Angiogenesis, Osseointegration, and Antibacterial Applications of Polyelectrolyte Multilayer Coatings Incorporated With Silver/Strontium Containing Mesoporous Bioactive Glass on 316L Stainless Steel.

Yi-Jie Kuo,Ren-Jei Chung,Pranjyan Dash,Chia-Hsien Chen,Shao-Ju Shih,Yu-Chien Lin,Chih-Wei Hsu

doi:10.3389/fbioe.2022.818137

Abstract

The main causes for failure in implant surgery are prolonged exposure of implants or wound and tissue ischemia. Bacterial infection caused by the surrounding medical environment and equipment is also a major risk factor. The medical risk would be greatly reduced if we could develop an implant coating to guide tissue growth and promote antibacterial activity. Mesoporous bioactive glasses are mainly silicates with good osteoinductivity and have been used in medical dentistry and orthopedics for several decades. Strontium ions and silver ions could plausibly be incorporated into bioactive glass to achieve the required function. Strontium ions are trace elements in human bone that have been proposed to promote osseointegration and angiogenesis. Silver ions can cause bacterial apoptosis through surface charge imbalance after bonding to the cell membrane. In this study, functional polyelectrolyte multilayer (PEM) coatings were adhered to 316L stainless steel (SS) by spin coating. The multilayer film was composed of biocompatible and biodegradable collagen as a positively charged layer, γ-polyglutamic acid (γ-PGA) as a negatively charged layer. Chitosan was incorporated to the 11th positively charged layer as a stabilizing barrier. Spray pyrolysis prepared mesoporous bioactive glass incorporated with silver and strontium (AgSrMBG) was added to each negatively charged layer. The PEM/AgSrMBG coating was well hydrophilic with a contact angle of 37.09°, hardness of 0.29 ± 0.09 GPa, Young’s modulus of 5.35 ± 1.55 GPa, and roughness of 374.78 ± 22.27 nm, as observed through nano-indention and white light interferometry. The coating’s antibacterial activity was sustained for 1 month through the inhibition zone test, and was biocompatible with rat bone marrow mesenchymal stem cells (rBMSCs) and human umbilical vein endothelial cells (HUVECs), as observed in the MTT assay. There was more hydroxyapatite precipitation on the PEM/AgSrMBG surface after being soaked in simulated body fluid (SBF), as observed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). In both in vitro and in vivo tests, the PEM/AgSrMBG coating promoted angiogenesis, osseointegration, and antibacterial activity due to the sustained release of silver and strontium ions.

Highlights

Surgical site infection is a common cause of surgical failure and occurs when pathogens proliferate at the site of a surgical incision or post-operative wound, and this includes infections from the medical environment through the implant
The concentrations of AgSrMBG were 1.028, 4.808, and 9.081 ppm at 1, 5, and 10 mol% Sr, respectively. These results suggest well-controlled Ag and Sr concentrations in the AgSrMBG
To determine the appropriate concentrations to be used in the Polyelectrolyte multilayer (PEM), cytotoxicity tests were performed by coculturing MC3T3-E1 cells with various concentrations of SrMBG and AgSrMBG with (Figure 1)

Summary

Introduction

Surgical site infection is a common cause of surgical failure and occurs when pathogens proliferate at the site of a surgical incision or post-operative wound, and this includes infections from the medical environment through the implant. The risk of re-infection is around 8% after revision surgery for prosthetic hips (Kunutsor et al, 2015) and knees (Kunutsor et al, 2016), though some studies have indicated values as high as 57.1% (Marculescu et al, 2006; Lee et al, 2010) These infections commonly occur due to a foreign body response between the wound and the surface of the material, which results in inadequate wound healing, repeated exposure to bacterial infection, and sensitivity to other related factors that can lead to implant failure (Esposito et al, 1998; Seebach and Kubatzky, 2019). The surfaces of these materials can be modified to incorporate beneficial properties (Hanawa, 1999) such as chemical stability, biocompatibility, and controllable mechanical properties similar to those of human bones (Niinomi, 2002; Liu et al, 2014; Liu et al, 2015)

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