The peptide forming
mixed secondary structures of beta sheets and random coils
(Fig. 1A) has been tested for its antimicrobial activity against E. coli,
Pseudomonas aeruginosa, Staphylococcus aureus and Staphylococcus
epidermidis in broth medium with minimum inhibitory concentration
(MIC) value in the range of 5–20 mM (Xu et al., 2015; Yang et al.,
2014). In this work, we will demonstrate the use of these peptides
as recognition sites for bacterial detection. To design the sensor, the
peptides were modified with an external cysteine (C) residue that
allows targeted attachment and site-specific orientation to a gold
surface using the affinity of cysteine for gold (Fig. 1). We use electrochemical
impedance spectroscopy (EIS) as transduction technique
to quantify the interaction between the synthetic sAMPs and
bacteria. The effect of the orientation of peptides on the electrode
surface was investigated by comparing the impedimetric responses
of the sensors modified with the engineered sAMPs with and
without cysteine.