Bioactive and Antimicrobial Layer-by-Layer Assembly on Titanium Surface

Abstract

The main contemporary problems in the dental implant industry are 1) formation of biofilm around the implant - a condition known as peri-implantitis and 2) inadequate bone formation around the implant - lack of osseointegration. Therefore, developing an implant to overcome these problems is of significant interest to the dental community. Chitosan has been reported to have good biocompatibility and also anti-bacterial activity. An osseo-inductive recombinant biopolymer (P-HAP), derived from the protein statherin has been reported to induce bone formation. In this study, chitosan/P-HAP bi-layers were built on titanium surface using layer-by-layer (LbL) assembly technique by exploiting the strong opposite electrostatic charge of each polymer. The LbL modified surfaces were characterized by contact angle measurement, diffuse reflectance infrared fourier transform spectroscopy (DRIFTS), atomic force microscopy (AFM) and X-Ray photoelectron spectroscopy (XPS). The substantial difference in water contact angle between consecutive layers, the representative peaks in DRIFTS and XPS, and the changes in topography between surfaces with different number of bi-layers observed in AFM indicated the successful establishment of chitosan/P-HAP LbL assembly on titanim surface. The LbL modified surfaces showed increased amount of biominerlization in osteogenic media (OS) supplemented with CaCl2, which is attributed to the well-established property of statherin. The amount of mineralization increased with the number of bi-layers. The mouse pre-osteoblastic cell line (MC3T3) adhered well, but a significant effect on cell differentiation was not observed on the LbL- modified surfaces. Osteoblast differentiation is a key step in bone formation. The discussion on the main causes for the lack of cell differentiation is provided. Notably, the LbL- modified surfaces showed significant anti-bacterial activity against gram positive Streptococcus gordonii.