Bioengineering Seminar Series

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“Defining, Refining and Redefining Biocompatibility: Evolutions in Ideas”

Buddy D. Ratner, PhD
University of Washington Engineered Biomaterials (UWEB)

Millions of medical devices made of synthetic or modified natural materials are implanted in humans each year saving millions of lives and improving the quality of life for millions more. These implants trigger a similar reaction, the foreign body reaction (FBR). Biocompatibility, for materials that pass routine cytotoxicity testing, is largely associated with a mild FBR, i.e., a thin, avascular, non-adherent foreign body capsule. The implant is incorporated into a “dead-zone” of acellular scar. The contemporary biomaterials and tissue engineering paradigm would suggest that all synthetic biomaterials and scaffolds (particularly those lacking cellular, biomolecule or biomimetic elements) will give this same fibrotic, avascular healing reaction.
In this talk, synthetic biomaterials will be described that readily integrate into tissue and may stimulate spontaneous reconstruction of tissue.  One such material is fabricated by sphere-templating and it can be made from many polymers including hydrogels, silicones and polyurethanes.  All pores are identical in size and interconnected. Studies from their group have shown optimal healing (as suggested by appropriate vascularity and minimal fibrosis) for spherical 30-40 microns pores. Good healing results have been seen upon implantation in skin, heart muscle, sclera, skeletal muscle, bone and vaginal wall.  Another material showing desirable biointegration is a zwitterionic hydrogels based on carboxybeteine. This material also heals in a non-fibrotic, pro-angiogenic manner. Other researchers have seen similar healing results, via completely different materials strategies, generally involving biological molecules. The in vivo results from their group and related results from other groups suggest they are on the cusp of a revolution in healing, biomaterials integration and tissue reconstruction. This challenges the present, widely accepted definition of biocompatibility:
“The ability of a material to perform with an appropriate host response in a specific application”  (Definitions in Biomaterials, Elsevier, 1987)
This definition is accurate, but is it useful given new discoveries relating to the biological reaction to implanted materials?
They believe the definition of biocompatibility needs refining and redefinition. As biomaterials are used in more challenging surgical environments, the needs to minimize fibrosis and enhance regeneration increase.  Thus, the boundaries between biomaterials and tissue engineering begin to blur.


  • Workflow Status: Published
  • Created By: Karen Ethier
  • Created: 11/12/2014
  • Modified By: Fletcher Moore
  • Modified: 04/13/2017