Synthetic materials capable of selectively recognizing proteins are important in separations, biosensors and the development of biomedical materials. The technique of molecular imprinting creates specific recognition sites in polymers by using template molecules. Molecular recognition is attributed to binding sites that complement molecules in size, shape and chemical functionality. But attempts to imprint proteins have met with only limited success. Here we report a method for imprinting surfaces with protein-recognition sites. We use radio-frequency glow-discharge plasma deposition to form polymeric thin films around proteins coated with disaccharide molecules. The disaccharides become covalently attached to the polymer film, creating polysaccharide-like cavities that exhibit highly selective recognition for a variety of template proteins, including albumin, immunoglobulin G, lysozyme, ribonuclease and streptavidin. Direct imaging of template recognition is achieved by patterning a surface at the micrometre scale with imprinted regions.

The purpose of this study was to further investigate the role of fibrinogen adsorbed from plasma in mediating platelet adhesion to polymeric biomaterials. Polystyrene was used as a model hydrophobic polymer; i.e., we expected that the role of fibrinogen in platelet adhesion to polystyrene would be representative of other hydrophobic polymers. Platelet adhesion was compared to both the amount and conformation of adsorbed fibrinogen. The strategy was to compare platelet adhesion to surfaces preadsorbed with normal, afibrinogenemic, and fibrinogen-replenished afibrinogenemic plasmas. Platelet adhesion was determined by the lactate dehydrogenase (LDH) method, which was found to be closely correlated with adhesion of 111In-labeled platelets. Fibrinogen adsorption from afibrinogenemic plasma to polystyrene (Immulon I(R)) was low and <10 ng/cm2. Platelet adhesion was absent on surfaces preadsorbed with afibrinogenemic plasma when the residual fibrinogen was low enough (<60 microg/mL). Platelet adhesion was restored on polystyrene preadsorbed with fibrinogen-replenished afibrinogenemic plasma. Addition of even small, subnormal concentrations of fibrinogen to afibrinogenemic plasma greatly increased platelet adhesion. In addition, surface-bound fibrinogen's ability to mediate platelet adhesion was different, depending on the plasma concentration from which fibrinogen was adsorbed. These differences correlated with changes in the binding of a monoclonal antibody that binds to the Aalpha chain RGDS (572-575), suggesting alteration in the conformation or orientation of the adsorbed fibrinogen. Platelet adhesion to polystyrene preadsorbed with blood plasma thus appears to be a strongly bivariate function of adsorbed fibrinogen, responsive to both low amounts and altered states of the adsorbed molecule.

Four plasma proteins have been shown to be able to mediate platelet adhesion to synthetic materials when they are adsorbed as purified proteins: fibrinogen (Fg), fibronectin (Fn), vitronectin (Vn), and von Willebrand factor (vWF). Among them, Fg is thought to play a leading role in mediating platelet adhesion to plasma-preadsorbed biomaterials, but this has been established for only three types of materials so far in our laboratory. Furthermore, the role of Fn, Vn, and vWF in mediating platelet adhesion to plasma-preadsorbed surfaces is still unclear. The aim of the current study was to assess the importance of Fg, Fn, Vn, and vWF in mediating platelet adhesion to a series of polystyrene-based surfaces. The strategy applied in the present investigation was to compare platelet adhesion to surfaces preadsorbed with normal plasma, plasma selectively depleted in Fn or Vn or both Fn and Vn, plasma from donors who were genetically deficient in vWF, and serum. Few platelets adhered to the surfaces preadsorbed with serum, whereas depletion of Fn, Vn, or vWF from plasma did not decrease platelet adhesion significantly. Replenishment of exogenous Fg to serum before protein adsorption restored platelet adhesion to the surfaces, suggesting that Fg was the major plasma protein that mediated platelet adhesion. Also, we found that a surface density of adsorbed Fg far below the amount that usually adsorbs to synthetic surfaces was sufficient to support full-scale platelet adhesion.

Osteointegration of titanium implants in bone defects is clinically important for long-term performance of orthopaedic implants. In this work, we developed a facile and effective "one-pot" deposition method based on dopamine polymerization for the development of cell-adhesive, osteoconductive, and osteoinductive titanium implants. Arg-Gly-Asp (RGD)-conjugated polymers, hydroxyapatite (HAp) nanoparticles, and bone morphogenic protein-2 (BMP-2) were mixed with an alkaline dopamine solution, and then, titanium substrates were immersed in the mixture for an hour. During poly(dopamine) coating, the three types of bioactive substances were immobilized on the titanium surfaces. Our results indicate that RGD conjugation enhanced the adhesion of human bone marrow stem cell line, while HAp incorporation facilitated cellular osteodifferentiation. The immobilization of BMP-2 induced the osteogenesis of the stem cells, indicated by reverse-transcriptase polymerase chain reaction (RT-PCR) analysis. The mineralization on the deposited substrates was also enhanced greatly. This functionalized layer on titanium substrate promoted mesenchymal stem cell to osteoblast and improved osteogenic differentiation and mineralization. In conclusion, the surface modification method shows a great potential for enhancement of osteointegration of orthopaedic and dental implants.