Rheometric study of chitosan/activated carbon composite hydrogels for medical applications using an experimental design

Abstract

Composite chitosan/activated carbon hydrogels were prepared with the vapor-induced phase separation process. A rheometric study was performed with a factorial fractional design to determine the formulation and process parameters significantly influencing the mechanical properties of the gels. The results revealed that three factors played a key role in the storage modulus of the gels. According to the model, these factors could be classified with respect to their relative influence on the storage modulus in the following descending order: chitosan concentration > gel time of exposure to ammonia vapors > temperature of the reactor. Increasing these parameters led to an increase in the physical crosslinking density within the matrices and resulted in a reinforcement of the mechanical properties of the hydrogels. Two interactions were also shown to be significant and promoted the formation of supplementary junction zones within the matrix: the first one corresponded to the interaction between the chitosan concentration and the exposure time to ammonia vapors, and the second one concerned the interaction between the chitosan concentration and the temperature of the reactor. A second-order model was obtained from statistical analysis. Because of the determination coefficient (89.4%) and the P value related to the lack of adjustment of the model (0.043), which was associated with a 95% confidence level, this model could be considered to be of good quality. Three gels were used to validate the model, and good accuracy was obtained. The maximum elastic modulus was obtained with the highest chitosan concentration [4% (w/v)], the highest temperature in the gelation chamber (50 C), and the longest time of exposure to ammonia vapors (24 h). V C 2010 Wiley Periodicals, Inc. J Appl Polym Sci 120: [808][809][810][811][812][813][814][815][816][817][818][819][820] 2011

Characterization of Neomycin-Loaded Xanthan-Chitosan Hydrogels for Topical Applications

“…A wide range of parameters influence the rheological properties of chitosan-based hydrogels: pH, ionic strength, solvent, concentration, molecular weight, and the distribution of the acetyl groups. 30 By increasing the pH of the solution, the hydrodynamic volume of the chitosan molecules decreases because of the reduction in the electrostatic repulsions between cationic charges, allowing the chains to come closer and thus increasing the number of the inter-and intra-chain hydrogen bonds. 20,30 Typical flow curves at 25 °C were recorded both for Xa-CS and Xa-CS-Ne hydrogels.…”

“…30 By increasing the pH of the solution, the hydrodynamic volume of the chitosan molecules decreases because of the reduction in the electrostatic repulsions between cationic charges, allowing the chains to come closer and thus increasing the number of the inter-and intra-chain hydrogen bonds. 20,30 Typical flow curves at 25 °C were recorded both for Xa-CS and Xa-CS-Ne hydrogels. Figure 1 illustrates the variation of the dynamic viscosity with shear rate, both in water and buffer solution as dispersion media.…”

Development and characterization of composite chitosan/active carbon hydrogels for a medical application

“…It has a viscosity of 100 cP at 25°C (data producer), a mass average molecular weight of 180,000 g mol −1 and a 20% degree of acetylation (producer data and Proton Magnetic Nuclear Resonance measurement deduced by the Hirai method) 15. The detailed characterization was described in a previous study 13. The AC used in this study is a commercial powdered product from Norit (Amersfoort, The Netherlands) listed in the European pharmacopoeia.…”

“…In our recent article, we investigated this novel “vapor gelation process” by a rheology study to show that some specific formulation and process parameters significantly influenced the viscoelastic properties of the gels. Increasing the chitosan concentration, the exposure time of chitosan systems to ammonia vapors and the temperature of the reactor led to an increase in the physical crosslink density of the networks and resulted in an improvement of the gel storage modulus of the hydrogels 13. We also developed a gelation model including mass transfers and reactions assuming a Fickian diffusion and neither influence of chitosan nor AC on the water and the ammonia activities to predict the concentration profiles of ammonia and chitosan species with reaction time 14…”

Recycling of Waste Cotton Sheets into Three-Dimensional Biodegradable Carriers for Removal of Methylene Blue

“…Molecules belonging to different classes, such as heavy metals and organics, can be removed by AC. 10 AC prepared from various precursors presented promising adsorption performance in dye removal processes. For example, AC made from rubber wood, oil palm waste, rubber wood sawdust, and sugar cane bagasse showed a maximum adsorption capacity of 1176 mg/g for acid blue 264, 11 1845 mg/g for basic blue 1, 12 1456 mg/g for Bismark Brown, 13 and 1060 mg/g for acid blue 25.…”