Practical considerations for medical applications using biological grafts and their derivatives

The art and science of using biological tissue grafts from animal and human sources for various ailments is nascent. Various research groups around the world are actively investigating the potential prostheses of biological origin. Biological tissue grafts are rendered acellular through various methods of processing and fabrication before they are used for the specific purpose. The remainder is a scaffold that offers framework for host cellular repopulation and revascularization. Different methods of fixation have been explored over several decades to render the biological grafts suitable for use with or without extraction of cells. Therefore, methods such as glutaraldehyde and polyepoxide crosslinking treatments and dye-mediated photooxidation have been developed to stabilize and deantigenize the tissue while attempting to maintain its natural mechanical properties. Also, residual cellular components in a bioprosthetic material have been associated with undesired effects, such as calcification and immunological recognition, and thus have been the motivation for various decellularization processes. The effects of these stabilization and decellularization treatments on mechanical, biological and chemical properties of treated tissues have been investigated, specifically with regard to calcification, immunogenicity, and cytotoxicity concerns. Naturally derived biological scaffolds offer many mechanical, chemical and biological advantages over synthetic materials, and thus hold tremendous potential for use in tissue engineering therapies. Therefore the rationale of using biological grafts in usable forms is gaining importance in order to avoid unwanted chronic inflammatory reactions. This review article discusses the need for such bioprosthetics and the potential role for natural tissues in various applications.