Advanced surface engineering of titanium materials for biomedical applications:From static modification to dynamic responsive regulation

Titanium(Ti)and its alloys have been widely used as orthopedic implants,because of their favorable mechanical properties,corrosion resistance and biocompatibility.Despite their significant success in various clinical applications,the probability of failure,degradation and revision is undesirably high,especially for the patients with low bone density,insufficient quantity of bone or osteoporosis,which renders the studies on surface modification of Ti still active to further improve clinical results.It is discerned that surface physicochemical properties directly influence and even control the dynamic interaction that subsequently determines the success or rejection of orthopedic implants.Therefore,it is crucial to endow bulk materials with specific surface properties of high bioactivity that can be performed by surface modification to realize the osseointegration.This article first reviews surface characteristics of Ti materials and various conventional surface modification techniques involving mechanical,physical and chemical treatments based on the formation mechanism of the modified coatings.Such conventional methods are able to improve bioactivity of Ti implants,but the surfaces with static state cannot respond to the dynamic biological cascades from the living cells and tissues.Hence,beyond traditional static design,dynamic responsive avenues are then emerging.The dynamic stimuli sources for surface functionalization can originate from environmental triggers or physiological triggers.In short,this review surveys recent developments in the surface engineering of Ti materials,with a specific emphasis on advances in static to dynamic functionality,which provides perspectives for improving bioactivity and biocompatibility of Ti implants.

Hydroxyapatite-modified micro/nanostructured titania surfaces with different crystalline phases for osteoblast regulation

Surface structures and physicochemical properties critically influence osseointegration of titanium(Ti)implants.Previous studies have shown that the surface with both micro-and nanoscale roughness may provide multiple features comparable to cell dimensions and thus efficiently regulate cell-material interaction.However,less attention has been made to further optimize the physicochemical properties(e.g.,crystalline phase)and to further improve the bioactivity of micro/nanostructured surfaces.Herein,micro/nanostructured titania surfaces with different crystalline phases(amorphous,anatase and anatase/rutile)were prepared and hydroxyapatite(HA)nanorods were deposited onto the as-prepared surfaces by a spin-assisted layer-by-layer assembly method without greatly altering the initial multi-scale morphology and wettability.The effects of crystalline phase,chemical composition and wettability on osteoblast response were investigated.It is noted that all the micro/nanostructured surfaces with/without HA modification presented superamphiphilic.The activities of MC3T3-E1 cells suggested that the proliferation trend on the micro/nanostructured surfaces was greatly influenced by different crystalline phases,and the highest proliferation rate was obtained on the anatase/rutile surface,followed by the anatase;but the cell differentiation and extracellular matrix mineralization were almost the same among them.After ultrathin HA modification on the micro/nanostructured surfaces with different crystalline phases,it exhibited similar proliferation trend as the original surfaces;however,the cell differentiation and extracellular matrix mineralization were significantly improved.The results indicate that the introduction of ultrathin HA to the micro/nanostructured surfaces with optimized crystalline phase benefits cell proliferation,differentiation and maturation,which suggests a favorable biomimetic microenvironment and provides the potential for enhanced implant osseointegration in vivo.

Cell osteogenic bioactivity mediated precisely by varying scaled micro-pits on ordered micro/nano hierarchical structures of titanium

Hierarchical surface structures with micro–nano scale play a crucial role in regulation of cell proliferation and osteogenic differentiation.It has been proven that cells are extremely sensitive to the nanoscaled structure and show multifarious phenotypes.Though a vital function of microstructure on osseointegration has been confirmed,the cell performances response to different microscaled structure is needed to be further dissected and in depth understood.In this work,the ordered micro–nano hierarchical structures with varying micro-scaled pits were precisely fabricated on titanium successfully by the combination of electrochemical,chemical etching and anodization as well.In vitro systematical assessments indicated that the micro–nano multilevel structures on titanium exhibited excellent cells adhesion and spreading ability,as well as steerable proliferation and osteogenic differentiation behaviors.It is shown that smaller micro-pits and lower roughness of the hierarchical structures enabled faster cell propagation.Despite cell growth was delayed on micro–nano titanium with relatively larger cell-match-size micro-pits and roughness,osteogenic-specific genes were significantly elevated.Furthermore,the alkaline phosphatase activity,collagen secretion and extracellular matrix mineralization of MC3T3-E1 on multiscaled titanium were suppressed by a large margin after adding IWP-2(an inhibitor of Wnt/b-catenin signal pathway),indicating this pathway played a crucial part in cell osteogenic differentiation modulated by micro–nano structures.