Altering Escherichia coli envelope integrity by mimicking the lipoprotein RcsF.

Escherichia coli cell envelope is crucial for stress sensing and signal transduction, mediated by numerous protein-protein interactions to enable adaptation and survival. Interfering with these interactions might affect envelope integrity leading to bacterial death. The outer membrane lipoprotein (RcsF) is the stress sensor of the regulator of capsule synthesis (Rcs) phosphorelay that senses envelope threats. RcsF interacts with two essential proteins, IgaA (repressing the Rcs system) and BamA (inserting ß-barrel proteins in the outer membrane). Disturbing RcsF interactions may alter Rcs signaling and/or membrane integrity thus affecting bacterial survival. Here, we derived the sequence of a peptide mimicking RcsF (RcsFmim), based on the in silico docking of RcsF with IgaA. Expression of rcsFmim caused 3-to-4-fold activation of the Rcs system and perturbation of the outer membrane. Both effects result in decreased E. coli growth rate. We anticipate that RcsFmim present a candidate for future antibacterial peptide development.

Curcumin Transferosome-Loaded Thermosensitive Intranasal in situ Gel as Prospective Antiviral Therapy for SARS-Cov-2.

Purpose: Immunomodulatory and broad-spectrum antiviral activities have motivated the evaluation of curcumin for Coronavirus infection 2019 (COVID-19) management. Inadequate bioavailability is the main impediment to the therapeutic effects of oral Cur. This study aimed to develop an optimal curcumin transferosome-loaded thermosensitive in situ gel to improve its delivery to the lungs. Methods: Transferosomes were developed by using 33 screening layouts. The phospholipid concentration as well as the concentration and type of surfactant were considered independent variables. The entrapment efficiency (EE%), size, surface charge, and polydispersity index (PDI) were regarded as dependent factors. A cold technique was employed to develop thermosensitive in-situ gels. Optimized transferosomes were loaded onto the selected gels. The produced gel was assessed based on shape attributes, ex vivo permeability enhancement, and the safety of the nasal mucosa. The in vitro cytotoxicity, antiviral cytopathic effect, and plaque assay (CV/CPE/Plaque activity), and in vivo performance were evaluated after intranasal administration in experimental rabbits. Results: The optimized preparation displayed a particle size of 664.3 ± 69.3 nm, EE% of 82.8 ± 0.02%, ZP of -11.23 ± 2.5 mV, and PDI of 0.6 ± 0.03. The in vitro curcumin release from the optimized transferosomal gel was markedly improved compared with that of the free drug-loaded gel. An ex vivo permeation study revealed a significant improvement (2.58-fold) in drug permeability across nasal tissues of sheep. Histopathological screening confirmed the safety of these preparations. This formulation showed high antiviral activity against SARS-CoV-2 at reduced concentrations. High relative bioavailability (226.45%) was attained after the formula intranasally administered to rabbits compared to the free drug in-situ gel. The curcumin transferosome gel displayed a relatively high lung accumulation after intranasal administration. Conclusion: This study provides a promising formulation for the antiviral treatment of COVID-19 patients, which can be evaluated further in preclinical and clinical studies.

Self-assembled tannic acid complexes for pH-responsive delivery of antibiotics: Role of drug-carrier interactions.

Self-assembled particles, based on non-covalent interactions, are attractive drug carriers with a relatively simple structure and easy preparation. Tannic acid (TA) is an anionic polyphenolic compound with a wide range of molecular interactions and diverse applications in drug delivery research. Here, we propose the use of TA complexes with cationic antibiotics as a new pH-responsive drug carrier of high drug loading and optimal stability. TA complexes were prepared with three water-soluble antibiotics; colistin sulfate (COL), gentamicin sulfate (GEN) and gatifloxacin (GAT). Complexes' size ranged from several-hundred nanometers to few microns. For selected particles, drug loading ranged from 30 to 36%. Importantly, we demonstrate the impact of drug-carrier interactions, studied via infrared spectroscopy and molecular modeling, on final complex stability and performance; the complexes resisted dissociation in presence of serum at physiological pH to variable degrees and showed different drug release profiles. However, all complexes dissociated upon medium acidification, releasing their drug payload and demonstrating expected antibacterial effect. These results demonstrate that TA/antibiotic self-assembled complexes represent an excellent carrier for pH-sensitive delivery of water-soluble drugs. In addition to system's simplicity and low cost, complexes were easily prepared with high drug loading and desirable pH-dependent association/dissociation profile.

Synthesis, antimicrobial activity and molecular modeling study of 3-(5-amino-(2H)-1,2,4-triazol-3-yl]-naphthyridinones as potential DNA-gyrase inhibitors.

Four series of triazolylnaphthyridinone derivatives were synthesized as structural surrogates of nalidixic acid. The targeted derivatives involve: 3-(5-acylamino-2H-1,2,4-triazol-3-yl)-naphtyridin-4-ones 6(a-e); 3-(5-benzylidineamino-2H-1,2,4-triazol-3-yl)-naphthyridin-4-ones 8(a-g) and their 6-bromonaphthyridin-4-one analogs 7(a-e); 9(a-g). The synthesized compounds were evaluated In vitro for their antimicrobial activity against selected resistant strains of G+ve, G-ve, and Mycobacterium phlei. The results revealed remarkable selectivity, of the tested compounds, against Bacillus subtilis and Aggregatibacter actinomycetemcomitans, which are resistant to nalidixic acid. The growth inhibition zones were ranging from 20 to 40 mm at 10 mg/ml and the respective MIC-values ∼3.68-6.3 µM. The results illustrate that the 6-bromo derivatives 7(a-e) and 9(a-g) were more potent than the non-brominated counterparts 6(a-e) and 8(a-e) respectively. Inhibition of E. coli DNA-gyrase supercoiling activity is also evaluated. The 5-(4-methoxybanzamido)-triazolyl-6-bromonaphthyridinone (7e) exhibits IC50 = 1.94 µg/ml, which is comparable to that of nalidixic acid (IC50: 1.74 µg/ml). In addition, the most prominent IC50-values are displayed by: (7a;IC50: 2.77 µg/ml); (8g; IC50: 3.78 µg/ml); and (9d;IC50: 3.21 µg/ml). Molecular docking to the active site of DNA-gyrase cleavage complex of Acinetobacter baumannii (PDB code: 2xkk) co-crystallized with moxifloxacin revealed similar binding modes in addition to new interactions. Assessment of drug-likeness characteristics illustrate that the synthesized compounds showed agreement to Lipinski's and Veper's parameters. The study could offer an exceptional framework that may lead to the discovery of new potent antimicrobial agents.