Chiral Cobalt Nanocluster-Driven Chemiluminescent System for the Facile Discrimination of Carnitine Enantiomers with a Hydrogel-Assisted Strategy

Facile chiral discrimination without relying on chromatographic techniques has long been a huge challenge due to the minimal differences in the physicochemical properties of enantiomers. Polysaccharide hydrogels with natural chiral selectivity can be promising materials for constructing chiral discrimination platforms. In this study, l-cysteine-induced cobalt nanoclusters (LC-CoNCs) were prepared and utilized as chiral nanozymes for promoting the chemiluminescent (CL) signal of a luminol-H₂O₂ system. Based on the competitive affinity of LC-CoNCs and carnitine enantiomers on a Ca²⁺ crosslinked sodium alginate (SA) hydrogel interface, a CL method was established for the effective discrimination of carnitine enantiomers. With this strategy, d-carnitine led to a significantly inhibited CL signal, whereas l-carnitine did not exhibit an inhibition effect on the CL signal. According to the results of density functional theory calculations and contact angle measurements, the hydrogel shows an affinity sequence of d-carnitine > LC-CoNCs > l-carnitine due to the synergistic effect of SA and Ca²⁺, which is the foundation for achieving effective discrimination. This approach demonstrated acceptable accuracy for assaying d-carnitine in complex matrices such as drug preparation and milk. This work pioneers the combination of a polysaccharide hydrogel as a chiral selector with a nanozyme as the CL indicator for the effective discrimination of enantiomers, offering an innovative tool for the development and production of chiral drugs.