<p>Multilayered composite coatings of titanium dioxide nanotubes decorated with zinc oxide and hydroxyapatite nanoparticles: controlled release of Zn and antimicrobial properties against <em>Staphylococcus aureus</em></p>

Abstract

Purpose: This study aimed to decorate the surface of TiO 2 nanotubes (TiO 2 NTs) grown on medical grade Ti-6Al-4V alloy with an antimicrobial layer of nano zinc oxide particles (nZnO) and then determine if the antimicrobial properties were maintained with a final layer of nano-hydroxyapatite (HA) on the composite. Methods: The additions of nZnO were attempted at three different annealing temperatures: 350, 450 and 550 °C. Of these temperatures, 350°C provided the most uniform and nanoporous coating and was selected for antimicrobial testing. Results: The LIVE/DEAD assay showed that ZnCl 2 and nZnO alone were >90% biocidal to the attached bacteria, and nZnO as a coating on the nanotubes resulted in around 70% biocidal activity. The lactate production assay agreed with the LIVE/DEAD assay. The concentrations of lactate produced by the attached bacteria on the surface of nZnO-coated TiO 2 NTs and ZnO/HA-coated TiO 2 NTs were 0.13±0.03 mM and 0.37±0.1 mM, respectively, which was significantly lower than that produced by the bacteria on TiO 2 NTs alone, 1.09±0.30 mM (Kruskal–Wallis, P <0.05, n=6). These biochemical measurements were correlated with electron micrographs of cell morphology and cell coverage on the coatings. Conclusion: nZnO on TiO 2 NTs was a stable and antimicrobial coating, and most of the biocidal properties remained in the presence of nano-HA on the coating.

Infectious Diseases Impact on Biomedical Devices and Materials

“…Combining materials can have a synergistic effect as it was demonstrated that TiO 2 /ZnO nanoparticles supported in 4A zeolite could lead to resilient activity as antimicrobial agents [ 72 ]. In fact, multilayered composite coatings of TiO 2 nanotubes combined with ZnO and hydroxyapatite nanoparticles were applied for controlled Zn release for antimicrobial activity against Staphylococcus aureus [ 73 ]. Biological compatibility of TiO 2 coatings by changing the surface chemical composition and nanotopography has supported its use in biomedical TiO 2 applications [ 74 ].…”

NanoZnO-modified titanium implants for enhanced anti-bacterial activity, osteogenesis and corrosion resistance

“…The hydrothermal method has been widely used in the preparation of ZnO with nanorod structures. Changing the factors, such as reaction temperature, vessel pressure, and reaction time, may affect the growth of ZnO nanocrystals on the substrate surface [ 74 , 75 ]. Seed layers can be prepared on the surface of Ti substrates and then hydrothermally treated to aid their growth [ 76 , 77 ], or nano-ZnO can be prepared directly on the substrate surface in a sealed pressure vessel [ 74 ].…”

“…HA has almost the same chemical composition as natural bone and teeth, and the size and rigidity of nano-sized HA (nHA) are highly similar to those of HA crystals in natural bone; thus HA has good biocompatibility and osteoinductive activity, and is often used as a coating material [ 121 , 122 ]. Therefore, some scholars obtained better biocompatibility and osteoinductivity while achieving a good antibacterial effect when nano-ZnO was doped with nHA [ 70 , 75 ]. In the latest research, polypyrrole (PPy) was used as a dual regulator of nHA and nano-ZnO through coordinating and doping of ions, which reduced the release rate of Ca 2+ and Zn 2+ , not only ensuring a good antibacterial effect but also improving the physiological stability of the composite coating [ 61 ] (Fig.…”

Nanoparticles in caries prevention: A review

“…[71] The liberation of oxygen species on the surface of ZnO can significantly damage microorganisms. [73] Zn is effective against S. aureus, [74] Porphyromonas gingivalis and Actinomyces naeslundii, [73] Escherichia coli, [71] Streptococcus sobrinus, [16,75] and S. mutans. [76] Zinc oxide nanoparticles have photocatalytic activity and high stability.…”