Local delivery of antimicrobial peptides using self‐organized TiO₂ nanotube arrays for peri‐implant infections

Abstract

Peri-implant infections have been reported as one of the major complications that lead to the failure of orthopedic implants. An ideal solution to the peri-implant infection is to locally deliver antimicrobial agents through the implant surface. The rising problem of infections caused by multiple antibiotic-resistant bacteria makes traditional antibiotics less desirable for the prevention of peri-implant infections. One of the promising alternatives is the family of antimicrobial peptides (AMPs). In this study, we report the local delivery of AMPs through the nanotubular structure processed on titanium surface. Self-organized and vertically oriented TiO2 nanotubes, about 80 nm in diameter and 7 μm thick, were prepared by the anodization technique. HHC-36 (KRWWKWWRR), one of the most potent broad-spectrum AMPs, was loaded onto the TiO2 nanotubes via a simple vacuum-assisted physical adsorption method. Antimicrobial activity testing against Gram-positive bacterium, Staphylococcus aureus, demonstrated that this AMP-loaded nanotubular surface could effectively kill the bacteria (≈ 99.9% killing) and reduce the total bacterial number adhered to the surface after 4 h of culture. In vitro AMP elution from the nanotubes was investigated using liquid chromatography-mass spectrometry (LC-MS). The release profiles strongly depended on the crystallinity of the TiO2 nanotubes. Anatase TiO2 nanotubes released significantly higher amounts of AMP than amorphous nanotubes during the initial burst release stage. Both followed almost the same slow release profile from 4 h up to 7 days. Despite the differences in release kinetics, no significant difference was observed between these two groups in bactericidal efficiency.

Antibacterial activity and cytocompatibility of an implant coating consisting of TiO₂ nanotubes combined with a GL13K antimicrobial peptide

“…Subsequently, the cumulative drug release was close to the linear regression with the square root of time, suggesting a slow and stable release up to 7 days. The release profile was similar to those reported by Ma et al 32 and Lai et al, 33 who used anodized titanium as an HHC-36 or enrofloxacin hydrochloride carrier. The release profiles were similar for GL13K-TNTs and MNA-TNTs, but a slower release was achieved by GL13K-TNTs.…”

In vivo evaluation of the anti-infection potential of gentamicin-loaded nanotubes on titania implants

“…15 It has been widely shown that antibiotic-loaded TNTs are able to reduce bacterial adhesion, while retaining or improving normal osteoblast adhesion and differentiation. 13,[16][17][18][19] Various metal cations that possess antibacterial properties, such as Ag, Zn, and Cu, have been introduced into TNT arrays to enhance the antibacterial activity of TNT-based Ti implants. [20][21][22][23][24] Nevertheless, their potential toxicity and antibacterial durability have yet to be improved and investigated.…”

Binding of plasma proteins to titanium dioxide nanotubes with different diameters

“…47,48 Peptide binding to TiO 2 NTs has been used predominantly for studying the increase of cell adhesion and osteogenic gene expression 22,23,49 as well as for soft tissue interactions 24 and local delivery of antimicrobial peptides. 50 A hexapeptide motif was found to bind electrostatically to titanium surfaces, with potential important osteogenic consequences. 17 Therefore, we tested the binding of plasma proteins with different molecular weights, charges, and functions to TiO 2 NTs with specific diameters.…”

“…EG-based electrolytes, with hydrofluoric acid as the source of F -ions with specific amount of water, were used in the second anodization step, under various applied potentials for obtaining the desired different diameter NTs. Specifically, the electrolyte was EG plus 8 M water plus 0.2 M hydrofluoric acid and the anodization time of 2.5 hours was used for obtaining all nanostructures (15,50, and 100 nm), while the applied potential was 58 V for 100 nm, 20 V for 50 nm, and 10 V for 15 nm. The NTs thus formed were kept in ethanol for 2 hours to remove all organic components from the electrolyte, washed with distilled water, and dried under nitrogen stream.…”