Validation of an inflation method for measuring the strength of engineered tissues

Living tissue equivalents (LTE), such as fibroblast-populated collagen lattices (CL) and fibrin gels (FG), are biologically-derived models of soil connective tissues that contain both cells and a biopolymer scaffold. These LTEs are becoming increasingly popular for the development of living connective tissue substitutes in the bourgeoning field of tissue engineering. Quantification of the mechanical properties of these engineered tissues is essential for assessing their ultimate functionality as tissue substitutes, optimizing processes for their manufacture, and providing insight into basic cell-matrix interactions. Although the mechanical properties of LTEs in linear, tubular, and annular geometries have been measured, characterization of the strength and extensibility of planar LTEs has been hindered by a lack of appropriate testing methodologies. We have developed an inflation system that overcomes previous difficulties with clamping and determining the deformation of delicate planar tissues. The goals of this study were to 1) demonstrate that a range of LTEs can be tested using the inflation device, and 2) to determine the curvature of the inflated tissues, a necessary quantity for calculating their strength. To this end, inflation tests were performed on CL and FG samples after only two to seven days in culture. The curvature of the inflated tissues and latex membranes was assessed using a laser scanning system and by digital image analysis.