Abstract
Propolis obtained from bee hives is a natural substance with antimicrobial properties. It is limited by its insolubility in aqueous solutions; hence ethanol and ethyl acetate extracts of Malaysian propolis were prepared. Both the extracts displayed antimicrobial and anti-biofilm properties against Enterococcus faecalis, a common bacterium associated with hospital-acquired infections. High performance liquid chromatography (HPLC) analysis of propolis revealed the presence of flavonoids like kaempferol and pinocembrin. This study investigated the role of propolis developed into nanoparticles with chitosan for its antimicrobial and anti-biofilm properties against E. faecalis. Bacteria that grow in a slimy layer of biofilm are resistant to penetration by antibacterial agents. The use of nanoparticles in medicine has received attention recently due to better bioavailability, enhanced penetrative capacity and improved efficacy. A chitosan-propolis nanoformulation was chosen based on ideal physicochemical properties such as particle size, zeta potential, polydispersity index, encapsulation efficiency and the rate of release of the active ingredients. This formulation inhibited E. faecalis biofilm formation and reduced the number of bacteria in the biofilm by ~90% at 200 μg/ml concentration. When tested on pre-formed biofilms, the formulation reduced bacterial number in the biofilm by ~40% and ~75% at 200 and 300 μg/ml, respectively. The formulation not only reduced bacterial numbers, but also physically disrupted the biofilm structure as observed by scanning electron microscopy. Treatment of biofilms with chitosan-propolis nanoparticles altered the expression of biofilm-associated genes in E. faecalis. The results of this study revealed that chitosan-propolis nanoformulation can be deemed as a potential anti-biofilm agent in resisting infections involving biofilm formation like chronic wounds and surgical site infections.
Highlights
Nanoparticles are widely used in healthcare sector as well as industry for varied applications including antimicrobials [1]
The extracts were analyzed by RP-High performance liquid chromatography (HPLC) using eight flavonoids as standard markers
Propolis nanoparticles as anti-biofilm agents anti-bacterial effect, which can be attributed to their highest content of phenolics and flavonoids [42], which validates our findings that Eth extract is more effective than ethyl acetate (EA) extract in terms of anti-bacterial effect
Summary
Nanoparticles are widely used in healthcare sector as well as industry for varied applications including antimicrobials [1]. In medicine, they are used as drug carriers encapsulating a broad range of therapeutic agents such as siRNA, drug molecules, proteins and peptides [2,3,4] leading to more efficient drug delivery into the target site. The choice of the carrier in a nanoparticle delivery system is crucial since it can affect protection, retention and bioavailability of the drug or the natural active ingredient. Its non-toxic and non-immunogenic properties make it an ideal delivery agent for topical as well as systemic applications in medicine for treatment against microbial infections
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