Antimicrobial materials

An alternative packaging is the combination of food-packaging materials with antimicrobial substances to control microbial surface contamination of foods. For both migrating and nonmigrating antimicrobial materials, intensive contact between the food product and packaging material is required and therefore potential food applications include especially vacuum or skin-packaged products (Vermeiren and others 2002). 

The capsules contained a mean of 82 mg feverfew and thus the level of activity calculated as parthenolide can be estimated as 0.67%. Other studies quote 0.87% sesquiterpene lactones calculated as parthenolide [27] and 0.25-0.30% of active (antimicrobial) material [33]. Bohlmann s extraction of individual components from the dried plant yielded 116 mg sesquiterpene lactones/kg dried feverfew which amounts to less than 0.01 % [17]. Another extraction yielded 330 mg endoperoxides/kg and 56 mg canin/kg alone [19] which would amount to a level of sesquiterpene lactones of at least 0.04%. Thus, the level of sesquiterpene lactones appears to vary with different sources of the plant and this could have been due to a number of factors including the conditions in which feverfew was grown, the season in which it was picked and the way in which it was stored. Another important determinant of the parthenolide content of feverfew appears to be the geographical location. A recent survey of commercial preparations found that all the North American commercial products tested contained less that 0.1% parthenolide, wheras much higher values were obtained for British products. A minimum level of 0.2% parthenolide in commercial products has been proposed by the Health Protection Branch of Health and Welfare Canada [71]. 

There are many applications in the medical and food sanitization fields for which antimicrobial surface coatings are needed. There are commercially available products making antibacterial claims, but they are limited in their applications by such factors as a poor spectra of activity, high cost, and toxicity. Work in the laboratories at Auburn Uifiversity over the past two decades has established a novel class of heterocyclic orgaific compounds termed A-halamines that have been demonstrated to be excellent antimicrobial materials for a broad variety of applications. 

In 2008, an antimicrobial ASA plastic type was introduced (39). This was the first ASA type with antimicrobial properties. The antimicrobial material contains silver compounds that are incorporated into the plastic in order to impart its surface with a germicidal effect. 

Bozja J, Sherrill J, Michielsen S et al. (2003) Porphyrin-based, light-activated antimicrobial materials. J Polym Sci A Polym Chem 41 2297-2303... 

Sambhy V, MacBride MM, Peterson BR et al. (2006) Silver bromide nanoparticle/polymer composites dual action tunable antimicrobial materials. J Am Chem Soc 128 9798-9808... 

Free silver ions are the active components of antimicrobial silvers, and it has been shown that as little as one part per million of elemental silver in solution is an effective antimicrobial. Materials such as polymers, charcoal, and hydrocolloids when formulated with silver not only aid wound management and healing but also regulate its release into the wound environment and surrounding tissues. Silver ions kill micro-organisms by inhibiting cellular respiration and cellular function. " It is known that their mode of action is exerted by binding cysteine residues on the cell walls of yeasts such as C. albicans thereby... 

To put the antimicrobial into a film, at the time when the film is produced. However, this is not cost effective and the antimicrobial material, which is then not exposed to the surface of the film is not effectively active. 

No.l, 1st Jan.2003, p.41-7 GRAFTING OF LIGHT-ACTIVATED ANTIMICROBIAL MATERIALS TO NYLON FILMS... 

The basic types of antinucrobial food packaging films are outlined and additives used in antimicrobial materials are discussed, with particular reference to potassium soibate, nisin, imazalil, allyl isothiocyanate and triclosan. The production of antimicrobial films by modification of the polymer chain itself is also mentioned and the natural antimicrobial activity of chitosan is considered. 17 refs. 

A method for producing an improved antimicrobial material is disclosed whereby a soft, diy, iodine/acetalised polyviityl alcohol complex sponge material is produced which has a pleasing yellow-gold colouration indicating activation of the antimicrobial elements in the complex. 

These biopolymers can be used for the immobilization of metal ions not only with the final objective of metal recovery (and subsequent valorization by desorption or chemical/thermal destmction of the polymer matrix) but also for elaborating new materials or designing new applications. Depending on the metal immobilized on the biopolymer, it is possible to design new sorbents (immobilization of iron on alginate [119], of molybdate on chitosan [59], for As(V) removal, of silver on chitosan for pesticide removal [120]), supports for affinity chromatography [121], antimicrobial material [122], drug release material [123], neutron capture therapy [124], and photoluminescent materials [125]. These are only a few... 

CHEMILUMINESCENT ANALYSIS OF HYDROGEN PEROXIDE GENERATION FROM NATURAL ANTIMICROBIAL MATERIALS... 

Standard strains of Staphylococcus aureus (IF012732) and Escherichia coli (IF03972), cultured in SCD agar, and a lO cfu/mL bacterial solution was prepared using 10% glycerol solution. The bacterial solution was diluted 10 times with a 100 mmol/L phosphate buffer (pH 7 or pH 10). Each plant extract was added to the solution, and the final concentration was 0.25%. These mixtures were incubated at 37 C for 24 h. After the incubation period, the reacted mixtures were again diluted with fresh SCD broth on a 96-well plate. These plates were then incubated at 37 C for 2 days. The turbidity (595 nm) of the broth in the plate was measured with a plate reader (Spectra image, Tecan, Austria), and the number of sterilized cells were estimated. We were able to define the antimicrobial materials that were able to sterilize over 10 cfu/mL of the bacteria used in this procedure. 

Hydrogen Peroxide Generation from Natural Antimicrobial Materials 321... 

In the case of natural polymers, polysaccharides like cellulose and chitosan are widely studied as antimicrobial films and barrier/coating materials. The following section reviews the recent studies on cellulose and chitosan having current and potential use as antimicrobial material for active food packaging systems. 

Infections caused by antibiotic-resistant bacteria expose an important risk to human health around the world. These bacteria are very resistant to traditional antibiotics owing to acquired resistance, inadequate diffusion and intracellular inactivation. Therefore, the development of novel antimicrobial materials with high protection and antibacterial activity, which lack bacterial resistance, is critical. 

Recently, a water-based polymer synthesised from N-chloro-2,2,6,6-tetramethyl-4-pipridinyl methacrylate (Cl-TMPM) was prepared via emulsion polymerisation (Figure 10.3). Furthermore, the addition of this antimicrobial material to commercial water-based latex paints led to antimicrobial activity against methicillin-resistant Staphylococcus aureus, vancomycin-resistant enterococcus, Escherichia coli, Candida tropicalis, bacteriophage MS2 virus and Staphylococcus chartarum [53]. 

Cationic polymer-functionalised gold NP have large concentrations of positive charge, which promote their adsorption onto negatively charged bacterial membranes via electrostatic interactions. This kind of antimicrobial material, with effective antibacterial activity and better biocompatibility, can promote the healing of microbially infected wounds and could have promising applications in the biomedical field. 

Textile fabrics are finished with effective antimicrobial substances like ammonium, chlorinated diphenylethers (Triclosan), bisphenols, silver zeolites or cyclodextrines. Silver is an effective antimicrobial material and the constant release of a small amount of silver ions will kill bacteria or fungal growth. Silver particles may be added to the molten polymer or a silver coating may be applied to the fibres by a galvanic process. 

A great contribution to R D of antimicrobial materials gave researchers fi-om Japan, USA, Switzerland, Great Britain, Russia, Poland, Austria and France. However, the greatest contribution undoubtedly belongs to Japanese, in this moment presenting world leaders in manufacturing of antimicrobial textile materials [1-20]. 

Fig.4. Inhibition of the groiwth of tested microorganisms treated with antimicrobial material "PP/viscose-gentamicin su te 0,lmg/cm, which spent 5, 10 and IS min in physiological solution.

Sambhy, V., MacBride, M.M., Peterson, B.R. and Sen, A. 2006. Silver bromide nanoparticle/ polymer composites Dual action tunable antimicrobial materials. 

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