Femtosecond laser-mediated anchoring of polymer layers on the surface of a biodegradable metal

Mg has received much attention as a next-generation implantable material owing to its biocompatibility,bone-like mechanical properties,and biodegradability in physiological environments.The application of various polymer coatings has been conducted in the past to reduce the rapid formation of hydrogen gas and the local change in pH during the initial phase of the chemical reaction with the body fluids.Here,we propose femtosecond(fs)laser-mediated Mg surface patterning for significant enhancement of the binding strength of the coating material,which eventually reduces the corrosion rate.Analyses of the structural,physical,crystallographic,and chemical properties of the Mg surface have been conducted in order to understand the mechanism by which the surface adhesion increases between Mg and the polymer coating layer.Depending on the fs laser conditions,the surface structure becomes rough owing to the presence of several microscaled pits and grooves of nanoporous MgO,resulting in a tightly bonded poly(lactic-co-glycolic acid)(PLGA)layer.The corrosion rate of the PLGA-coated,fs laser-treated Mg is considerably slow compared with the non-treated Mg;the treated Mg is also more biocompatible compared with the non-treated Mg.The fs laser-based surface modification technique offers a simple and quick method for introducing a rough coating on Mg;further,it does not require any chemical treatment,thereby overcoming a potential obstacle for its clinical use.

Corrosion characteristics of single-phase Mg-3Zn alloy thin film for biodegradable electronics

Biodegradable metals as electrodes, interconnectors, and device conductors are essential components in the emergence of transient electronics, either for passive implants or active electronic devices, especially in the fields of biomedical electronics. Magnesium and its alloys are strong candidates for biodegradable and implantable conducting materials because of their high conductivity and biocompatibility, in addition to their well-understood dissolution behavior. One critical drawback of Mg and its alloys is their considerably high dissolution rates originating from their low anodic potential, which disturbs the compatibility to biomedical applications. Herein, we introduce a single-phase thin film of a Mg-Zn binary alloy formed by sputtering, which enhances the corrosion resistance of the device electrode, and verify its applicability in biodegradable electronics. The formation of a homogeneous solid solution of single-phase Mg-3Zn was confirmed through X-ray diffraction and transmission electron microscopy. In addition, the dissolution behavior and chemistry was also investigated in various biological fluids by considering the effect of different ion species. Micro-tensile tests showed that the Mg-3Zn alloy electrode exhibited an enhanced yield strain and elongation in relation to a pure Mg electrode. Cell viability test revealed the high biocompatibility rate of the Mg-3Zn binary alloy thin film. Finally, the fabrication of a wireless heater demonstrated the integrability of biodegradable electrodes and highlighted the ability to prolong the lifecycle of thermotherapy-relevant electronics by enhancing the dissolution resistance of the Mg alloy.

Computational design of Mg alloys with minimal galvanic corrosion

Formation of galvanic cells between constituent phases is largely responsible for corrosion in Mg-based alloys.We develop a methodology to calculate the electrochemical potentials of intermetallic compounds and alloys using a simple model based on the Born-Haber cycle.Calculated electrochemical potentials are used to predict and control the formation of galvanic cells and minimize corrosion.We demonstrate the applicability of our model by minimizing galvanic corrosion in Mg-3wt%Sr-x Zn alloy by tailoring the Zn composition.The methodology proposed in this work is applicable for any general alloy system and will facilitate efficient design of corrosion resistant alloys.

Fostering tissue engineering and regenerative medicine to treat musculoskeletal disorders in bone and muscle

The musculoskeletal system,which is vital for movement,support,and protection,can be impaired by disorders such as osteoporosis,osteoarthritis,and muscular dystrophy.This review focuses on the advances in tissue engineering and regenerative medicine,specifically aimed at alleviating these disorders.It explores the roles of cell therapy,particularly Mesenchymal Stem Cells(MSCs)and Adipose-Derived Stem Cells(ADSCs),biomaterials,and biomolecules/external stimulations in fostering bone and muscle regeneration.The current research underscores the potential of MSCs and ADSCs despite the persistent challenges of cell scarcity,inconsistent outcomes,and safety concerns.Moreover,integrating exogenous materials such as scaffolds and external stimuli like electrical stimulation and growth factors shows promise in enhancing musculoskeletal regeneration.This review emphasizes the need for comprehensive studies and adopting innovative techniques together to refine and advance these multi-therapeutic strategies,ultimately benefiting patients with musculoskeletal disorders.

Regulation of cell locomotion by nanosecond-laser-induced hydroxyapatite patterning

Hydroxyapatite,an essential mineral in human bones composed mainly of calcium and phosphorus,is widely used to coat bone graft and implant surfaces for enhanced biocompatibility and bone formation.For a strong implant-bone bond,the bone-forming cells must not only adhere to the implant surface but also move to the surface requiring bone formation.However,strong adhesion tends to inhibit cell migration on the surface of hydroxyapatite.Herein,a cell migration highway pattern that can promote cell migration was prepared using a nanosecond laser on hydroxyapatite coating.The developed surface promoted bone-forming cell movement compared with the unpatterned hydroxyapatite surface,and the cell adhesion and movement speed could be controlled by adjusting the pattern width.Live-cell microscopy,cell tracking,and serum protein analysis revealed the fundamental principle of this phenomenon.These findings are applicable to hydroxyapatite-coated biomaterials and can be implemented easily by laser patterning without complicated processes.The cell migration highway can promote and control cell movement while maintaining the existing advantages of hydroxyapatite coatings.Furthermore,it can be applied to the surface treatment of not only implant materials directly bonded to bone but also various implanted biomaterials implanted that require cell movement control.

Improving hydroxyapatite coating ability on biodegradable metal through laser-induced hydrothermal coating in liquid precursor:Application in orthopedic implants

During the past decade,there has been extensive research toward the possibility of exploring magnesium and its alloys as biocompatible and biodegradable materials for implantable applications.Its practical medical application,however,has been limited to specific areas owing to rapid corrosion in the initial stage and the consequent complications.Surface coatings can significantly reduce the initial corrosion of Mg alloys,and several studies have been carried out to improve the adhesion strength of the coating to the surfaces of the alloys.The composition of hydroxyapatite(HAp)is very similar to that of bone tissue;it is one of the most commonly used coating materials for bone-related implants owing to favorable osseointegration post-implantation.In this study,HAp was coated on Mg using nanosecond laser coating,combining the advantages of chemical and physical treatments.Photothermal heat generated in the liquid precursor by the laser improved the adhesion of the coating through the precipitation and growth of HAp at the localized nanosecond laser focal area and increased the corrosion resistance and cell adhesion of Mg.The physical,crystallographic,and chemical bondings were analyzed to explore the mechanism through which the surface adhesion between Mg and the HAp coating layer increased.The applicability of the coating to Mg screws used for clinical devices and improvement in its corrosion property were confirmed.The liquid environment-based laser surface coating technique offers a simple and quick process that does not require any chemical ligands,and therefore,overcomes a potential obstacle in its clinical use.