Lipid Nanoparticle Enabled Co-Delivery of Tetrahedral DNA Framework and Antimicrobial Peptides

Abstract

In the context of persistent wound infections, the delivery of antimicrobial agents is challenging. The bacterium in skin presents several strategies to avoid antimicrobial exposure by hiding inside cells and via the formation of biofilms. Additionally, several virulence strategies facilitate the progression of persistent bacterial infections. Although antibiotics are considered very advanced, they suffer poor penetration within biofilms and in infected cells. Antimicrobial peptides (AMPs) can work as new drugs to treat persistent infections, but inherent toxicity concerns have restricted clinical applications. In this study, a new lipid nanoparticle system co-loaded with a tetrahedral DNA (TDN) (anti-virulent) and L12 peptide (antimicrobial) was developed. Three formulations, the TDN, TDN loaded lipid nanoparticles (TL) and TDN/peptide co-loaded lipid nanoparticles (TLP) were developed and compared via different techniques. Characterization was performed via DLS and TEM, followed by checking the pH responsiveness of the formulations. The stability of the formulations was monitored over a month. The bactericidal efficiency of the nanoparticle formulations against S. aureus was assessed via time-kill kinetics. According to the findings, the TLP-ET formulation, in which the peptide was dissolved in the lipid phase, exhibited considerable antibacterial activity, while the TLP-AQ formulation, in which the peptide was dissolved in the aqueous buffer, only exhibited weak antimicrobial activity. The TLP-ET formulation with higher drug content, demonstrated an enhanced antibacterial activity which was consistent peptide quantification. Furthermore, it was shown that TDN was successfully encapsulated in the lipid nanoparticles with an entrapment efficiency of 89 ± 6.6%. An enhanced binding affinity of TDN for the autoinducer peptide II (AIPII) (produced by S. aureus) was observed demonstrating its potential anti-virulence property. Overall, this study highlights critical information on formulation design and assessment of TDN/peptide co-loaded lipid nanoparticles to potentially achieve combined antibacterial and anti-virulence effects.