Correction: Platinum nanoparticles inhibit bacteria proliferation and rescue zebrafish from bacterial infection

[This corrects the article DOI: 10.1039/C6RA03732A.].

Activity of lipid-loaded lectin against co-infection of Candida albicans and Staphylococcus aureus using the zebrafish model

AIM

Nosocomial infection caused by mixed species of methicillin-resistant Staphylococcus aureus (MRSA) and Candida albicans (CA) is difficult to manage with existing antimicrobials, particularly in the presence of mixed-species biofilm. This study evaluates the activity of cationic lipid, specifically functionalized with lectin, against mixed biofilms of MRSA and CA and their effectiveness in vivo using the zebrafish model.

METHODS AND RESULTS

The present study demonstrates for the first time the antimicrobial activity of 2-((N-[2-hydroxyethyl]palmitamido)methyl)-1-methylpyridin-1-ium iodide (cN16E) against MRSA and mixed species of MRSA + CA. The cN16E functionalized with Butea monosperma seed lectin (BMSL) showed a lower minimum inhibitory concentration (MIC) as compared with cN16E. BMSL-cN16E (BcN16E) exhibited strong membrane-damaging activity at a lower concentration than cN16E. Crystal violet assay showed that BcN16E inhibits mixed-species biofilm at the concentration of 15.63 µM, which is four-fold lower than the MIC. Especially, BcN16E was found to be effective in disturbing mature mixed biofilm at 31.25 µM, which is two-fold lower than the MIC, suggesting true antibiofilm activity without pressurizing the microorganisms. The treatment with BcN16E significantly reduced the exopolysaccharide synthesis (> 78%), cell surface hydrophobicity (> 70 %), hyphae formation, staphyloxanthin biosynthesis (> 41 %), and antioxidant enzyme and hemolysin activity (> 70 %). Notably, BcN16E was efficient in reducing the in vivo colonization of bacterial and fungal burden in the blood and muscle tissues of zebrafish.

CONCLUSION

Antimicrobial and antibiofilm efficacy of BcN16E against MRSA, and mixed species of MRSA + CA were demonstrated. Importantly, BcN16E treatment rescued Zebrafish coinfected with mixed species of MRSA + CA. Significance and Impact of the study: The results highlight that antimicrobial loaded on lectin provides an additional advantage to recognize microorganism surface glycans and maximize drug delivery to treat polymicrobial infections caused by MRSA and CA.

Hybrid of Metapenaeus dobsoni lectin and platinum nanoparticles exert antimicrobial and immunostimulatory effects to reduce bacterial bioburden in infected Nile tilapia

A novel antibacterial immunostimulant using Platinum nanoparticles (PtNPs) and lectin from Metapenaeus dobsoni (Md-Lec) was developed. The Md-Lec and PtNPs (Pt-lec) hybrid formed through non-covalent interaction exhibits antimicrobial activity against fish specific pathogens by affecting membrane integrity and producing excess reactive oxygen species. The therapeutic efficacy of Pt-lec was demonstrated through rescuing Aeromonas hydrophila infected Nile Tilapia. Pt-lec prevents the infection spreading and reduces the bacterial bioburden in less than 12 h, and as a result of this the fish were restored to normalcy. To assess immunostimulation, we studied the expression of three different immune related genes, namely LEC, Myd88 and COX-2 in the gills, liver, spleen and kidney of fish under various experimental conditions. Our results showed that Pt-lec treatment appeared to be better when compared to lectin alone in enhancing the expression of Myd88 and COX-2, but LEC was not as expected. These results suggest that Pt-lec has the ability to protect Nile Tilapia against bacterial infection by restricting bacterial bioburden through their direct effects on the bacterial membrane and indirectly through their effects on host immune-related gene expression. This hybrid could have potential “green” application in fish farming in rescuing infected animals when compared to widely and unregulated antibiotics.

Phytolectin conjugated positively charged fatty acid amide impairs virulence factors and inhibits cross-kingdom biofilm formation of Candida albicans and uropathogenic Escherichia coli

AIM

Polymicrobial biofilm encasing cross-kingdom microorganisms are apparent in medicine, which imposes serious resistance to conventional antimicrobial treatment. The objective of the study was to explore Butea monosperma seed lectin (BMSL) conjugated antimicrobial lipid, 2-((N-(2-hydroxyethyl)palmitamido)methyl)-1-methylpyridin-1-ium iodide (cN16E) to inhibit mixed-species biofilm of uropathogenic Escherichia coli-Candida albicans.

METHODS AND RESULTS

Antimicrobial activity and antibiofilm of cN16E and cN16E-BMSL conjugate (BcN16E) were analyzed against single- and mixed microbial cultures. The minimum inhibitory concentration (MIC) indicates that the MIC of cN16E-BMSL conjugate (BcN16E) against cohabiting UPEC-C. albicans was eightfold lower than the cN16E. BcN16E affects membrane integrity to elicit antimicrobial activity. BcN16E inhibits the dual-species biofilm even with 16 times lower MIC of cN16E. BcN16E impairs the biofilm-associated virulence factors which include extracellular polysaccharides, cell surface hydrophobicity, swimming, swarming motilities, hyphal filamentous morphology, curli formation, and hemolysin activity. As a proof of concept, we demonstrated BcN16E ability to inhibit dual-species biofilm formation on a urinary catheter.

CONCLUSION

The study revealed that the BcN16E is better than cN16E in impairing biofilm-associated virulence factors and exerting antimicrobial activity.

SIGNIFICANCE AND IMPACT OF THE STUDY

The findings emphasize that phytolectin has the potential to enhance the anti-virulence strategies of antimicrobials against cross-kingdom biofilm-related infections.

A study on the interaction of nile blue with Uracils: A spectroscopic and computational approach

The present work focuses the investigation on fluorescence quenching of nile blue (NB) in presence of various substituted uracil molecules. UV-Visible absorption studies signify the possibility of ground state complex formation between NB and uracil molecules. The increase in concentration of quencher molecules greatly influences the emission spectra of NB. The bimolecular quenching rate constant (k_q) were calculated and found to depend on the position and electronic properties of substituent in quencher molecules. Fluorescence quenching experiments were performed at different temperature to calculate the thermodynamic parameters. The fluorescence lifetime measurements show that the quenching process proceeds through static quenching. The mechanism of fluorescence quenching includes the possibility of proton transfer. The bond dissociation enthalpy (BDE) reveals the release of H from the quencher molecules. The quencher molecules possess antioxidant activity and identified using deoxyribose degradation assay. The position of substituent and its electronic property are key features to address the antioxidant activity of uracil molecules.

Targeting the glycan of receptor binding domain with jacalin as a novel approach to develop a treatment against COVID-19

In silico analysis revealed that a lectin, jacalin from jackfruit seeds, recognizes a glycosylated region of the receptor-binding domain (RBD) of SARS-CoV2. Jacalin binding induces conformational changes in RBD and significantly affects its interaction with human angiotensin-converting enzyme 2. The result may open up exploration of lectin-based strategies against COVID-19.

The metal centre in salen-acridine dyad N2O2 ligand–metal complexes modulates DNA binding and photocleavage efficiency

Metal centre in a coordination complex modulates DNA binding.

Evaluation of the toxicities of silver and silver sulfide nanoparticles against Gram-positive and Gram-negative bacteria

In this study, the endogenous lipid signalling molecules, N-myristoylethanolamine, were explored as a capping agent to synthesise stable silver nanoparticles (AgNPs) and Ag sulphide NPs (Ag₂S NPs). Sulphidation of the AgNPs abolishes the surface plasmon resonance (SPR) maximum of AgNPs at 415 nm with concomitant changes in the SPR, indicating the formation of Ag₂S NPs. Transmission electron microscopy revealed that the AgNPs and Ag₂S NPs are spherical in shape with a size of 5-30 and 8-30 nm, respectively. AgNPs and Ag₂S NPs exhibit antimicrobial activity against Gram-positive and Gram-negative bacteria. The minimum inhibitory concentrations (MIC) of 25 and 50 μM for AgNPs and Ag₂S NPs, respectively, were determined from resazurin microtitre plate assay. At or above MIC, both AgNPs and Ag₂S NPs decrease the cell viability through the mechanism of membrane damage and generation of excess reactive oxygen species.

Facile synthesis of gold nanoparticles using carbon dots for electrochemical detection of neurotransmitter, dopamine in human serum and as a chemocatalyst for nitroaromatic reduction

Herein, the authors reported a carbon dots mediated synthesis of gold nanoparticles (AuNPs) at room temperature. Transmission electron microscopy revealed that the AuNPs are spherical in shape with a size of 10 nm. As-prepared AuNPs was immobilised on carbon paste electrode and subjected to electrochemical sensing of an important neurotransmitter dopamine. Differential pulse voltammetry studies revealed sensitive and selective determination of dopamine in the presence of commonly interfering ascorbic acid and uric acid. The linear detection range was 10-600 μM and the limit of detection was 0.7 ± 0.18 μM. The practical application was demonstrated by measuring dopamine in human blood serum and urine samples. The catalytic activity of AuNPs was evaluated by sodium borohydride mediated reduction of nitroaromatic compounds. The reduction kinetics was found to be pseudo-first-order kinetics. All the tested nitroaromatics reduced to corresponding amines in <10 min.

A functional Ag-TiO2 nanocomposite solar selective absorber with antimicrobial activity by photochemical reduction process

A functional nanocomposite coating developed by wet chemical route in a photochemical reduction process will be a good candidate for low temperature solar thermal application. The low-temperature curable cermet comprises of two different type of nanoparticles, generated by photocatalytic reduction of silver ions under the sunlight with the aid of crystalline TiO₂ (~8 nm) nanoparticles. The optimized base absorber layer of Ag-TiO₂ nanocomposite exhibited absorptance (α) of 0.90 and emittance (ε) of 0.18 at 200 °C. Further to improve the optical properties a second layer of MgF₂ has been added to get high selective (α/ε = 0.93/0.19 at 200 °C) nature. In addition, the coating was demonstrated to possess an antimicrobial activity against both Gram-negative and Gram-positive bacteria. The presented work will provide a new insight into the spectrally selective absorbers and its antimicrobial nature, which may useful for water disinfection, hot water, industrial heating and swimming pool applications.

Remarkable Effect of Jacalin in Diminishing the Protein Corona Interference in the Antibacterial Activity of Pectin-Capped Copper Sulfide Nanoparticles

Herein, we report a new strategy based on jacalin functionalization to diminish the impact of biological fluids in the antibacterial applications of nanoparticles (NPs). Precoating pectin-capped copper sulfide NPs (pCuS) with bovine serum albumin produced a protein corona, which affects the antibacterial activity of pCuS. It was found that the minimum inhibitory concentration (MIC) increases fourfold because of the formation of the protein corona. Interestingly, the pCuS functionalized with jacalin enhance the targeting capabilities through bacterial cell surface glycan recognition with no interference from the protein corona. The MIC of pCuS decreases 16-fold on functionalization with jacalin. Mechanistic studies indicated that the pCuS functionalized with jacalin impede the protein corona interference and induce bacterial cell death by impairing the GSH/reactive oxygen species balance and disrupting the bacteria cell membrane. As a proof of concept, we used a bacteria-infected zebrafish animal model to demonstrate the interference of biological fluids in the antibacterial activity of NPs. Infected zebrafish treated with 1× MIC of pCuS failed to recover from the infection, but 4× MIC rescues the fish. The requirement of a high dose of NPs to treat the infection confirms the interference of biological fluids in nanotherapeutic applications. At the same time, the jacalin-pCuS complex rescues the infected fish at 16-fold lesser MIC. The results obtained from this study suggest that jacalin-mediated NP targeting may have broad implications in the development of future nanomedicine.

Simple admixture of 4-nitrobenzaldehyde and 2,4-dimethylpyrrole for efficient colorimetric sensing of copper(II) ions

An easily accessible chemo-probe based on physical mixture of 2,4-dimethylpyrrole and 4-nitrobenzaldehyde has been developed. Based on NMR spectroscopic analysis, catalyst free formation of dipyrromethane was observed in the physical mixture of chemo-probe. The probe is utilized in effective colorimetric sensing of copper(II) ions present in environmental solutions by instantaneous appearance of red colour, even in the co-existence of various metal ions. The lowest detection limit of 2.51 μM for this chemo-probe towards copper(II) sensing is significantly lower than the WHO prescribed level (<30 μM of copper(II) ions) in potable water. The sensing mechanism is explained via rapid formation of bis(dipyrrinato)copper(II) complex, as confirmed by Jobs plot, UV-Vis spectroscopy and IR spectroscopy.

Rapid and selective colorimetric sensing of Au3+ions based on galvanic displacement of silver nanoparticles

Au³⁺decolorizes AgNPs through a galvanic displacement reaction.

Analysis and assessment of heavy metals in soils around the industrial areas in Mettur, Tamilnadu, India

Industrialization and extraction of natural resources have resulted in large-scale environmental contamination and pollution. We have collected the soil samples from five different industrial areas of Mettur (Chemplast Sanmar Limited, SIDCO-1, SIDCO-2, SIDCO-3, thermal power plant), Salem district, Tamil Nadu, India, and estimated the physical properties (pH, EC, and alkalinity), chemical properties (major and minor elements), and heavy metal analysis. Thermal power plant soil sample showed higher pH 5.01, EC 29.33 μmhos/cm compared with rest of the samples. Acidic nature of the soil samples near thermal power plant was due to the effect of ash disposal. The high electrical conductivity is due to the disposal of soluble electrolytes and deposition of dust particles released from Thermal Power Plant. Alkalinity of the SIDCO-2 soil (410 ppm) was higher than that of rest of the soil samples. Soil samples show higher concentrations of chloride (10,400 ppm) from thermal power plant when compared with soil sample collected from all 15 sample areas. It was found that heavy metal concentrations lie in the following ranges: Cu (3.780-86.360 ppm) > Pb (0.018-1.710 ppm) > As (0.053-0.342 ppm) in Mettur area. The maximum concentration of copper (Cu) found in SIDCO-1 (86.360 ppm) was due to electroplating industry, smelting and refining, mining, and biosolids. Maximum concentrations of arsenic (As) recorded (0.342 ppm) in thermal Power plant was due to ash disposal from the coal-fired thermal power plant. And maximum concentrations of lead (Pb) (1.710 ppm) in Chemplast area are due to the effluent discharge of manufacturing units like PVC resins, chlorochemicals, and piping systems in Chemplast which are main source of heavy metal pollutants. Therefore, major mining and smelting of metalliferous ores, burning of leaded gasoline, municipal sewage, industrial wastes enriched with Pb, and paints, which exceeded WHO (2011) and BIS (2003) recommended standard for lead (0.090 ppm) and arsenic (0.010 ppm). The geo-accumulation index (Igeo) study indicates that there is no significant contamination with lead and arsenic but there is a moderate contamination with copper (86.360 ppm). According to the calculated values of PLI, area 1 (0.061) has been contaminated high compared with other areas.

Synthesis of copper sulfide nanoparticles and evaluation of in vitro antibacterial activity and in vivo therapeutic effect in bacteria-infected zebrafish

Copper sulfide nanoparticles rescue bacteria infected zebrafish.

C–H oxidation and chelation of a dipyrromethane mediated rapid colorimetric naked-eye Cu(ii) chemosensor

Selective C–H oxidation and chelation of DPMs mediated by copper is demonstrated and utilized in the development of a rapid colorimetric naked-eye Cu(ii) chemosensor.

N-lauryltyramine capped copper nanoparticles exhibit a selective colorimetric response towards hazardous mercury(ii) ions and display true anti-biofilm and efflux pump inhibitory effects in E. coli

Hg²⁺ ions selectively decolorize CuNPs through aggregation.

Jacalin-capped silver nanoparticles minimize the dosage use of the anticancer drug, shikonin derivatives, against human chronic myeloid leukemia

Silver nanoparticles enhance the anticancer efficacy of shikonin derivatives.

An easily accessible and recyclable copper nanoparticle catalyst for the solvent-free synthesis of dipyrromethanes and aromatic amines

A facile method to prepare a reusable copper nanocatalyst is reported.

Platinum nanoparticles inhibit bacteria proliferation and rescue zebrafish from bacterial infection

Platinum nanoparticles rescue zebrafish from bacterial infection.

Myoepithelial cells in pathology

Myoepithelial cells are a normal constituent of the salivary acini and ducts and are found between the epithelial cells and the basement membrane. Microscopically myoepithelial cells are thin and spindle-shaped and ultrastructurally they possess a number of Cytoplasmic processes that extend between and over the acinar and ductal-lining cells, and they show features of both smooth muscle and epithelium. They play a vital role during expulsion of saliva and regulates the electrolytic exchange. They also perform as tumor suppressors and are considered to play a very important role in differentiation of various salivary gland tumors and help in the diagnosis of tumors. Neoplastic myoepithelial cells in both benign and malignant tumors can take numerous forms including epithelioid, plasmacytoid, spindle and clear cell variant, and this variability largely accounts for difficulties in histopathological diagnosis.

Spectroscopic investigation on the interaction of ruthenium complexes with tumor specific lectin, jacalin

Several ruthenium complexes are regarded as anticancer agents and considered as an alternative to the widely used platinum complexes. Owing to the preferential interaction of jacalin with tumor-associated T-antigen, we report the interaction of jacalin with four ruthenium complex namely, tris(1,10-phenanthroline)ruthenium(II)chloride, bis(1,10-phenanthroline)(N-[1,10]phenanthrolin-5-yl-pyrenylmethanimine)ruthenium(II)chloride, bis(1,10-phenanthroline)(dipyrido[3,2-a:2',3'-c]-phenazine)ruthenium(II)chloride, bis(1,10-phenanthroline)(11-(9-acridinyl)dipyrido[3,2-a:2',3'-c]phenazine)ruthenium(II) chloride. Fluorescence spectroscopic analysis revealed that the ruthenium complexes strongly quenched the intrinsic fluorescence of jacalin through a static quenching procedure, and a non-radiative energy transfer occurred within the molecules. Association constants obtained for the interaction of different ruthenium complexes with jacalin are in the order of 10(5) M(-1), which is in the same range as those obtained for the interaction of lectin with carbohydrate and hydrophobic ligand. Each subunit of the tetrameric jacalin binds one ruthenium complex, and the stoichiometry is found to be unaffected by the presence of the specific sugar, galactose. In addition, agglutination activity of jacalin is largely unaffected by the presence of the ruthenium complexes, indicating that the binding sites for the carbohydrate and the ruthenium complexes are different. These results suggest that the development of lectin-ruthenium complex conjugate would be feasible to target malignant cells in chemo-therapeutics.

Copper nanoparticles as an efflux pump inhibitor to tackle drug resistant bacteria

Casein capped copper nanoparticles at sub inhibitory concentrations function as an efflux pump inhibitor and restores susceptibility to antibiotics in drug resistant bacteria.

Sulfidation of silver nanoparticle reduces its toxicity in zebrafish

Chemical transformations of metal nanoparticles can be an important way to mitigate nanoparticle toxicity. Sulfidation of silver nanoparticle (AgNPs) is a natural process shown to occur in environment. Very few studies, employing microbes and embryonic stages of zebrafish, have shown reduction in AgNPs toxicity as a direct result of sulfidation. However the feasibility of reducing nanoparticle toxicity by sulfidation of AgNPs has never been studied in adult vertebrates. In this study, we have used adult zebrafish as a model to study the efficacy of sulfidation of AgNPs in reducing nanoparticle toxicity by employing a battery of biomarkers in liver and brain. While AgNPs enhanced liver oxidative stress, altered detoxification enzymes and affected brain acetylcholinesterase activity, sulfidation of AgNPs resulted in significant alleviation of changes in these parameters. Histopathological analyses of liver and sulphydryl levels also support the significance of sulfidated AgNPs in controlling the toxicity of AgNPs. Our study provides the first biochemical data on the importance of sulfidation of AgNPs in reducing biological toxicity in adult vertebrates.

Green synthesis of silver and gold nanoparticles employing levan, a biopolymer from Acetobacter xylinum NCIM 2526, as a reducing agent and capping agent

With a vision of finding greener materials to synthesize nanoparticles, we report the production and isolation of levan, a polysaccharide with repeating units of fructose, from Acetobacter xylinum NCIM2526. The isolated levan were characterized using potassium ferricyanide reducing power assay, Fourier transform infra-red (FTIR) spectroscopy and (1)H nuclear magnetic resonance spectroscopy ((1)H NMR). To exploit levan in nanotechnology, we present a simple and greener method to synthesize silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) using biopolymer, levan as both reducing and stabilizing agents. The morphology and stability of the AgNPs and AuNPs were examined by transmission electron microscopy (TEM) and UV-vis absorption (UV-vis) spectroscopy. The possible capping mechanism of the nanoparticles was postulated using FTIR studies. As synthesized biogenic nanoparticles showed excellent catalytic activity as evidenced from sodium borohydride mediated reduction of 4-nitro phenol and methylene blue.

A facile route to synthesize casein capped copper nanoparticles: an effective antibacterial agent and selective colorimetric sensor for mercury and tryptophan

A simple method was developed for the synthesis of copper nanoparticles (CuNPs) with relatively high concentration by using casein as a capping agent.

Isothermal titration calorimetric studies on the interaction of the major bovine seminal plasma protein, PDC-109 with phospholipid membranes

The interaction of the major bovine seminal plasma protein, PDC-109 with lipid membranes was investigated by isothermal titration calorimetry. Binding of the protein to model membranes made up of diacyl phospholipids was found to be endothermic, with positive values of binding enthalpy and entropy, and could be analyzed in terms of a single type of binding sites on the protein. Enthalpies and entropies for binding to diacylphosphatidylcholine membranes increased with increase in temperature, although a clear-cut linear dependence was not observed. The entropically driven binding process indicates that hydrophobic interactions play a major role in the overall binding process. Binding of PDC-109 with dimyristoylphosphatidylcholine membranes containing 25 mol% cholesterol showed an initial increase in the association constant as well as enthalpy and entropy of binding with increase in temperature, whereas the values decreased with further increase in temperature. The affinity of PDC-109 for phosphatidylcholine increased at higher pH, which is physiologically relevant in view of the basic nature of the seminal plasma. Binding of PDC-109 to Lyso-PC could be best analysed in terms of two types of binding interactions, a high affinity interaction with Lyso-PC micelles and a low-affinity interaction with the monomeric lipid. Enthalpy-entropy compensation was observed for the interaction of PDC-109 with phospholipid membranes, suggesting that water structure plays an important role in the binding process.

The membrane environment modulates self-association of the human GpA TM domain--implications for membrane protein folding and transmembrane signaling

The influence of lipid bilayer properties on a defined and sequence-specific transmembrane helix-helix interaction is not well characterized yet. To study the potential impact of changing bilayer properties on a sequence-specific transmembrane helix-helix interaction, we have traced the association of fluorescent-labeled glycophorin A transmembrane peptides by fluorescence spectroscopy in model membranes with varying lipid compositions. The observed changes of the glycophorin A dimerization propensities in different lipid bilayers suggest that the lipid bilayer thickness severely influences the monomer-dimer equilibrium of this transmembrane domain, and dimerization was most efficient under hydrophobic matching conditions. Moreover, cholesterol considerably promotes self-association of transmembrane helices in model membranes by affecting the lipid acyl chain ordering. In general, the order of the lipid acyl chains appears to be an important factor involved in determining the strength and stability of transmembrane helix-helix interactions. As discussed, the described influences of membrane properties on transmembrane helix-helix interactions are highly important for understanding the mechanism of transmembrane protein folding and functioning as well as for gaining a deeper insight into the regulation of signal transduction via membrane integral proteins by bilayer properties.