Electroformation of liposomes and phytosomes using copper electrode

Gymnema saponin-induced lipid flip-flop identifies rigid membrane phenotype of methicillin resistant S. aureus and enhances it's antibiotic susceptibility

Our previous study revealed that lipid flip-flop inducing phytochemicals from Gymnema sylvestre increase membrane permeability of antimicrobials in S. aureus. However, their lipid flipping and membrane permeabilizing effect on methicillin resistant S. aureus (MRSA) membrane that has intrinsically higher aminoacylated lipid content compared to methicillin sensitive S. aureus (MSSA) is poorly characterized. Gymnema saponins, gymnemic acid I and IV significantly increased the antibiotic susceptibility in both MSSA and MRSA. MRSA exhibited a rigid membrane with lipid diffusion coefficient 0.0002 μm2/s compared to the MSSA membrane lipids with diffusion coefficient 1.48 μm2/s. Further, unlike MSSA, MRSA cells inhibited fusion of fluid liposomes with their plasma membrane. In vitro assay on reconstituted membrane vesicles revealed that Gymnema saponins induced 60 % lipid flipping in MSSA membrane compared to only 20 % lipid flipping in MRSA, indicating significantly lower Gymnema saponin-induced trans-bilayer lipid mobility in MRSA. Gymnema saponins induced significantly lower crystal violet uptake, release of cellular protein, cell shrinkage and lysis in MRSA compared to MSSA. Gymnema saponins led to dose-dependent inhibition of lipid-aminoacylation in both MSSA and MRSA making their membranes more negative compared to untreated control cells. In silico analysis reveals binding of both gymnemic acid I and IV to multiple peptide resistance factor (binding energy ∼ 7.5 kCal), the protein responsible for lipid aminoacylation in S. aureus. For the first time, our study reveals that MRSA membrane with higher aminoacyl-PG compared to MSSA shows significantly lower rate of diffusion and trans-bilayer flip-flop of lipids. Further, gymnemic acids are useful probes for identification, characterization and drug sensitization of rigid membrane MRSA phenotypes.

Manufacturing of Liposomes Using a Stainless-Steel Microfluidic Device: An Investigation into Design of Experiments

Liposomes are highly beneficial nanocarrier systems due to their biocompatibility, low toxicity, and exceptional inclusiveness, which lead to improved drug bioavailability. For biological applications, accurate control over these nanoparticles' mean size and size distribution is essential. Micromixers facilitate the continuous production of liposomes, enhancing the precision of size regulation and reproducibility. In this research, the performance of a stainless steel 316L micromixer was evaluated by using COMSOL Multiphysics simulations. The liposomes were precisely optimized using design of experiments techniques in a microfluidic setup, and then dexamethasone sodium phosphate (DSP) was successfully encapsulated in liposome nanoparticles. The physicochemical characteristics of liposomes, such as their ζ-potential, size, DSP loading capacity, encapsulation efficiency, and drug release, were assessed. Transmission electron microscopy and dynamic light scattering analysis were used to examine the structures of the liposomes. The drug release kinetics study was conducted to analyze the drug delivery system, and the Higuchi equation was determined to be the most suitable equation. The microfluidic chip was shown to be capable of creating small-sized liposomes with a size as small as 130 nm, exhibiting monodispersed characteristics and low polydispersity liposome populations.

Lipid Flip-Flop-Inducing Antimicrobial Phytochemicals from Gymnema sylvestre are Bacterial Membrane Permeability Enhancers

An amphiphilic phytochemical fraction isolated from methanol extract of Gymnema sylvestre leaf powder contained six terpenoids, two flavonoids, and one alkaloid that induced rapid flip-flop of fluorescent phospholipid analog in the phosphatidyl choline bilayer. Lipid-flipping activity of the methanol-extracted fraction of G. sylvestre (MEFGS) was dose-dependent and time-dependent with a rate constant k = (12.09 ± 0.94) mg^-1 min^-1 that was saturable at (40 ± 1) % flipping of the fluorescent lipid analogue. Interactions of MEFGS phytochemicals with large unilamelar vesicles led to time-dependent change in their rounded morphology into irregular shapes, indicating their membrane-destabilizing activity. MEFGS exhibited antibacterial activity on Escherichia coli (MTCC-118), Staphylococcus aureus (MTCC-212), and Pseudomonas aeruginosa (MTCC-1035) with IC₅₀ values 0.5, 0.35, and 0.1 mg/mL, respectively. Phytochemicals in MEFGS increased membrane permeabilization in all three bacteria, as indicated by 23, 17, and 17% increase in the uptake of crystal violet, respectively. MEFGS enhanced membrane damage, resulting in a 3-5 fold increase in leakage of cytosolic ions, 0.5-2 fold increase in leakage of PO₄ ^-, and 15-20% increase in loss of cellular proteins. MEFGS synergistically increased the efficacy of curcumin, amoxillin, ampicillin, and cefotaxime on S. aureus probably by enhancing their permeability into the bacterium. For the first time, our study reveals that phytochemicals from G. sylvestre enhance the permeability of the bacterial plasma membrane by facilitating flip-flop of membrane lipids. Lipid-flipping phytochemicals from G. sylvestre can be used as adjuvant therapeutics to enhance the efficacy of antibacterials by increasing their bioavailability in the target bacteria.

Giant Unilamellar Vesicle Electroformation: What to Use, What to Avoid, and How to Quantify the Results

Since its inception more than thirty years ago, electroformation has become the most commonly used method for growing giant unilamellar vesicles (GUVs). Although the method seems quite straightforward at first, researchers must consider the interplay of a large number of parameters, different lipid compositions, and internal solutions in order to avoid artifactual results or reproducibility problems. These issues motivated us to write a short review of the most recent methodological developments and possible pitfalls. Additionally, since traditional manual analysis can lead to biased results, we have included a discussion on methods for automatic analysis of GUVs. Finally, we discuss possible improvements in the preparation of GUVs containing high cholesterol contents in order to avoid the formation of artifactual cholesterol crystals. We intend this review to be a reference for those trying to decide what parameters to use as well as an overview providing insight into problems not yet addressed or solved.