Decoding interactions between biofilms and DNA nanoparticles

Biofilms present a great challenge in antimicrobial therapy due to their inherent tolerance to conventional antibiotics, promoting the need for advanced drug delivery strategies that improve therapy. While various nanoparticles (NPs) have been reported for this purpose, DNA-based NPs remain a largely unexploited resource against biofilm-associated infections. To fill this gap and to lay the groundwork for their potential therapeutic exploitation, we investigated the diffusion, penetration, and retention behaviors of three DNA-based nanocarriers -plain or modified-within <i>P. aeruginosa</i> biofilms. Watson-Crick base pairing or hydrophobic interactions mediated the formation of the plain NPs whilst electrostatic interaction enabled optimization of coated NPs via microfluidic mixing. We assessed the interactions of the nanocarriers with biofilm structures via Single Plane Illumination Microscopy - Fluorescence Correlation Spectroscopy (SPIM-FCS) and Confocal Laser Scanning Microscopy (CLSM). We demonstrate the impact of microfluidic parameters on the physicochemical properties of the modified DNA NPs and their subsequent distinct behaviors in the biofilm. Our results show that single stranded DNA micelles (ssDNA micelle) and tetrahedral DNA nanostructures (TDN) had similar diffusion and penetration profiles, whereas chitosan-coated TDN (TDN-Chit) showed reduced diffusion and increased biofilm retention. This is attributable to the relatively larger size and positive surface charge of the TDN-Chit NPs. The study shows first and foremost that DNA can be used as building block in drug delivery for antibiofilm therapeutics. Moreover, the overall behavioral findings are pivotal for the strategic selection of therapeutic agents to be encapsulated within these structures, possibly affecting the treatment efficacy. This research not only highlights the underexplored potential of DNA-based NPs in antibiofilm therapy but also advocates for further studies using different optimization strategies to refine these nanocarrier systems for targeted treatments in biofilm-related infections.