Effective gamma-ray sterilization and characterization of conductive polypyrrole biomaterials

Semin Kim,Hui-Jeong Gwon,Sanghun Lee,Jin-Oh Jeong,Jae Young Lee,Youn-Mook Lim,Jong-Seok Park,Sung In Jeong,John George Hardy

doi:10.1038/s41598-018-22066-6

Abstract

Conductive polymers, including polypyrrole (PPy), have been extensively explored to fabricate electrically conductive biomaterials for bioelectrodes and tissue engineering scaffolds. For their in vivo uses, a sterilization method without severe impairment of original material properties and performance is necessary. Gamma-ray radiation has been commonly applied for sterilization of medical products because of its simple and uniform sterilization without heat generation. Herein we describe the first study on gamma-ray sterilization of PPy bioelectrodes and its effects on their characteristics. We irradiated PPy bioelectrodes with different doses (0–75 kGy) of gamma-rays. Gamma-ray irradiation of the PPy (γ-PPy) increased the oxygenation and hydrophilicity of the surfaces. Interestingly, gamma-ray irradiation did not alter the electrical impedances and conductivities of the PPy substrates. Additionally, γ-PPy prepared with various dopants (e.g., para-toluene sulfonate, polystyrene sulfonate, and chlorine) showed the electrochemical properties similar to the non-irradiated control. Gamma-ray irradiation at doses of ≥15 kGy was required for effective sterilization as evidenced by complete eradication of gram positive and negative bacteria. γ-PPy substrates also showed cytocompatibility similar to untreated control PPy, indicating no substantial alteration of cytocompatibility. In conclusion, gamma ray sterilization is a viable method of sterilization of conducting polymer-based biomaterials for biomedical applications.

Highlights

Conducting polymers (CPs) have attracted attention from scientists and engineers due to their high electrical conductivity, simple synthesis, and excellent biocompatibility[1,2]
A PPy/para-toluene sulfonate (pTS) was electrochemically polymerized on indium-tin oxide (ITO) or gold electrodes (Supplementary Fig. S1), followed by exposure to gamma-rays
We found that autoclave of PPy/pTS led to dramatic increases in impedance, and five out of ten PPy electrodes lost their original electrochemical activities

Summary

Introduction

Conducting polymers (CPs) have attracted attention from scientists and engineers due to their high electrical conductivity, simple synthesis, and excellent biocompatibility[1,2]. Sterilization of CP-based biomaterials for in vivo uses is challenging because it may lead to the deterioration of the CP’s inherent electrical and biochemical properties, and there is a lack of systematic studies validating the effects of sterilization methods on the properties of such CP-based biomaterials. Conventional sterilization methods, such as steam, ultraviolet radiation (UV), ethylene oxide (EO), and gamma-irradiation sterilization, can be employed for CPs18,19. The cytocompatibility of the γ-PPy substrates was studied using various types of cells (e.g., neuronal cells, myoblasts, and fibroblasts)

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Conclusion