Department of Materials Engineering, Bu-Ali Sina University, Hamedan, 65178-38695, Iran.
Environmental Science and Engineering Program, University of Texas at El Paso, El Paso, TX, 79968, USA.
J Trace Elem Med Biol. 2021 Jul;66:126756. doi: 10.1016/j.jtemb.2021.126756. Epub 2021 Apr 2.
The poor biological performance of zirconium implants in the human body resulting from their bio-inertness and vulnerability to corrosion and bacterial activity reflects the need for further studies on substitution or performing the surface modification. The suggestion of employing zirconia (ZrO) bioceramic coatings for surface modification seems beneficial.
This systematic review aims to identify and summarize existing documents reporting the biological responses for ZrO coatings produced by the PEO process on zirconium implants.
PubMed, Scopus, and Web of Science international databases were searched for the original and English-language studies published between 2000 and 2021. All publications reported at least one study about in-vitro (cellular and immersion studies), in-vivo (animal studies), and antibacterial topics for ZrO-PEO coated zirconium implants.
Throughout the initial search, 496 publications were found, and 296 papers remained following the elimination of duplicates. Finally, after multiple screening and eligibility assessments, 25 publications were qualified and included in the review. Among them, 25 in-vitro (cellular and immersion in SBF and Hanks' solutions studies), one in-vivo (animal studies), and eight antibacterial studies were found.
The ZrO coated samples demonstrate no cytotoxicity, high cell viability rate, and excellent biocompatibility. However, changing the solution composition and electrical parameters during the PEO procedures result in significant changes to in-vitro responses. As an instance, the ZrO coating surface demonstrates greater biocompatibility after irradiated by UV, which makes the surface more suitable for cell growth. Due to weak apatite-forming ability, the zirconium sample shows low bioactivity in SBF. However, most cases (13 out of 16) show that the specific morphology and chemical composition of the ZrO coating promote apatite-forming ability with good bioactivity in SBF. Nevertheless, few papers (three out of 16) showed that the ZrO coatings immersed in SBF had no apatite precipitates and so no bioactivity. These cases limit the bioactivity enhancement to treatment by UV-light irradiation, hydrothermal and chemical treatment, thermal evaporation, and cathodic polarization post-treatment on ZrO coatings. Both zirconium and ZrO coated samples do not show apatite-forming ability in Hanks' solution. The ZrO coated implant with the bone together indicates a greater shear strength and rapid new bone formation ability during 12 weeks because of containing Ca-P compounds and porous structure. The UV post-treated ZrO coating induces faster new bone formation and firmer connection of bond with bone than those of untreated ZrO coatings. A stronger antibacterial activity of ZrO coatings is confirmed in half of the selected papers (four out of eight studies) compared to the bare zirconium samples. The antibacterial protection of ZrO coatings can be influenced by the PEO procedure variables, i.e., solution composition, electrical parameters, and treatment time. In three cases, the antibacterial activity of ZrO coatings is enhanced by deposition of Zn, Ag, or Cu antibacterial layers through thermal evaporation post-treatment.
由于生物惰性、易腐蚀和易受细菌活动影响，锆植入物的生物性能较差，这反映出需要进一步研究替代或进行表面改性。采用氧化锆（ZrO）生物陶瓷涂层进行表面改性的建议似乎是有益的。
本系统评价旨在确定和总结现有文献，报告通过 PEO 工艺在锆植入物上制备的 ZrO 涂层的生物学反应。
在 PubMed、Scopus 和 Web of Science 国际数据库中检索了 2000 年至 2021 年间发表的原始和英文研究。所有出版物均至少报道了一项关于 ZrO-PEO 涂层锆植入物的体外（细胞和浸泡研究）、体内（动物研究）和抗菌主题的研究。
通过初始搜索共发现 496 篇文献，消除重复后仍有 296 篇。最后，经过多次筛选和资格评估，有 25 篇文献符合条件并被纳入综述。其中，有 25 篇为体外（细胞和在 SBF 和 Hank's 溶液中的浸泡研究）、1 篇体内（动物研究）和 8 篇抗菌研究。
ZrO 涂层样品表现出无细胞毒性、高细胞存活率和良好的生物相容性。然而，在 PEO 过程中改变溶液组成和电参数会导致体外反应发生显著变化。例如，经 UV 照射后的 ZrO 涂层表面表现出更好的生物相容性，使表面更适合细胞生长。由于较弱的磷灰石形成能力，锆样品在 SBF 中表现出较低的生物活性。然而，大多数情况下（16 例中有 13 例）表明，ZrO 涂层的特定形貌和化学组成促进了磷灰石形成能力，在 SBF 中具有良好的生物活性。然而，少数文献（16 例中有 3 例）表明，ZrO 涂层在 SBF 中浸泡后没有形成磷灰石沉淀，因此没有生物活性。这些情况限制了通过 UV 光照射、水热处理和化学处理、热蒸发和阴极极化后处理来增强生物活性。Zr 和 ZrO 涂层样品在 Hank's 溶液中均不具有磷灰石形成能力。ZrO 涂层植入物与骨骼一起，由于含有 Ca-P 化合物和多孔结构，在 12 周内显示出更大的剪切强度和更快的新骨形成能力。经 UV 后处理的 ZrO 涂层诱导更快的新骨形成和更牢固的与骨的结合，比未经处理的 ZrO 涂层更强。在选定的论文中（8 项研究中有 4 项）有一半（4 项中的 8 项）证实了 ZrO 涂层具有更强的抗菌活性，优于裸锆样品。ZrO 涂层的抗菌保护作用可受 PEO 过程变量的影响，如溶液组成、电参数和处理时间。在三种情况下，通过热蒸发后处理沉积 Zn、Ag 或 Cu 抗菌层可增强 ZrO 涂层的抗菌活性。
