The authors Ponnurengam Malliappan Sivakumar, Suresh Ganesan and Prabhawathi Veluchamy wishes to dedicate this work to their guide Prof MD on the occassion of his birthdayNovel sixteen chalcones and thirteen 1,3,5-triphenyl-2-pyrazolines were synthesized and characterized using FT-IR, HR-Mass, NMR ( C CoSY) and XRD. These compounds were evaluated for their antibacterial activity against six micro-organisms, namely Bacillus subtilis NCIM 2718, Staphylococcus aureus NCIM 5021, Salmonella typhi NCIM 2501, Enterobacter aerogenes NCIM 5139, Pseudomonas aeruginosa NCIM 5029, and Proteus vulgaris NCIM 2813 by twofold dilution method using resazurin as the indicator dye. In the case of chalcones, compounds with hydroxyl and bromo substitutions in the B-ring favor activity and benzyloxy substitution irrespective of its position in the A-ring. In the case of 1,3,5-triphenyl-2-pyrazolines, chloro substitution in the A-ring favors activity. Hydrophilic ⁄ lipophilic balance of the compounds plays a major role in their antibacterial activity.

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Silver and gold nanoparticles (of average size ∼20–27 nm) were incorporated in PU (Polyurethane), PCLm (Polycaprolactam), PC (polycarbonate) and PMMA (Polymethylmethaacrylate) by swelling and casting methods under ambient conditions. In the latter method the nanoparticle would be present not only on the surface, but also inside the polymer. These nanoparticles were prepared initially by using a cosolvent, THF. PU and PCLm were dissolved and swollen with THF. PC and PMMA were dissolved in CHCl3 and here the cosolvent, THF, acted as an intermediate between water and CHCl3. FTIR indicated that the interaction between the polymer and the nanoparticle was through the functional group in the polymer. The formation of E.coli biofilm on these nanocomposites under low (in a Drip flow biofilm reactor) and high shear (in a Shaker) conditions indicated that the biofilm growth was higher (twice) in the former than in the latter (ratio of shear force = 15). A positive correlation between the contact angle (of the virgin surface) and the number of colonies, carbohydrate and protein attached on it were observed. Ag nanocomposites exhibited better antibiofilm properties than Au. Bacterial attachment was highest on PC and least on PU nanocomposite. Casting method appeared to be better than swelling method in reducing the attachment (by a factor of 2). Composites reduced growth of organisms by six orders of magnitude, and protein and carbohydrate by 2–5 times. This study indicates that these nanocomposites may be suitable for implant applications.

Subtilisin was immobilized on polycaprolactam and used for food packaging applications to reduce the transference of microorganisms from the packaging material to the packaged food material. The optimized conditions for subtilisin immobilization was as follows: pH, 8; temperature, 4 °C; glutaraldehyde, 0.5%; incubation time, 25 h; and subtilisin concentration, 600 μL. The formation of -CH═N- at 1576 cm(-1) in the Fourier transform infrared (FTIR) spectrum confirmed the immobilization. Subtilisin-immobilized polycaprolactam (SIP) exhibited the highest residual activity of 106.67 ± 4.41% and 104.67 ± 0.88% at 40 °C and pH 8 and retained residual activity of 94% at the end of 56 days when compared to 21.33 ± 4.10% in the case of free subtilisin. SIP significantly (p < 0.05) lowered the colony forming units (CFU), dry weight, and protein and carbohydrate contents in bacterial and fungal biofilm. Practical application of the SIP on ham steaks at 4 and 20 °C showed a 2-3 times reduction of Staphylococcus aureus as well as Escherichia coli cells in the range of p < 0.05.

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