Several small (<25aa) peptides have been designed based on the sequence of the dentin phosphoprotein, one of the major noncollagenous proteins thought to be involved in the mineralization of the dentin extracellular matrix during tooth development. These peptides, consisting of multiple repeats of the tripeptide aspartate-serine-serine (DSS), bind with high affinity to calcium phosphate compounds and, when immobilized, can recruit calcium phosphate to peptide-derivatized polystyrene beads or to demineralized human dentin surfaces. The affinity of binding to hydroxyapatite surfaces increases with the number of (DSS)n repeats, and though similar repeated sequences—(NTT)n, (DTT)n, (ETT)n, (NSS)n, (ESS)n, (DAA)n, (ASS)n, and (NAA)n—also showed HA binding activity, it was generally not at the same level as the natural sequence. Binding of the (DSS)n peptides to sectioned human teeth was shown to be tissue-specific, with high levels of binding to the mantle dentin, lower levels of binding to the circumpulpal dentin, and little or no binding to healthy enamel. Phosphorylation of the serines of these peptides was found to affect the avidity, but not the affinity, of binding. The potential utility of these peptides in the detection of carious lesions, the delivery of therapeutic compounds to mineralized tissues, and the modulation of remineralization is discussed.

Microbial biofilm formation can be influenced by many physiological and genetic factors. The conventional microtiter plate assay provides useful but limited information about biofilm formation. With the fast expansion of the biofilm research field, there are urgent needs for more informative techniques to quantify the major parameters of a biofilm, such as adhesive strength and total biomass. It would be even more ideal if these measurements could be conducted in a real-time, non-invasive manner. In this study, we used quartz crystal microbalance (QCM) and microjet impingement (MJI) to measure total biomass and adhesive strength, respectively, of S. mutans biofilms formed under different sucrose concentrations. In conjunction with confocal laser scanning microscopy (CLSM) and the COMSTAT software, we show that sucrose concentration affects the biofilm strength, total biomass, and architecture in both qualitative and quantitative manners. Our data correlate well with previous observations about the effect of sucrose on the adherence of S. mutans to the tooth surface, and demonstrate that QCM is a useful tool for studying the kinetics of biofilm formation in real time and that MJI is a sensitive, easy-to-use device to measure the adhesive strength of a biofilm.

Cell adhesion to material surfaces is one of the fundamental phenomena of cellular response to implanted devices. Controlling the strength, dynamics, and mechanics of cell adhesion offer opportunities for designing novel biomaterials for tissue engineering and biotechnology. Many techniques have been developed for the purpose of quantifying various types of cell-biomaterial interaction. One method to evaluate cell affinity for a biomaterial is to measure the stress required to remove adherent cells from the material. This study investigates the possibility of using laser spallation, a technique previously developed for measuring the tensile strength of thin film interfaces, for evaluation of initial cell attachment strength. MC3T3-E1 preosteoblasts were cultured on fibronectin-coated polystyrene, a surface known to engage cells in receptor mediated adhesion, and untreated polystyrene, which elicit nonspecific adhesion mechanisms during early stages of cell attachment. The laser spallation technique effectively detached cells from polymer substrates and also distinguished relative cell adhesion strengths to surfaces with known differences in cell binding affinities. Scanning electron micrographs determined that cell detachment resulting from laser spallation left a cleaner surface than jet impingement, possibly suggesting a more complete detachment mechanism. Absolute values of adhesion strengths determined by laser spallation were significantly higher than those found using jet impingement, a previously reported hydrodynamic technique.

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Rapid resealing of the mucosal epithelia is imperative following injuries to the small intestine because the mucosa is responsible for the adsorption of nutrients as well as providing a barrier to noxious agents present in the lumen. Tissue engineering may provide a possible solution for treating intestinal erosions, ulcerations, inflammatory bowel disease, and infection. Cell-biomaterial interaction is a critical component in tissue engineering that can determine the success of the tissue construct. Cell-biomaterial interactions can be enhanced by various types of surface modification, which promote integrin ligation leading to increased cell function. In order to relate the effect of surface adhesion molecules to signaling events and macroscopic cell response, an intestinal epithelial cell line, IEC-6, was plated on fibronectin (receptor-mediated) and poly-L-lysine (non-specific) surfaces. Focal adhesion kinase (FAK) phosphorylation, cell spreading, and cell adhesion strength were measured. Results showed increases in FAK phosphorylation generally corresponded to increases in cell spreading and adhesion strength for IEC-6 cells. Therefore, in a simplified system, initial adhesion and signaling mechanisms appeared to correspond to subsequent physical responses in IEC-6 cells relevant to tissue engineering applications.