Antibacterial Activity of Selected Silver Nanoparticles Coatings - Our Initial Experience

Nanoparticles exhibits chemical and physical properties significantly different to their macro-scale counterparts composed of the same substance (due higher surface/volume ratio, colour, solubility, diffusivity,material strength, toxicity, thermodynamic, magnetic, optical and other
properties) and may have unique impacts on health and environment.
Extremelly small size (1-100 nm) enables them to enter the human body through usual or unusual routes, pass through cell membranes, or cross the blood-brain barrier. Gravity loses impact and importance, surface tension and Van der Waals constants has more importance in system of nano particles.
Nanotechnology is already used in various applications, with potential tobe applied at any stage in food industry: production, preservation, processing, packaging,transport, nanobarcodes for food authenticity and tracing, labelling, keeping the quality of food products, extend the products shelf-life, removal of undesirable tastes, flavours or allergens from food products, nano (bio)sensors for food safety, water filtration.
Risks of nanotechnology are still unknown and unpredictable. Initial scientific studies showed negative effects on living organisms and a potential for serious threat to human health.
Authorities of the most developed countries, have set up, guidance documents and procedures for nanoenabled products based on existing regulations, appropriate in vitro and in vivo ADME studies (absorption, distribution, metabolism and excretion) and requirements for standardised and harmonised analytical test methods for proper risk assesments, clear identification and characterization of nano-hazards.
Nanotechnology in medicine (Nanomedicine) apply for rapid and sensitive detection of pathogenic bacteria and low levels of viruses, in small sample volumes, at lower costs than current in-use technologies. This advance in early detection enables accurate and prompt treatment.
Nano-robots to make repairs at the cellular level are under development. Rapid and sensitive detection methods, based on nano (bio) senzors, are developed for food-borne pathogens E. coli, especially E. coli O157:H7, S. aureus, S. typhimurium, C. jejuni, E. cloacae, B. subtilis, L. monocytogenes. Detection sensor to detect bacterial biofilm formation on surfaces are under development.
New strategies to combat multydrug resistant microorganisms (MDR) are urgently needed and nanomaterials are very promising approach. Small size provides large surface of
nanoparticles and at least 50% of molecules will react to the microorganisms.
Metal nanomaterials (silver, gold, copper, titanium, zinc, magnesium,cadmium, and alumina) possess advantage of unique antimicrobial activities. Scientists offers also new complex antibacterial and antiviral nano systems on the basis of metal oxides or intermetallic oxide compounds (such as TiO2, ZrO2, SnO and SiO2).
Inside the human body ionic silver quickly combines with chloride to form an insoluble compound called silver chloride which is far less reactive than metallic silver nanoparticles.
Some studies established that silver ions has strongest bactericidal effect, cooper and gold weaker one.
In our preliminary study on antibacterial activity of several different compositions of nanoparticle coatings (titanium, inox and silver), we found antimicrobial activity of silver, double composition of titanium and
silver against Staphylococcus aureus and Staphylococcus epidermidis, but not for E. coli, Pseudomonas aeruginosa, Listeria monocytogenes and Candida albicans. More extensive studies will follow.

Key words: Nanoscience, nanoparticles, silver, ions, biofilm, antimicrobial, antibiotic, resistance.