The detection of viruses like SARS-CoV-2 and influenza A is a challenge that requires simple and fast diagnostic platforms. To address this issue, we have synthesized a gold-binding peptide that exhibits an antigen affinity for the helix-loop-helix structure of virus nucleic acids [1, 2]. This peptide has been used to form a gold-peptide nanoparticle (GPNP) composite as a promising platform for viral diagnosis.
To investigate peptide-gold interactions, we employed a photochemical strategy where the peptide functions as an in situ reducing, capping, and stabilizing agent without the addition of toxic reducing agents. Upon UV exposure, the aromatic residue on the peptide surface allows for the reduction of gold ions through photoionization. The resulting GPNP composites were characterized by TEM, XPS, and HR-TEM. The results show that GPNPs are face-centered cubic in structure and have a well-defined d-spacing of about 0.2 nm.
The GPNP exhibited good stability, as indicated by the low values of zeta potential and the FTIR spectra in Figure S3. The XPS spectra confirmed that the peptide-gold interface has a strong electrostatic interaction and is stabilized by lysine binding to the gold ions. Furthermore, we observed that GPNPs could self-assemble on the peptide nanotemplate and are arranged in a highly organized manner. This organization is attributed to a possible bridging effect induced by the peptide helix-loop-helix binding to multiple gold particles. We have also demonstrated that the degree of gold colloid flocculation can be controlled by modifying the peptide’s overall ionic charge.