Differences in Viscoelasticity of Ophthalmic Polymer Solution after Sterilization

Abstract

Polymer solution has been used for increasing viscosity of ophthalmic solution in order to prolong the retention of active drug in the eye. The ophthalmic solution must be sterilized, which may affect the rheology properties of viscosity-inducing polymers. The aim of this study was to investigate the effect of sterilization treatment on viscosity-inducing agents (i.e., poloxamer, polyvinyl alcohol; (PVA), methyl cellulose (MC), polyvinylpyrrolidone (PVP) and carbomer). The effect of membrane filtration and steam sterilization or autoclaving (121 °C, 15 Ib/inch2, 15 min) were determined. A rheometer was used to investigate the viscosity and viscoelastic properties between treated and untreated polymer solutions. The power law model, consistency index (k), and power law index (n) of polymer solution viscosity were compared. For viscoelastic properties, storage modulus and loss modulus were examined. The results demonstrated that, viscosity of carbomer and MC solution (1 and 2 %) were changed after steam sterilization. No difference in viscosity was observed for PVP, PVA and poloxamer solution, between untreated and treated samples. The storage and loss moduli of PVA solution after autoclaving were not different when comparing with the untreated polymer solution. From this study, it could be concluded that the sterilization treatment influenced the viscosity behavior and viscoelastic properties of polymer solution used as viscosity-inducing agent in ophthalmic solution. Therefore, the selection of polymer and sterilization method should be carefully considered.

Sustained release gel (polymer-free) of itraconazole-loaded microemulsion for oral candidiasis treatment: time-kill kinetics and cellular uptake

“…The amplitude or shear strain was obtained by examining the amplitude sweep, and the linear viscoelastic region (LVE) of each sample was determined by plotting the logarithmic correlation between the strain and modulus (Stojkov et al., 2021 ). The LVE region was selected for a certain shear strain value in this range to be used in subsequent flow behavior studies (Weerapol & Sriamornsak, 2020 ).…”