Background and Aim: Resistance to antifungal agents is a serious public health concern that has not been investigated enough because most studies on antimicrobials are dedicated to antibacterial resistance. This study aimed to synthesize silver nanoparticles (AgNPs) using Aloe vera extract, and to assess its antifungal activity against Candida albicans. Materials and Methods: Silver nanoparticles were synthesized by reducing Ag nitrate with aqueous A. vera extracts. Physicochemical properties of synthesized AgNPs were determined by ultraviolet–visible spectrophotometry, photon cross-correlation spectroscopy, energy-dispersive X-ray fluorescence spectrometry, X-ray diffraction analysis, and Fourier-transform infrared spectroscopy. An antifungal investigation was performed against four clinical C. albicans (C1, C2, C3, and C4) and a reference strain, C. albicans ATCC 10321. Results: Cubic AgNPs with a mean X50 hydrodynamic diameter of 80.31 ± 10.03 nm were successfully synthesized. These AgNPs exhibited maximum absorbance at 429.83 nm, and X-ray fluorescence (XRF) confirmed the presence of Ag in AgNPs solution by a characteristic peak in the spectrum at the Ag Kα line of 22.105 keV. Infrared spectra for AgNPs and A. vera extract indicated that the compounds present in the extract play an essential role in the coating/capping of synthesized AgNPs. Different concentrations (200, 100, 50, 25, 10, and 5 μg/mL) of AgNPs were tested. The antifungal activity was shown to be dose-dependent with inhibition zones ranging from 10 mm to 22 mm against C. albicans ATCC 10231, 0 mm to 15 mm against C1, 0 mm to 16 mm against C2 and C3, and 0 mm to 14 mm for C4. Minimum inhibitory concentration ranged from 16 μg/mL to 32 μg/mL against clinical C. albicans (C1, C2, C3, and C4) and was 4 μg/mL against C. albicans ATCC 10231. Conclusion: This study showed the ability of A. vera to serve as an efficient reducing agent for the biogenic synthesis of AgNPs with excellent antifungal activity.

The complexation of biogenic molecules with metals is the widespread strategy in screening for new pharmaceuticals with improved therapeutic and physicochemical properties. This paper demonstrates the possibility of using simple QSAR modeling based on topological descriptors for chelates study. The presence of a relationship between the structure (J) and lipophilic properties (logP) of zinc complexes with amino acids, where two molecules coordinate the central atom through carboxyl oxygen and amino group nitrogen, and thus form a double ring structure, was predicted. Using a cellular biosensor model for Gly, Ala, Met, Val, Phe and their complexes Zn(AA)₂, we experimentally confirmed the existence of a direct relationship between logP and biological activity (Ea). The results obtained using topological analysis, Spirotox method and microbiological testing allowed us to assume and prove that the chelate complex of zinc with methionine has the highest activity of inhibiting bacterial biofilms, while in aqueous solutions it does not reveal direct antibacterial effect.

Background and Aim: Antibiotic resistance, especially in Gram-negative bacteria, is a major public health risk affecting all industries requiring the use of antibiotics, including agriculture and animal breeding. This study aimed to use papaya extracts to synthesize silver nanoparticles (AgNPs) and evaluate their antimicrobial activity against various Gram-negative bacteria. Materials and Methods: Silver nanoparticles were synthesized from the aqueous extracts of papaya seed, root, and bark, with AgNO3 used as a reducing agent. The phytofabricated AgNPs were analyzed by ultraviolet–visible absorbance, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy, and photon cross-correlation spectroscopy (PCCS). The disc-diffusion method was used to perform antibacterial analysis, and the minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations were determined. We also investigated the antibiofilm activity of AgNPs and attempted to elucidate the potential mechanism of action on Escherichia coli ATCC 25922. Results: Phytofabrication of AgNPs was successful with papaya root (PR-AgNPs) and papaya seed (PS-AgNPs), but not with papaya bark. Silver nanoparticles using papaya root and PS-AgNPs were both cubic and showed maximum absorbances of 2.6 and 0.3 AUs at 411.6 and 416.8 nm wavelengths and average hydrodynamic diameters X50 of 59.46 ± 7.03 and 66.57 ± 8.89 nm, respectively. The Ag in both AgNPs was confirmed by X-ray fluorescence by a distinctive peak in the spectrum at the silver Ka line of 22.105 keV. Both AgNPs exhibited broad-spectrum antimicrobial and antibiofilm activity against all Gram-negative bacteria, and PR-AgNPs were slightly better than AgNPs-PS. The MIC ranged from 16 µg/mL–28 µg/mL and 16 µg/mL–64 µg/mL, respectively, for PS-AgNPs and PR-AgNPs. The elucidation of the mechanism of action revealed interference with E. coli ATCC 25922 growth kinetics and inhibition of HM+-ATPase proton pumps. Conclusion: Papaya seed and root extracts were efficient reducing agents for the biogenic synthesis of AgNPs, with noteworthy antibacterial and antibiofilm activities. Future studies should be conducted to identify the phytochemicals and the mechanism involved in AgNPs synthesis. Keywords: antibiotic resistance, biogenic synthesis, Carica papaya, Gram-negative, silver nanoparticles.

In this study, using the Box–Behnken model, we optimized the ethanolic extraction of phytochemicals from Enantia chloranta bark for the first time, assessed the composition with HPLC-MS/MS, performed the green synthesis of silver nanoparticles (AgNPs) and characterized them with UV-Vis spectrophotometry, photon cross-correlation spectroscopy, energy-dispersive X-ray fluorescence spectrometry, and Fourier transform infrared spectroscopy. The antibacterial and antibiotic-resistance reversal properties of optimized extract (O-ECB) and AgNPs were assessed on various microorganisms (15 Gram−, 7 Gram+, and 2 fungi) using the well diffusion method and microbroth dilution assay. The mechanism of action was investigated on growth kinetic and proton pumps of Escherichia coli. The in vivo antimicrobial activity and toxicity were assessed on Galleria mellonella larvae. The optimal mass yield (14.3%) related to the highest antibacterial activity (31 mm vs. S. aureus ATCC 6538) was obtained with the following operating conditions: % EtOH—100%; ratio m/v—20 g/mL; and extraction time—6 h. All the compounds identified in O-ECB were alkaloids and the major constituents were palmatine (51.63%), columbamine +7,8-dihydro-8-hydroxypalmatine (19.21%), jatrorrhizine (11.02%), and pseudocolumbamine (6.33%). Among the minerals found in O-ECB (S, Si, Cl, K, Ca, Mn, Fe, Zn, and Br), Br, Fe, and Cl were the most abundant with mean fluorescence intensities of 4.6529, 3.485,4, and 2.5942 cps/uA, respectively. The synthesized AgNPs revealed a strong absorption plasmon band between 430 and 450 nm and an average hydrodynamic diameter ×50 of 59.74 nm, and the presence of Ag was confirmed by a characteristic peak in the spectrum at the silver Kα line of 22.105 keV. Both O-ECB and AgNPs displayed noteworthy and broad-spectrum antimicrobial activities against 20/24 and 24/24 studied microorganisms, respectively, with recorded minimal inhibitory concentrations (MICs) ranging from 8 to ≥1024 µg/mL and 2 to 64 µg/mL. O-ECB and AgNPs showed antibiofilm properties and significantly enhanced the efficacy of conventional antibiotics against selected multidrug-resistant bacteria, and the mechanistic investigations revealed their interference with bacterial growth kinetic and the inhibition of H+-ATPase proton pumps. LD50s were 40 mg/mL and 0.6 mg/mL for O-ECB and AgNPs, respectively. In conclusion, the current study provides a strong experimental baseline to consider Enantia chlorantha bark and their green synthetized AgNPs as potent antimicrobial compounds in this era of antimicrobial resistance.

Objective: To investigate kinetic changes in the spectral characteristics by Fourier Transform Infrared spectroscopy (FTIR) of water-lactose complexes (SMC), derived during the manufacturing process of the drug, containing release-active forms of antibodies. Methods: lactose monohydrate substance, saturated with release-active forms of affinity-purified polyclonal rabbit antibodies to recombinant human interferon-gamma (RA forms of Abs); tablets produced from this substance by direct compression after the addition of excipients (microcrystalline cellulose, magnesium stearate). Powdered and tableted placebo samples saturated with technologically processed water or phosphate-buffered saline, as well as with intact ethanol were used as control. Kinetic changes in SMC were studied using an Agilent Cary 630 FTIR spectrophotometer with a diamond ATR accessory (Agilent Technologies, USA). We used the method of X-ray fluorescence spectroscopy (EDX-7000 Shimadzu energy dispersive X-ray fluorescence spectrometer) to track changes in the fluorescence signal at certain wavelengths. The range of measured elements–11Na-92U. Results: Control of some technological characteristics of the obtained active substance (moisture, flowability) and dosage form (mean mass, disintegration rate) was used as indirect indicators of quality, but they did not allow reliably distinguishing intact lactose from the saturated one. Long-period oscillations on FTIR spectra were characteristic for all types of samples; oscillations occur at approximately two-week intervals; S/N indices were more stable for samples of RA forms of Abs than for placebo samples. On some days, the substance saturated with RA forms of Abs significantly differed from the intact lactose powder. The kinetics of the X-ray fluorescence intensity at certain wavelengths indicates the possibility of a periodic cooperative trigger transition of the system. Reversible conformational transitions are observed for powders on the 30th and 130th days (Kα 3.313 keV). For tablets at Kα 3.313 keV and Kα 1.740 keV small changes were visualized on those days (100–110th day) when hysteresis phenomena were recorded in the IR spectra of these samples. Conclusion: As a result, the evidence for a long-period dramatic conformational mobility of the water-lactose complex was obtained. Based on the data on the semiannual kinetics of IR spectra, a universal criterion for the identity of lactose powder saturated with RA forms of Abs was obtained. Also, it was confirmed that the lactose conformation state was changed by saturation with RA forms of Abs.

Introduction. The production, standardization and quality control process of various dietary supplements containing chelated zinc requires validated quantitative assessment methods. In this work, we propose an X-ray fluorescence spectroscopy (XRF) technique for determining the zinc content in the composition of coordination compounds using the example of a synthesized chelate complex with methionine.Aim. To synthesize Zn(Met)₂ chelate complex, to develop and validate a method for its quantitative analysis using the XRF method.Materials and methods. The synthesized zinc chelate complex was investigated by IR spectroscopy. The XRF method was used to develop a method for quantifying the zinc content in the synthesized complex. We used dry mixtures of zinc sulfate monohydrate and L-methionine (Met) in a molar ratio of Zn to Met – 1 : 1, 1 : 2, 1 : 4, 1 : 8 and 1 : 16 and also aqueous solutions of zinc sulfate and L-methionine in a molar ratio of Zn to Met 1 : 2 with Zn concentrations from 0.5 to 100 mmol/l as calibration standards. Complexometric titration was used as an arbitration method for the quantitative determination of zinc content in the samples under study.Results and discussion. The IR spectrum of chelate complex confirmed the presence of a donor-acceptor bond between Zn²⁺ and the nitrogen atom of amino group in methionine. The titration results showed chelate compounds have a composition corresponding to the stoichiometric formula Zn(Met)₂. XRF analysis of dry standard mixed samples demonstrated the presence of matrix effect, that makes impossible an accurate assessment of zinc content in the chelate compound. According to the XRF spectra of aqueous solutions containing zinc sulfate and methionine in a ratio of 1 : 2 at a zinc concentration of 0.5; 1; 2; 3; 4; 5; 10; 25; 50 and 100 mmol/L, a calibration graph was constructed – the dependence of the fluorescence signal intensity for the Kα line of zinc on the concentration of zinc in the solution (r = 0.9996). The method was evaluated by the following validation parameters: specificity, linearity, correctness, precision, and analytical range. The specificity of the validated method was proven in the presence of copper, iron, and silver.Conclusion. The developed method make it possible to determine with sufficient precision and correctness the content of Zn²⁺ in its aqueous solutions of inorganic and organic nature by the XRF method in the concentration range from 3 to 100 mmol/l without the influence of the matrix.