Previous theoretical work by Pogodin et al. and Xue et al. on the mechanics of bactericidal effect on the nanopatterned surfaces show that optimal bactericidal surface can be achieved with specific dimensions of the nanofeatures on the surface. According to Xue et al., sharper pillars and less dense pillars provide better bactericidal activity compared to the one found on cicada wing [1, 2]. Recently, another model on the bactericidal effect of the nanopillars suggests that one can have higher bactericidal properties if the surface has broader and denser pillars. This project aims to understand how the differences in topography effects the bactericidal properties and how the bacteria interact/behave with the nanostructured surfaces .
A template method (anodisation and hot embossing) is used to design and fabricate three different polymeric nanopillars on polyethylene terephthalate (PET) substrate that differs in terms of sharpness and density of the nanopillars. Contact angle and surface energy of the test surfaces was measured using KRÜSS Drop Shape Analyzer (DSA100). Two Gram-negative bacteria (E. coli and K. Pneumoniae) and one Gram-positive bacteria (S. aureus) were tested against the nanostructured surfaces for three hours. The membrane susceptibility and vitality were determined using Live/Dead and Bactiter Glo assays, respectively. Colloidal probe AFM was performed to investigate the adhesion force, shear force and friction coefficient of the test surfaces. AFM, SEM, FIB-SEM and fluorescence microscope images were used to understand the nanopillar-bacteria interaction. 3D model of the bacteria adhere to the nanostructured surface was reconstructed using Avizo software (Fig 1).
1. Pogodin, S., Hasan, J., Baulin, V.A., Webb, H.K., Truong, V.K., Nguyen, T.H.P., Boshkovikj, V., Fluke, C.J., Watson, G.S., Watson, J.A. and Crawford, R.J. (2013) Biophysical model of bacterial cell interactions with nanopatterned cicada wing surfaces. Biophysical journal, 104(4) pp.835 – 840
2. Xue, F., Liu, J., Guo, L., Zhang, L. and Li, Q., (2015). Theoretical study on the bactericidal nature of nanopatterned surfaces. Journal of theoretical biology, 385, pp.1-7.
3. Li, X., (2016). Bactericidal mechanism of nanopatterned surfaces. Physical Chemistry Chemical Physics, 18(2), pp.1311-1316