Atomic layer deposition of nano-TiO_2 thin films with enhanced biocompatibility and antimicrobial activity for orthopedic implants

Abstract

Titanium (Ti) and its alloys have been extensively used as implant materials in orthopedic applications. Nevertheless, implants may fail due to a lack of osseointegration and/or infection. The aim of this in vitro study was to endow an implant surface with favorable biological properties by the dual modification of surface chemistry and nanostructured topography. The application of a nanostructured titanium dioxide (TiO 2 ) coating on Ti-based implants has been proposed as a potential way to enhance tissue-implant interactions while inhibiting bacterial colonization simultaneously due to its chemical stability, biocompatibility, and antimicrobial properties. In this paper, temperature-controlled atomic layer deposition (ALD) was introduced for the first time to provide unique nanostructured TiO 2 coatings on Ti substrates. The effect of nano-TiO 2 coatings with different morphology and structure on human osteoblast and fibroblast functions and bacterial activities was investigated. In vitro results indicated that the TiO 2 coating stimulated osteoblast adhesion and proliferation while suppressing fibroblast adhesion and proliferation compared to uncoated materials. In addition, the introduction of nano-TiO 2 coatings was shown to inhibit gram-positive bacteria ( Staphylococcus aureus ), gram-negative bacteria ( Escherichia coli ), and antibiotic-resistant bacteria (methicillin-resistant Staphylococcus aureus ), all without resorting to the use of antibiotics. Our results suggest that the increase in nanoscale roughness and greater surface hydrophilicity (surface energy) together could contribute to increased protein adsorption selectively, which may affect the cellular and bacterial activities. It was found that ALD-grown TiO 2 -coated samples with a moderate surface energy at 38.79 mJ/m 2 showed relatively promising antibacterial properties and desirable cellular functions. The ALD technique provides a novel and effective strategy to produce TiO 2 coatings with delicate control of surface nanotopography and surface energy to enhance the interfacial biocompatibility and mitigate bacterial infection, and could potentially be used for improving numerous orthopedic implants.

Antimicrobial Nanostructured Coatings: A Gas Phase Deposition and Magnetron Sputtering Perspective

“…In maxillofacial prostheses, the reduction of the incidence of tissue inflammation surrounding the prostheses has been explored by coating the surface with nanostructured TiO 2 . As a result, the introduction of nano-TiO 2 coatings has been shown to inhibit a rather large range of bacteria strains [101]. These few examples suggest that the combination of different elements into the coating is likely needed to provide a wide spectrum of anti-biofilm activity, though the role of the coating roughness has not been explored in detail.…”

“…These few examples suggest that the combination of different elements into the coating is likely needed to provide a wide spectrum of anti-biofilm activity, though the role of the coating roughness has not been explored in detail. On the other hand, investigations into the effect of individual NPs on the biofilm disruption has been obtained for Au [36,102], Ag [103], Mg [104], ZnO [42,102,105], CuO [102,106], CeO [102], Fe 3 O 4 [107], YF [108] and TiO 2 [101], indicating that smaller NPs with high surface to volume ratio have a remarkable effect on biofilm destruction [98].…”

Evaluation of Microbial Adhesion and Biofilm Formation on Nano-Structured and Nano-Coated Ortho-Prosthetic Materials by a Dynamic Model

“…The bio-engineering technologies of medical devices through nano-structuring and coating has recently been proposed, not only to prevent microbial adhesion, but also to improve the biocompatibility of materials [5][6][7][8] to develop the ideal orthopedic implant.…”

Antibacterial photocatalytic activity of different crystalline TiO2 phases in oral multispecies biofilm

“…Several methods are used for TiO 2 deposition on biomaterials such as sol-gel [24,25], spin-coating [12,26], anodization [9,10,27], atomic layer deposition [28] and magnetron sputtering [11,13,[29][30][31] . Magnetron sputtering is a extensively used method as it produces films with greater adhesion, hardness and hydrophilicity [19,30,32,33], and it is also able to generate isolated phases of anatase and rutile [34].…”

“…This is due to the high variability in the test conditions used for different studies. In one hand, studies reported that TiO 2 has an antibacterial effect [8][9][10]27,28,[37][38][39][40], while on the other hand, different studies revealed no influence on early biofilm formation [9,36], highlighting the need for further studies.…”