The goal of this work is to make an injectable physically and chemically cross-linking NIPAAmbased copolymer system for endovascular embolization. A copolymer with N-isopropylacrylamide (NIPAAm) and hydroxyethyl methacrylate (HEMA) was synthesized and converted to poly (NIPAAm-co-HEMA-acrylate) functionalized with olefins. When poly(NIPAAm-co-HEMAacrylate) was mixed with pentaerythritol tetrakis 3-mercaptopropionate (QT) stoichiometrically in 0.1 N PBS solution of pH 7.4, it formed a temperature-sensitive hydrogel with low swelling through the Michael-Type Addition reaction and showed improved elastic properties at low frequency compared to physical gelation. This material could be useful for applications requiring water-soluble injection but lower swelling and lower creep properties than available with other soluble in situgelling materials.

The objective of this work was to create an in situ physically and chemically cross-linking hydrogel for in vivo applications. N-Isopropylacrylamide (NIPAAm) was copolymerized with N-acryloxysuccinimide (NASI) via free radical polymerization. Poly(NIPAAm-co-NASI) was further modified to obtain poly(NIPAAm-co-cysteamine) through a nucleophilic attack on the carbonyl group of the NASI by the amine group of the cysteamine. Modification was verified by nuclear magnetic resonance. In addition to thermoresponsive physical gelling due to the presence of NIPAAm, this system also chemically gels via a Michael-type addition reaction when mixed with poly(ethylene glycol) diacrylate. The presence of both physical and chemical gelation resulted in material properties that are much improved compared to purely physical gels. The chemical gelation time of the copolymers was not significantly affected by the amount of thiol present due to the increased pKa of the copolymer containing more thiols. In addition, the swelling of the copolymers was highly dependent on the temperature and thiol content. Last, the rate of nucleophilic attack in the Michael-type addition reaction was shown to be highly dependent on pH and on the mole ratio of thiol to acrylate. Due to the improved mechanical properties, this material may be better suited for long-term functional replacement applications than other thermosensitive physical gels. With further development and biocompatibility testing, this material could potentially be applied as a temperature-responsive injectable biomaterial for functional embolization.

SUMMARY Physiological trade-offs arise because multiple processes compete for the same limiting resources. While competition for resources has been demonstrated between reproduction and immune function, the regulation of this competition remains unclear. Corticosterone (CORT) is a likely mediator due to its dual role in mobilizing energy stores throughout the body and regulating physiological responses to stressors. We manipulated CORT concentrations and resources in pre-reproductive and reproductive female tree lizards(Urosaurus ornatus) to test the hypothesis that CORT regulates the distribution of limiting resources between the reproductive and immune systems. To manipulate circulating concentrations of CORT we utilized a novel method of hormone implantation, in which a polymeric compound is mixed with hormone and injected in liquid form into the animal. After injection, the liquid quickly gels in situ forming a slow release hormone implant. This method of hormone delivery eliminated the need for substantial wounds to the animal or repeated handling required by other methods. In this study, the hormone-treated animals had plasma CORT concentrations comparable to high physiological concentrations. We found that CORT treatment suppressed immune function, but only when animals were energetically compromised. We assessed immune function by measuring the healing rate of a cutaneous biopsy. Healing was suppressed in all CORT-treated reproductive animals and in all CORT-treated animals (pre-reproductive and reproductive) undergoing food restriction, but CORT had no effect in ad libitum non-reproductive females. The context-dependent action of CORT renders its response adjustable to changing environmental conditions and may allow for the suppression of specific functions depending on resource availability.

Gradient insulator-based dielectrophoresis used to generate separation and concentration of Staphylococcus epidermidis, gentamicin-resistant and susceptible strains.