Adhesive properties of laminated alginate gels for tissue engineering of layered structures

A significant challenge in tissue engineering is the creation of tissues with stratified morphology or embedded microstructures. This study investigated methods to fabricate composite gels from separately deposited alginate layers and examined the effects of processing methods on the mechanics of adhesion. Laminated alginate gels were created through a three step process which included: treatment of the interfaces with citrate; annealing of the gels to allow for molecular rearrangement of the alginate chains; and exposure to a CaCl2 to crosslink the alginate sheets. Process variables included volume and concentration of applied citrate, annealing time, incubation time in CaCl2, and CaCl2 concentration. Laminated sheets were tested in lap-shear geometry to characterize failure phenomena and mechanical properties. The site of failure within the gel depended on the integrity of the interface, with weaker gels delaminating and gels with mechanical properties similar to that of bulk gels failing randomly throughout the thickness. Citrate volume, citrate concentration, CaCl2 incubation time, and CaCl2 concentration altered the mechanical properties of the laminated alginate sheets, while annealing time had little effect on all measured parameters. This study demonstrates the integration of separately fabricated alginate layers to create mechanically or chemically anisotropic or heterogeneous structures. (C) 2007 Wiley Periodicals, Inc.