Tailoring the network properties of Ca2+ crosslinked Aloe vera polysaccharide hydrogels for in situ release of therapeutic agents.

Properties of Aloe vera galacturonate hydrogels formed via Ca(2+) crosslinking have been studied in regard to key parameters influencing gel formation including molecular weight, ionic strength, and molar ratio of Ca(2+) to COO(-) functionality. Dynamic oscillatory rheology and pulsed field gradient NMR (PFG-NMR) studies have been conducted on hydrogels formed at specified Ca(2+) concentrations in the presence and absence of Na(+) and K(+) ions in order to assess the feasibility of in situ gelation for controlled delivery of therapeutics. Aqueous Ca(2+) concentrations similar to those present in nasal and subcutaneous fluids induce the formation of elastic Aloe vera polysaccharide (AvP) hydrogel networks.

Advances in the synthesis of amphiphilic block copolymers via RAFT polymerization: stimuli-responsive drug and gene delivery.

Controlled/'living' radical polymerization methods, including the versatile reversible addition-fragmentation chain transfer (RAFT) polymerization process, are rapidly moving to the forefront in construction of drug and gene delivery vehicles. The RAFT technique allows an unprecedented latitude in the synthesis of water soluble or amphiphilic architectures with precise dimensions and appropriate functionality for attachment and targeted delivery of diagnostic and therapeutic agents. This review focuses on the chemistry of the RAFT process and its potential for preparing well-defined block copolymers and conjugates capable of stimuli-responsive assembly and release of bioactive agents in the physiological environment.

Thermoreversible hydrogels from RAFT-synthesized BAB triblock copolymers: steps toward biomimetic matrices for tissue regeneration.

Narrowly dispersed, temperature-responsive BAB block copolymers capable of forming physical gels under physiological conditions were synthesized via aqueous reversible addition fragmentation chain transfer (RAFT) polymerization. The use of a difunctional trithiocarbonate facilitates the two-step synthesis of BAB copolymers with symmetrical outer blocks. The outer B blocks of the triblock copolymers consist of poly(N-isopropylacrylamide) (PNIPAM) and the inner A block consists of poly(N,N-dimethylacrylamide).