W. Garrett Matthews

Solvent specific persistence length of molecular type I collagen

Type I collagen is a fibril-forming protein largely responsible for the mechanical stability of body tissues. The tissue level properties of collagen have been studied for decades, and an increasing number of studies have been performed at the fibril scale. However, the mechanical properties of collagen at the molecular scale are not well established. In the study presented herein, the persistence length of pepsin digested bovine type I collagen is extracted from the conformations assumed when deposited from solution onto two-dimensional surfaces. This persistence length is a measure of the flexibility of the molecule. Comparison of the results for molecules deposited from different solvents allows for the study of the effect of the solutions on the flexibility of the molecule and provides insight into the molecules behavior in situ.

Static adhesion of cancer cells to glass surfaces coated with glycosaminoglycans

Using a previously described method for the functionalization of glass substrates with glycosaminoglycans (GAGs), in vitro experimental comparison of adhesion levels of cancer cells to glycosaminoglycan-modified substrates was performed with non-treated and heparin-treated human cancer cells of different metastatic activity. For both non-treated and heparin-treated cells, our results indicate that heparan sulfate is the preferred substrate for adhesion while keratan sulfate shows anti-adhesive properties. The observed net effect of heparin is a cell-dependent reduction in the adhesion figures. Overall, our results suggest that tissues with higher composition of heparan sulfate chains may be preferential metastatic targets and indicate that the effective use of heparin as anti-metastatic or anti-inflammatory agent may also depend on glycosaminoglycan composition of the affected organs.

Examining the Mechanical Dependency of Molecular Type I Collagen on ion Species and Concentration

In the work to be presented, the polyampholyte behavior of molecular type I collagen was explored. The success of tissue engineering is dependant upon the development of suitable scaffolds for proper cell differentiation. Differentiation is guided, in part, by the mechanical properties of the scaffold housing the cells. Thus, characterization of the mechanics of the native scaffold is of looming importance to this field. The fibrillar collagens, in particular type I collagen, form the native scaffold. The mechanics of these fibrils are determined by the properties of the collagen molecules from which they are formed, and these properties are sensitive to the surrounding ionic environment.The persistence length of molecular collagen was measured as a function of both ionic strength and species in the solvent. It was found that the persistence length increases with ionic strength, for all ion species tested, as might be predicted for a polyampholyte such as collagen. However, the functional form of this increase was not constant for all ionic species, preventing the behavior from being ascribed simply to ionic strength and the effects of electrostatic screening. Using the curves resulting from this work, one can predictably tune the stiffness of molecular collagen by controlling ion type and concentration in the solvent. The research outcomes inform those interested in the physics of biopolymers and those seeking to design biomimetic scaffolds for tissue engineering applications.