Collagen gels have been widely studied for applications in tissue engineering because of their biological implications. Considering their use as scaffolds for vascular tissue engineering, the main limitation has always been related to their low mechanical properties. During the process of in vitro self-assembly, which leads to collagen gelation, the size of the fibrils, their chemical interactions, as well as the resulting microstructure are regulated by three main experimental conditions: pH, ionic strength and temperature. In this work, these three parameters were modulated in order to increase the mechanical properties of collagen gels. The effects on the gelation process were assessed by turbidimetric and scanning electron microscopy analyses. Turbidity measurements showed that gelation was affected by all three factors and scanning electron images confirmed that major changes occurred at the microstructural level. Mechanical tests showed that the compressive and tensile moduli increased by four-and three-fold, respectively, compared to the control. Finally, viability tests confirmed that these gels are suitable as scaffolds for cellular adhesion and proliferation.

None of the replacements proposed in the literature for small-calibre blood vessels (SCBV) fully satisfies the stringent requirements that these grafts have to fulfil. Here, an electrospun silk fibroin tubular construct is hybridized with type I collagen gel to produce a biomimetic SCBV graft with physiologically relevant compliance and burst pressure and optimal cytocompatibility. The hybridization of the two polymers results in the formation of a nanofibrillar hydrated matrix, where the collagen gel enhances the mechanical properties of the SF tubular construct and improves the early response of the material to in vitro cell adhesion and proliferation.

Collagen-based vascular substitutes represent in VTE a valid alternative for the replacement of diseased small-calibre blood vessels. In this study, collagen gel-based scaffolds were crosslinked combining modulation of pH and UV-C radiation. The effects on the mechanical properties, on the molecular structure and on cell viability and morphology were investigated. The mechanical response increased as a function of pH or UV-C dose and strongly depended on the test speed. Collagen molecular conformation resulted only slightly modified. While cell adhesion was not significantly altered, cell proliferation partially decreased in function of pH and UV-C. These findings suggest that UV-C treated collagen gels can represent an adequate substrate for VTE applications.

Reconstituted collagen gels are widely used as scaffolds even though their low strength and poor elasticity limit their applications in VTE. Here, two approaches are adopted to modify their mechanical behavior: in the first, gels prepared under physiologic conditions are remodeled by cell‐mediated contraction; in the second, gels prepared in non‐physiologic conditions are chemically crosslinked. Samples are tested under cyclic loading and their viscoelastic behavior is assessed. The results show that both approaches result in lattices with adequate strength, and crosslinking significantly reduces hysteresis and permanent deformation. SEM shows that SMCs are capable of contracting and remodeling all the lattices, confirming that these are suitable supports for tissue regeneration.

Collagen gels have been investigated for a number of applications in tissue engineering because of their excellent biological properties. However, their limited mechanical behavior represents a major bottleneck for clinical use, especially for vascular tissue engineering. The targeting of their mechanical properties may be envisaged by the addition of other biopolymers, such as konjac glucomannan (KGM), a neutral high-molecular weight polysaccharide extracted from the tubers ofAmorphophallus konjac, which has already been studied for biomedical applications due to its biocompatibility and biodegradable activity. In the present study, reconstituted collagen gels were prepared at pH 10 and room temperature, by mixing collagen with NaOH, NaCl and 0.05 to 0.2% of KGM. Collagen fibrillogenesis was monitored by spectrophotometric analysis at 310 nm. Gel samples were analyzed by compression tests, FTIR and SEM. Comparing to the control, the addition of KGM reduced the half-time (t1/2) of gelation fromca. 3 h to 2 h and the mechanical tests showed increases in the compressive strain energy of up to 3 times, and in compressive modulus of almost 4 times. Scanning electron images of collagen gel samples with KGM revealed the presence of micro-domains of KGM in the collagen matrix, revealing a phase separated scaffold for vascular tissue engineering.