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  • Title: Surface-Adaptive, Antimicrobially Loaded, Micellar Nanocarriers with Enhanced Penetration and Killing Efficiency in Staphylococcal Biofilms.
    Author: Liu Y, Busscher HJ, Zhao B, Li Y, Zhang Z, van der Mei HC, Ren Y, Shi L.
    Journal: ACS Nano; 2016 Apr 26; 10(4):4779-89. PubMed ID: 26998731.
    Abstract:
    Biofilms cause persistent bacterial infections and are extremely recalcitrant to antimicrobials, due in part to reduced penetration of antimicrobials into biofilms that allows bacteria residing in the depth of a biofilm to survive antimicrobial treatment. Here, we describe the preparation of surface-adaptive, Triclosan-loaded micellar nanocarriers showing (1) enhanced biofilm penetration and accumulation, (2) electrostatic targeting at acidic pH toward negatively charged bacterial cell surfaces in a biofilm, and (3) antimicrobial release due to degradation of the micelle core by bacterial lipases. First, it was established that mixed-shell-polymeric-micelles (MSPM) consisting of a hydrophilic poly(ethylene glycol) (PEG)-shell and pH-responsive poly(β-amino ester) become positively charged at pH 5.0, while being negatively charged at physiological pH. This is opposite to single-shell-polymeric-micelles (SSPM) possessing only a PEG-shell and remaining negatively charged at pH 5.0. The stealth properties of the PEG-shell combined with its surface-adaptive charge allow MSPMs to penetrate and accumulate in staphylococcal biofilms, as demonstrated for fluorescent Nile red loaded micelles using confocal-laser-scanning-microscopy. SSPMs, not adapting a positive charge at pH 5.0, could not be demonstrated to penetrate and accumulate in a biofilm. Once micellar nanocarriers are bound to a staphylococcal cell surface, bacterial enzymes degrade the MSPM core to release its antimicrobial content and kill bacteria over the depth of a biofilm. This constitutes a highly effective pathway to control blood-accessible staphylococcal biofilms using antimicrobials, bypassing biofilm recalcitrance to antimicrobial penetration.
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