Paper-Based Fluorogenic Device for Detection of Copper Ions in a Biological System

A new paper-based device is fabricated for the detection of copper ions in a biological system, which is inexpensive, fast, and environmentally friendly. Compared with the advanced diagnostics, which have been used widely in well-equipped laboratories, the paper-based devices are affordable in resource-limited settings because basic infrastructure and trained operators are not prerequisites for using such devices. This work presents a novel fluorogenic device for rapid, highly accurate, sensitive, and selective detection of copper ions (Cu²⁺) based on fluorescence "turn on" of the probe, which is consisted of fluorescein moieties and oxyalkyl chain on the microfluidic paper-based analytical devices. The probe exhibits emissions at 520 nm, under the excitation wavelength of 460 nm. The fluorescence can be selectively "turned on" upon exposure to Cu²⁺, and the signal will be enlarged due to the higher concentration. The lowest detection limit of this fluorogenic device is 0.41 pM. In addition, this device can be employed to effectively detect Cu²⁺ in the biological system as urine, serum, and cytochylema. In the presence of Cu²⁺, the device would undergo a distinct fluorescence intensity increase, which can be readily observed in the trace amount of Cu²⁺ concentrations. Compared with references on Cu²⁺ detection, our test paper presents a lower detection limit and more portable fabrication. The paper-based fluorogenic sensor is cost-effective and user-friendly and has a high sensitivity and good selectivity, indicating its great application promise for comprehensive sample and point-of-care detection.