Bringing multi-functionality to tissue scaffolds through deposition of hybrid coating

Abstract

Introduction
Hybrid coating consists of alternative layers of positively charged chitosan (CS) and negatively charged graphene oxide (GO) has been deposited onto a porous polyurethane (PU) scaffold through an electrostatic layer-by-layer (LbL) assembly technique. The resulting scaffold allows for high photothermal conversion efficiency and pH controlled co-delivery of multiple therapeutic agents.

Methods
PU foam templates were immersed in 1M NaOH solution for 10 mins before dipping in 0.01 M PEI solution to generate a primer layer. The foams were then immersed into GO (2mg/ml) and 0.5 wt% CS solution (in 2% (v/v) acetic acid aqueous solution) alternatively. This procedure was repeated until a desired number of layers were formed. FL (Fluorescein Sodium, 1.2 wt%) loaded GO and MB (Methylene blue, 0.2 mg/ml) loaded CS were used for the preparation of the scaffolds for drug release tests.

Results and Discussion
FL from the coated scaffold shows a pH dependent release (high releases under pH 7.4 and minimal release under pH 4). Whereas MB, shows an opposite trend where drug release was greater under pH4 than pH 7.4. The scaffold also exhibits strong photo-thermal conversion under irradiation of a NIR laser (808nm, 0.15 W) due to the presence of GO. Specifically, the irradiated scaffold surface temperature exceeded 55 °C after 1min of laser irradiation, a temperature range suitable for photothermal cancer therapy. In vitro study confirmed that this multi-functional scaffolds exhibit excellent biocompatibility.

Conclusions
Electrostatic layer-by-layer assembly technique has been successfully deployed to deposit a novel nanoscale GO/CS hybrid coating onto a porous polyurethane scaffold. The coated scaffold is biocompatible and can offer pH-dependent delivery of multiple therapeutic agents as well as on-demand localized photo hyperthermia. It may be potentially used for applications such as cancer photo chemeotherapy. .