New materials and devices are radically changing the medical treatment of injury and disease, yet because of the rapid pace of this segment of the materials industry an adequate measurement infrastructure does not yet exist. Our program on the Interface of Materials with Biology develops measurement methods, standards, and fundamental scientific understanding at the interface between materials science and biological science. Within the health care industry we focus on dental and medical sectors that apply synthetic materials for replacement, restoration, and regeneration of damaged or diseased tissue. Within this program we focus on biocompatibility, materials properties, and materials science techniques applied to biological systems.

Whether the medical issue involves implanting a hip or knee joint prosthesis, a synthetic bone graft, or a tissue engineering scaffold into the human body, one of the primary issues is biocompatibility. We are working to develop suitable Reference Materials (RM) for investigating biocompatibility and implant suitability. Our research focuses on measuring the cellular response to powders and bulk materials, to identify suitable candidates. We are collaborating with the American Dental Association’s Health Foundation (ADAHF) to develop metrology methods to characterize the biocompatibility of synthetic bone grafts. Quantitative methods being developed include assays for adhesion, viability, proliferation, and differentiation of bone cells, as well as optical coherence tomography and confocal microscopy for measuring tissue ingrowth. We are developing biochemical assays to quantify inflammatory responses to synthetic materials. Finally, current research is working to bridge the gap between knowledge generation by cell biologists and product development in industry. In collaboration with NIST's Chemical Science and Technology Laboratory, we are developing measurement methodologies and reference materials to use in assessing interactions in complex systems of living cells with synthetic materials. The expected outcomes of this work are reference substrates that induce specific cellular responses, and engineered DNA vectors to act as fluorescent reporters of cellular responses.

It also is critical that the materials can withstand the mechanical and environmental stresses placed on them. For metallic implants one concern is the corrosion pitting resistance of the implant materials and the associated potential for stress corrosion cracking (SCC). To address this issue metal standards are being subjected to a simulated biological environment, which then will be used to develop tests to assess the susceptibility for SCC.

Mechanical properties issues also arise when considering synthetic bone grafts and tissue engineering scaffolds. In addition to traditional bulk mechanical property measurements, combinatorial approaches are used to identify compositions and surface features that affect properties such as biocompatibility and mechanical durability. Finally, because the dental industry is primarily composed of small manufacturers with limited R&D capability, collaborations with the ADAHF, located in MSEL, are filling the gap by developing improved materials and techniques, patenting and licensing these inventions, and most importantly, providing a technical foundation. Research focuses on improved understanding of the synergistic interaction of the phases of polymer based composites and the mechanisms of adhesion to dentin and enamel. This approach ultimately will lead to materials with improved durability, toughness, and adhesion to contiguous tooth structure.

In this era of interdisciplinary approach to research, we provide an added dimension. By taking a physical/mechanical approach to how cells function, respond, and remodel in interaction with synthetic materials, we can provide skill sets typically absent in the biomedical community. Our concentration on mechanical property metrology extends to biological systems, spanning a considerable size range from individual neurons and muscle cells to complete pulmonary arteries. This necessitates the development of unique mechanical testing platforms and application of a materials science approach to understanding integrated properties.

Fundamental to much of our work is the recognition that surfaces and interfaces play a critical role in biological systems and, in particular, in the interactions of synthetic or designed materials with biological systems and function.