Researchers at the Indian Institute of Technology Mandi have developed a nature-inspired surface coating for 3D-printed bone implants that could help address two major challenges in orthopaedic implants—bacterial infections and poor integration with surrounding bone.

Published in the Chemical Engineering Journal, the study describes a dual-layer hydroxyapatite coating featuring microscopic needle-like structures resembling sea urchins. 

The coating is designed to mechanically disrupt bacteria while simultaneously improving the bone compatibility of biodegradable polymer implants.

The research was led by Dr. Sumit Murab, along with Ankita Negi, Aakash Verma, K.M. Mohammed Sufiyan and Vedante Mishra.

Large bone defects caused by traumatic injuries, infections or tumour removal remain challenging to treat. While 3D printing enables the fabrication of patient-specific implants using materials such as polylactic acid (PLA), the hydrophobic nature of PLA can limit its ability to bond effectively with bone. 

At the same time, bacterial adhesion and biofilm formation on implant surfaces can lead to infections, implant failure and the need for revision surgery.

To address these challenges, the IIT Mandi team developed a hydroxyapatite-based surface architecture inspired by structures found in nature. Hydroxyapatite is a major inorganic component of human bone and is widely studied for its ability to support bone growth and integration.

The coating process involves two stages. First, the surface of a 3D-printed PLA scaffold is chemically activated using an alkaline treatment, creating sites for mineral deposition. The scaffold is then subjected to hydrothermal treatment at 90°C, resulting in the formation of clusters of hydroxyapatite needles that form a distinctive sea-urchin-like structure.

According to the researchers, the resulting surface combines the bone-compatible properties of hydroxyapatite with microscale structures capable of physically damaging bacterial cells. Unlike conventional approaches that rely on antibiotics or antibacterial chemicals, the approach uses the physical characteristics of the surface to inhibit bacterial colonisation.

The combination of patient-specific 3D printing and the bio-inspired coating could therefore offer a potential route towards implants that integrate more effectively with bone while reducing the risk of bacterial colonisation.

The researchers also highlight the simplicity and relatively low temperature of the surface-modification process as an advantage. The technique could potentially be adapted to other biodegradable polymer constructs and may find applications in orthopaedic and dental implants, as well as biomedical devices where infection prevention is critical.

The study demonstrates how bio-inspired surface engineering can be combined with 3D-printing technologies to develop next-generation biomedical materials that address both biological integration and infection-related challenges.