A research team has created a photocurrent-responsive coating that speeds up bone-implant integration to just two weeks, potentially reshaping orthopaedic implant design.
The innovative surface technology promises to revolutionise outcomes in orthopaedic surgeries, including knee and joint replacements, by expediting recovery and reducing the risk of implant rejection.
Post-implantation complications, such as implant loosening, are often tied to disorders in the osteoimmune microenvironment – delaying recovery and increasing the risk of failure.
To address this, a team at HKUMed, Hong Kong, led by Professor Kelvin Yeung Kwok of the Department of Orthopaedics and Traumatology, designed an implant coating that responds to near-infrared (NIR) light, which is widely recognised for its ability to penetrate biological tissues.
The NIR-responsive surface generates a photocurrent modulating macrophage activity to reduce acute inflammation in the early stages of implantation.
This approach promotes the recruitment of mesenchymal stem cells (MSCs), enhancing bone formation and significantly improving bone-to-implant integration.
The foreign body reaction initiated by implant insertion often leads to acute inflammation.
While this response is necessary to recruit MSCs and initiate bone regeneration, an imbalance in the host immune system can result in chronic inflammation, fibrous capsule formation, and implant loosening – factors linked to over 10% of implant failures.
The new coating harnesses hydroxyapatite (HA), the primary component of bone, to generate photoelectric signals under NIR exposure.
These signals control macrophage differentiation and foster a favourable immune microenvironment, creating optimal conditions for MSC recruitment and bone regeneration.
The technology demonstrated remarkable success in preclinical trials using a tibial defect animal model, reducing bone integration time from 28 to 14 days. This is the first study to use photocurrents to regulate immune cells noninvasively, paving the way for biomaterials that remotely control the local immune environment.
Professor Kelvin Yeung said: ‘This engineered surface modulates macrophage activity according to the patient’s immune cycle, significantly accelerating integration and doubling the fusion rate. We aim to expand this technology to enhance patient outcomes in orthopaedic surgeries, addressing challenges such as implant rejection.’
The team envisions wide-scale adoption of this technology in artificial joint replacements, including knee surgeries.
