SWH Research Campbell & Weiss

Fibrin-Based Plastics

Phil Campbell, PhD and Lee Weiss, PhD

Our goal is to develop off-the-shelf tissue engineered materials to direct wound repair and regeneration in long bone defects.  In searching for new solutions to address this challenging problem we rediscovered old technology for fabricating fibrin-based plastics, which were originally developed and successfully used in WWII. We are revitalizing and adapting this technology to address the needs of modern tissue engineering applications by developing novel manufacturing processes for protein-based plastic scaffolds that enable:  i. incorporation of growth factors, other hormones, drugs, and native cross-linking agents within scaffolds; ii. controlled scaffold porosity; and, iii. custom 3D shapes.  The advantages of these fibrin-based plastics are: 1) biocompatibility of native materials; 2) degradation by proteolysis in register to tissue regeneration; 3) binds growth factors, thus minimizing the dosages needed to produce therapeutic results; 4) mechanical properties can be engineered to range from elastic, to rubbery, to hard; 5) can be stored for off-the-shelf usage; 6) and can be shaped in the O.R.; and, 7) can be composited with other materials, including other extracellular matrix compositions.

We have successfully developed manufacturing approaches to fabricate such protein-based plastics. These are low temperature/pressure methods that permit the direct inclusion of biologicals such as growth factors during fabrication. Elastomeric films/sheets can be formed from hydrogels using a controlled vacuum drying dehydration approach, and then these sheets can be formed into 3D structures by rolling or layered assembly. Another method is used to make bulk materials with rubbery to hard properties.  In this method, gels are first dried and milled into a powder.  This powder can be extended and augmented with growth factors, drugs, nanocrystalline calcium phosphate fillers, porogens, and vegetable-based cross-linkers, and then formed into slurries by mixing with plasticizers such as glycerin. The slurries are then compression molded into plastic shapes. Porosity, if desired, is achieved using a sublimation porogen which is removed in a vacuum, post-molding, without the need for organic or aqueous solvents. We are currently evaluating these materials in various in vitro and in vivo models.