Hydrogels are hydrophilic polymer networks that are able to retain large amounts of water. They generally exhibit excellent biocompatibility and are accordingly of interest for biomedical and pharmaceutical applications such as systems for the controlled delivery of biologically active agents. Hydrogels are networks that can be physically crosslinked by non-covalent interactions and/or chemically crosslinked by covalent bonds. Both approaches have been used in recent years for the preparation of hydrogels that can be applied under physiological conditions. Of special interest are biodegradable injectable hydrogels, also called “in situ” forming hydrogels. These gels are formed at the injection site after the introduction of fluid precursors in a minimally invasive manner. “In situ” forming hydrogels offer several advantages over implantation of pre-shaped devices. There is no need for surgical procedures and their initially flowing nature ensures proper shape adaptation as well as a good fit with the surrounding tissue. Moreover, cells or biologically active agents can be easily incorporated in the injectable fluid. Hydrogel based controlled drug delivery systems can potentially be used to address a number of issues that are encountered in conventional drug delivery, such as poor control of local or systemic drug concentration and the low solubility of many therapeutic agents in biological fluids. Most physically and chemically crosslinked biodegradable hydrogels that have been applied as controlled drug delivery systems are based on linear amphiphilic block copolymers of poly(ethylene glycol) (PEG) and aliphatic polyesters. Star block copolymers offer various advantages over linear polymers, such as increased solubility in aqueous media and a higher concentration of functional end groups. Starting from an 8-armed PEG block we designed and explored different block copolymers composed of outer poly(lactide) (PLA) or poly(trimethylene carbonate) (PTMC) blocks, for the preparation of physically or chemically crosslinked injectable hydrogels. The gelation and hydrogel degradation mechanisms involved were investigated in detail and their potential as systems for the controlled delivery of biologically active agents was evaluated.
|Award date||8 Dec 2011|
|Place of Publication||Enschede|
|Publication status||Published - 8 Dec 2011|