Impact of Site-Specific Bioconjugation on the Interfacial Activity of a Protein Biosurfactant

Development of nanoemulsions for the delivery of hydrophobic and hydrophilic compounds against carbapenem-resistant Klebsiella pneumoniae

Antimicrobial resistance (AR), particularly the limited antimicrobial activities of antibiotics and natural compounds, has prompted research into new antimicrobials. Nanoemulsions (NEs) have been found to improve the activity of antimicrobial compounds. This study developed clove essential oil-in-water NEs (CEO-NEs) and water-in-oil-in-water NEs co-encapsulating CEO and meropenem (CEO-MEM-NEs) to investigate the antibacterial activity of these loaded NEs against carbapenem-resistant Klebsiella pneumoniae. Ultrasonication was used to prepare CEO-NEs and CEO-MEM-NEs. Tween 80 and Imwitor 375 surfactants were used to produce CEO-NEs while Tween 80, Imwitor 375, and PGPR were used to produce CEO-MEM-NEs. Droplets' sizes were 138 ± 1.769 and 183.600 ± 0.889 for CEO-NEs and CEO-MEM-NEs, respectively. The resultant NEs were monodispersed, negatively charged, and physically stable. The antibacterial activities of NEs were investigated using broth microdilution, checkerboard, and time-kill assays to determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). CEO-NEs (0.16% CEO MIC) and CEO-MEM-NEs (0.08% CEO and 1 μg mL-1 MEM MICs) completely inactivated K. pneumoniae, and showed functional stability after two weeks of storage at 4 °C. In conclusion, the formulated NEs significantly enhanced the antibacterial activity of CEO and MEM and have great potential as delivery systems of antimicrobial compounds.

Nanoemulsions: Formulation, characterization, biological fate, and potential role against COVID-19 and other viral outbreaks

Viral diseases are emerging as global threats. Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), that causes coronavirus disease (COVID-19), has severe global impacts. Safety, dosage, and potency of vaccines recently approved for emergency use against SARS-CoV-2 need further evaluation. There is still no effective treatment against COVID-19; therefore, safe, and effective vaccines or therapeutics against SARS-CoV-2 are urgently needed. Oil-in-water nanoemulsions (O/W NEs) are emerging as sophisticated, protective, and therapeutic platforms. Encapsulation capacity, which offers better drug pharmacokinetics, coupled with the tunable surfaces present NEs as promising tools for pharmaceutical applications. The challenges facing drug discovery, and the advancements of NEs in drug delivery demonstrate the potential of NEs against evolving diseases, like COVID-19. Here we summarize current COVID-19 knowledge and discuss the composition, stability, preparation, characterization, and biological fate of O/W NEs. We also provide insights into NE structural-functional properties that may contribute to therapeutic or preventative solutions against COVID-19.

Droplet shape control using microfluidics and designer biosurfactants

Many uses of emulsion droplets require precise control over droplet size and shape. Here we report a 'shape-memorable' micro-droplet formulation stabilized by a polyethylene glycol (PEG)-modified protein -surfactant, the droplets are stable against coalescence for months and can maintain non-spherical shapes for hours, depending on the surface coverage of PEGylated protein. Monodisperse droplets with aspect ratios ranging from 1.0 to 3.4 were controllably synthesized with a flow-focusing microfluidic device. Mechanical properties of the interfacial protein network were explored to elucidate the mechanism behind the droplet shape conservation phenomenon. Characterization of the protein film revealed that the presence of a PEG layer at interfaces alters the mechanical responses of the protein film, resulting in interfacial networks with improved strength. Taking advantage of the prolonged stabilization of non-spherical droplets, we demonstrate functionalization of the droplet interface with accessible biotins. The stabilization of micro-droplet shape with surface-active proteins that also serve as an anchor for integrating functional moieties, provides a tailorable interface for diverse biomimetic applications.