Coordination of di-Histidine-containing hexapeptides with cupric ion and its application in electrochemical detection

Surface immobilization strategies for the development of electrochemical nucleic acid sensors

Following the recent pandemic and with the emergence of cell-free nucleic acids in liquid biopsies as promising biomarkers for a broad range of pathologies, there is an increasing demand for a new generation of nucleic acid tests, with a particular focus on cost-effective, highly sensitive and specific biosensors. Easily miniaturized electrochemical sensors show the greatest promise and most typically rely on the chemical functionalization of conductive materials or electrodes with sequence-specific hybridization probes made of standard oligonucleotides (DNA or RNA) or synthetic analogues (e.g. Peptide Nucleic Acids or PNAs). The robustness of such sensors is mostly influenced by the ability to control the density and orientation of the probe at the surface of the electrode, making the chemistry used for this immobilization a key parameter. This exhaustive review will cover the various strategies to immobilize nucleic acid probes onto different solid electrode materials. Both physical and chemical immobilization techniques will be presented. Their applicability to specific electrode materials and surfaces will also be discussed as well as strategies for passivation of the electrode surface as a way of preventing electrode fouling and reducing nonspecific binding.

Supramolecular assemblies of histidine-containing peptides with switchable hydrolase and peroxidase activities through Cu(II) binding and co-assembling

Modulating enzyme activities or functionalities is one of the primary features of biological systems, which is, however, a great challenge for artificial enzyme systems. In this work, we designed and synthesized a series of self-assembling peptides from histidine and other amino acids (Asp, Ser, Lys or Arg), which exist in the active site of natural enzymes. These peptides could undergo a conformational transition from random coils to β-sheet structures under physiological conditions and formed self-assembled nanotubes with obvious hydrolase activities. After incorporation of transition metal ions such as Cu²⁺, these peptides could coordinate with Cu²⁺ ions, switch molecular conformations, and self-assemble into hybrid nanomaterials with altered morphologies and peroxidase-like activities. This work illustrates a facile approach for constructing artificial enzymes from self-assembling peptides with histidine residues whose catalytic functions could be modulated by incorporation of Cu²⁺ ions.