Control of thermo reversible gelation of methylcellulose using polyethylene glycol and sodium chloride for sustained delivery of ophthalmic drug

Abstract

ABSTRACT:The effect of molecular weight of polyethyleneglycol (PEG) and sodium chloride (NaCl) on the gelation temperature of methylcellulose (MC) was studied with the objective to develop a MC based formulation for sustained delivery of ophthalmic drug. The gelation temperature of 1% MC was 60 6 0.40 C. It was found that the gelation temperature of MC was reduced with the addition of 10% PEG and extent of reduction of gelation temperature was depended on the molecular weight of PEG at same PEG concentration of 10%. The gelation temperature of MC was reduced by 10.4 to 5.9 C with the increasing molecular weight of PEG starting from 400 to 20,000 (Mn) depending on the method of determination of gelation temperature. To reduce the gelation temperature of MC close to physiological temperature (37 C), 6% NaCl was added in the different MC-PEG combinations containing different molecular weight of PEG. It was observed that the drug release time increased from 5 to 8 h with the increase in molecular weight of PEG from 400 to 20,000 (Mn) and this was due to the maximum viscosity and gel strength of MC-PEG20000-NaCl ternary combination.

Effect of PVA on the gel temperature of MC and release kinetics of KT from MC based ophthalmic formulations

“…The gel strength depends on the degree of substitution and the molecular weight [13,14]. Recently, the effect of molecular weight of PEG on the gelation temperature of MC has been studied [3]. MC undergoes swelling and erosion in vivo, so it is not necessary to remove the gel after complete release of drug [15].…”

“…Hydrogels are hydrophilic polymer networks, which absorb enough quantity of water [1][2][3]. Hydrogels can be prepared by physical or chemical crosslinking of polymers.…”

“…During heating at a certain temperature, the polymer-polymer interactions become stronger than the polymer-solvent interactions and then gelation takes place. The characteristic temperature is called gelation temperature [3].…”

Analysis of Water State and Gelation of Methylcellulose Thermo-reversible Hydrogels by Thermal Analysis and NMR

“…15 NaCl is used for decreasing the gelation temperature of MC for the formation of drug delivery. 16,17 On the other hand, polyethylene glycol (PEG) belongs to the group of polyols; it can alter the physical properties of MC hydrogels. PEG is nontoxic and biocompatible.…”

“…The drug release time has been reported to increase with the increase in the molecular weight of PEG in an MC-PEG-salt system. 16 The gelation mechanism of MC hydrogels is not sufficiently clear. The gel state of MC hydrogels exhibits a fibrillary diameter of 14 -15 nm.…”