The overall goal of this research is to develop a new class of in situ-forrning, injectable, and biodegradable polymeric biomaterials based on time-dependent molar mass and lower critical solution temperature (LCST) properties for localized delivery of an anti-cancer agent, phenstatin. Many current biodegradable, injectable, and in situ-forming biomaterials under development have disadvantages including the use of water miscible organic solvents for delivery, low molecular weight toxic byproducts, reactive chemistries and the need for external light sources (i.e., for photopolymerization). Ideal replacement materials for these applications would be easily injected and form in a timely fashion without detrimental effects to surrounding tissue from temperature increases, toxicity or invasive techniques. Many of these difficulties can be addressed using NIPAAm copolymers with time-dependent molar mass and lower critical solution temperature (LCST) properties. Copolymers of N-isopropylacrylamide (NIPAAm), methacrylic anhydride(MA) and maleic anhydride (MAn) will possess time-dependent LCST properties in an aqueous environment due to the conversion of maleic anhydride side chains to maleic acid and time-dependent molar mass due to conversion of methacrylic anhydride to methacrylic acid, both by hydrolysis. Copolymers of NIPAAm, methacrylic anhydride, and maleic anhydride will be synthesized and be characterized for initial and final LCST, initial and final molar mass, the initial strength of the gel, and degradation time. Drug release profiles will be evaluated from selected materials. The cytotoxicity and biocompatibility of these materials will be assessed using cell proliferation (MTT) and live/dead assays on BALB/c 3T3 cells. Tissue irritation potential of these materials will be evaluated in vitro by macrophage and lymphocyte activation experiments. Finally, a selected material will be injected subcutaneously into Sprague Dawley rats to verify injectability and in situ formation. In vivo compatibility will be assessed using selected histological techniques. In vivo efficacy of phenstatin released from this material will be evaluated using a SCID mouse ovarian cancer model.
