Smart Coating with Biomimetic Antimicrobial Nanostructures and Strain-Mapping Electronics for Osseointegrated Prostheses to Address Infection and Mechanical Failure Risks
Abstract
Background and Problem Statement: This work directly addresses CDMRP-PRORP 2020, Applied Research Award; Focus Area, Identification of best practices to address infection and failure of percutaneous osseointegrated prosthetic limbs. One in 190 Americans is currently living with the loss of a limb, and the prevalence is four times higher among Veterans. Between 2000 and 2011 alone, in Operation Enduring Freedom and Operation Iraqi Freedom, there were 6,144 incident cases of traumatic amputations sustained by 5,694 Service members. The majority of these amputees are eager to regain functions, but many of them frequently experience problems related to the use of conventional socket-suspended prostheses. Bone-anchored limb prostheses, which allow for the direct transfer of external load from the prosthesis to the skeleton without the vulnerable soft-tissue envelope as the intermediate, eliminate complications associated with the socket-stump interface and offer multiple clinical benefits, including improved range of motion, walking ability, sitting comfort, enhanced prosthetic use, and heightened perception of pressure, load, position, and balance. Despite these advantages, current osseointegrated prosthetic limbs are plagued by high infection rate, especially at the implant-skin interface. In addition, the mechanical integrity of the implant system and bone must be preserved under constant stresses induced by the prosthesis and body movement. Application/Innovation: With this research proposal, we address the critical issues of preventing infections and monitoring the structural health of percutaneous osseointegrated prosthetic limbs. We seek to develop a smart coating in the form of a flexible polymer foil that can be easily wrapped around the cylindrical surface of the skin-penetrating implant exiting the human body. The coating has two key functionalities. First, on its outer surface, we fabricate high-density nanopillar arrays to mimic the surface features of cicada and dragonfly wings. These biomimetic nanostructures have the unique capability to kill attached bacteria through purely physical biomechanical interactions, preventing bacteria-causing infections from adhering onto the implant surface. Because the bactericidal mechanism is based on physical interactions, compared to conventional antimicrobial coatings relying on the controlled release of antibiotics, this biomimetic design exhibits long-term effectiveness and does not cause antibiotic resistance or any toxic side effects to human cells, tissues, or organs. Second, on its inner surface intended for conformal contact with the implant, we fabricate an array of strain sensors to monitor the stresses applied on the implant in real time. The results will be used as diagnostic tools during the rehabilitation to quantitatively assess the mechanical quality of osseointegration and guide patients to avoid dangerous overloads in their daily use of prostheses. Since the normal strain for implants is very low, we build our strain sensors based on high-quality single-crystalline silicon (the same material used to make high-performance computer microprocessors) to achieve the required sensitivity. Although single-crystalline silicon is usually rigid and brittle, by reducing its thickness to ~100 nm, i.e., one thousandth the width of a human hair, silicon films become flexible enough to be applied on the curved surfaces of implants. Electronic control circuits will be built on such ultrathin silicon membranes at the same time to enable mapping the strain distribution over the entire surface of the skin-penetrating implant. Therefore, localized maximum strain at weak points will not be neglected under any loading conditions to achieve the accuracy and reliability as required for medical applications. Timeline to Achieve Clinical Relevance: Upon completion of this project, we will have a technology prototype with functionalities and safety fully verified
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Dec 05, 2021
- Source ID
- W81XWH2110290
Entities
People
- Qing Cao
Organizations
- United States Army
- University of Illinois Urbana–Champaign