pH-responsive LBL coated silica nanocarriers for controlled release of chlorhexidine.

As resistant microbial strains continue to appear, antibiotic-based therapies become less effective. Hence, development of non-antibiotic antimicrobial delivery systems, such as those containing chlorhexidine, is urgently needed for the prevention and treatment of infections. For many biological applications as well as for efficient therapy, controlling the release kinetics of these antimicrobials is crucial. In this study, chlorhexidine was loaded into silica nanoparticles via layer-by-layer (LbL) coating technique. Different polyelectrolytes including polyacrylic acid (PAA), poly(diallyldimethylammonium) chloride (PDDA), poly(allylamine hydrochloride) (PAH) and poly(4-styrenesulfonic acid) (PSS) were utilized in LbL coatings. Three types of coatings were studied: (1) PSS and PDDA (2) PAA and PAH (3) PSS and PAH. Zeta potential, transmission electron microscope, and a thermogravimetric analysis were used to characterize the nanoparticles. Acetate buffer pH 5 and PBS pH 7.4 were used as release media to assess the chlorhexidine release from nanoparticles. The chlorhexidine LbL-coated nanoparticles were effective in extending the duration of the medication release to 40 days. Chlorhexidine release was affected by pH of the release media and type of LbL coating, with a greater release at pH 5. PAA and PAH LbL coating had the highest amount of chlorhexidine release. This work illustrates that the LbL coating is an efficient technique for controlling the release of chlorhexidine from silica nanocarriers, with PAA and PAH coat being most effective among other polyelectrolytes tested. Different release profiles can be adapted for a variety of biomedical uses such as orthopedic or dental applications.