Tailoring the Network Properties of Ca 2+ Crosslinked Aloe vera Polysaccharide Hydrogels for in Situ Release of Therapeutic Agents

作者：Shawn D. McConaughy, Stacey E. Kirkland, Nicolas J. Treat, Paul A. Stroud, Charles L. McCormick · 发表于：Biomacromolecules · 年份：2008 · DOI：10.1021/bm8008457 · 被引用次数：37 · 研究领域：Polysaccharides Composition and Applications、Polysaccharides and Plant Cell Walls、Hydrogels: synthesis, properties, applications

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. By altering the ratio of Ca(2+) to COO (-) functionality, networks may be tailored to provide elastic modulus (G') values between 20 and 20000 Pa. The Aloe vera polysaccharide exhibits time-dependent phase separation in the presence of monovalent electrolytes. Thus the relative rates of calcium induced gelation and phase separation become major considerations when designing a system for in situ delivery applications where both monovalent (Na(+), K(+)) and divalent (Ca(2+)) ions are present. PFG-NMR and fluorescence microscopy confirm that distinctly different morphologies are present in gels formed in the presence and absence of 0.15 M NaCl. Curve fitting of theoretical models to experimental release profiles of fluorescein labeled dextrans indicate diffusion rates are relat...