How We Think

RAPID MANUFACTURING + COLLAGEN

Of the various proteins used in biomaterials, collagen is the most applicable component. It is synthesized by fibroblasts among other cell types and is the most abundant protein in the mammalian body, accounting for 20–30% of the total protein (Gomes et al., 2011). Collagen that forms fibrils can be divided into three types, which provide mechanical support and control cell adhesion, cell migration and tissue repair. Type I can be found in skin, tendon, and bone; type II is predominant in cartilage; and type III is a vital component of the blood vessel wall; type IV is found in basement membrane of epithelial tissues and does not form fibrils. Why is collagen so popular in the fields of tissue engineering? In addition to its natural biodegradability, bio-compatibility and plasticity, it is also easy to modify and process. The properties of collagen-based materials are influenced by the source of collagen and by the method of preparation (i.e. purification, fibril formation, cross-linking) (Sionkowska, 2011). It is being widely used in reconstructive medicine, pharmacy and cosmetics; more specifically, in soft tissue repair, vascular and dermal tissue engineering (Ratner et al., 2004), bone repair, and as a carrier for the delivery of drugs and biologically active molecules (Gomes et al., 2011). Collagen is insoluble in water due to its highly cross-linked structure, but exhibits low thermal stability. Therefore, a need to combine this natural polymer with a synthetic one with good thermal properties can yield a truly effective biomaterial.
Structural order of collagen. Inspired by (Ratner, Hoffman, Schoen, & Lemons, 2004). Illustration by Alena Iouguina, 2011
Structural order of collagen. Inspired by (Ratner et al., 2004). Illustration by Alena Iouguina, 2011
Rapid Manufacturing + Collagen Recently, a freeform fabrication technique (FF), based on the on-demand printing/patterning of cells and collagen hydrogel, was developed to improve upon limitations of elaborated production and alignment procedures, thus expediting the construction of 3D artificial tissues. The technique can be applied to print different types of hydrogel materials, generating biological scaffolds with properties of composite materials. Collagen is especially a suitable scaffold material due to its ability to support cell adhesion and culture.
Picture of the modular tissue printing platform shown with [1] 4 syringes as 'cartridges' to load cell suspensions and hydrogel precursors; [2] an array of 4-channel dispensers; [3] target substrate; [5] vertical stage; [6] range finder; [7] vertical stage heater/cooler; [8] optional independent heating/cooling unit for the dispenser. Inset: close-up view of the 4-channel micro-dispensers. For more info: Lee et al., 2009. Multi-layered culture of human skin fibroplasts and keratinocytes through three-dimensional freeform fabrication. Biomaterials, 30, 1587-1595.
Picture of the modular tissue printing platform shown with [1] 4 syringes as 'cartridges' to load cell suspensions and hydrogel precursors; [2] an array of 4-channel dispensers; [3] target substrate; [5] vertical stage; [6] range finder; [7] vertical stage heater/cooler; [8] optional independent heating/cooling unit for the dispenser. Inset: close-up view of the 4-channel micro-dispensers. For more info: Lee et al., 2009. Multi-layered culture of human skin fibroplasts and keratinocytes through three-dimensional freeform fabrication. Biomaterials, 30, 1587-1595.
References
Gomes, S., Leonor, B. I., Mano, J. F., Reis, R. L., & Kaplan, D. L. (2011, July 18). Natural and genetically engineered proteins for tissue engineering. Elsevier , 1–17.
Ratner, B. D., Hoffman, A. S., Schoen, F. J., & Lemons, J. E. (Eds.). (2004). Biomaterials Science: An Introduction to Materials in Medicine (2nd Edition ed.). San Diego, California, USA: Elsevier Inc.
Sachlos, E., Czernuszka, J. T., 2003. Making tissue engineering scaffolds work. Review: the application of solid freeform fabrication technology to the production of tissue engineering scaffolds. Eur. Cell. Mater, 5, 29-39.
Sionkowska, A. (2011, May 25). Current research on the blends of natural and synthetic polymers as new biomaterials: Review. Elsevier , 1254– 1276.  

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