l-Cysteine-Functionalized Ru in Chain-like Nanostructures for Colorimetric Detection of Lysophosphatidylcholine

Understanding the interaction of capping molecules with inorganic nanozymes to modulate catalytic activity is of great interest because it could bring them one step closer to natural enzymes. This study demonstrates the ability of l-cysteine (Cys) to modulate the enzymatic activity of nanozymes by varying their thickness on nanoparticle surfaces. The Cys-functionalized Ru nanoparticles in chain-like two-dimensional nanostructures (Cys-Ru NSs) with excellent peroxidase-like activity were synthesized using a one-pot wet chemical method. Surprisingly, Cys tunes the peroxidase-like activity of Cys-Ru NSs at a specific concentration. Furthermore, Cys excels at controlling the surface properties of Ru nanoparticles, which induces nanoparticle self-assembly and improves colloidal dispersion and stability. A colorimetric assay for lysophosphatidylcholine (LPC) detection was developed by combining hydrogen peroxide produced by enzymatic oxidation of LPC with Cys-Ru NS-catalyzed 3,3′,5,5′-tetramethylbenzidine oxidation. The colorimetric assay demonstrated a broad linear detection range of 10–800 μM with a regression constant of 0.99 and a limit of detection of 10 μM. These colorimetric changes can be seen with the naked eye. In addition, the assay showed good specificity and 106.1–118.1% recovery of LPC from spiked human serum samples. The present Cys-Ru NS-based LPC assay is an excellent way to overcome the shortcomings of existing LPC assays, which does not require expensive equipment, skilled technicians, and lengthy analysis times.