Induction of bactericidal activity by degradable implants

Introduction The problem of implant-associated infections is far from being solved in arthroplasty, osteosynthesis of fractures, and spinal pathology. The development of biodegradable implants with bioactive properties is a promising direction. The purpose of this study was to evaluate the in vitro bactericidal activity of implants made from a degradable material polycaprolactone (PCL) impregnated with hydroxyapatite and an antibiotic.Material and methods To study antibiotic availability, antibiotic-impregnated PCL cylindrical samples (n = 6) were incubated in distilled water at 37 °C. To evaluate the antibacterial properties, samples in the form of porous disks were used: control samples from PCL; 1) PCL samples coated with antibiotic and hydroxyapatite; 2) PCL samples coated only with antibiotic; 3) PCL samples coated only with hydroxyapatite; (n = 6 for each type of tested samples). The disk diffusion method was used to determine the sensitivity of microorganisms to antibiotics. The microbial strains used were S. aureus ATCC 25923, P. aeruginosa ATCC 27853 and E. coli ATCC 25922. Test microorganisms were cultivated on beef peptone agar (MPA) at 37 °C for 24 hours. Quantitative data were subjected to statistical processing.Results It was determined that 82.6 % of the antibiotic was released during the first day of incubation and 8.2 % on the second day. Control samples did not show a bactericidal effect. Samples 3 showed an antibacterial effect against E. coli culture. Samples 1 and 2 equally demonstrated significant inhibition of the growth of S. aureus, P. aeruginosa, and E. coli.Discussion Most of the antibiotic is released into the hydrolyzate during the first two days of incubation. Porous implants made of PCL and impregnated with an antibiotic have pronounced antimicrobial activity against the most common gram-negative and gram-positive bacteria that cause purulent complications in surgical practice. Nanostructured hydroxyapatite on the surface of the implant does not reduce bactericidal activity.Conclusions Porous polycaprolactone implants filled with hydroxyapatite and antibiotics are targeted to stimulate bone regeneration and simultaneously ensure antimicrobial activity. Nanostructured hydroxyapatite on the implant surface does not decrease bactericidal activity.