Injectable nanofiber-reinforced bone cement with controlled biodegradability for minimally-invasive bone regeneration

Injectable materials show their special merits in regeneration of damaged/degenerated bones in minimally-invasive approach.Injectable calcium phosphate bone cement(CPC)has attracted broad attention for its bioactivity,as compared to non-degradable polymethyl methacrylate cement.However,its brittleness,poor anti-washout property and uncontrollable biodegradability are the main challenges to limit its further clinical application mainly because of its stone-like dense structure and fragile inorganic-salt weakness.Herein,we developed a kind of injectable CPC bone cement with porous structure and improved robustness by incorporating poly(lactide-co-glycolic acid)(PLGA)nanofiber into CPC,with carboxymethyl cellulose(CMC)to offer good injectability as well as anti-wash-out capacity.Furthermore,the introduction of PLGA and CMC also enabled a formation of initial porous structure in the cements,where PLGA nanofiber endowed the cement with a dynamically controllable biodegradability which provided room for cell movement and bone ingrowth.Inter-estingly,the reinforced biodegradable cement afforded a sustainable provision of Ca^(2+)bioactive components,together with its porous structure,to improve synergistically new bone formation and osteo-integration in vivo by using a rat model of femur condyle defect.Further study on regenerative mechanisms indicated that the good minimally-invasive bone regeneration may come from the synergistic enhanced osteogenic effect of calcium ion enrichment and the improved revascularization capacity contributed from the porosity as well as the lactic acid released from PLGA nanofiber.These results indicate the injectable bone cement with high strength,anti-washout property and controllable biodegradability is a promising candidate for bone regeneration in a minimally-invasive approach.

Effect of laser-discrete-quenching on bonding properties of electroplated grinding wheel with AISI 1045 steel substrate and nickel bond

To improve the bonding strength between the nickel bond and the hub of the electroplated diamond grinding wheel,a hybrid technique was proposed to combine laser prequenching steel substrate and post-electroplating nickel.To validate the effectiveness of the proposed technique,AISI 1045 substrate was nickel-coated.The bonding properties between the electroplated nickel coating and substrate with or without laser-discrete-quenching were discussed comparatively by scratch,indentation,and thermal shock tests.The results show that the prequenching treatment leads to phase transformation of AISI 1045 microstructure from the mixed pearlite and ferrite phases into the martensitic phase.Since the martensitic phase is characterized as a high corrosion resistance,the interface of substrate/coating is smooth and flat in the prequenched zone,and the coating is bonded well with the steel substrate.In contrast to the steel substrate without pre-quenching treatment,the proposed technique significantly enhanced the bonding strengths of the electroplated nickel-coating.On one hand,the average hardness of electroplated nickel-coating on the laser pre-quenched zone is increased by 18.7%,and the scratch depth with the same load become narrower and shallower.On the other hand,the coefficient of friction(CoF)and the vibration amplitude are reduced,and the coating is bonded effectively with the substrate to inhibit the crack initialization at the interface.This prevents effectively the coating from peeling off and improves significantly the thermal shock resistance property.

Incorporating redox-sensitive nanogels into bioabsorbable nanofibrous membrane to acquire ROS-balance capacity for skin regeneration

Facing the high incidence of skin diseases,it is urgent to develop functional materials with high bioactivity for wound healing,where reactive oxygen species(ROS)play an important role in the wound healing process mainly via adjustment of immune response and neovasculation.In this study,we developed a kind of bioabsorbable materials with ROS-mediation capacity for skin disease therapy.Firstly,redox-sensitive poly(N-isopropylacrylamide-acrylic acid)(PNA)nanogels were synthesized by radical emulsion polymerization method using a disulfide molecule as crosslinker.The resulting nanogels were then incorporated into the nanofibrous membrane of poly(L-lactic acid)(PLLA)via airbrushing approach to offer bioabsorbable membrane with redox-sensitive ROS-balance capacity.In vitro biological evaluation indicated that the PNA-contained bioabsorbable membrane improved cell adhesion and proliferation compared to the native PLLA membrane.In vivo study using mouse wound skin model demonstrated that PNA-doped nanofibrous membranes could promote the wound healing process,where the disulfide bonds in them were able to adjust the ROS level in the wound skin for mediation of redox potential to achieve higher wound healing efficacy.