Antibacterial characteristics and accelerated degradation of ZnCu-filled poly(L-lactide) scaffold

Abstract

Poly-l-lactide (PLLA) is a promising bone implant material because of its favorable biocompatibility, biodegradability and outstanding processability. Nevertheless, it lacks antibacterial activity, which greatly limits its clinical application. In this study, degradable ZnCu particles were incorporated into PLLA scaffolds to endow them with antibacterial function via selective laser sintering. The mechanism was that copper ions and zinc ions released from the PLLA-ZnCu scaffold could kill bacteria by damaging cell membrane integrity, inactivating enzymes and restraining deoxyribonucleic acid replication. The relative bacterial viability of Escherichia coli and Staphylococcus aureus incubated with the PLLA-8ZnCu scaffold for 48 h was only 6.4 ± 1.7% and 9.4 ± 2.7%, respectively. Meanwhile, the weight loss percentage of the PLLA-16ZnCu scaffold (6.47 ± 0.2%) was approximately three times greater than that of the PLLA scaffold (1.89 ± 0.17%). The larger weight loss was mainly attributed to the acid-alkali neutralization reaction occurring between the alkaline degradation product of the ZnCu particles and the acidic degradation product of the PLLA matrix, which could simultaneously promote the degradation of both ZnCu particles and the PLLA matrix, ultimately accelerating scaffold degradation. Besides, the compressive strength and elastic modulus of the PLLA-ZnCu scaffolds were also enhanced owing to the dispersion strengthening effect of ZnCu particles. In addition, the PLLA-ZnCu scaffolds exhibited excellent cell viability and adhesion. These results suggest that the PLLA-ZnCu scaffold may be a potential candidate material for orthopedic implants.