Real Time Observation and Quantification of Shear-Induced Collagen Self-Assembly

Collagen is the most abundant protein in the extracellular matrix (ECM) of vertebrates and is distributed widely throughout connective tissues. Fibrillar collagen is the principal load-bearing molecule in vertebrates (e.g. type I in tendon and ligament and type II in cartilage). Its inherent biocompatibility makes collagen an attractive scaffolding material candidate for tissue engineering. Although use of 2-D or 3-D collagen networks as a substrate for cell culturing have provided invaluable information about cell-ECM interactions, it has not been very successful in producing load-bearing tissue-engineered constructs. We attribute the fundamental problem to the use of disorganized collagen which may interfere with the ability of cells to generate organization. Several research groups have developed methods to produce organized layer(s) of collagen fibrils de novo (often with the intention of using them for guiding cell culture systems). Methods employed to influence collagen fibril organization during self-assembly include, electro-spinning [1], the use of strong magnetic fields [2–4], electrical gradients [5], flows through a microfluidic channel [6, 7], a combination of fluid flow and magnetic field [8], dip-pen nanolithography [9], cholesteric methods [10], and even freezing and thawing [11]. Although there has been some progress in controlling the alignment of collagen fibrils in vitro, there are many unknown factors which govern directed collagen self-assembly.