Titanates and Titanate-Metal Compounds in Biological Contexts

Abstract

Metal ions are notorious environmental contaminants, some causing toxicity at exquisitely low (ppm-level) concentrations. Yet, the redox properties of metal ions make them attractive candidates for bio-therapeutics. Titanates are insoluble particulate compounds of titanium and oxygen with crystalline surfaces that bind metal ions; these compounds offer a means to scavenge metal ions in environmental contexts or deliver them in therapeutic contexts while limiting systemic exposure and toxicity. In either application, the toxicological properties of titanates are crucial. To date, the accurate measurement of the in vitro toxicity of titanates has been complicated by their particulate nature, which interferes with many assays that are optical density (OD)-dependent, and at present, little to no in vivo titanate toxicity data exist. Compatibility data garnered thus far for native titanates in vitro are inconsistent and lacking in mechanistic understanding. These data suggest that native titanates have little toxicity toward several oral and skin bacteria species, but do suppress mammalian cell metabolism in a cells-pecific manner. Titanate compounds bind several types of metal ions, including some common environmental toxins, and enhance delivery to bacteria or cells. Substantial work remains to address the practical applicability of titanates. Nevertheless, titanates have promise to serve as novel vehicles for metal-based therapeutics or as a new class of metal scavengers for environmental applications.

Titanate-Metal Complex as a Novel Antimicrobial in Dentistry

“…The use of metal ions as medicinal drugs is made possible by their unique and wide variety of redox potentials, geometries, thermodynamic and kinetic properties, and other intrinsic properties as therapeutic agents [1]. Metal ions have been used in medicinal contexts in the treatment of cancers, inflammation, and arthritis, among others [2]. Metal ions have also long been known to contain chemical properties that cause them to successfully inhibit bacterial growth.…”

“…Given the growing resistance of microbes to current antimicrobial agents, the need for a new class of antimicrobials has become increasingly apparent, and metal ions may serve as a new treatment modality in this context. Concerns over the potential systemic toxicity of metals to the host have halted their widespread use as therapeutic agents, but if the use of metal ions is localized and controlled, their toxicity to the host could be greatly minimized [2]. This creates a unique niche for the novel approach of using metal-titanate complexes to fight pathogen-causing microbes due to the ability of such complexes to deliver metal ions in a controlled manner.…”

“…Dental Oral Biology and Craniofacial Research doi: 10.31487/j.DOBCR.2018.02.003 Volume 1(2): [2][3][4][5][6] Titanates are insoluble particulate compounds of titanium and oxygen with crystalline surfaces that bind metal ions [2]. Titanates combined with metal ions are very effective as broad-spectrum antibiotics, antifungals, and anti-proliferative agents because of their redox potentials [3].…”

“…Additionally, metaltitanates have a higher affinity for more highly positively charged species (M3+) than for less positively charged species (M2+). Therefore, competition between protons, sodium ions, and metal ions with titanate binding sites makes the successful delivery of metals to tissues probable in biological settings [2].…”