Our Business
Disclosure under Regulation 46 of SEBI (LODR) RegulationsEmployee Speak
From ancient time, silver (Ag) and copper (Cu) are renowned for their anti-microbial efficiency. Ag and Cu nano-particles have attracted attentions for their applications in numerous fields. In past few years, copper being heavy metal, having known its side effects on human being and other living organisms, copper's direct use as preservative has been controlled in many industries.
However, silver nano-particles have unparalleled advantages due to its broad antimicrobial spectrum, high stability, low human toxicity.
Mechanism of anti-microbial effect of silver is not completely understood. Three mechanisms are proposed for silver nano-particles are, (i) gradual release of silver ions, followed by disruption of ATP production and DNA replication, (ii) direct damage to cell membrane by silver nano-particles and (iii) silver nano-particles and silver ion generation of reactive oxygen species.
Figure 1 explains possible mechanisms of silver to kill microbes.
These mechanism involves interaction of silver with thiols or disulfide groups of enzymes (4,6,9,13). Various routes are studied by scientists to use Ag NPs in textile, biomedical, dentistry, food packaging industries but rarely work has been done in paint industry. Though AG NPs are popular due to their unique properties, some detrimental effects of them are release of free silver ions, easy agglomeration, difficulty to be immobilized on surfaces, lack of controllability in synthesis etc. It leads to reduction in their efficiency (4,13,14,15).
The release of free silver ions is strictly controlled by many national law and control agencies worldwide (5,9). Polymerization is one of the best routes to control many of the above factors and enhance.
Antimicrobial polymers:
Another approach to achieve antimicrobial activity is antimicrobial polymers. Such polymers are designed with low surface energy and are engineered to release active agents from their surfaces. Antimicrobial polymers can be produced by synthesis of monomers having bio-cidal moiety and their polymerization or it can be co-polymerized with another monomer also.
Figure 2 explains the low surface energy of antimicrobial coating which reduces the microbial attachment and bio-cidal moiety kills the attached microbes subsequently.
Examples of antimicrobial polymers are N-halamine based polymers, quaternary amino functional polymers. These polymers can be used as binder or in an additive form.
Research work in this area is receiving more attention for their application in textile, food, biomedical industries. Synthesised polymers using N-halamine monomers, silver sulfadiazine which can be used as polymeric biocidal agents. N-halamine is a compound which contains one or more halogen-nitrogen bonds. This bond formation can be done by halogenation like bromination or chlorination of imide, amide or amine groups. Reaction for Halogen transfer from halamine in microbial cells results in disruption of cell and finally cell death. This patent invented the novel method of polymerization to incorporate halogenated monomer for textile application. B. Qian and coworkers studied micro/nanocapsules based on pickering emulsions showing dual self-healing and antibacterial properties.
Polysulfone/silica hybrid Pickering microcapsules have prepared using linseed oil. Silica particle modification have done with quaternary ammonium salts to make their surface active against bacteria. Modified silica surface can be adsorbed on negatively charged bacterial cell wall, resulting in cell death. Polymers containing reactive groups like trimethylsilyl (TMOS), (dimethylamino) ethyl methacrylate etc. have modified with silica particles.
Resulting polymer showed superhydrophilicity and antimicrobial performance against E.coli due o presence of quaternary ammonium group. Modified glass surfaces prepared using composite polymer showed high stability, antifogging property, easy cleaning and antibacterial efficiency. "Green" antimicrobial agent has synthesized by S.B. Aidarova and coworkers. Sio, nanoparticles as a shell and (trimethoxysilyl) propyl methacrylate (TMSPMA) loaded with 5-Dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT) as a core were synthesized as "submicrocontainers" and studied their antimicrobial activity. Pickering emulsion prepared using silica aqueous solution and oil phase added along with emulsifier for stabilisation.
In second stage photoinitiator used to carry out polymerization. Submicrocontainers with DCOIT showed 72% growth inhibition for A. niger, A. awamori and B. cereus, whereas free DCOIT showed 52% in 5 days duration.
Essential oils:
Essential oils are plant originated compounds that have antioxidant, antimicrobial, antiradical properties and hence are widely getting used in fields like paper, food, medical, cosmetics from centuries. Essential oils are basically complex mixture of volatile & non-volatile constituents which are produced by plants as secondary metabolites. They consists of terpene and terpenoids, aldehydes and phenols as a major functional groups.
Mechanism of antimicrobial action of essential oils is not fully understood yet, but few possible theories have explained the interaction of their different constituents with microorganism cells. For example, cinnamaldehyde, Carvacrol, Eugenol interact with intracellular protein and enzymes to disrupt protein synthesis and ATP production resulting in cell death. Whereas, Thymol, p-Cymene disturb cell membrane.
Figure 3 illustrates possible antimicrobial action of essential oils as per constituents.
