Exploring the interconnectivity of biomimetic hierarchical porous Mg scaffolds for bone tissue engineering:Effects of pore size distribution on mechanical properties,degradation behavior and cell migration ability

Interconnectivity is the key characteristic of bone tissue engineering scaffold modulating cell migration,blood vessels invasion and transport of nutrient and waste.However,efforts and understanding of the interconnectivity of porous Mg is limited due to the diverse architectures of pore struts and pore size distribution of Mg scaffold systems.In this work,biomimetic hierarchical porous Mg scaffolds with tailored interconnectivity as well as pore size distribution were prepared by template replication of infiltration casting.Mg scaffold with better interconnectivity showed lower mechanical strength.Enlarging interconnected pores would enhance the interconnectivity of the whole scaffold and reduce the change of ion concentration,pH value and osmolality of the degradation microenvironment due to the lower specific surface area.Nevertheless,the degradation rates of five tested Mg scaffolds were no different because of the same geometry of strut unit.Direct cell culture and evaluation of cell density at both sides of four typical Mg scaffolds indicated that cell migration through hierarchical porous Mg scaffolds could be enhanced by not only bigger interconnected pore size but also larger main pore size.In summary,design of interconnectivity in terms of pore size distribution could regulate mechanical strength,microenvironment in cell culture condition and cell migration potential,and beyond that it shows great potential for personalized therapy which could facilitate the regeneration process.

Concerting magnesium implant degradation facilitates local chemotherapy in tumor-associated bone defect

Effective management of malignant tumor-induced bone defects remains challenging due to severe systemic side effects,substantial tumor recurrence,and long-lasting bone reconstruction post tumor resection.Magnesium and its alloys have recently emerged in clinics as orthopedics implantable metals but mostly restricted to mechanical devices.Here,by deposition of calcium-based bilayer coating on the surface,a Mg-based composite implant platform is developed with tailored degradation characteristics,simultaneously integrated with chemotherapeutic(Taxol)loading capacity.The delicate modulation of Mg degradation occurring in aqueous environment is observed to play dual roles,not only in eliciting desirable osteoinductivity,but allows for modification of tumor microenvironment(TME)owing to the continuous release of degradation products.Specifically,the sustainable H2 evolution and Ca2+from the implant is distinguished to cooperate with local Taxol delivery to achieve superior antineoplastic activity through activating Cyt-c pathway to induce mitochondrial dysfunction,which in turn leads to significant tumor-growth inhibition in vivo.In addition,the local chemotherapeutic delivery of the implant minimizes toxicity and side effects,but markedly fosters osteogenesis and bone repair with appropriate structure degradation in rat femoral defect model.Taken together,a promising intraosseous administration strategy with biodegradable Mg-based implants to facilitate tumor-associated bone defect is proposed.

Research and development strategy for biodegradable magnesium-based vascular stents:a review

Magnesium alloys are an ideal material for biodegradable vascular stents,which can be completely absorbed in the human body,and have good biosafety and mechanical properties.However,the rapid corrosion rate and excessive localized corrosion,as well as challenges in the preparation and processing of microtubes for stents,are restricting the clinical application of magnesium-based vascular stents.In the present work we will give an overview of the recent progresses on biodegradable magnesium based vascular stents including magnesium alloy design,high-precision microtubes processing,stent shape optimisation and functional coating preparation.In particular,the Triune Principle in biodegradable magnesium alloy design is proposed based on our research experience,which requires three key aspects to be considered when designing new biodegradable magnesium alloys for vascular stents application,i.e.biocompatibility and biosafety,mechanical properties,and biodegradation.This review hopes to inspire the future studies on the design and development of biodegradable magnesium alloy-based vascular stents.