Iodine-Loaded Calcium Titanate for Bone Repair with Sustainable Antibacterial Activity Prepared by Solution and Heat Treatment

Abstract

In the orthopedic and dental fields, simultaneously conferring titanium (Ti) and its alloy implants with antibacterial and bone-bonding capabilities is an outstanding challenge. In the present study, we developed a novel combined solution and heat treatment that controllably incorporates 0.7% to 10.5% of iodine into Ti and its alloys by ion exchange with calcium ions in a bioactive calcium titanate. The treated metals formed iodine-containing calcium-deficient calcium titanate with abundant Ti-OH groups on their surfaces. High-resolution XPS analysis revealed that the incorporated iodine ions were mainly positively charged. The surface treatment also induced a shift in the isoelectric point toward a higher pH, which indicated a prevalence of basic surface functionalities. The Ti loaded with 8.6% iodine slowly released 5.6 ppm of iodine over 90 days and exhibited strong antibacterial activity (reduction rate >99%) against methicillin-resistant Staphylococcus aureus (MRSA), S. aureus, Escherichia coli, and S. epidermidis. A long-term stability test of the antibacterial activity on MRSA showed that the treated Ti maintained a >99% reduction until 3 months, and then it gradually decreased after 6 months (to a 97.3% reduction). There was no cytotoxicity in MC3T3-E1 or L929 cells, whereas apatite formed on the treated metal in a simulated body fluid within 3 days. It is expected that the iodine-carrying Ti and its alloys will be particularly useful for orthopedic and dental implants since they reliably bond to bone and prevent infection owing to their apatite formation, cytocompatibility, and sustainable antibacterial activity.

Antibacterial Coatings for Titanium Implants: Recent Trends and Future Perspectives

“…The resultant calcium titanate, which is deficient in calcium, progressively released 5.6 ppm of iodine ions over a period of 90 days. The titanium substrate loaded with 8.6% iodine exhibited antibacterial activity against MRSA, Staphylococcus aureus , Escherichia coli , and Staphylococcus epidermidis , and the antibacterial activity for MRSA persisted for six months when soaked in phosphate buffer solution (PBS) under physiological conditions [ 84 ].…”

Conferring Antioxidant Activity to an Antibacterial and Bioactive Titanium Surface through the Grafting of a Natural Extract

“…In the oxygen region, the difference between the functionalized and non-functionalized samples was clearer and more visible ( Figure 2 a). Three peaks were observable on the Ti_Ca+I sample at 530.44 eV, 531.5, and 532.5 eV and can be correlated with the Ti-O bond of the titanium oxide, with the –OH acid (OH a ), and with the basic (OH b ) groups exposed by the surface titanium oxide layer after the treatment, respectively [ 22 , 49 ]. In the spectrum of the Ti_Ca+I+TPH sample, these peaks are still observable, but a new peak is visible at 533.8 eV, related to the OH aromatic band that is attributable to polyphenols [ 49 ].…”

“…The antibacterial effect of iodine is well known and has been already studied in previous works [ 22 ]. An antibacterial test was carried out according to the ISO22196 standard on Ti, Ti_Ca+TPH, Ti_Ca_I+TPH, and Ti_Ca_I samples.…”

“…These substrates have been extensively characterized in previous works and their osseointegration ability is already verified. In fact, a high long-term sustainable bone-bonding capacity was confirmed by in vivo tests and mechanical and histological experiments [ 19 , 22 ]. In addition, the same type of green tea used here (TPH) has been previously tested and was found to have good ability to promote osteoblast differentiation and mineralization [ 43 ].…”

“…Attention then shifted to iodine ions as excellent candidates for antibacterial, biocompatible, and noncytotoxic agents. When an iodine-containing calcium titanate is produced on Ti by a chemical and heat treatment, the treated metal exhibits in vitro and in vivo antibacterial activity, in vitro apatite formation, and in vivo bone bonding ability [ 19 , 20 , 21 , 22 ].…”