HKUMed develops a near-infrared-activated smart titanium implant surface that clears bacteria in 15 minutes and promotes bone integration. The research is led by Professor Kelvin Yeung Wai-kwok (middle).
A research team from the Department of Orthopaedics and Traumatology, School of Clinical Medicine, LKS Faculty of Medicine at the University of Hong Kong (HKUMed), has developed a titanium implant surface that can be activated by near-infrared (NIR). With just 15 minutes of NIR irradiation, this surface can eliminate 99.94% of Staphylococcus aureus (S. aureus) biofilms without the use of antibiotics, while simultaneously promoting bone-implant fusion. Based on titanium dioxide (TiO2), the same compound found in titanium's natural surface oxide layer, the design may offer practical advantages for compatibility with existing titanium implants and future clinical translation. This innovative technology could be applied to various common orthopaedic implants, including joint replacements, fracture fixation devices, spinal fusion cages, dental implants and craniofacial implants. It offers a new solution to combat implant infections. The findings were published as a cover story in the international journal Cell Biomaterials [link to the publication].
Implant-associated infections remain a major clinical challenge in orthopaedic practice. Once bacteria adhere to an implant surface and form biofilms, they become highly tolerant to antibiotics and can evade the patient's immune system. Consequently, patients often require repeated invasive debridement, revision surgeries and prolonged courses of high-dose systemic antibiotics. These treatments extend recovery time, increase healthcare costs, contribute to antibiotic resistance and often fail to prevent recurrent infections.
Professor Kelvin Yeung Wai-kwok, from the Department of Orthopaedics and Traumatology, School of Clinical Medicine, HKUMed, who led the research, stated, 'Implant-associated infection is a major cause of implants failure. Bacterial colonisation and biofilm formation on implant surfaces can be difficult to eradicate, often resulting in persistent inflammation, compromised implant fixation and, ultimately, loosening and failure.'
'Although existing antibacterial coatings can provide some level of protection, they typically rely on loaded agents such as antibiotics, metal ions or complex bioactive molecules,' he added. 'Their effectiveness, however, is limited by their loading capacity, uncontrolled release, potential cytotoxicity and loss of function once these agents are exhausted. These limitations underscore the urgent need for an in situ, controllable and durable strategy that can both eliminate biofilms and promote bone-to-implant integration without the use of additional drugs or agents. This is precisely what our research seeks to achieve.'
Light-triggered defence enables rapid bacterial elimination
Currently, titanium and titanium alloys, which are widely used in orthopaedic surgery, naturally form a very thin TiO2 layer on the implant surface. While this layer is highly biocompatible, it offers minimal defence against infection and lacks the ability to actively promote bone growth. When bacteria such as S. aureus form biofilms on these surfaces, antibiotics are often unable to eradicate the infection effectively, resulting in the need for invasive revision surgeries.
Using a customised template-assisted technique, the HKUMed team precisely engineered nano-honeycomb structures on the titanium surfaces and introduced oxygen vacancies through hydrogenation treatment, creating a remotely activatable smart surface. Under NIR irradiation, this smart surface generates reactive oxygen species and a mild local photothermal effect, rapidly disrupting biofilm architecture and killing bacteria.
In vitro experiments found that a single 15-minute irradiation was sufficient to eliminate 99.94% of S. aureus. In a rat tibial defect infection model, the same treatment removed 91.58% of biofilms. Compared to unmodified titanium implants, the engineered surface can efficiently perform biofilm clearance and lead to marked reductions in pus formation and local inflammation, resulting in a notable increase in new bone formation around the implant.
Enhancing the osteoimmune microenvironment supports new bone formation
Beyond its strong antibacterial performance, the research demonstrated that the new implant surface effectively modulates the local immune response. It shifts macrophages from a prolonged pro-inflammatory state to a pro-healing, tissue remodelling phenotype, thereby creating a more favourable osteoimmune microenvironment. This attracts more osteogenic cells and facilitates their differentiation, leading to a significant increase new bone formation. As a result, the implant achieves faster and more stable integration with the bone, demonstrating that the new technology prevents infection while accelerating bone fusion.
'By adopting an agent-free strategy, our newly developed smart surface demonstrates remarkable antibacterial and pro-osteogenic capabilities without the use of additional drugs,' explained Professor Yeung. 'This technology offers high translational potential, as it relies solely on native implant materials and mature manufacturing processes. This will facilitate regulatory approval, support scalable manufacturing and pave the way for future clinical adoption. We believe this innovation will broadly improve orthopaedic surgical outcomes and benefit more patients.'
About the research team
The research study was led by Professor Kelvin Yeung Wai-Kwok, Department of Orthopaedics and Traumatology, School of Clinical Medicine, HKUMed. The first author is Dr Zhu Yizhou, Research Assistant Professor in the same department.
Acknowledgments
The research is jointly supported by funding from the Chinese Mainland, including the National Key Research and Development Programme of China, the National Natural Science Foundation of China, the Shenzhen Science and Technology Innovation Commission, the Guangdong Basic and Applied Basic Research Foundation, and the National Science Fund for Distinguished Young Scholars; as well as the General Research Fund, the Collaborative Research Fund, the Hong Kong Innovation Technology Fund, the Health and Medical Research Fund, the National Natural Science Foundation of China/ RGC Joint Research Scheme, the Government of the Hong Kong Special Administrative Region of the People's Republic of China.
