Antimicrobial peptides (AMPs) belong to a class of relatively short peptides family that have the ability to penetrate the cell membrane, form pores which eventually lead to cell death. Cecropin P1 (CP1, sequence SWLSTAKKLENSAKKRLSEGIAIAIQGGPR), an AMP with 31 amino acids and with a net positive charge of 5, was found to exhibit much higher antimicrobial activity against Gram-negative bacteria E. coli O157:H7 EDL933 compared to Gram-positive bacteria Listeria monocytogenes F4244. The minimum inhibitory concentration (MIC) of CP1 against E. coli O157:H7 EDL933 was 3.125 μg/well and exhibited the same antimicrobial activity against E. coli O157:H7 EDL933 when adsorbed onto silica nanoparticles. This was found to be consistent with preservation of α-helical secondary structure of CP1 upon adsorption as indicated by circular dichroism (CD) and molecular dynamics (MD) simulation. C-terminus cysteine modified Cecropin P1 (CP1C) was chemically immobilized onto silica nanoparticles with a Maleimide-PEG-NHS Ester linker of molecular weight 2000. The secondary structure of tethered CP1C as characterized by Fourier Transform Infrared Spectroscopy (FTIR) and Circular Dichroism (CD) was found to be the same as that of CP1C in solution and adsorbed. However, tethered Cecropin P1C exhibited much lower antimicrobial[GN1] activity against E.coli O157:H7 EDL933 compared to those in solution and adsorbed[GN2] . The interactions of 3:1 DOPC/DOPG mixed membrane (mimic of bacterial cell membrane) as well as DOPC pure membrane (mimic of mammalian cell membrane) with free CP1C and CP1C tethered with (PEO)3 linker were characterized using all atom molecular dynamics simulation and results compared with experiments.

Investigation of effects of adsorption and immobilization onto silica nanoparticles on antimicrobial activity of Cecropin P1 and Cecropin P1C

250th National Meeting (2015)

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