Repurposing an antimicrobial peptide for the development of a dual ion channel/molecular receptor-like platform for metal ion detection

Abstract

The presence of non-essential metals in the environment as contaminants is prone to cause hazardous health problems following accumulation in the human body and the ensuing toxic effects. This calls for continuous discovery and innovation in the realm of developing easy-to-operate, cheap and sensitive sensors. Herein, we describe the proof of concept approach for designing a molecular receptor-like, chimeric sensor based on the pore-forming peptide alamethicin (Alm), tethered via a linker with an ultrashort peptide nucleic acid (PNA) moiety, capable of generating functional ion channel oligomers in planar lipid membranes. The working principle of the sensor exploits the ability of Hg²⁺ ions to complex mismatching thymine–thymine sequences between the PNA receptor moiety on Alm oligomers and free, thymine-based, single-stranded DNAs (ssDNAs) in solution, thus creating a stable base pair at the oligomer entrance. This generates a transducing mechanism which converts the metal ion complexation into a specific electrical signature of the self-assembled Alm oligomers, enabling selective Hg²⁺ ion detection. The platform is programmable, whereby the simple exchange of the PNA sequence and its ssDNA counterpart in solution rendered the system selective for Cu²⁺ ion detection. With further optimization, the presented solution has the potential to translate into miniaturized, cost-effective biosensors suitable for the real-time, label-free and continuous detection of metal ions or other biomolecules.