Development of a zinc chloride-based chemo-mechanical system for potential minimally invasive dental caries removal system.

Background/purpose: The chemo-mechanical caries-removal technique is known to offer advantages of selective dentin caries treatment while leaving healthy dental tissues intact. However, current sodium hypochlorite based reagents usually excessively damage dentin collagen. Therefore, the purpose of this study was to develop a novel chemo-mechanical caries-removal system to preserve the collagen network for subsequent prosthetic restorations. Materials and methods: The calfskin-derived collagen was chosen as a model system to investigate the dissolution behavior of collagen under different operating conditions of chemical-ultrasonic treatment systems. The molecular weight, triple-helix structure, the morphology, and functional group of collagen after treatment were investigated. Results: Various concentrations of sodium hypochlorite or zinc chloride together with ultrasonic machinery were chosen to investigate. The outcomes of circular dichroism (CD) spectra demonstrated stability of the triple-helix structure after treatment of a zinc chloride solution. In addition, two apparent bands at molecular weights (MWs) of 130 and 121 kDa evidenced the stability of collagen network. The positive 222 nm and 195 nm negative CD absorption band indicated the existence of a triple-helix structure for type I collagen. The preservation of the morphology and functional group of the collagen network on the etched dentin surface were investigated by in vitro dentin decalcification model. Conclusion: Unlike NaOCl, the 5 wt% zinc chloride solution combined with ultra-sonication showed dissolution rather than denature as well as degradation of the dentin collagen network. Additional in vivo evaluations are needed to verify its usefulness in clinical applications.

Self-nanoemulsifying drug delivery system (SNEDDS) mediated improved oral bioavailability of thymoquinone: optimization, characterization, pharmacokinetic, and hepatotoxicity studies.

Thymoquinone (TQ) is an antioxidant, anti-inflammatory, and hepatoprotective compound obtained from the black seed oil of Nigella sativa. However, high hydrophobicity, instability at higher pH levels, photosensitivity, and low oral bioavailability hinder its delivery to the target tissues. A self-nanoemulsifying drug delivery system (SNEDDS) was fabricated using the microemulsification technique to address these issues. Its physicochemical properties, thermodynamic stability studies, drug release kinetics, in vivo pharmacokinetics, and hepatoprotective activity were evaluated. The droplet size was in the nano-range (< 90 nm). Zeta potential was measured to be -11.35 mV, signifying the high stability of the oil droplets. In vivo pharmacokinetic evaluation showed a fourfold increase in the bioavailability of TQ-SNEDDS over pure TQ. Furthermore, in a PCM-induced animal model, TQ-SNEDDS demonstrated significant (p < 0.05) hepatoprotective activity compared to pure TQ and silymarin. Reduction in liver biomarker enzymes and histopathological examinations of liver sections further supported the results. In this study, SNEDDS was demonstrated to be an improved oral delivery method for TQ, since it potentiates hepatotoxicity and enhances bioavailability.