A novel enzyme-free long-lasting chemiluminescence system based on a luminol functionalized β-cyclodextrin hydrogel for sensitive detection of HO in urine and cells.

A novel long-lasting chemiluminescent (CL) hydrogel (β-CD@luminol-Co) was synthesized by embedding luminol and cobalt ions (Co) into β-cyclodextrin (β-CD) through non-covalent interactions. Due to its porous structure and viscosity, the synthesized β-CD@luminol-Co hydrogel exhibited long-lasting CL properties and can emit light for 12 h under both alkaline and neutral conditions. In addition, the CL intensities of β-CD@luminol-Co were linear with the logarithm of the hydrogen peroxide (HO) concentration in the range of 1.0 × 10-1.0 × 10 M, and the limit of detection (LOD) was 0.63 × 10 M and 0.85 × 10 M under alkaline and neutral conditions, respectively. On this basis, an enzyme-free CL sensor based on β-CD@luminol-Co was fabricated for the sensitive detection of HO in human urine samples under alkaline conditions, and showed good accuracy and recovery. Since β-CD@luminol-Co showed good CL properties under neutral conditions, it can be applied to detect HO in cells. In order to prolong the emission wavelength of β-CD@luminol-Co for better cell imaging, β-CD@luminol-FL-Co was prepared by adding fluorescein (FL) to β-CD@luminol-Co. The as-prepared β-CD@luminol-FL-Co also displayed long-lasting CL properties and showed a linear relationship with HO concentrations. In addition, the maximum emission wavelength of β-CD@luminol-FL-Co was 520 nm, which was red-shifted by 95 nm compared with β-CD@luminol-Co. The methyl thiazolyl tetrazolium (MTT) assay results and confocal microscopy images illustrated that β-CD@luminol-FL-Co had low toxicity and can be taken up by A549 cells. Finally, β-CD@luminol-FL-Co was successfully applied for CL imaging and detection of intracellular HO in A549 cells under neutral conditions. This enzyme-free long-lasting CL system with high sensitivity can also be extended to real-time monitoring of HO.