Biofunctionalization of Porous Titanium Oxide through Amino Acid Coupling for Biomaterial Design

Abstract

Porous transition metal oxides are widely studied as biocompatible materials for the development of prosthetic implants. Resurfacing the oxide to improve the antibacterial properties of the material is still an open issue, as infections remain a major cause of implant failure. We investigated the functionalization of porous titanium oxide obtained by anodic oxidation with amino acids (Leucine) as a first step to couple antimicrobial peptides to the oxide surface. We adopted a two-step molecular deposition process as follows: self-assembly of aminophosphonates to titanium oxide followed by covalent coupling of Fmoc-Leucine to aminophosphonates. Molecular deposition was investigated step-by-step by Atomic Force Microscopy (AFM) and X-ray Photoemission Spectroscopy (XPS). Since the inherent high roughness of porous titanium hampers the analysis of molecular orientation on the surface, we resorted to parallel experiments on flat titanium oxide thin films. AFM nanoshaving experiments on aminophosphonates deposited on flat TiO2 indicate the formation of an aminophosphonate monolayer while angle-resolved XPS analysis gives evidence of the formation of an oriented monolayer exposing the amine groups. The availability of the amine groups at the outer interface of the monolayer was confirmed on both flat and porous substrates by the following successful coupling with Fmoc-Leucine, as indicated by high-resolution XPS analysis.

DNA Sensing Platforms: Novel Insights into Molecular Grafting Using Low Perturbative AFM Imaging

“…In nanoshaving mode, the tip of the AFM works as a shaver capable of removing molecules from selected areas of the sample. We previously applied this method to SAMs of alkanethiols [26], amino phosphonates [34,35], thiolated DNA [36], and protein films [37] to evaluate the thickness of organic films by studying the difference in height between the film and the bare substrate where the molecules were removed. In the multi-technique approach we have developed, the AFM evaluation of the film thickness is an important point for the analysis of the correlated optical data.…”

Morphological Investigation of Protein Crystals by Atomic Force Microscopy

“…AFM can examine samples of different stiffness, regardless of their electrical conductivity, in different environments, from liquid to ultra-high vacuum. This wide range of operating conditions offers the possibility of measuring an equally wide range of samples such as cells [17][18][19], bacteria [20][21][22][23], extracellular vesicles [24,25], self-assembled molecular films [26][27][28][29][30][31][32][33][34][35][36][37][38], Langmuir-Blodgett films [39][40][41][42], supported lipid bilayers (SLB) [43][44][45][46][47][48][49], polymers [50][51][52][53], oxides [54][55][56][57], 2D materials [58][59][60][61][62], and other various materials [63]…”