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

Application of a near-infrared viscosity-responsive fluorescent probe for lysosomal targeting in fatty liver mice

Viscosity is a fundamental property in biological systems, influencing organelle function and molecular diffusion. Abnormal viscosity is associated with diseases such as metabolic disorders, neurodegeneration, and cancer. Lysosomes, central to cellular degradation and recycling, are sensitive to viscosity changes, which can disrupt enzymatic activity and cellular homeostasis. Monitoring lysosomal viscosity provides essential information on lysosomal health, helping to uncover underlying mechanisms in various diseases. Recognizing the need for effective monitoring of lysosomal viscosity changes in living cells, we have developed a near-infrared (NIR) viscosity-responsive fluorescent probe, VFLyso, specifically designed for lysosomal targeting. Based on the twisted intramolecular charge transfer (TICT) mechanism, VFLyso exhibits strong NIR fluorescence, a fast response, and a notable fluorescence response to viscosity variations (F/F0 = 65.5-fold), along with excellent selectivity and stability under physiological conditions. Our studies demonstrated that VFLyso could accurately monitor lysosomal viscosity changes in both cell cultures and animal models, including zebrafish and mouse models of fatty liver. This work not only provides a powerful tool for real-time monitoring of lysosomal viscosity but also offers valuable insights into the role of viscosity in disease progression, paving the way for potential diagnostic applications in related disorders.

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.