Effects of steam sterilization on thermogelling chitosan-based gels

Abstract

A new thermogelling chitosan-glycerophosphate system has been recently proposed for biomedical applications such as drug and cell delivery. The objectives of this work were to characterize the effect of steam sterilization on the in vitro and in vivo end performances of the gel and to develop a filtration-based method to assess its sterility. Autoclaving 2% (w/v) chitosan solutions for as short as 10 min resulted in a 30% decrease in molecular weight, 3-5-fold decrease in dynamic viscosity, and substantial loss of mechanical properties of the resulting gel. However, sterilization did not impair the ability of the system to form a gel at 37 degrees C. The antimicrobial activity of chitosan against several microorganisms was evaluated after inoculation of chitosan solutions and removal of the cells by filtration. It was found that, although chitosan was bacteriostatic against the heat sterilization bioindicator Bacillus stearothermophilus, the bacteria could rapidly grow after separation from the chitosan solution by filtration. This indicated that B. stearothermophilus is an adequate strain to validate a heat sterilization method on chitosan preparations, and accordingly this strain was used to assess the sterility of chitosan solution following a 10 min autoclaving time.

Hydrogels: Methods of Preparation, Characterisation and Applications

“…The hydroxyl radicals react with hyaluronan with a rate constant k 2 = 0.9 x 10 9 mol -1 dm 3 s -1 , whereas H atoms rate is a lower order of magnitude k 2 = 7 x 10 7 mol -1 dm 3 s -1 (Myint et al, 1987). Figure 11 shows the various hydrolysis, rearrangement, and fragmentation reactions during aqueous radiolysis of cellobiose to gives possible chain break (Sonntag, 1987 Fei et al, 2000;Liu et al, 2002b;Wach et al, 2003a;) (Fei et al, 2000;Liu et al, 2002b;Wach et al, 2001;Wach et al, 2003a;) Hydroxy ethyl cellulose (Fei et al, 2000;Wach et al, 2003a) (Fei et al, 2000;Wach et al, 2001) chitin, chitosan & derivatives (Ershov et al, 1993;Ershov, 1998;Jarry et al, 2001;Jarry et al, 2002;) (Wasikiewicz et al, 2005) Cellulose & derivatives (Ershov, 1998;Nakamura et al, 1985;Phillips, 1961;Phillips, 1963;Wach et al, 2002) (Phillips & Moody, 1959;Wach et al, 2002) Starch and derivatives (Ershov, 1998;Nagasawa et al, 2004;Phillips, 1961;Zhai et al, 2003) D-glucose (Phillips, 1963;Schiller et al, 1998) (Sharpatyi, 2003) Hyaluronan & hyaluronic acid (Al-Assaf et al, 1995;Al-Assaf et al, 2006a;Ershov, 1998;…”

Chitosan-Based Thermosensitive Materials

“…There have been documented some investigations about the influence of different sterilization procedures on the thermogelling ability of this system. Autoclaving and steam sterilization may significantly affect the molecular weight and viscosity of chitosan, but do not impair its ability to form gels upon heating [12,13]. However, γ-radiation markedly changed its thermogelling properties [13].…”

125I-Iododeoxyuridine for the Treatment of a Brain Tumor Model: Selection of Conditions for Optimal Effectiveness

“…Chitosan (1.7% w/w) was dissolved in 0.1 M hydrochloric acid at room temperature and sterilized by autoclaving (121°C, 20 min) [15]. To the cooled solution chilled aqueous 45% (w/w) ß-glycerophosphate (ß-GP) solution (sterilized by filtration) was carefully added drop-wise to obtain clear and homogeneous liquid solution which was mixed for an additional 10 min at 4° C. The pH of the final cold solutions ranged from 6.9 to 7.2.…”

“…During the last decade, injectable in situ gelforming systems have received increased interest in drug delivery and tissue engineering. These devices can overcome many of the problems associated with polymers or microspheres in that they are both injectable and produce solid biodegradable implants with a range of mechanical characteristics in terms of rigidity and load bearing making them compatible with both soft and hard tissues [14][15][16]. In the study described here we have used a chitosan polymer to formulate a biodegradable and biocompatible implant for controlled delivery of a radiopharmaceutical in a slowrelease manner directly into a intra-cranial implant of a rat glioblastoma.…”