Experimental evaluation of solvents with a biological substrate based on solubility parameter theory: Solubility parameter determinations by computational chemistry using a rational design process

Maximal approximation of dentin resin bonding agents with acid decalcified human Type 1 dentin collagen is desired at the resin/substrate interface. Human Type 1 dentin collagen is a complex substrate consisting primarily of highly cross-linked protein but also proteoglycans. This study utilized purified, proteoglycans free, reconstituted Type 1 rat-tail collagen to minimize substrate variables. Solubility parameters were used to establish liquid-solid interaction energies and thus miscibility. Computational chemistry models to predict solubility parameters of various chemical structures were developed. The solubility parameter for Type 1 rat-tail collagen was calculated from predicted solubility parameters for amino acids. Rat-tail Type 1 collagen was treated with experimental solvents with solubility parameters above and below the calculated solubility parameter of rat-tail collagen. Interactions of solvents with rat-tail collagen based on solubility parameter theory were observed visually and with scanning electron microscopy (SEM). It was hypothesized that the fibrous nature of the rat-tail collagen would change when solubility parameters of solvents approximated the calculated rat-tail collagen solubility parameter due to interaction energies between solvent and collagen.; Statistical analyses of all QSPR models and experimental solvent/collagen interactions results were performed to test hypotheses. All models were internally and externally validated. All chemical descriptors of predictive QSPR models were statistically significant. The calculated solubility parameter for rat-tail Type 1 collagen was calculated and determined to be similar to the solubility parameter for Type 1 human dentin collagen reported in the literature. Statistically significant differences occurred between interactions of solvents and rat-tail collagen based on solubility parameter theory. Rat-tail collagen was fibrous in solvents whose solubility parameters were below the rat-tail calculated solubility parameter. Rat-tail collagen formed a gel/sol in solvents whose solubility parameters were above the rat-tail calculated solubility parameter. This fundamental theoretical and experimental study suggested that solvent or solution solubility parameters should approximate the solubility of the substrate to insure maximum solvent/substrate interaction when applied to dentin/adhesive interfaces.