Synthesis and Characterization of Photocurable Polyionic Hydrogels
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Synthesis and Characterization of Photocurable Polyionic Hydrogels Pooja N Desai, and Hu Yang Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA, 23284 ABSTRACT In this study we describe preparation of polyionic hydrogels based on PEGylated polyamidoamine (PAMAM) dendrimers. Polyethylene glycol (PEG) with varied chain length (MW=1500, 6000, or 12000) was first conjugated to the Starburst™ G3.0 PAMAM dendrimer to form stealth dendrimers. The free hydroxyl group of PEG was further converted to an acrylate group using acrolyl chloride and triethylamine. The conjugation was characterized with 1HNMR. The loading degree of PEG on the dendrimer surface was estimated by using both the ninhydrin assay and 1H-NMR. Hydrogel formation was realized by subjecting dendrimer-PEG acrylate to UV exposure for a brief period of time at the presence of Eosin Y, triethanolamine and 1-vinyl-2-pyrrolidinone. PEGylated G3.0 PAMAM dendrimer served as cross-linking agent to form hydrogels because of its multiple functionalities. The surface charges conferred by terminal groups on the dendrimer surface made the hydrogel polyionic with controllable charge density. This new type of hydrogel has many favorable biological properties such as non toxicity and non immunogenecity and multifunctional ties for a variety of in vivo applications. Current studies have demonstrated feasibility of chemistry and hydrogel formation. INTRODUCTION Hydrogels are cross linked insoluble network of polymer chains that swell in aqueous solutions, which have found many applications including drug delivery and tissue regeneration. Hydrogels are useful in biomedical and pharmaceutical applications because of their biocompatibility, high water content, low surface tension, hydrodynamic properties being very similar to those of natural biological gels and tissues, and their minimal mechanical irritation due to their soft and rubbery state [1]. Due to their high water content, these gels resemble natural living tissue more than any other type of synthetic biomaterial [2]. In addition to being used as carriers of bioactive agents, they can also provide protection for proteins or drugs [3]. The perm selective nature of hydrogels makes them suited for diverse applications ranging from controlled drug delivery to cellular and tissue transplantation [4]. Dendrimers provide an ideal platform for drug delivery as they possess a well-defined highly branched nanoscale architecture with many reactive surface groups. Drug molecules either can be physically entrapped inside the dendritic structure or can be covalently attached onto the surface. In particular, their highly clustered surface groups allow for targeted drug delivery and high drug payload to enhance therapeutic effectiveness [5]. Dendrimers have also been studied as crosslink agents because of their multiple reactive surface groups. In particular, hydrogels formulated based on PEGylated dendrimers are of great interest because they have many biologically favorable properties.
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