Preventing Surgical Site Infections Using a Natural, Biodegradable, Antibacterial Coating on Surgical Sutures.

Surgical site infections (SSIs) are one of the most common nosocomial infections, which can result in serious complications after surgical interventions. Foreign materials such as implants or surgical sutures are optimal surfaces for the adherence of bacteria and subsequent colonization and biofilm formation. Due to a significant increase in antibiotic-resistant bacterial strains, naturally occurring agents exhibiting antibacterial properties have great potential in prophylactic therapies. The aim of this study was to develop a coating for surgical sutures consisting of the antibacterial substance totarol, a naturally occurring diterpenoid isolated from Podocarpustotara in combination with poly(lactide-co-glycolide acid) (PLGA) as a biodegradable drug delivery system. Hence, non-absorbable monofilament and multifilament sutures were coated with solutions containing different amounts and ratios of totarol and PLGA, resulting in a smooth, crystalline coating. Using an agar diffusion test (ADT), it became evident that the PLGA/totarol-coated sutures inhibited the growth of Staphylococcus aureus over a period of 15 days. A 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay showed that the coated sutures were not cytotoxic to murine fibroblasts. Overall, the data indicates that our innovative, biodegradable suture coating has the potential to reduce the risk of SSIs and postoperative biofilm-formation on suture material without adverse effects on tissue.

Application of totarol as natural antibacterial coating on dental implants for prevention of peri-implantitis.

Peri-implantitis is the most important issue threatening the long-term survival rate of dental implants. Various efforts have been made to reduce implant surface plaque formation, which is one of the essential causes of peri-implantitis. In our study, we applied the natural antibacterial agent totarol as a coating on experimental silicon wafer and titanium implant surfaces. To analyze the interaction between the totarol coating and the oral primary colonizer S. gordonii and isolates of mixed oral bacteria, samples were incubated in a model system simulating the oral environment and analyzed by Live/Dead staining, crystal violet staining and scanning electron microscopy (SEM). After 4 d, 8 d, 12 d, 16 d, and 24 d salivary incubation, the stability and antibacterial efficiency of totarol coating was evaluated through SEM. The results indicated that totarol coatings on both silicon wafer and Ti surfaces caused efficient contact killing and an inhibition effect towards S. gordonii and mixed oral bacterial film growth after 4 h, 8 h, 24 h, and 48 h incubation. After longtime salivary incubation of 12 d, the bactericidal effect started to weaken, but the anti-adhesion and inhibition effect to biofilm development still exist after 24 d of salivary incubation. The application of a totarol coating on implant or abutment surfaces is a promising potential prophylactic approach against peri-implantitis.

Biodegradable rifampicin-releasing coating of surgical meshes for the prevention of bacterial infections.

Polypropylene mesh implants are routinely used to repair abdominal wall defects or incisional hernia. However, complications associated with mesh implantation, such as mesh-related infections, can cause serious problems and may require complete surgical removal. Hence, the aim of the present study was the development of a safe and efficient coating to reduce postoperative mesh infections. Biodegradable poly(lactide-co-glycolide acid) microspheres loaded with rifampicin as an antibacterial agent were prepared through single emulsion evaporation method. The particle size distribution (67.93±3.39 µm for rifampicin-loaded microspheres and 64.43±3.61 µm for unloaded microspheres) was measured by laser diffraction. Furthermore, the encapsulation efficiency of rifampicin (61.5%±2.58%) was detected via ultraviolet-visible (UV/Vis) spectroscopy. The drug release of rifampicin-loaded microspheres was detected by UV/Vis spectroscopy over a period of 60 days. After 60 days, 92.40%±3.54% of the encapsulated rifampicin has been continuously released. The viability of BJ fibroblasts after incubation with unloaded and rifampicin-loaded microspheres was investigated using an MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, which showed no adverse effects on the cells. Furthermore, the antibacterial impact of rifampicin-loaded microspheres and mesh implants, coated with the antibacterial microspheres, was investigated using an agar diffusion model with Staphylococcus aureus. The coated mesh implants were also tested in an in vivo mouse model of staphylococcal infection and resulted in a 100% protection against mesh implant infections or biofilm formation shown by macroscopic imaging, scanning electron microscopy, and histological examinations. This effective antibacterial mesh coating combining the benefit of a controlled drug delivery system and a potent antibacterial agent possesses the ability to significantly reduce postoperative implant infections.

Development and in vitro characterization of poly(lactide-co-glycolide) microspheres loaded with an antibacterial natural drug for the treatment of long-term bacterial infections.

Biodegradable polymers, especially poly(lactide-co-glycolide) (PLGA), have good biocompatibility and toxicological properties. In combination with active ingredients, a specialized drug delivery system can be generated. The aim of the present study was to develop a drug delivery system consisting of PLGA microspheres loaded with the natural active ingredient totarol, which has several antimicrobial mechanisms. Totarol, isolated from the Podocarpus totara tree, was purified using column chromatography, and the eluate was checked for purity using thin layer chromatography. The spherically shaped microspheres with mean diameters of 147.21±3.45 µm and 131.14±3.69 µm (totarol-loaded and -unloaded microspheres, respectively) were created using the single emulsion evaporation method. Furthermore, the encapsulation efficiency, in a range of 84.72%±6.68% to 92.36%±0.99%, was measured via UV/vis spectroscopy. In a 90-day in vitro drug release study, the release of totarol was investigated by UV/vis spectroscopy as well, showing a release of 53.76%. The toxicity on cells was determined using BJ fibroblasts or Human Embryonic Kidney cells and an 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, which showed no influence on the cell growth. The minimal inhibitory concentration was ascertained. A totarol concentration between 64 µg/mL and 128 µg/mL was necessary to inhibit the bacterial growth over a period of 24 hours. Biofilm formation on the surface of totarol-loaded microspheres was determined using transmission electron microscopy. No biofilm formation could be detected, even if the totarol concentration was below the minimal inhibitory concentration. The hemocompatibility investigations on various markers with fresh heparinized blood (1.5 IU/mL) showed that totarol and totarol-loaded microspheres have no influence on different blood parameters. The PLGA microspheres characterized by slow release of totarol and great entrapment efficiency represent a novel drug delivery system, which may be highly beneficial for the long-term therapy of bacterial infections.