Overview of methods for enhancing bone regeneration in distraction osteogenesis: Potential roles of biometals

BACKGROUND

Distraction osteogenesis (DO) is a functional tissue engineering approach that applies gradual mechanical traction on the bone tissues after osteotomy to stimulate bone regeneration. However, DO still has disadvantages that limit its clinical use, including long treatment duration.

METHODS

Review the current methods of promoting bone formation and consolidation in DO with particular interest on biometal.

RESULTS

Numerous approaches, including physical therapy, gene therapy, growth factor-based therapy, stem-cell-based therapy, and improved distraction devices, have been explored to reduce the DO treatment duration with some success. Nevertheless, no approach to date is widely accepted in clinical practice due to various reasons, such as high expense, short biologic half-life, and lack of effective delivery methods. Biometals, including calcium (Ca), magnesium (Mg), zinc (Zn), copper (Cu), manganese (Mn), and cobalt (Co) have attracted attention in bone regeneration attributed to their biodegradability and bioactive components released during in vivo degradation.

CONCLUSION

This review summarizes the current therapies accelerating bone formation in DO and the beneficial role of biometals in bone regeneration, particularly focusing on the use of biometal Mg and its alloy in promoting bone formation in DO. Translational potential: The potential clinical applications using Mg-based devices to accelerate DO are promising. Mg stimulates expression of multiple intrinsic biological factors and the development of Mg as an implantable component in DO may be used to argument bone formation and consolidation in DO.

Electrochemical biosensors for biometal-protein interactions in neurodegenerative diseases

Electrochemical biosensors have been adopted into a wide range of applications in the study of biometal-protein interactions in neurodegenerative diseases. Transition metals such as zinc, copper, and iron that are significant to biological functions have been shown to have strong implications in the progressive neural degeneration in Alzheimer's disease (AD), Parkinson's disease (PD), and prion protein diseases. This review presents a summative examination of the progress made in the design, fabrication, and applications of electrochemical biosensors in recent literature at understanding the metal-protein interactions in neurodegenerative diseases. The focus will be drawn on disease-causing biomarkers such as amyloid-β (Aβ) and tau proteins for AD, α-synuclein (α-syn) for PD, and prion proteins (PrP). Topics such as the use of electrochemical biosensing in monitoring biometal-induced conformational changes, elucidation of complexation motifs, production of reactive oxygen species (ROS) as well as the influence on downstream biomolecular interactions will be discussed. Major results and important concepts presented in these studies will be summarized in the hope to spark inspiration for the next generation of electrochemical sensors.

Recommendation for modifying current cytotoxicity testing standards for biodegradable magnesium-based materials

As one of the most promising medical metal implants, magnesium (Mg) or its alloys have shown significant advantages over other candidates attributed to not only their excellent biodegradability and suitable mechanical properties but also their osteopromotive effects for bone applications. Prior to approval mandated by the governmental regulatory body, the access to the medical market for Mg-based implants requires a series of testing for assurance of their safety and efficacy via preclinical evaluations and clinical tests including phase 1 and 2 evaluations, and phase 3 of multi-center randomized double blind and placebo-controlled clinical trials. However, as the most widely used protocols for biosafety evaluation of medical devices, current ISO 10993 standards should be carefully reevaluated when directly applying them to predict potential health risks of degradable Mg based biomaterials via cytotoxicity tests due to the huge gap between in vitro and in vivo conditions. Therefore, instead of a direct adoption, modification of current ISO standards for in vitro cytotoxicity test is desirable and justified. The differences in sensitivities of cells to in vitro and in vivo Mg ions and the capability of in vivo circulation system to dilute local degradation products were fully considered to propose modification of current ISO standards. This paper recommended a minimal 6 times to a maximal 10 times dilution of extracts for in vitro cytotoxicity test specified in ISO 10993 part 5 for pure Mg developed as potential orthopedic implants based on literature review and our specifically designed in vitro and in vivo tests presented in the study. Our work may contribute to the progress of biodegradable metals involved translational work.