Design, preparation and assessment of citrate-linked monosaccharide cellulose conjugates with elastase-lowering activity

Abstract

Elastase-sequestering wound dressings were prepared as the fructose and glucose citrate–cellulose conjugates on the cotton fibers of gauze dressings. The modified dressings were designed for chronic wounds, which contain destructively high levels of neutrophil elastase. The design of the modified gauzes was based on anionic citrate-esterified cellulose and the open chain isomers of the hemiketal and hemiacetal of fructose and glucose, which possess partial ketone, and aldehyde functionality as is found in synthetic elastase inhibitors. The cellulose–citrate conjugates of glucose and fructose were prepared on cotton gauze by rapid acid-catalyzed esterification of fibrous cellulose with citric acid as an ester cross-linking agent. The glucose and fructose citrate ester conjugates of cellulose were characterized as both intermolecular ester bonds of citrate-cross-linked cellulose and as citrate esters of glucose and fructose. Glucose and fructose were released from the fabric through hydrolysis of the citrate ester of the monosaccharide and were characterized using high performance anion exchange chromatography with pulsed amperometric detection and a modified Fehling's test. Chromatographic analysis of the hydrolyzed glucose and fructose ester products revealed the cellulose conjugates to be formed at levels of 4 mg of glucose per gram of cotton and 0.9 mg of fructose per gram of cotton. Fourier transform infrared spectroscopy was employed to detect the citrate-esterified conjugates on the cotton fiber. The modified cotton gauzes containing the monosaccharide ester conjugates and citrate-cross-linked cellulose were compared with untreated gauze for reduction of elastase activity in buffered saline, and in solutions of chronic wound fluid. The monosaccharide and citric acid conjugates of cellulose demonstrate a sequestration effect by extracting elastase from solution. The order of elastase-lowering potency of the monosaccharide–citrate cellulose conjugates in wound fluid was judged to be fructose–citrate>glucose–citrate=citrate. Elastase-lowering activity displayed a linear response over a range of 10–75 mg of gauze samples with the fructose–citrate cellulose conjugate (11.5–0.5 μmol of sugar/unit of elastase activity).