Optimization and Evaluation of a Chitosan/Hydroxypropyl Methylcellulose Hydrogel Containing Toluidine Blue O for Antimicrobial Photodynamic Inactivation.

Chueh-Pin Chen,Chien-Ming Hsieh,Tsuimin Tsai,Chin-Tin Chen,Jen-Chang Yang

doi:10.3390/ijms160920859

Abstract

Photodynamic inactivation (PDI) combined with chitosan has been shown as a promising antimicrobial approach. The purpose of this study was to develop a chitosan hydrogel containing hydroxypropyl methylcellulose (HPMC), chitosan and toluidine blue O (TBO) to improve the bactericidal efficacy for topical application in clinics. The PDI efficacy of hydrogel was examined in vitro against the biofilms of Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa). Confocal scanning laser microscopy (CSLM) was performed to investigate the penetration level of TBO into viable S. aureus biofilms. Incorporation of HMPC could increase the physicochemical properties of chitosan hydrogel including the hardness, viscosity as well as bioadhesion; however, higher HMPC concentration also resulted in reduced antimicrobial effect. CSLM analysis further demonstrated that higher HPMC concentration constrained TBO diffusion into the biofilm. The incubation of biofilm and hydrogel was further performed at an angle of 90 degrees. After light irradiation, compared to the mixture of TBO and chitosan, the hydrogel treated sample showed increased PDI efficacy indicated that incorporation of HPMC did improve antimicrobial effect. Finally, the bactericidal efficacy could be significantly augmented by prolonged retention of hydrogel in the biofilm as well as in the animal model of rat skin burn wounds after light irradiation.

Highlights

Microorganisms, such as bacteria and yeast, have been recognized for decades to cause human and animal diseases
toluidine blue O (TBO) with chitosan and TBO alone were used as controls to evaluate the Photodynamic inactivation (PDI) efficacy of HCT hydrogel
These formulations were prepared with an intention to optimize the content of hydroxypropyl methylcellulose (HPMC) in HCT hydrogel and understand its influence on the mechanical properties and the antimicrobial effect

Summary

Introduction

Microorganisms, such as bacteria and yeast, have been recognized for decades to cause human and animal diseases. Biofilm is the main growth form of microorganisms in nature. It is a non-homogeneous body consisting of microorganisms and extracellular polymer substrate (EPS). This EPS matrix provides structural stability and protection to the biofilm against adverse environmental conditions. Biofilm has a higher resistance to antimicrobial drugs, 500–1000 times higher when compared to the planktonic cells [1]. Biofilm presents a difficult challenge to clinicians due to their persistent nature, inability to be cultured with standard techniques, and resistance to conventional antimicrobial therapy

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