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In the advent of the post-antibiotic era, new strategies are urgently required to improve the efficacy of antimicrobials and outsmart multi-drug resistant bacteria. Exploiting a basic survival mechanism of bacteria, lipase production, monoolein liquid crystal nanoparticles (MO-LCNPs) were investigated as a bacterial-triggered drug delivery system for three different antimicrobial compounds and compared with model sn-1/3 regiospecific and non-regiospecific lipases via pH-stat titration, proton nuclear magnetic resonance and in situ synchrotron small-angle X-ray scattering. The release of model hydrophobic (rifampicin) and macromolecular (alginate lyase) antimicrobials were triggered from MO-LCNPs at 82-fold and 7-fold higher rates (respectively) due to bacterial lipase digestion of MO-LCNPs, which could not be stimulated with a small hydrophilic antibiotic (ciprofloxacin HCl) or non-digestible, phytantriol-LCNPs. While sn-1/3 regiospecific lipase rapidly digested MO-LCNPs in a two-phase process, the single-phase digestion kinetics of the non-regiospecific lipase steadily digested the cubic Im3m structure and gave rise to lamellar structures that ultimately stimulated the triggered antibiotic release. Accordingly, MO-LCNPs have an application for localised Pseudomonas aeruginosa and Staphylococcus aureus infections that produce non-regiospecific lipases and for concentration-dependent antibiotics that have macromolecular (MW ~ 30 kDa) or hydrophobic (logP ~ 4) chemistries, as a triggered bolus release would be clinically efficacious for improved bacterial eradication. Refereed/Peer-reviewed

Staphylococcal biofilms cause many infectious diseases and are highly tolerant to the effects of antimicrobials;this is partly due to the biofilm matrix, which acts as a physical barrier retarding the penetration and reducing susceptibility to antimicrobials, thereby decreasing successful treatment outcomes. In this study, both single and mixed micellar systems based on poly vinyl caprolactam (PCL)-polyethylene glycol (PEG) copolymers were optimised for delivery of chlorhexidine (CHX) to S. aureus, MRSA and S. epidermidis biofilms and evaluated fortheir toxicity using Caenorhabditis elegans. The respective polyethylene glycol (PEG) and poly vinyl caprolactam(PCL) structural components promoted stealth properties and enzymatic responsive release of CHX inside biofilms,leading to significantly enhanced penetration (56%) compared with free CHX and improving the efficacy against Staphylococcus aureus biofilms grown on an artificial dermis (2.4 log reduction of CFU). Mixing Soluplus-based micelles with Solutol further enhanced the CHX penetration (71%) and promoted maximumr eduction in biofilm biomass (> 60%). Nematodes-based toxicity assay showed micelles with no lethal effects as indicated by their high survival rate (100%) after 72 h exposure. This study thus demonstrated that bio-responsivecarriers can be designed to deliver a poorly water-soluble antimicrobial agent and advance the controlof biofilm associated infections. Refereed/Peer-reviewed

The deposition of pre-metered doses (i.e., defined before and not after exposition) at the air–liquid interface of viable pulmonary epithelial cells remains an important but challenging task for developing aerosol medicines. While some devices allow quantification of the deposited dose after or during the experiment, e.g., gravimetrically, there is still no generally accepted way to deposit small pre-metered doses of aerosolized drugs or pharmaceutical formulations, e.g., nanomedicines. Here, we describe a straightforward custom-made device, allowing connection to commercially available nebulizers with standard cell culture plates. Designed to tightly fit into the approximately 12-mm opening of either a 12-well Transwell® insert or a single 24-well plate, a defined dose of an aerosolized liquid can be directly deposited precisely and reproducibly (4.8% deviation) at the air–liquid interface (ALI) of pulmonary cell cultures. The deposited dose can be controlled by the volume of the nebulized solution, which may vary in a range from 20 to 200 μl. The entire nebulization-deposition maneuver is completed after 30 s and is spatially homogenous. After phosphate-buffered saline (PBS) deposition, the viability and barrier properties transepithelial electrical resistance (TEER) of human bronchial epithelial Calu-3 cells were not negatively affected. Straightforward in manufacture and use, the device enables reproducible deposition of metered doses of aerosolized drugs to study the interactions with pulmonary cell cultures grown at ALI conditions.

Pseudomonas aeruginosa biofilms cause persistent and chronic infections, most known clinically in cystic fibrosis (CF). Tobramycin (TOB) is a standard anti-pseudomonal antibiotic; however, in biofilm infections, its efficacy severely decreases due to limited permeability across the biofilm matrix. Herewith, a biomimetic, nanostructured, lipid liquid crystal nanoparticle-(LCNP)-formulation is discovered to significantly enhance the efficacy of TOB and eradicate P. aeruginosa biofilm infections. Using an advanced, biologically-relevant co-culture model of human CF bronchial epithelial cells infected with P. aeruginosa biofilms at an air–liquid interface, nebulized TOB-LCNPs completely eradicated 1 × 109 CFU mL−1 of P. aeruginosa after two doses, a 100-fold improvement over the unformulated antibiotic. The enhanced activity of TOB is not observed with a liposomal formulation of TOB or with ciprofloxacin, an antibiotic that readily penetrates biofilms. It is demonstrated that the unique nanostructure of the LCNPs drives the enhanced penetration of TOB across the biofilm barrier, but not through the healthy lung epithelium barrier, significantly increasing the available antibiotic concentration at the site of infection. The LCNPs are an innovative strategy to improve the performance of TOB as a directed pulmonary therapy, enabling the administration of lower doses, reducing the toxicity, and amplifying the anti-biofilm activity of the anti-pseudomonal antibiotic. Refereed/Peer-reviewed

Bacterial infections are an imminent global healthcare threat evolving from rapidly advancing bacterial defence mechanisms that antibiotics fail to overcome. Antibiotics have been designed for systemic administration to target planktonic bacteria, leading to difficulties in reaching the site of localized bacterial infection and an inability to overcome the biological, chemical and physical barriers of bacteria, including biofilms, intracellular infections and antimicrobial resistance. The amphiphilic, biomimetic and antimicrobial properties of lipids provide a promising toolbox to innovate and advance antimicrobial therapies, overcoming the barriers presented by bacteria in order to directly and effectively treat recalcitrant infections. Nanoparticulate lipid-based drug delivery systems can enhance antibiotic permeation through the chemical and physical barriers of bacterial infections, as well as fuse with bacterial cell membranes, release antibiotics in response to bacteria and act synergistically with loaded antibiotics to enhance the total antimicrobial efficacy. This review explores the barriers presented by bacterial infections that pose bio-pharmaceutical challenges to antibiotics and how different structural and functional mechanisms of lipids can enhance antimicrobial therapies. Different nanoparticulate lipid-based systems are presented as valuable drug delivery systems to advance the efficacy of antibiotics, including liposomes, liquid crystalline nanoparticles, solid lipid nanoparticles, nanostructured lipid carriers and lipid nanocarriers. In summary, liquid crystalline nanoparticles are emerging with the greatest potential for clinical applications and commercial success as an “all-rounder” advanced lipid-based antimicrobial therapy that overcomes the multiple biological, chemical and physical barriers of bacteria. Refereed/Peer-reviewed

Bacterial biofilms account for up to 80% of all communityacquired infections for which bacterial eradication is currently not achievable using conventional antimicrobial treatments. The protective matrix that engulfs biofilm-associated bacteria frequently renders antibiotics ineffective. Glycoside hydrolases are a class of enzymes that break down the biofilm matrix, thereby increasing the effectiveness of antibiotics. Herein, nanostructured liquid crystals composed of glyceryl monooleate (GMO) were investigated as an infection responsive delivery system for alginate lyase (glycoside hydrolase) and gentamicin (antibiotic) to treat Pseudomonas biofilms. The presence of Pseudomonas lipase triggered the release of alginate lyase and gentamicin from the GMO liquid crystals. Treatment with the liquid crystals containing alginate lyase and gentamicin resulted in a greater than 2-log reduction in mucoid Pseudomonas aeruginosa (clinical isolate) biofilm. The anti-biofilm activity of alginate lyase and gentamicin from the liquid crystals was sustained for 2 days and equivalent to the respective unformulated solution treatments. Accordingly, GMO based liquid crystals are a promising responsive delivery system for alginate lyase and gentamicin to combat topical Pseudomonas infections Refereed/Peer-reviewed

Bacterial biofilms are associated with a number of recurring infectious diseases and are a majorcause for antibiotic resistance. Despite the broad use of polymeric microparticles and nanoparticles in biomedical research it is not clear which particle size is more effective against biofilms. The purpose of this study was to evaluate the efficacy of sustained release poly-lactic-co-glycolic acid(PLGA) micro- and nanoparticles containing ciprofloxacin against biofilms of Staphylococcus aureus and Pseudomonas aeruginosa The PLGA particles were prepared by the double emulsion solvent evaporation method. The resulting microparticles (12 μm) and nanoparticles (300 nm) contained drug loads of 7.3% and 4.5%(w/w) ciprofloxacin, respectively. Drug release was complete within one week following comparable release profiles for both particle sizes. Micro- and nanoparticles demonstrated a similar in vitro antibiofilm performance against mature P. aeruginosa and S. aureus with marked differences between the two strains. The sustained release of ciprofloxacin from micro- and nanoparticles over 6 days was equally effective as the continuous treatment with ciprofloxacin solution over the same period resulting in the eradication of culturable S. aureus suggesting that reformulation of ciprofloxacin as sustained release PLGA micro- and nanoparticles might be valuable formulation approaches for the treatment of biofilms. Refereed/Peer-reviewed