Ionically Imprinting-Based Copper (II) Label-Free Detection for Preventing Hearing Loss

Copper is a microelement with important physiological functions in the body. However, the excess copper ion (Cu²⁺) may cause severe health problems, such as hair cell apoptosis and the resultant hearing loss. Therefore, the assay of Cu²⁺ is important. We integrate ionic imprinting technology (IIT) and structurally colored hydrogel beads to prepare chitosan-based ionically imprinted hydrogel beads (IIHBs) as a low-cost and high-specificity platform for Cu²⁺ detection. The IIHBs have a macroporous microstructure, uniform size, vivid structural color, and magnetic responsiveness. When incubated in solution, IIHBs recognize Cu²⁺ and exhibit a reflective peak change, thereby achieving label-free detection. In addition, benefiting from the IIT, the IIHBs display good specificity and selectivity and have an imprinting factor of 19.14 at 100 μmol·L⁻¹. These features indicated that the developed IIHBs are promising candidates for Cu²⁺ detection, particularly for the prevention of hearing loss.