Orientation distribution of highly oriented type I collagen deposited on flat samples with different geometries.

The structural arrangement of type I collagen in vivo is critical for the normal functioning of tissues, such as bone, cornea, tendons, and blood vessels. At present, there are no established low-cost techniques for fabricating aligned collagen structures for applications in regenerative medicine. Here, we report on a straightforward approach to fabricate collagen films, with defined orientation distributions of collagen fibrillar aggregates within a matrix of oriented collagen molecules on flat sample surfaces. Langmuir-Blodgett (LB) technology was used to deposit thin films of oriented type I collagen onto flat substrates exhibiting various shapes. By varying the shapes of the substrates (e.g., rectangles, squares, circles, parallelograms, and various shaped triangles) as well as their sizes, a systematic study on collagen alignment patterns was conducted. It was found that the orientation and the orientation distribution of collagen along these various shaped substrates are directly depending on the geometry of the substrate and the dipping direction of that sample with respect to the collagen/water subphase. An important factor in tissue engineering is the stability, durability, and endurance of the constructed artificial tissue and thus its functioning in regenerative medicine applications. By testing these criteria, we found that the coated films and their alignments were stable for at least three months under different conditions and, moreover, that these films can withstand temperatures of up to 60 °C for a short time. Therefore, these constructs may have widespread applicability in the engineering of collagen-rich tissues.

Controlled deposition of highly oriented type I collagen mimicking in vivo collagen structures.

The structural arrangement of type I collagen in vivo is critical for the normal functioning of tissues, such as bone, cornea, and blood vessels. At present, there are no low-cost techniques for fabricating aligned collagen structures for applications in regenerative medicine. Here, we report a straightforward approach to fabricate collagen films, with defined orientation of collagen fibrillar aggregates within a matrix of oriented collagen molecules. Langmuir-Blodgett (LB) technology was used to deposit thin films of oriented type I collagen onto substrates. It was found that collagen does not behave like classical LB materials, such as amphiphilic hydrocarbon acids or lipids. The thickness of the deposited collagen films and the area-pressure isotherms were found to depend on the amount of material spread. In addition, no film collapse was detected and the deposited LB films were thicker than the theoretical dimension of a collagen monolayer (1.5 nm) formed by triple helical collagen molecules. Individual LB films with thicknesses of up to 20 nm were obtained, and multiple depositions yielded overall film thicknesses of up to 100 nm. Films consisted of a matrix of collagen molecules containing thicker fibrillar aggregates of collagen (micrometers in length). These fibrillar aggregates were built up of shorter unit molecules forming "spun thread" structures, some of which exhibited a zigzag pattern. In addition to aligning collagen unidirectionally (similar for example to tendon), we performed a two-step deposition procedure, in which the substrate was turned 90 degrees between two consecutive collagen deposition steps. The resulting films showed orthogonally aligned collagen layers, mimicking the structure of cornea. Thus, this technique permits control of the thickness of individual layers, the orientation of successive layers, and the number of layers within the construct. Therefore, it may have widespread applicability for the engineering of collagen-rich tissues.