Antimicrobial Activity Research Articles

Inhibition of Staphylococcus epidermidis and Pseudomonas aeruginosa biofilms by grape and rice agroindustrial residues

Agroindustrial wastes are generated daily and seem to be rich in bioactive molecules. Thus, they can potentially be used as source of compounds able to control bacterial biofilms. We investigated the potential of extracts from the residues of rice and grape to combat clinically important bacterial biofilms. Extracts of grape pomace and rice bran were obtained using different extractive methodologies and subjected to the evaluation of its antimicrobial and antibiofilm activities. After the in vivo toxicity, the chemical characterization of the most promising extract was assessed. The mass spectrometry analysis revealed the presence of dipeptides, alkaloids and phenolic compounds. Most grape extracts presented antibiofilm and antimicrobial activities against Staphylococcus epidermidis ATCC 35984 and Pseudomonas aeruginosa PA14. The hydromethanolic grape pomace extract obtained by ultrasound assisted extraction (MeOH 80 UAE) presented the most promising activity, being able to inhibit in 99% and 80% the biofilm formation of S. epidermidis and P. aeruginosa, respectively. Against the gram-negative model, this extract eradicated the biofilm by 80%, induced the swarming motility and displayed a physical effect. It also did not present acute or chronic toxicity in Caenorhabditis elegans model. In this way, agroindustrial residues represent a promising source of molecules capable of controlling bacterial biofilms.

UV-exposure decreases antimicrobial activities of a grapevine cane extract against Plasmopara viticola and Botrytis cinerea as a consequence of stilbene modifications-a kinetic study.

Stilbenoid extracts, such as those originating from grapevine by-products (e.g. canes), are of interest for use as biopesticides in vineyard owing to their antimicrobial activities. However, stilbenoids are unstable in the environment, especially under light. This study aimed to chemically characterize the effect of UV light on stilbenoids present in a grapevine cane extract (CE), and to evaluate the antimicrobial activities against two major grapevine pathogens (Plasmopara viticola and Botrytis cinerea) of grapevine extracts exposed to UV. Treatment with UV (365 nm) on a grapevine CE led to degradation of stilbenoids (up to 71% after 1 h). The stilbenoid stability depended on their chemical structure: only those possessing CC, as trans-resveratrol and trans-ε-viniferin, were affected with first their isomerization and secondly their oxidation/cyclization. As a consequence, UV-exposed extracts (UV-CEs) showed reduced antimicrobial activities against the two pathogens (mycelium and spores). For instance, regarding P. viticola, an UV-CE exposed during 4 h showed an almost total loss of its activity on oomycete development and a 2.4-fold inhibition of zoospore mobility in comparison to CE. For B. cinerea, the inhibition capacity of the same UV-CE was reduced by only 1.1-fold on mycelial development and by 3.2-fold on conidial germination compared to CE. UV light triggered modifications on the structure of bioactive stilbenoids, resulting in losses of their antimicrobial activities. Photoprotection of stilbenoids has to be considered in the perspective of using them in vineyards as biopesticides. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Multifunctional scaffolds of β-tricalcium phosphate/bioactive glass coated with zinc oxide and copper oxide nanoparticles

Incorporating nanoparticles into scaffolds with regenerative potential is a promissory strategy to provide them with antimicrobial activity. Bioceramics, such as β-tricalcium phosphate (β-TCP) and bioactive glasses (BGs), stand out among synthetic materials for bone regeneration. In this context, we report the incorporation of zinc oxide (ZnO) and copper oxide/copper nitrate (CuO/Cu2H3NO5) nanoparticles onto the surface of the β-TCP/BG scaffolds. This report addresses the physicochemical characterization of the scaffolds, their antimicrobial activity, and their response to MC3T3-E1 cells. Our findings show that the incorporation of both nanoparticles effectively inhibited S. aureus growth, including its biofilm formation. While the presence of the nanoparticles initially decreased MC3T3-E1 cell viability, cell proliferation improved with prolonged incubation. Overall, the β-TCP/BG_Zn and β-TCP/BG_Cu scaffolds showed an early antimicrobial response, aiding infection eradication, while also supporting cell proliferation over time.

Long-term storage of pink pepper essential oil microencapsulated by chickpea protein/pectin complexes: volatile release, antioxidant and antimicrobial activities.

Pink pepper essential oil was microencapsulated with chickpea protein (CP) and chickpea protein/pectin (CP-HMP) by spray drying. The reconstitution and storage properties of the powders were evaluated after drying. The impact of microencapsulation in the volatiles release, antioxidant and antimicrobial activity of oil was evaluated during 135days of storage. CP resulted in more soluble powders (93.52%), CP/HMP resulted in denser powders (0.39g/mL) while wall material did not influence the wettability. Free pink pepper essential oil (FEO) showed a slight loss of the predominant terpenes (α-pinene, β-pinene, β-mircene, δ-3-carene and D-limonene) after encapsulation. In general, all samples showed an increase in the volatiles release during storage. The evaluation of mass loss showed that FEO had a high release of volatiles, followed by CP and CP-HMP. The antioxidant activity of the FEO decreased (10.8μg Trolox/mg of oil) after 135days of storage, whereas the antioxidant activity of CP (14.9) and CP-HMP (14) increased. Both microcapsules presented antimicrobial activity against Bacillus subtilis and Staphylococcus aureus during storage. CP microcapsules had a strong inhibitory effect against the strains tested, and this advantage was even more evident in long-term storage.

Evaluation of Novel HLM Peptide Activity and Toxicity against Planktonic and Biofilm Bacteria: Comparison to Standard Antibiotics.

Antibiotic resistance is one of the main concerns of public health, and the whole world is trying to overcome such a challenge by finding novel therapeutic modalities and approaches. This study has applied the sequence hybridization approach to the original sequence of two cathelicidin natural parent peptides (BMAP-28 and LL-37) to design a novel HLM peptide with broad antimicrobial activity. The physicochemical characteristics of the newly designed peptide were determined. As well, the new peptide's antimicrobial activity (Minimum Inhibitory Concentration (MIC), Minimum Bacterial Eradication Concentration (MBEC), and antibiofilm activity) was tested on two control (Staphylococcus aureus ATCC 29213, Escherichia coli ATCC 25922) and two resistant (Methicillin-resistant Staphylococcus aureus (MRSA) ATCC BAA41, New Delhi metallo-beta- lactamase-1 Escherichia coli ATCC BAA-2452) bacterial strains. Furthermore, synergistic studies have been applied to HLM-hybridized peptides with five conventional antibiotics by checkerboard assays. Also, the toxicity of HLM-hybridized peptide was studied on Vero cell lines to obtain the IC50 value. Besides the percentage of hemolysis action, the peptide was tested in freshly heparinized blood. The MIC values for the HLM peptide were obtained as 20, 10, 20, and 20 μM, respectively. Also, the results showed no hemolysis action, with low to slightly moderate toxicity action against mammalian cells, with an IC50 value of 10.06. The Biomatik corporate labs, where HLM was manufactured, determined the stability results of the product by Mass Spectrophotometry (MS) and High-performance Liquid Chromatography (HPLC) methods. The HLM-hybridized peptide exhibited a range of synergistic to additive antimicrobial activities upon combination with five commercially available different antibiotics. It has demonstrated the biofilm-killing effects in the same concentration required to eradicate the control strains. The results indicated that HLM-hybridized peptide displayed a broad-spectrum activity toward different bacterial strains in planktonic and biofilm forms. It showed synergistic or additive antimicrobial activity upon combining with commercially available different antibiotics.

Characterization of bioactive compounds, antioxidants and antimicrobial properties of Allagoptera leucocalyx

Allagoptera leucocalyx is a non-studied tropical fruit distributed in the Bolivian Chiquitania region. This study aimed to investigate its bioactive compounds as well as its antioxidant and antimicrobial properties to encourage its consumption and explore potential applications in various industries. The bioactive compounds: polyphenols, flavonoids, and anthocyanins were determined by the Folin-Ciocalteu, AlCl3, and differential pH methods. Antioxidant activity was assessed by the DPPH● and ABTS● assays, while antimicrobial activity by turbidimetry and antibiogram. The highest results obtained revealed significant levels of polyphenols (209 ± 12 mg GAE/100 g), and flavonoids (7.9 ± 0.1 mg QE/100 g). Moreover, the fruit exhibit antioxidant activity (9.3 ± 0.2 μmol Trolox/g by ABTS● and 5.9 ± 0.2 μmol Trolox/g by DPPH●) and antimicrobial activity against Shigella sp. In conclusion, these promising findings suggest that this fruit could be utilized in the development of new products within the cosmetic, food, and pharmaceutical industries.

Discovery of the Aminated Quinoxalines as Potential Active Molecules

Background: In recent years, as the biological activity of the quinoxaline skeleton has been revealed in numerous studies, interest in synthesizing new prototype molecules for the treatment of many chronic diseases, especially cancer, has increased. Methods: The desired alkoxy substituted aminoquinoxalines (AQNX1-9) were synthesized by the reaction of QNX and alkoxy substituted aryl amines such as 2-methoxyaniline, 4-methoxyaniline, 2- ethoxyaniline, 3-ethoxyaniline, 4-ethoxyaniline, 4-butoxyaniline, 2,4-dimethoxyaniline, 3,4- dimethoxyaniline, and 3,5-dimethoxyaniline according to the previously published procedure. QNX was aminated in DMSO at 130°C. We synthesized various alkoxy-substituted aminoquinoxaline compounds (AQNX1-9) and evaluated their anticancer and antimicrobial activities in order to expand the search to related structures. In particular, two aminoquinoxaline (AQNX5 and AQNX6) compounds, coded as NSC D-835971/1 and NSC D-835972/1 by the National Cancer Institute in the USA, were screened for anticancer screening at a dose of 10-5 M on a full panel of 60 human cell lines obtained from nine human cancer cell types (leukemia, melanoma, non-small cell lung, colon, central (nervous system, ovarian, kidney, prostate, and breast cancer). Results: Further in silico studies were also conducted for the compound AQNX5 (NSC D- 835971/1), which was found to be the most active antiproliferative agent, especially against leukemia cell lines. Molecular docking studies showed that AQNX5 interacted with Glu286 and Lys271 through hydrogen bonding and π-stacking interaction in the ATP binding region of Abl kinase, which is indicated as a potential target of leukemia. Besides, AQNX5 occupied the minor groove of the double helix of DNA via π-stacking interaction with DG-6. Conclusion: According to in silico pharmacokinetic determination, AQNX5 was endowed with drug-like properties as a potential anticancer drug candidate for future experiments. In the light of these findings, more research will focus on aminated quinoxalines' ability to precisely target leukemia cancer cell lines.

Formulation and Development of Clove and Coriander Combination Herbal Dental Anticaries Gel and Evaluation of its Antimicrobial Activity

Background:: Dental caries is one of the Periodontal diseases that has been recognized as a major public health problem for decades throughout the world. It occurs in all groups, ethnicities, races, and genders at all socioeconomic levels. Natural remedies are more acceptable in the belief that they are safer with fewer side effects than synthetic ones. Clove and coriander oil are established herbal drugs for periodontal diseases. Objective:: This research work was intended to formulate a dental gel containing clove and Coriander as the major constituents and evaluate it for dental caries treatment. Both of the herbal oils have a vast range of antimicrobial activity against a great number of periodontal pathogens; therefore, they are used for periodontitis treatment. Methods:: The combination gel was prepared using carbopol 934 as a gelling agent, clove oil and coriander oil as therapeutic constituents, polyethylene glycol as a co-solvent, methyl paraben and propyl paraben as a preservative and a required quantity of distilled water as vehicle. Results:: The gel was analyzed for various properties like antimicrobial activity, pH, spreadability, extrudability, drug content etc., and it was shown that the combination gel is a satisfactory dosage form that is used in periodontitis treatment. The combination gel revealed the ZI (zone of inhibition) of about 22.05±0.04 mm. Conclusion:: The present study concluded that the combination gel preparations of clove oil and coriander oil reported satisfactory physicochemical properties along with good drug content compared to the single gel preparation.

Cu nanoparticles, a candidate biocide for the conservation of stone monuments against biodeterioration

Nanomaterials, such as TiO2, ZnO, and Cu, have become popular materials for controlling the growth of microorganisms that cause the deterioration of stone monuments, but it is not clear which material is best. In this study, the dominant strains from two stone monuments, the Klippe Statue and Lingyan Temple, were used to compare the antimicrobial activities of the three materials. The minimum inhibitory concentrations (MICs) of the three materials were obtained using the microdilution and macrodilution methods, a linear regression model of the relationship between the addition of the nanomaterial and the color change of the stone was constructed, and the antimicrobial effect of the screened nanomaterial applied to the stone samples was also evaluated. Among the three materials, only the Cu nanoparticles exhibited a broad antimicrobial activity, and its MIC was 0.5%. There was a linear relationship between the addition of Cu nanoparticles and the color change of the stone, the maximum addition without significant effect on the aesthetic appearance was 67 μg/cm2, and there was no difference between the limestone and sandstone. However, the antimicrobial activity of the Cu nanoparticles was only observed in limestone due to the low concentration of the material that could be retained on the sandstone surface. In addition, the adsorption between the Cu nanoparticles and limestone was weak and easily removed by various factors, indicating that the microorganisms could re-colonize the Cu-treated limestone after the limestone was exposed to environmental influences such as rainfall. In this paper, we propose a candidate biocide, Cu nanoparticles, to inhibit the growth of microorganisms on stone monuments, the Klippe Statue and Lingyan Temple, and our results provide a reference for the application of nanomaterials in stone monuments.

Antimicrobial activity of herbal biomass derived metabolites fabricated wound dressing material against microbial strains causing skin infection

In the present study, anti-microbial activity of wound dressing material coated with Aloe vera and Azadirachta indica metabolites was investigated on pathogenic microbial strains associated with skin infection. Anti-microbial active metabolites extracted from the respective medicinal plant were fabricated on the wound dressing material by simple, in situ green science principles. Confirmation of phytochemicals fabrication on the fibre surface of the material was studied by Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) Additionally, the impact of phyto-constituents fabrication on mechanical properties such as thickness and tensile strength was assessed. The anti-microbial efficacy of the fabricated dressing against pathogenic microorganisms (Candida albicans, Escherichia coli ATCC 25922, and Staphylococcus aureus ATCC 25923) was evaluated using agar diffusion assay. The release profile of phytochemical constituents from the fabricated wound dressing was investigated using ethanol and distilled water as solvents. The results showed that the phytochemical constituents were fabricated effectively on the wound dressing material and exhibiting notable growth inhibition potential against tested pathogenic strains. The release profile study revealed an initial burst release of phytochemical constituents followed by a controlled or sustained pattern. In conclusion, wound dressings infused with plant extracts present a promising approach for wound care applications and show potential for various healing-related purpose.

Cholesteryl ester transfer protein inhibition: a pathway to reducing risk of morbidity and promoting longevity.

To review the evidence and describe the biological plausibility for the benefits of inhibiting cholesteryl ester transfer protein (CETP) on multiple organ systems through modification of lipoprotein metabolism. Results from observational studies, Mendelian randomization analyses, and randomized clinical trials support the potential of CETP inhibition to reduce atherosclerotic cardiovascular disease (ASCVD) risk through a reduction of apolipoprotein B-containing lipoproteins. In contrast, raising high-density lipoprotein (HDL) particles, as previously hypothesized, did not contribute to ASCVD risk reduction. There is also an expanding body of evidence supporting the benefits of CETP inhibition for safeguarding against other conditions associated with aging, particularly new-onset type 2 diabetes mellitus and dementia, as well as age-related macular degeneration, septicemia, and possibly chronic kidney disease. The latter are likely mediated through improved functionality of the HDL particle, including its role on cholesterol efflux and antioxidative, anti-inflammatory, and antimicrobial activities. At present, there is robust clinical evidence to support the benefits of reducing CETP activity for ASCVD risk reduction, and plausibility exists for the promotion of longevity by reducing risks of several other conditions. An ongoing large clinical trial program of the latest potent CETP inhibitor, obicetrapib, is expected to provide further insight into CETP inhibition as a therapeutic target for these various conditions.

Azelaic acid-based lyotropic liquid crystals gel for acne vulgaris: Formulation optimization, antimicrobial activity and dermatopharmacokinetic study

The proposed study aimed to develop a topical gel containing azelaic acid (AZA)-based lyotropic liquid crystals (LLCs) for the treatment of acne vulgaris. AZA-based LLCs were optimized by varying Poloxamer-407 and polyvinyl alcohol concentration using a central composite design, which showed that both independent variables had a significant effect on the formulation. The highest desirable trial of AZA-based LLCs (Batch-7) containing 300 mg poloxamer-407 and 100 mg polyvinyl alcohol depicted the particle size, zeta potential, and entrapment efficiency of 184.2 nm, −16.1 mV, and 79.96 %, respectively. TEM images confirmed the globular vesicles of LLCs, and ATR-FTIR and DSC results confirmed the compatibility of formulation excipients. In vitro, the release of AZA, AZA-based LLCs, AZA-based LLC gel, and marketed gel showed a release of 23.29, 95.24, 91.07 and 59.88 %, respectively, after 24 h in phosphate buffer pH 6.8. Ex vivo release of AZA-based LLC gel displayed an 86.56 % release after 24 h. The antimicrobial activity of AZA-based LLC gel exhibited a comparable efficacy with marketed gel against Cutibacterium acnes, Staphylococcus epidermis and Staphylococcus aureus. The acute dermal irritation study indicated excellent safety and skin compatibility of AZA-based LLC gel without any erythema and edema. The dermatopharmacokinetic study displayed an enhanced drug retention for AZA-based LLC gel (146.121 ± 21.13 µg/cm2) than marketed gel (58.58 ± 15.95 µg/cm2) in the dermal layer, which would improve its therapeutic effect. These outcomes proved that AZA-based LLC gel has the potential to enhance skin penetration and retention for effective management of acne vulgaris.

Strengthened Antimicrobial and Biocompatible of Jelleine-1 Analogs: A Step Toward Food Preservation

Antimicrobial peptides (AMPs), as important components of the innate immune system, are deemed to have the potential to replace antibiotics and traditional chemical preservatives due to their natural antibacterial properties and less likely to cause bacterial resistance. In this study, the antimicrobial peptide Jelleine-1 derived from bee royal jelly was used as a template, which provided an effective design scheme for short-chain AMPs based on a natural structure. The peptide structure was characterized by circular dichroism and fluorescence spectroscopy, and the antimicrobial activity and biocompatibility were evaluated. Additionally, a preliminary study on the antibacterial mechanism was carried out. The results indicated that the designed peptides predominantly exhibited a regular β-sheet conformation, in which J-R and F-K had strong antibacterial activity and excellent biocompatibility, the average therapeutic index (TI) was 23.83 and 30.67. The antibacterial mechanism suggested that the increased outer membrane permeability caused strong fluctuation of bacterial cell membrane potential and cytoplasmic depolarization through electrostatic adsorption to the bacterial membrane surface, and further induced inner membrane damage, eventually leading to bacterial death. This study provides a promising approach to the design and development of innovative biological preservatives.

Synergistic impacts of novel tantalum doping in BiVO4 for effective photocatalytic applications, antimicrobial activity, and antioxidant aspect

This paper reports the production of pure and Ta-doped (1 %, 2 %, 3 %, and 4 %) BiVO4 nanoparticles (NPs) for MB dye degradation. UV–Vis, FTIR, SEM, PL, and XRD techniques were used to analyze the samples. Photocatalysts (BiVO4, Ta-doped BiVO4) NPs have been used to study the photocatalytic activity of these materials for the degradation of methylene blue (MB) in response to visible light. The band gap reduction from 2.7 to 1.98 eV and the photogeneration of electron-hole pairs have also been demonstrated by UV–visible and PL spectroscopy. According to FTIR spectroscopy analysis, Bismuth, Tantalum, Vanadium, Oxygen, and Carbon are all present in the synthesized material. As the dopant concentration rises, the XRD data show that the crystallite size decreases. The crystallite size of the optimal (4 % Ta-doped BiVO4) is 23 nm, whereas the crystallite size of the 2 % Ta-doped BiVO4 is 39 nm. The SEM image shows that particle size reduces when dopant concentration rises. In comparison to previous synthesized materials, the 4 % Ta-doped BiVO4 NPs have a smaller band gap, crystalline size, and recombination rate. Therefore, using the co-precipitation process, 4 % Ta-doped BiVO4 NPs degrade the MB dye (86 %) in 120 min, making them an ideal material. The findings of this study will be applied to wastewater treatment.

A perspective on nanomaterials against Campylobacter jejuni biofilm - new control strategies.

Campylobacter jejuni - a Gram-negative bacterium - is considered the fourth cause of diarrheic diseases that can form biofilms (mono and multi-species) or colonize pre-existing biofilms adhering to both, inert or biotic surfaces; its biofilms contribute to transmission through the food chain and survival under harsh environmental conditions. Thus, developing alternatives against this pathogen is compulsory. Nanomaterials have revolutionized the way of fighting infections related to biofilms due to their unique properties compared to traditional antibiotics. Nanomaterials have also been used against C. jejuni based on zinc, titanium, silver, molybdenum, magnesium, cobalt, erbium, lithium, nickel, hydroxide, polyethylene, graphene, lipids, chitosan, and poly(lactic-co-glycolic acid) (PLGA). Those organic and inorganic materials have synthesized nanoparticles, nanofillers, nanowires, nanoferrites, double layers, nanocomposites, and films that have encapsulated, entrapped, coated or doped molecules. Additionally, bare metal nanoparticles have been tested by their antimicrobial activity on planktonic and sessile forms. Therefore, the present review aimed to describe general biology virulence factors, host-pathogen relationships and biofilm formation, as well as nanomaterials and nanoparticles fighting against C. jejuni biofilms. Considerations are presented and placed in perspective.

Antimicrobial effects of peptides from fenugreek and ginger proteins using Fe3O4@PDA-MWCNT conjugated trypsin by improving enzyme stability & applications

Trypsin was immobilized onto a newly formulated nanocomposite (NC) comprising magnetic (Fe3O4) multiwalled carbon nanotubes (MWCNTs) anchored with polydopamine (PDA). The fabricated NC and the NC-bound trypsin were subjected to comprehensive characterization using various biophysical techniques including Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and fluorescence spectroscopy. The NC-bound trypsin exhibited significantly enhanced thermostability and increased tolerance to various organic solvents and denaturants. The enzymatic activity of trypsin was notably augmented through its coupling with the nano support, yielding an effectiveness factor (η) of 2.65. Fenugreek and ginger protein hydrolysates, prepared using both native and NC-bound enzyme, were evaluated for their antimicrobial activities. The analysis revealed that peptides generated by NC-bound trypsin showed higher antimicrobial activity (~ 10) in most cases compared to peptides obtained by using native trypsin. This strategy presents an innovative methodology for the production of potential biopeptides, with the prospect of their incorporation into pharmaceutical and therapeutic sectors through the utilization of NC-bound trypsin in protein hydrolysis.

Preparation and properties of calcium oxide and calcium peroxide from eggshell waste for enhanced antimicrobial activity

Calcium peroxide (CaO2), which releases hydrogen peroxide (H2O2) upon contact with water, has garnered attention as a potential alternative to liquid H2O2. Researchers have explored various methods to enhance the production of CaO2 with reduced environmental impact. This study focuses on the preparation of two potent antimicrobial agents, calcined calcium oxide (C-CaO) and synthesized calcium peroxide (S-CaO2) from eggshell waste. These agents were then incorporated into ethylene vinyl alcohol (EVOH) composite films for antimicrobial packaging. The synthesized CaO and CaO2 were analyzed using Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Thermogravimetric analysis (TGA) and Scanning electron microscopy (SEM). The results confirmed the successful synthesis of high-purity CaO and CaO2 from eggshell waste. Compared to CaO (a well-known antimicrobial agent), CaO2 exhibited approximately 1.6 to 2 times higher antimicrobial activity, which is attributed to its release of H2O2. EVOH films containing 3% of CaO2 demonstrated significant microbial growth deactivation, reaching 99.99% and 97.24% for gram-negative and gram-positive bacteria, while EVOH films containing 3% of CaO exhibited relatively low deactivation ability of 79.01% and 48.82, respectively. This study underscores the potential of eggshell waste as a valuable resource for producing high-value materials. Moreover, CaO2 emerges as an effective antimicrobial agent, particularly in antimicrobial packaging applications, showcasing its versatility across various sectors.

Silver nanoparticles/carbon dots nanocomposite with potent antibiofilm and long-term antimicrobial activity doped into chitosan/polyvinyl alcohol film for food preservation.

Exploration of robust antiseptics with antibiofilm performance and long-term antimicrobial activity is of great significance to effectively destroy foodborne pathogenic bacteria. Herein, a silver nanoparticles (Ag NPs) /carbon dots (CDs) nanocomposite (Ag@CDs) was constructed by the reaction of Ag+ with CDs, which has strong antibacterial ability, and mighty biofilm inhibition and destruction ability toward E. coli and S. aureus. Notably, low concentration of Ag@CDs (40.0 and 80.0μg/mL) could ablate 86.11% E. coli and 75.86%S. aureus biomass of mature biofilm. To our knowledge, this is the first bactericide with powerful biofilm destruction activity. In addition, Ag@CDs exhibited long-term (30 d) antibacterial effect on the substrates of plastic, cotton, gauze, and glass. Ag@CDs was evenly dispersed into the matrix of chitosan (CS)/polyvinyl alcohol (PVA) to fabricate well-blended food packaging films. Among which, the 3% Ag-CP film exhibited improved mechanical performance, excellent UV-Vis light blocking ability, and intensive antimicrobial activity. Despite seven days of storage, 3% Ag-CP still could preserve the freshness and safety of the pork and shrimp, certifying it extends the storage life of packaged foods.

Green synthesis of silver nanoparticles from supercritical CO2 mediated Lagerstroemia speciosa extract: Characterization, antimicrobial and antibiofilm activity

In the current study, optimal supercritical fluid extract (SFE) of Lagerstroemia speciosa (LS) leaves at pressure 29.59 megapascal (MPa), temperature 89.50 ºC and extraction time 53.85 min. was used to extract phenolic compounds for the synthesis of silver nanoparticles (AgNPs). The synthesis was studied for 0-20 hrs. Initially the synthesis of nanoparticles (SFELS-AgNPs) was confirmed using UV -spectroscopy. It demonstrated a maximum surface plasmon resonance at 430 nm. The crystallite dimension of nanoparticles was determined using X-ray diffraction (XRD) (13.47 nm), Transmission electron microscopy (TEM), zeta potential analysis and energy-dispersive X-ray analysis (EDAX) were used to analyze the morphology, surface charge and presence of differential elements in SFELS-AgNPs respectively. Developed nanoparticles revealed antimicrobial activity against two gram-positive viz. Staphylococcus aureus and Bacillus cereus, and three gram-negative bacteria viz. Klebsiella pneumonia, Pseudomonas aeruginosa and Escherichia coli. The nanoparticle showed a minimum inhibitory concentration (MIC) of 64 μg/ml whereas the minimum bactericidal concentration (MBC) 128 μg/ml against K. pneumonia. They significantly inhibited K. pneumonia biofilm formation which was confirmed using scanning electron microscopy (SEM). The results were encouraging compared to the standards drug Chloramphenicol and other controls. The generated nanoparticles have highly effective antimicrobial properties against pathogenic bacteria.

Impact of mutations in carbohydrate binding sites of tandem-repeat type galectin from Takifugu obscurus on its antimicrobial activity

Galectins belong to a family of galactoside-binding proteins and exhibit diverse biological functions. In the present research, a tandem-repeat type galectin (named ToGalectin) was identified from obscure puffer Takifugu obscurus. The 296 amino acids ToGalectin contained two carbohydrate recognition domains (CRDs), one of which possessed two conserved carbohydrate binding motifs. Phylogenetic analysis showed that ToGalectin clustered tightly with other galectin-8 proteins from teleost fish. ToGalectin transcripts were ubiquitously expressed in all tissues examined and its expression was significantly upregulated in the liver, kidney, and intestine after Vibrio harveyi or Staphylococcus aureus infection. To investigate the effect of carbohydrate binding sites on biological activity, ToGalectin and its mutant (MUT-ToGalectin) were expressed and purified. The recombinant ToGalectin and MUT-ToGalectin proteins showed strong agglutinating activity against both V. harveyi and S. aureus. rToGalectin could bind to all tested carbohydrates and bacteria, whereas rMUT-ToGalectin bound to some carbohydrates and bacteria with specific and relatively strong affinity. rToGalectin significantly suppressed the growth of all six bacteria detected and promoted bacterial clearance in vivo, whereas MUT-ToGalectin inhibited the growth of only two bacterial species, which could be attributed to the differences in conserved motifs within the CRDs. Our results suggested that ToGalectin is involved in the immune response against bacterial infection and the clearance of pathogens in T. obscurus.