Scanning probe microscopy for the characterization of biomaterials and biological interactions

Surface Characterization of Polymers for Medical Devices

A survey is given on analytical techniques currently applied to the surface characterization of biomedical polymers. The techniques include spectroscopies, thermodynamic and electrochemical measurements and microscopies, respectively. To illustrate the motivation for surface analysis, the hypotheses on the correlations between surface parameters and hemocompatibility of polymers are briefly examined.

The applications of the examined methods are illustrated by a number of examples. These examples include the characterization of cellulose membranes (low-flux hemodialysis membranes) by streaming potential measurements and by inverse contact angle measurements. The use of surface spectroscopies (ATR-FTIR and XPS) is demonstrated by considering the optimization of surface modification procedures of vascular prostheses made from poly(tetrafluoroethylene). Furthermore, the characterization of water-swollen cellulose membranes by scanning force microscopy is shown. Finally, the extended application of physico-chemical surface analysis to the investigation of protein adsorption is considered. An example deals with in situ spectroscopic ellipsometry used to study the adsorption of fibrinogen onto a plasma-deposited hydrophobic fluoropolymer and onto poly(ethyleneoxide)-grafted fluoropolymer, respectively.

Coagulation property of hyaluronic acid-collagen/chitosan complex film

Biomacromolecule has been widely used as biomedical material. Because different biomacromolecules possess different properties, how to exhibit the respective advantages of different components on one type of biomaterial becomes the hot spot in the field of biomaterial studying. This work reported a type of complex film that consisted of hyaluronic acid (HA), type I collagen (Col-I), and chitosan (CS) (HA-Col-I/CS, HCC). Then, a series of experiments were performed, such as inverted microscopic observation, atomic force microscopic (AFM) imaging, flow cytometry (FCM) measurement, MTT assay, and MIC assay. In the present work, we observed the growing condition of 3T3 fibroblasts on the surface of the HCC complex film, visualized the morphological changes of platelets during the coagulation process, and discovered microparticles on the platelet membrane. Moreover, we confirmed the microparticles are the platelet-derived microparticles (PMPs) using the FCM. In addition, the minimal inhibitory concentration (MIC) of HCC against Escherichia coli (E. coli) 8099 was 0.025 mg/ml, against Staphylococcus aureus (S. aureus) ATCC 6538 was 0.1 mg/ml. The results together indicated that the HCC film possessed promising coagulation property, cell compatibility and anti-bacteria property, and the potential in future clinical application such as wound healing and bandage.

Effects of amelogenin on the transforming surface microstructures of Bioglass in a calcifying solution

Topographies of a bioactive glass (45S5 type Bioglass(R)) during 0-4 h of immersion in a supersaturated calcifying solution (SCS) and the SCS containing recombinant porcine amelogenin rP172 (SCS(rP172)) were observed by atomic force microscopy. Other techniques including X-ray diffraction, scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, and transmission electron microscopy were used for some complementary microstructural investigations. The smooth Bioglass surface changed to be very rough after 0.5 h of SCS immersion because of glass network dissolution. Spherical silica-gel particles with diameters of 150-300 nm consisting of substructures of 20-60 nm across had formed on the sample surfaces after 1 h of SCS immersion. The chemisorption of amorphous calcium phosphate and crystallization of nanophase apatite were seen to occur epitaxially on the silica-gel structures during 1-4 h of SCS immersion. During the first 0.5 h of SCS(rP172) immersion, more than 95% of rP172 protein in solution was adsorbed onto the sample surfaces and generated spherical assemblies of 10-60 nm diameters. During 0.5-4 h of SCS(rP172) immersion, the protein assemblies of rP172 remarkably induced the formation of orientated silica-gel plates (approximately 100-nm wide and 50-nm thick) and subsequently of long and thin apatite needle crystals. The recombinant amelogenin rP172-modulated apatite crystals resembled those formed in the early stage of tooth enamel biomineralization, suggesting the functional roles of amelogenins during the oriented growth of enamel crystallites and a great potential for amelogenins in applications designed to fabricate enamel-like calcium phosphate biomaterials.