Thin films of silk-fibroin and its blend with chitosan strongly promote biofilm growth of Synechococcus sp. BDU 140432.

The activating role of different polymer thin films coated over polystyrene support on the Synechococcus sp. biofilm growth was examined concurrently by measuring biofilm florescence using a dye and by measuring cell density in the isolated biofilm. Compared to blank (no coating), the increase in biofilm formation (%) on silk, chitosan, silk-chitosan (3:2) blend, polyaniline, osmium, and Nafion films were 27.73 (31.16), 21.55 (23.74), 37.21 (38.34), 5.35 (8.96), 6.70 (6.55) and (nil), respectively with corresponding cell density (%) shown in the parentheses. This trend of biofilm formation on the films did not significantly vary for Escherichia coli and Lactobacillus plantarum strains. The films of 20 residues long each of glycine-alanine repeat peptide, which mimics a silk fibroin motif, and a hydrophobic glycine-valine repeat peptide, increased the biofilm growth by 13.53 % and 26.08 %, respectively. Silk and blend films showed highest adhesion unit (0.48-0.49), adhesion rate ((4.2-4.8)×10(-6), m/s) and Gibbs energy of adhesion (-8.5 to -8.6kT) with Synechococcus sp. The results confirmed interplay of electrostatic and hydrophobic interaction between cell-surface and polymer films for promoting rapid biofilm growth. This study established that the thin films of silk and the blend (3:2) promote rapid biofilm growth for all the tested microorganisms.