Antimicrobial Nanomaterials in the Food Industry

Nanoparticles of metals interacting with cellular components and biomacromolecules including DNA and RNA alter cellular processes. Concerning the antimicrobial activity, the metal nanoparticles in nanomolar concentrations inhibit the growth of bacterial strains. Even though the general mechanism of metal nanoparticle action has not been fully understood yet, among current accepted schemes belong the damage of the microbial enzymes by the release of metal ions, the membrane integrity changes, penetration into the cytoplasm of bacteria and accumulation in the periplasmic space or the reactive oxygen species formation due to the effect of metal nanoparticles. Moreover, G+ bacteria react remarkably later on the effect of metal nanoparticles compared to G- bacteria, which is reflected in the later inhibition of cell division. The aim of this study is to describe the properties of metal nanoparticles (silver, selenium, copper or zinc nanoparticles) and to compare their antimicrobial properties in complex with chitosan on the bacterial strains Staphylococcus aureus and Escherichia coli

Development of new silver nanoparticles suitable for materials with antimicrobial properties.

Silver nanoparticles are the most important nanoparticles in connection with the antimicrobial effect. Nowadays, the green synthesis of various types of nanoparticles is rapid, effective and produce less toxic nanoparticles often with specific properties. In our experiment we have developed and described in details various types of silver nanoparticles synthesized chemically or by the green synthesis. Nine different silver nanoparticles were synthesized, three by citrate method at different pHs (8; 9; 10), four using gallic acid at alkaline pHs (10; 11), and two by green synthesis using green tea and coffee extracts, both at pH 9. Characterisation of silver nanoparticles was performed using dynamic light scattering, scanning electron microscopy, and ultraviolet-visible absorption spectroscopy. Silver nanoparticles prepared by green synthesis showed the highest antioxidant activity and also ability for quenching of free radicals. Antibacterial activity of silver nanoparticles was determined on bacterial cultures such as Staphylococcus aureus and Escherichia coli. Silver nanoparticles synthesized using green tea and coffee extracts showed the highest antibacterial activity for both bacterial strains. Minimal inhibition concentration for both strains was found to be 65 {aelig}M at each silver nanoparticle synthesized using green synthesis

Dependence of antibacterial properties of silver nanoparticles on their surface modification.

Nanosilver, in the form of colloidal silver, has been used for many years. In recent years, the development of efficient green chemistry methods for the synthesis of metal nanoparticles by organisms has become a major focus of researchers. The different forms of nanoparticles prepared by green synthesis using plants are dependent on the structure as well as the potential reactions of molecules present in plant extracts. These forms of nanoparticles can exhibit antibacterial activity to any bacterial strain. The surface of silver nanoparticles (AgNPs) prepared by green synthesis using plants is modified with polyphenols, terpenoids and flavonoids that increase their antibacterial activity. Five types of AgNPs using inorganic synthesis as well as five types of AgNPs using green synthesis were successfully prepared. The AgNPs generated by inorganic synthesis differed in various concentrations of reducing agent (NaBH4, gallic acid). In addition, the AgNPs prepared by green synthesis are easily identified according to the plant extract entering into the synthetic reactions. Extracts of C. sinensis (green tea 1 and 2), T. erecta (Marigold), H. perforatum (St.John's wort) and A. cepa (onion) were utilised for the green synthesis. Green synthesized AgNPs had a higher ability for quenching of radicals. Antibacterial activity of AgNPs was determined on bacterial cultures S. aureus and 'E. coli. AgNPs synthesized using green tea showed the highest antibacterial activity which was for S. aureus 96 % and for E. coli 95 %. The changes in bacterial biochemical parameters were also determined. AgNPs synthesized using St. John's wort caused the highest numbers of biochemical changes (9 cases) in comparison with control. Changes in bacterial biochemical parameters due to effect of AgNPs is a significant discovery which will be worth of further investigation

Biophysical study of CdTe quantum dots interactions with albumin and antibody as the base of photodynamic therapy.

Photodynamic therapy is a relatively new type of cancer treatment, or eventually it is used at the elimination of undesirable pathogenic microorganisms. Quantum dots (QDs) are semiconducting nanocrystals with a size of 2-20 nm and can be used in photodynamic therapy. Two types of CdTe QDs were prepared by microwave synthesis (500 W), typical absorption spectra had maxima 'green = 554 nm, - yellow = 580 nm. The determined size of the generated nanoparticles ranged between 5 - 10 nm. CdTe QDs were further studied by fluorescence analysis at excitation wavelength - = 250 nm to obtain emission maxima (?em552) for green and (?em582) for yellow nanoparticles. Interaction study of CdTe QDs with bovine serum albumin (BSA) and with polyclonal chicken antibodies against sarcosine (AntiSar) was performed. BSA (100, 50, 25, 12.5, 6.3, 3.1, 1.6 and 0 'M) and AntiSar (20, 10, 5, 2.5, 1.3, 0.7, 0.3, and 0 g/L) were monitored with 1:1 addition of 50 'M QDsgreen or QDsyellow. The decrease in intensity of the normalized fluorescence signal in the presence of BSA or AntiSar was observed by 70-90%. The observed dependencies showed a linear trend (R2 = 0.9) with relative error of 9-12% calculated from 5 independent repetitions. In addition, it was possible to monitor the signal shift to shorter wavelengths at the highest applied BSA concentration by 4-16 nm. The obtained data suggest that the size of individual QDs will affect intensity of an interaction with biomolecule. Nanoconstructs should therefore be targeted according to these experimental data for their intended use. In further experiments, CdTe QDs modified with AntiSar will be used for targeted prostate cancer therapy using photodynamic effect

The effect of platinum derivatives on both bacterial and human cells after application of platinum derivatives alone or encapsulated in liposomes.

<p>Relative change of growth rate of (A) <i>S</i>. <i>aureus</i> bacterial culture and (C) HFF after treatment with Pt-derivatives (100 μg/mL of Pt) during 24 h (bacterial culture) and 100 h (HFF) long experiments. (a) Cell culture without any treatment, (b) LipoCisPt, (c) CisPt, (d) LipoPtNPs and (e) PtNPs. Percentage survival of (B) <i>S</i>. <i>aureus</i> bacterial culture and (D) human foreskin fibroblasts (HFF) after 24 and 100 h of treatment with Pt-derivatives (100 μg/mL of Pt) alone and encapsulated in liposomes. For all measurement n = 3.</p

The Composites of Graphene Oxide with Metal or Semimetal Nanoparticles and Their Effect on Pathogenic Microorganisms

The present experiment describes a synthesis process of composites based on graphene oxide, which was tested as a carrier for composites of metal- or metalloid-based nanoparticles (Cu, Zn, Mn, Ag, AgP, Se) and subsequently examined as an antimicrobial agent for some bacterial strains (Staphylococcus aureus (S. aureus), methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli (E. coli). The composites were first applied at a concentration of 300 µM on all types of model organisms and their effect was observed by spectrophotometric analysis, which showed a decrease in absorbance values in comparison with the control, untreated strain. The most pronounced inhibition (87.4%) of S. aureus growth was observed after the application of graphene oxide composite with selenium nanoparticles compared to control. Moreover, the application of the composite with silver and silver phosphate nanoparticles showed the decrease of 68.8% and 56.8%, respectively. For all the tested composites, the observed antimicrobial effect was found in the range of 26% to 87.4%. Interestingly, the effects of the composites with selenium nanoparticles significantly differed in Gram-positive (G+) and Gram-negative (G−) bacteria. The effects of composites on bacterial cultures of S. aureus and MRSA, the representatives of G+ bacteria, increased with increasing concentrations. On the other hand, the effects of the same composites on G− bacteria E. coli was observed only in the highest applied concentration

Selected haematological parameters of erythrocytes mixture with platelets and oxidative stress (GSH/GSSG) in the mixture after application of Pt derivatives encapsulated in liposomes or alone in concentrations 0, 12.5, 25, 50, 100 and 200 μg/mL of Pt and 0, 0.6, 1.3, 2.5, 5 and 10 mg/mL of liposomes.

<p>(A) Histograms of (a) erythrocytes and (b) platelets, and (c) visualisations of liposomes in the Baso channel after application of LipoCisPt, CisPt, LipoPtNPs and PtNPs. GSH/GSSG ratio of erythrocytes mixture with platelets in the same concentrations as in A—(B) LipoCisPt, (C) CisPt, (D) LipoPtNPs, and (E) PtNPs. (F) Mean of GSH/GSSG ratio. For all measurement n = 3, significant difference is indicated by *p<0.05.</p