The Effect Of UV-irradiation On The Bioactivity Of Absorbed Protein On TiO₂ Film

Protein is the basic units of living organism,and protein absorption always occur immediately after interventional device was implanted in with transient water molecules and ions absorption.The types,amounts and activity of absorbed proteins play a critical role in modulating the subsequent cell adhesion,immune response,tissue repair,and other physiological/pathological behaviors.At present,both the composition and structure of absorbed proteins and cell adhesion activity were commonly modulated via modifying the physical chemistry properties of material surface,such as wettability,chargeability,surface tension and molarity,by which the cell adhesion behaviors and histocompatibility can be regulated accordingly,and these processes have been widely used thereby.Inhibiting the activity of absorbed proteins on materials surface can be applied for anti-bacteria,anti-coagulation,cell harvesting and other uses;also promoting that for bone repair,vascular intima repair and other applications;additionally,enhancing or reducing the protein activity via patterning material surface can produce micro-patterned cells,providing support for biochip development.Therefore,a responsive material,inhibiting or promoting the activity of absorbed proteins on demand,has a broad application prospect.In this study,the results showed that titanium dioxide?TiO₂?in anatase type is a responsive material,which could be controlled in an "on-off" manner depending on the presence and absence of both the ultraviolet?UV?light and water to inhibit or promote the activity of absorbed proteins.The main results are as follows.We firstly found that when treated with UV irradiation under water environment?UV?W??,the TiO₂ surface for protein pre-absorption can inhibit cell adhesion and obtain micro-patterned cells.The inhibition ability was related with TiO₂ crystal type,and the anatase one has the strongest inhibition effect.Also,the further investigation showed that this inhibition effect based on UV?W?has wide applicability,not just applicable for three kinds of TiO₂ surfaces pre-absorbed with bovine serum albumin?BSA?,fibrinogen?FGN?and collagen?COL?,as well as proteins pre-absorbed at low concentration,with mixed components,with single layer and other conditions,wherein treating TiO₂ surface with single FGN layer by UV?W?inhibited the consequential adhesion of COL and molecules,indicating that UV?W?treatment inhibited the activity of pre-absorbed protein.Then,the role of time on UV?W?effect has been studied.Results indicated that excellent inhibition effect on cell adhesion could be achieved within 1-2 hours.interestingly,when over 4 hours,partial region of sample surface showed promotion effect since long-time UV?W?resulted water evaporation.Therefore,when TiO₂ surface of anatase type with pre-absorbed proteins was treated by UV irradiation under dry environment UV?D?,cell adhesion would be prompted to gain micro-patterned cells.Next,respectively treated by UV?W?and UV?W?,the structure and physicochemical properties of pre-absorbed protein on sample surface were researched.Results illustrated that UV?W?/UV?D?respectively reduce/enhance the ?-helix amounts of pre-absorbed protein,which may be the reason for the effect of UV?W?and UV?D?on protein bioactivity.We then treated via UV?W?and UV?D?TiO₂ pre-absorbed with BAS and FGN(TiO₂@BSA.TiO₂@FGN,and the results of platelet adhesion showed big difference with that of cell adhesion.On TiO₂@BSA surface,UV?W?/UV?D?respectively promoted/inhibited platelet adhesion,and the cell adhesion behaviors were on the contrary.Interestingly,on TiO₂@FGN surface,both UV?W?and UV?D?inhibited platelet adhesion,and samples treated by UV?D?had better anti-coagulant property.Finally,we evaluated the cytocompatibility and histocompatibility of TiO₂@BSA.TiO₂@FGN.TiO₂@COL treated by UV?W?,including cytocompatibility of endothelial cells,smooth muscle cells,mesenchymal stem cells,the abilities of anti-inflammation and anti-bacteria,and histocompatibility of subcutaneous/vascular implantation.Results indicated that samples treated by UV?W?can all effectively inhibit the adhesion of vascular cells,inflammatory cells and bacteria.Most importantly,TiO₂@FGN treated by UV?W?had stronger inhibition effect on intima hyperplasia than TiO₂ under same treatment,having the potential to be a new promising blood-contacting material.