Materials Research Express | 2021
Thermogelling behaviour of PEG-enclatherated Methylcellulose/Alginate sols
Abstract
Thermogelling systems offer several advantages over conventional cross-linked hydrogels with respect to showing stimuli responsiveness and reversibility. They also offer functional and fabrication flexibility in terms of the design, injectability, and performance control offered by the in situ phase transition at various temperatures. Once gelled at the site of application or after injection, thermogels provide passive targeting with increased efficacy and decreased toxicity of the incorporated drugs. In this research, we describe methylcellulose-based thermogels blended with sodium alginate and enclatherated with poly(ethylene glycol) 400 (PEG400). The concentration of methylcellulose (MC) was kept constant at 4.0%w/v while that of sodium alginate (ALG) varied from 0.5 to 2.0%w/v. Clear sols were obtained and PEG400 were added (1 ml or 2 ml/10 ml of sol) to obtain final thermogels. The tripolymeric blend displayed hydrogen bonded O–H…C=O which was not evident in the bipolymeric systems (FTIR analysis). The DSC analysis corroborated the above with the absence of MC exotherm in tripolymeric blend formulations and the hijacking of MC-ALG interaction by the enclatherated PEG chains. The temperature ramp rheological profiling of the thermogels (20 °C–50 °C) revealed an increase in elastic modulus of M4A20P2 (sol with highest weight content) due to PEG400 interactions with ALG which in turn interacted with MC forming a self-assembled repeating network structure: PEG400-ALG-{hydrophillicMChydrophobic}-{hydrophobicMChydrophilic}-ALG-PEG400. With MC forming the hydrophobic or dehydrated part of the thermogel, ALG and PEG chains concentrated in the aqueous medium and were compressed from both side by the stiff MC architecture creating ‘intra- and inter-network stress’ induced polymer-polymer interactions. In conclusion, MC-ALG-PEG formed as complex thermoresponsive system showing physical restructuring induced chemical stabilization (PRICS) and can be employed in various biomedical applications.