The multilayer of polyethylenimine (PEI) and carrageenan (κ, ι, λ) formed by layer-by-layer assembly was investigated for its antibacterial activity against Enterobacter cloaceae, Staphylococcus aureus and Enterococcus faecalis 29505 for potential use as coating on biomaterial surface. All the multilayers exhibited growth inhibition. PEI/Iota carrageenan multilayer was effective in inhibiting the growth of the E. cloaceae, S. aureus and E. faecalis while PEI/Lambda carrageenan was effective in inhibiting the growth of E. cloaceae. Results of the paper strip test for combined action of carrageenan and PEI showed synergism with regards to bacterial growth inhibition. The multilayers had also contact-killing effect with the test organisms. The multilayer was also characterized by atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and biomolecular interaction analysis.
The tensile and tear strength of carrageenan film from Philippines Eucheuma species were investigated using NEC tensilon universal-testing machine according to American Society for Testing Materials methods. These properties are important for assessing carrageenan film as packaging material. The kappa and iota types were used in the study. The effect of glycerine on the tensile and tear strength including elongation was also evaluated. Addition of glycerine tended to lower the tensile strength of the film and increase its elongation properties including the tear strength. Carrageenan film without glycerine was much stronger. Glycerine made the film more flexible and easy to deform. The composite film of carrageenan and konjac gum did not exhibit elongation. It also showed higher tensile strength than did the composite film of carrageenan and xanthan gum. Compared with iota-type carrageenan film, kappa-type carrageenan film without glycerine was more comparable to low-density polyethylene (LDPE) film in terms of tensile strength as was the composite film of carrageenan-konjac gum. The kappa-type carrageenan film with glycerine was more comparable to LDPE film in terms of tear strength. The elongation reading for carrageenan film was lower than that for LDPE film. Morphologic studies showed that the carrageenan film had sets of pores distributed randomly at different places as compared to LDPE film. It also showed that the carrageenan film was more fibrous than LDPE film.
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