(670e) Chitosan-Coated Selenium Nanoparticles for Anti-Acne Applications

Introduction: The skin is the bodyâ??s strongest form of protection against infectious and pathogenic microbes, and when this barrier is perforated by wounds, lesions or other chronic skin conditions, the body is vulnerable to more serious diseases. Among these skin diseases, acne vulgaris is one of the most prevalent, affecting up to 95% of all adolescents and persisting in up to 10% of adults. Proprionibacterium acnes has been suggested as the main contributor to acne vulgaris. Our lab has synthesized selenium nanoparticles to combat bacterial infection, and have found them to be effective against several bacterial strains, and relatively non-toxic to healthy fibroblasts and other mammalian cells. Here, to make such particles suitable for skin applications, we employed a new synthesis of chitosan-coated selenium nanoparticles as an effective topical treatment for P. acnes, as well as common skin denizens, such as S. aureus, while preserving the healthy skin tissue surrounding the acne lesions.

Materials and Methods: Chitosan-coated selenium nanoparticles (Ch-SeNP) were synthesized in a precipitation reaction, in which chitosan (dissolved in 1% acetic acid) was added dropwise to sodium selenite solution, followed by an addition of ascorbic acid. The resulting Ch-SeNP are separated via centrifugation and resuspended in DI water. Characterization was performed via dynamic light scattering and transmission electron microscopy. P. acnes (ATCC 11827) were cultured in modified reinforced clostridial broth medium or on tripticase soy agar plates with defibrinated sheep blood, while S. aureus was cultured in 3% tryptic soy broth or on agar plates. For S. aureus, kinetic growth curves were tracked by measuring the optical densities of treated cultures via spectrophotometry over 24 hrs. P. acnes, an anaerobic bacterium, required anaerobic conditions to grow, and were thus tested via a colony-forming unit assay in anaerobic gas chambers over 4 days. All experiments were repeated three times, and statistical significance were analyzed via a two-talked Studentâ??s T-test.

Results and Discussion: Ch-SeNP were found to be as effective, if not more, as antibacterial agents as the previously studied BSA-coated SeNP on S. aureus, with lag times lengthening as Ch-SeNP concentrations increased. At a mid-range concentration of Ch-SeNP (0.023 mg/ml), P. acnes growth was completely absent compared to untreated colonies, suggesting that Ch-SeNP were strongly effective at preventing P. acnes proliferation.

Conclusions: Chitosan-coated selenium nanoparticles were found here to be exceedingly more stable in solution than their BSA-coated predecessors without sacrificing their antibacterial efficacy. Additionally, we found the Ch-SeNP to be effective in preventing the proliferation of the anaerobe P. acnes, suggesting a novel SeNP application in topical skin infections.

Acknowledgements: The authors thank Northeastern University and the College of Engineering for funding.