Enhanced antibacterial and mechanical performance of 3D printed bone reconstruction implants

Florin Miculescu

Faculty of Materials Science and Engineering, National University of Science and Technology Politehnica Bucharest, Romania;

Bone infections and post-surgical complications present significant challenges in orthopedic treatments, often leading to delayed healing due to bacterial contamination. Conventional methods, such as systemic antibiotic administration, can cause unwanted side effects and bacterial resistance. Therefore, the development of biodegradable materials capable of delivering antibiotics locally is crucial.

In this work, polylactic acid granules, graphene nanoplatelets, and biogenic hydroxyapatite were used as base materials. Ampicillin, amoxicillin, and gentamicin were tested as antibacterial agents. PLA, HA, and GnP were mixed with different antibiotic ratios.

Characterization included FTIR-ATR for structural analysis, SEM/EDS for morphology and composition, TGA for antibiotic thermal stability, and contact angle measurements for wettability. The in vitro degradation was assessed in PBS over 100 days, while drug release was monitored via UV-Vis spectrophotometry. Antibacterial activity was also tested.

The TGA curves revealed the thermal stability of only AMP antibiotic up to 221°C, while the FTIR analysis confirmed that the antibiotic maintained its structural integrity after processing, making it suitable for composite fabrication. The morphology revealed a uniform dispersion of AMP and HA particles within the PLA matrix, with GnP helping to reduce the antibiotic particle agglomeration. Contact angle measurements indicated enhanced hydrophilicity of the composites as the amount of antibiotic, HA, and GnP increased, improving their potential for biological applications and reducing bacterial adhesion. In vitro degradation tests showed a controlled mass loss, with a significant burst in the first 28 days followed by a slower degradation. The antibiotic release profiles indicated a gradual, sustained release, influenced by HA and GnP presence. Antibacterial tests demonstrated strong inhibition against Staphylococcus aureus and moderate effects against Escherichia coli, confirming the antibacterial efficiency of the developed composites.

The results clearly demonstrate that the careful selection of antibiotic ensured its thermal stability during processing, preserving also the antibacterial properties. The uniform distribution of HA and GnP within the PLA matrix contributed to improved structural homogeneity and enhanced surface roughness, promoting better cell interaction. The observed increased hydrophilicity suggests future favorable conditions for tissue integration and bacterial inhibition.