chemistry and Biochemistry https://umassd.primo.exlibrisgroup.com. 

 

 

Research in Biology

Human-Induced Fear in Free-Living Raccoons 

By Ruby Sanger 
Abstract 

This past June and July, I spent time at Norcross Wildlife Sanctuary in Wales, Massachusetts. Norcross is a large intact forest of approximately 4200 ha with restricted human access and a small 17ha area near the visitor center, where human access is permitted for hiking along 4km of natural trails. 

I intended to study the effects of human-induced fear on the foraging effects of free-living white-tailed deer, both in the human-accessible area and the forest. This design included audio treatments (human talking and birdsong) and food treatments (plain corn and plain corn mixed with molasses) at eight different stations across the sanctuary. However, after a few weeks of experimentation, there was no deer activity at any of the stations. While thorough background research was conducted to decide the most appealing foods to bait deer with, and there was known to be a high density of deer at the sanctuary, it is possible that because the forest is so dense with natural browse and plants the deer eat, they simply not interested in what was being offered. As a result, Dr. Sherriff and I decided to adapt the experiment to study the foraging behaviors of raccoons, as there were reoccurring raccoon visits at select feeding stations on the public trails. 

None of the stations with molasses had traffic, nor did any of the stations in the deep woods, so we cut the molasses treatment while adding two audio treatments (human yelling and dog barking) for a total of four treatments. The experiment was limited to the public trails of the sanctuary. 

Introduction 

While predators can kill prey, they can also alter prey fitness through non–consumptive effects. The risk of predation can subsequently alter prey’s behavior, morphology, and physiology, which may all impact prey survival and reproduction. These effects may then influence prey population sizes (Sheriff et al., 2020). For example, a study by Cherry et al. (2016) showed that the presence of coyotes led to reduced lactation and ovulation in white-tailed deer, and an absence of coyotes related to an increase in feeding, lactation, and ovulation. These non-consumptive effects may reduce prey population size due to a lack of reproductive success and fecundity (Say-Sallaz et al., 2019). 

The term “landscape of fear” is defined as the spatial variation in prey perception of predation risk. These “landscapes” combine the elements of the physical environment that prey may inhabit or forage in, the predation risk and how it varies across locations, and a prey’s response to predation risk. There are generally two methods of prey response, one being avoiding areas perceived as higher risk, and the other being changes in behaviors while in the areas perceived as higher risk. The perception and fear of predation may be able to drive community-level changes within ecosystems, such as trophic cascades. (Gaynor et al., 2019). A common way to study the spatial variation resulting from risk response is by looking at giving-up densities (GUDs) and analyzing foraging behaviors within the context of risk. GUDs are used to provide insight into metabolic and predation costs of foraging by determining when an individual may stop foraging (Brown, 1987). 

In a study by Darimont et al. (2015), it has been shown that human predators kill far more prey than non-human predators, as well as killing carnivores nine times more than natural predators (Smith et al. 2017). While humans kill at an unparalleled rate, they more often affect prey behavior through disturbance (Frid, Dill 2002). Fear of humans as a “super predator” is also known to lead to behavioral changes in both predators and prey, and the subsequent effects on populations and communities may be larger than those resulting from non-human predators (Crawford et al. 2022). Experimental non-consumptive behaviors from humans have even led to a decrease in feeding times for pumas, an animal without any natural predators (Smith et al. 2017). A landscape of fear of the perception of humans can result in significant changes in wildlife behavior and community dynamics. Suraci et al. (2019) conducted studies with free-living mountain lions, bobcats, medium-sized carnivores (such as opossums and skunks) and deer mice in the Santa Cruz mountains. 

Human predation risk was simulated by using playbacks of human vocalization. The carnivore groups all experienced behavioral changes in response to perceived predation risk: avoiding areas, making temporal changes, and being less efficient in foraging. 

However, deer mice seemingly benefited from human presence; they increased space use as well as foraging intensity. The fear that the carnivores perceived affected lower trophic levels, influencing the surrounding wildlife system (Suraci et al., 2019).

Methods 

i. Feeding Station Set-ups 

Figure 1: Map of the 8 feeding stations, marked on the GAIA app. 

 

Figure 2: Camera and speaker set-ups. The cups were used as a shield for the exposed speakers from the rain. 

 

Eight feeding stations were chosen among the public trails of Norcross Wildlife Sanctuary in Wales, Massachusetts (Figure 1). Each station consisted of a painted feeding bin, a field camera, and a speaker (Figure 2). 

The speaker and camera were programmed to be used together, using Arduino, so that when the camera was triggered by motion, the speaker was triggered to play a programmed playback. Two speakers were programmed to play conversational human speaking, two to play dogs barking, two to play bird songs native to the area, and two to play humans yelling. Each speaker was programmed to play at about 65-70 decibels. The camera-speaker set-ups were programmed for the speaker to trigger 20 seconds after the camera was triggered. 

80 ounces of dried whole grain corn (5 lbs) were set into the feeding tubs. Each empty tub, when closed with the lid, weighed 70 ounces. 

ii. Daily Protocol 

The stations were filled with 80 ounces of corn, and the cameras and speakers were switched on June 30th. Every morning from July 1st to July 10th, the combined weight of the corn and the tub were taken at each of the eight locations by closing the tub and weighing it with a digital fishing scale. If the weight was below 120 ounces, the corn was later refilled to the base weight of 150 ounces (80 ounces of corn plus the weight of the tub). Additionally, the SD cards in the cameras were checked to see if there was any raccoon activity or other significant animal activity during the night. The battery levels of the cameras and speakers, as well as the SD card storage amounts, were also checked every morning to ensure proper performance for the following night. In the case of heavy rain, the tubs were covered to prevent the corn from being waterlogged, which could provide inaccurate weights. 

Table 1: Key of auditory playbacks per feeding station

Feeding Station  Treatment 6/30-7/05  Treatment 7/05-7/10 
1  Talking  Birdsong 
2  Yelling  Dog barking 
3  Dog barking  Yelling 
4  Birdsong  Talking 
5  Talking  Birdsong 
6  Yelling  Dog barking 
7  Birdsong  Yelling 
8  Dog barking  Talking 

On July 5th, after 5 nights of data collection, the playback treatments were changed to different locations (Table 1). At the end of data collection, the SD cards were collected, and the feeding stations were broken down. 

iii. Data Analysis 

The footage captured from the feeding stations are currently being analyzed manually. I will be scoring for behaviors including fleeing (running/leaving quickly), leaving (walking away), looking up, head-up foraging, head-down foraging, playing, freezing, and leaving a group. There are many cases of corn being eaten by mice, chipmunks, squirrels, and occasionally deer. The footage of these animals will be used to separate their consumption from the raccoon’s consumption. Additionally, statistics of each night of the experimental run are being gathered. I am counting the total number of foraging events as well as the time spent eating each night. The footage is currently being analyzed. 

Conclusion 

While the results are still being analyzed, information regarding how raccoons react to auditory playbacks will provide useful insight into the effectiveness of using sound as a method of pest control, as well as how small mammals such as raccoons are affected by the presence of humans. I hope to continue in this line of study and resume with the original design for studying white-tailed deer in the future. 

Works Cited 

Sheriff MJ, Peacor SD, Hawlena D, Thaker M. (2020). “Non‐consumptive predator effects on prey population size: A dearth of evidence.” Journal of Animal Ecology vol 89. 

Cherry, M. J., K. E. Morgan, B. T. Rutledge, L. M. Conner, and R. J. Warren. (2016). “Can coyote predation risk induce reproduction suppression in white-tailed deer?” Ecosphere 7(10):01481. 

Say-Sallaz, E., Chamaille-Jammes, S., Fritz, H., Valeix, M. (2019). “Non-consumptive effects of predation in large terrestrial mammals: Mapping our knowledge and revealing the tip of the iceberg.” Biological Conservation vol.235: 46-52. 

Suraci, J.P, Clinchy, M., Zanette, L.Y., Wilmers, C.C. (2019). “Fear of humans as apex predators has landscape-scale impacts from mountain lions to mice.” Ecology letters vol. 22,10: 1578-1586. 

Gaynor, K.M., Brown, J.S., Middleton, A.D., Power, M.E., Brashares, J.S. (2019). “Landscapes of Fear: Spatial Patterns of Risk Perception and Response.” Trends in ecology & evolution vol. 34,4: 355-368. 

Darimont, C.T, Fox, C.H, Bryan, H.M, Reimchen, T.E. (2015). “HUMAN IMPACTS. The unique ecology of human predators.” Science vol. 349,6250: 858-60. 

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Gaynor K., Hojnowski C., Carter N., Brashares J. (2018). “The influence of human disturbance on wildlife nocturnality.” Science vol. 360,6394 (2018): 1232-1235. 

Research in Bioengineering

Smart Microparticles for On-Demand Drug Delivery 

By Abid Neron
Abstract 

Drug delivery systems represent a cornerstone of contemporary medical research, particularly in addressing intractable diseases such as cancer and neurological disorders. Current treatment modalities often result in collateral damage to healthy cells, underscoring the need for targeted delivery methods. Microparticles have emerged as promising candidates for precise drug delivery. This study explores the use of PLGA microparticles, fabricated via double emulsion, for sustained vancomycin hydrochloride release. The microparticles were loaded with Indocyanine Green (ICG) for near-infrared–responsive (NIR) drug delivery. Process parameters were optimized for size, morphology, drug loading, and release kinetics. Anti-bacterial tests showed higher drug release and antibacterial efficiency when exposed to NIR light. Chitosan coating halted drug release in the absence of NIR light, demonstrating controlled, on-demand release. This system offers the potential for targeted and efficient drug delivery. 

Introduction

Drug delivery systems are a crucial component of the drug manufacturing process. An effective drug is rendered useless if it fails to reach its target area. Thus, a drug delivery vehicle must be manufactured to ensure that the drug is properly administered. Traditional drug delivery methods, including oral, topical, and injection, are effective, but all have certain disadvantages, namely, poor bioavailability, instantaneous release of the drug, and lack of site-specific targeting1. These disadvantages can be mediated by using higher concentrations or continuous intaking of the specified drug, which steadily uses more drugs for treatment and can cause damage to other areas. Novel drug delivery systems have been at the forefront of bioengineering research, as finding a more effective vehicle for a drug will increase its effectiveness, thus reducing the amount of the drug needed for treatment and potential side effects. 

Microcarriers are currently spearheading novel drug delivery systems. Most notably, much research is being conducted on microparticles. They are spherical particles that are 1 to 100 μm in diameter. Microparticles have been chosen as a suitable drug delivery vector as they can be tailored to the specific task since they are highly customizable. This degree of customization is due to the different fabrication processes and the numerous materials used to manufacture them. Further, multiple materials can be used in conjunction for a higher degree of complexity when desired. Most importantly among the properties of microparticles is their ability to hold drugs inside of them. An effective drug delivery vector must have numerous properties; among them are drug encapsulation, biodegradability, biocompatibility, sustained release, and implementation of surface modifications. Depending on the fabrication, microparticles can have all these properties. 

Background

The fabrication process is crucial for microparticles as it is the process that gives the particles their properties. Thus, when creating a microparticle for drug delivery, deliberate thought is put into the fabrication process and the desired properties. For instance, a microparticle made with a toxic polymer is rendered useless in the field of drug delivery as it will harm the patient. All microparticles made for drug delivery use a biocompatible polymer such as PLGA, Chitosan, Gelatin, and PCL. Further, surface modifications can be implemented to help increase uptake of the drug by the cells or to target certain cells. Targeted drug delivery increases the effectiveness of the treatment. Lack of site targeting can lead to the drug not working effectively or having undesirable consequences. The most infamous treatment that lacks targeting delivery is Chemotherapy. Chemotherapy targets rapidly dividing cells, a property of cancerous cells. However, it is also a property of hair, skin, and gastrointestinal tract cells. This causes multiple side effects that wouldn’t occur if Chemotherapy only targeted the cancerous cells. 

Microparticles are potential candidates for cancer treatment. They can be modified for targeted drug delivery because cancerous cells can be targeted since they express certain proteins and have special receptors. A biocompatible microparticle fabricated with an effective anti-cancer drug and a specific targeting ligand could revolutionize the way cancer is treated. While cancer treatment is a major application for microparticle-mediated drug delivery, other important applications include treatment for neurological disorders, diabetes, and respiratory and inflammatory diseases.

Poly Lactic-co-Glycolic Acid (PLGA) is the most widely used polymer for microparticle fabrication due to its biocompatibility and FDA approval. PLGA is a co-polymer, meaning it is made using two different monomers: Lactic Acid and Glycolic Acid. The ratio of both these monomers affects the properties of PLGA, giving an extra layer of customization in the fabrication process. Among the properties affected by the ratios is the rate of biodegradation, which increases with the increase of Glycolic Acid. In addition, it supports numerous fabrication methods as well as surface modifications and has good drug encapsulation properties. 

Near-infrared (NIR) light, which includes wavelengths from 800 to 2,500 nm, is invisible to the naked eye. Indocyanine Green (ICG) is a photothermal material and thus will react with certain wavelengths of light and convert light energy into heat energy. This central concept was utilized in fabricating the microparticles for targeted drug release, as the use of NIR light in PLGA-ICG particles should accelerate drug release, providing a vessel for on-demand delivery. To further prevent drug elution, chitosan-coated microparticles were fabricated as well. The chitosan should prevent drugs from eluting except when exposed to NIR light due to the photothermal reaction occurring. 

Methods

Microparticles Fabrication: 

The PLGA-ICG-Van. HCl microparticles were fabricated using the double emulsion method as shown in Figure 1, with the external phase being 1% PVA. 

Figure 1: Schematic for Fabrication of PLGA-ICG-Van.HCl microparticles 

 

Drug Release: 

To test for drug release from the MPs, 10 mg of fabricated PLGA MPs containing ICG and Van.HCl was placed into a 2 ml solution of phosphate-buffered saline (PBS) with a pH of 7.4 inside a Cytivia dialysis kit with a cut-off of 8 kDa. The microparticles were exposed to near-infrared (NIR) light at a wavelength of 808nm. The experiment set up is shown in Figure 2. Sample absorbance values were recorded, and a vancomycin hydrochloride standard curve was used to determine the drug’s concentration. 

Figure 2: Drug Release Set Up 

 

Anti-Bacterial Activity: 

Escherichia coli S17 (E. coli) was cultured in LB broth and incubated overnight at 37°C at 250 RPM for 24 hours. Fresh bacterial cultures were prepared for each antibacterial test using the previously refreshed culture. For the antibacterial test, a new batch of bacteria was cultured overnight until reaching an optical density at 600 nm (OD600) of 0.5, corresponding to approximately 8 × 10^8 cells/ml. In a microcentrifuge tube, 10 mg of microparticles were combined with 1 ml of LB broth and inoculated with 10 µl of the bacterial culture. Each microparticle group was tested in duplicate: one sample was exposed to NIR light at 1 W for 30 minutes, while the other sample was not exposed to NIR light. To ensure consistency, the unexposed sample was kept at room temperature for 30 minutes. Both samples were then incubated at 37°C for 2 hours. After incubation, 100 µl of each sample was spread onto an LB agar plate and incubated at 37°C for 24 hours to allow visualization of bacterial growth where bacterial colonies were counted. A control group prepared using the same protocol but without microparticles, was included for comparison. 

Results 

I: Microparticle Fabrication: 

Four different microparticle concentrations were fabricated: PVI2, PVI4, PVI5, and PVI6. Each variation had a different concentration of ICG. ICG concentrations can be found in Table 1. 225 mg of PLGA and 75 mg were used for the fabrication of all the microparticles. PVI4 was chosen to be coated with chitosan as it was found to have the highest drug release (Figure 3) and the highest antibacterial activity (Figure 4). 

Table 1: ICG Concentrations in Microparticle Variations 

Variation  ICG Concentration (mg) 
PVI2  3.875 
PVI4  38.75 
PVI5  19.375 
PVI6  7.75 

 

II. Drug Release:

Vancomycin hydrochloride release for each microparticle variation with and without exposure to NIR light can be seen in Figure 3. NIR light-exposed samples consistently have a higher drug release. The PVI4 exposed to NIR light had the highest drug release, followed by the PVI4 sample not exposed to NIR light. 

Figure 3: Vancomycin Hydrochloride Release for Each Microparticle Variation 

 

III. Antibacterial Activity: 

Antibacterial activity, when subjected to microparticles, is utilized as a visualization of the microparticles’ drug release and to further verify the drug release results. It is used as an in vitro test for fabricated microparticles. Antibacterial activity is shown by the number of colonies present on the LB agar plate. The resulting colony counts are found in Figure 4. Chitosan-coated particles’ antibacterial activity can be seen in Figure 5. 

Figure 4: Bacterial Colonies Counted for each Microparticle Variation 

Figure 5: Bacterial Colonies Counted for Chitosan Coated PVI4 

Discussion 

The microparticles exhibited good drug encapsulation and drug release with varying results depending on the specific variation used. Fabrication of four variations of the microparticles with differing ICG content demonstrated the effects of ICG in drug release when subjected to NIR light. PVI4 had the highest drug release and antibacterial activity as the ICG accelerated the release and deterioration of the PLGA microparticles. The uncoated samples released vancomycin hydrochloride almost instantly when subjected to solution. To mitigate undesired drug release, chitosan-coated microparticles released less vancomycin hydrochloride when not exposed to NIR light. Meanwhile, when exposed to NIR light, the vancomycin hydrochloride was released in a larger concentration. The concentration of drug release is less than its uncoated counterpart (PVI4). Chitosan-coated PLGA – ICG microparticles are potentially an excellent candidate for targeted and on-demand drug release as the drug inside is trapped and released when subjected to NIR light. Both drug release and antibacterial activity further emphasize the potential applications of PLGA – ICG microparticles in drug delivery. 

Future Directions

Further research into the usage of unstable drugs such as alkylating agents must be undertaken. Cancer drugs are unstable and further modifications to the microparticles might be needed for the PLGA to hold these drugs. Moreover, further in vitro testing with mammalian cell lines is needed. Finally, specific cell targeting surface modifications on the microparticles will enhance the targeting of the microparticles to the desired cell. 

Acknowledgements 

I would like to thank Mr. Mishal Pokharel, a BMEBT Ph.D. student; without his guidance and expertise, this project wouldn’t have existed. He invited me into his lab and allowed me to assist with his Ph.D. project, for which these results were gathered for. I’d also like to thank Dr. Tracie Ferreira for being an extraordinary supervisor and always being open to my questions and new ideas. Finally, I’d like to thank the Office of Undergraduate Research and the Honors College for their generous support and for believing in me and my project. Their funding allowed the continuation of this project.

 

 

 

Research in Art and Design

Through Another Lens 

By Omauri Byron-Edwards
Introduction

Through Another Lens is an independent Art and Design project, funded by the Office of Undergraduate Research (OUR). The focus of this project was to create dialogue and context to different themes of the human experience such as mental health, interpersonal relationships, and the relationship between society and intersectionality. My research is guided by two questions: a) What environment or factors influence a college students’ mental health? and b) How does society influence our perceptions of race, sexuality, class and gender? 

The significance of Through Another Lens involves the start of challenging discussions between students and families while portraying identities overlooked in Art History. Themes such as mental health, interpersonal relationships, and intersectionality are critical. A lack of comprehension for any of them results in obstacles in how they navigate their own life, as well as understanding other people and their truth. 

Thanks to OUR, I received funds, and I was alleviated of financial endeavors to obtain my materials. This allowed me to focus solely on my body of work during the summer of 2024. 

Process

I started the process by brainstorming ideas to answer my research questions. I narrowed my inquiry to focus on the loneliness of college students, stress from academic obligations, and the relationship between black men and toxic masculinity. After gathering sources, I reached out for volunteers to be models for my paintings. This required meeting up together, discussing my questions, staging reference photos, and setting up backgrounds and props. After gathering all this information, I made sketches to decide on a final composition relating to each concept.  

Securing the funds from OUR, I utilized new art materials to create my paintings, along with my reference photos and final drawing as a guiding point. 

Process photo of Omauri Byron-Edwards painting. 

 

“solitude” by Omauri Byron-Edwards, 36”x 24”, oil on canvas, 2024. 

“solitude” 

The intention of this painting is to answer my first research question relating to factors impacting the mental health of college students. Many assume that students living on campus share the mutual goal of education and this creates an easy avenue to interact with one another. However, this is simply not the case. Students are often met with obstacles to engaging in social lives. In 2007, research conducted on 268 university students determined that psychological well-being was one of the main factors of predicting loneliness. (Bhagchandani 2017). 

There are obstacles such as academic pressure, social anxiety, introversion, living away from home for the first time, or recipients of friendships not being interested. This makes the process of making friends more difficult and overwhelming, causing emotional discomfort. College students enter what could be considered the most harsh and confusing part of adulthood. Part of one’s survival is to have the social connection that is desired, to make us feel appreciated, understood, and vulnerable. Loneliness causes students to feel empty inside, alone, and unwanted. This heavily impacts how they value themselves, interpersonal relationships along the way, and other symptoms such as depression. 

“malachite” by Omauri Byron-Edwards, 36”x 24”, oil on canvas, 2024. 

“malachite” 

This painting focuses on the second research question about society’s relationship with race, gender, sexuality, and class. Specifically, the painting explores society’s relationship with black men, and how society perpetuates toxic masculinity to black men.  

There are combinations of systems set up among Black men involving cultural and social factors. Black men exist in a society where their identities are portrayed by harmful stereotypes, exhibiting aggression and hypermasculinity. The misrepresentation from media and communities molds societal expectations and perceptions, thus solidifying toxic beliefs about what masculinity is. This started a cultural stigma that would discourage Black men’s expression, emotion, and vulnerability. As black men are desperate to protect and assert their identity, many would adapt to the norms that were designed for them. Consequently, they fall victim to a toxic cycle of emphasizing dominance, violence, and emotional suppression. To emphasize the danger of toxic masculinity, I chose to involve an abstraction of a toxic stone called malachite as a symbol of society’s expectations for black male identities. 

Black men aren’t monoliths, and we must understand the importance of experiencing identity development as oneself. When black men become more open to complexity and engage in healthier behaviors, such as expressing emotions and vulnerability, it restores the representation and mental well-being of our identities. 

“cortisol” by Omauri Byron-Edwards. 36”x 24”, oil and collage on canvas, 2024. 

“cortisol”  

This piece reflects on the relationship college students have with academic stress, which negatively impacts their mental health. Presently, students struggle with staying accustomed to their competitive academic environment. This is all while students also face constant pressure from financial burdens, future employment, and career decisions. These significant obstacles inflict alarming amounts of stress, which impacts their mental and physical wellbeing. In an article from Transformation Education, a study shows that over 60 percent of students report feeling stressed daily, indicating a high amount of stress among the student body.  

With this alarming rate of stress among student populations, this calls for action in which institutions address their students’ problems and create better support systems so they can navigate their academic careers easier. 

Conclusion 

As far as the question of what’s next for Through Another Lens, I will continue the series. As my research questions are complex and broad, there are more ideas that I want to expand on. Through my process of this project, I received massive support and great reactions to my work. Many students on campus shared how they felt validated by the subject matter in my work such as loneliness, depression, or academic stress. Personally, I think it’s important to have work such as Through Another Lens, not just because it conveys a message, but because it’s a contribution to the community. By opening discussions between other students that relate to my themes, communities could gather new perspectives and challenge their thinking. 

References 

Bhagchandani, Revati K. Effect of Loneliness on the Psychological Well-Being of College Students, Jan. 2017, www.ijssh.org/vol7/796-C009.pdf. 

Etowa, Josephine, et al. “De-problematizing masculinity among heterosexual African, Caribbean, and Black Male Youth and men.” Canadian Journal of Public Health, vol. 113, no. 4, 15 Mar. 2022, pp. 611–621, https://doi.org/10.17269/s41997-021-00596-3. 

Diversity, National Center for Institutional, et al. “Let’s Discuss the Complexities of Black Masculinities.” Medium, Spark: Elevating Scholarship on Social Issues, 25 June 2024, medium.com/national-center-for-institutional-diversity/lets-discuss-the-complexities-of-black-masculinities-ce09b157701f. 

“Lonely Students at Greater Risk of Mental Health Problems, Study Finds.” Targeted News Service, 2017. 

Transformingeducation.org. “Student Stress Statistics [2024 Update].” Transforming Education for People, 23 Sept. 2024, transformingeducation.org/student-stress-statistics/#:~:text=1.,major%20contributor%20to%20student%20stress.