Multifactor analysis on the effect of collagen concentration, cross-linking and fiber/pore orientation on chemical, microstructural, mechanical and biological properties of collagen type I scaffolds.

This work evaluates the effect of processing variables on some physicochemical and mechanical properties of multi- and unidirectional laminar collagen type I scaffolds. The processing variables considered in this study included microstructure orientation (uni- and multidirectional fiber/pore controlled by freeze-drying methodology), cross-linking (chemical - using genipin and glutaraldehyde, and physical - using a dehydrothermal method), and collagen concentration (2, 5 and 8mg/ml). The biocompatibility of the scaffolds obtained in each of the evaluated manufacturing processes was also assessed. Despite previous research on collagen-based platforms, the effects that these processing variables have on the properties of collagen scaffolds are still not completely understood. Unidirectional scaffolds presented higher resistance to failure under stress than multidirectional ones. The cross-linking degree was found to decrease when the concentration of collagen increased whilst using chemical cross-linkers, and to increase with the concentration of collagen for the dehydrothermal cross-linked scaffolds. Pore orientation indexes of both unidirectional and multidirectional scaffolds were not influenced by collagen concentration. Cross-linked scaffolds were more hydrophobic than non-cross-linked ones, and presented water vapor permeability adequate for use in low-to-moderate exuding wounds. Pore size ranges were compatible with cell in-growth, independently of the employed cross-linking and freezing methodologies. Moreover, scaffolds cross-linked with glutaraldehyde presented higher in-growth of primary oral mucosa fibroblasts than those cross-linked with genipin or with the dehydrothermal treatment. This multi-factor analysis is expected to contribute to the design of collagen type I platforms, which are usable on several potential soft tissue-engineering applications.