Ratiometric fluorescence detection of superoxide anion based on AuNPs-BSA@Tb/GMP nanoscale coordination polymers.

A novel ratiometric fluorescence nanosensor for superoxide anion (O2•- ) detection was designed with gold nanoparticles-bovine serum albumin (AuNPs-BSA)@terbium/guanosine monophosphate disodium (Tb/GMP) nanoscale coordination polymers (NCPs) (AuNPs-BSA@Tb/GMP NCPs). The abundant hydroxyl and amino groups of AuNPs-BSA acted as binding points for the self-assembly of Tb3+ and GMP to form core-shell AuNPs-BSA@Tb/GMP NCP nanosensors. The obtained probe exhibited the characteristic fluorescence emission of both AuNPs-BSA and Tb/GMP NCPs. The AuNPs-BSA not only acted as a template to accelerate the growth of Tb/GMP NCPs, but also could be used as the reference fluorescence for the detection of O2•- . The resulting AuNPs-BSA@Tb/GMP NCP ratiometric fluorescence nanosensor for the detection of O2•- demonstrated high sensitivity and selectivity with a wide linear response range (14 nM-10 µM) and a low detection limit (4.7 nM).

Portable hydrogel test kit integrated dual-emission coordination polymer nanocomposite for on-site detection of organophosphate pesticides.

It is of great significance to on-site detection of organophosphate pesticides (OPs) for pollution monitoring and poisoning estimation. Herein, we developed a portable hydrogel test kit for on-site detection of OPs, which is based on the integration of agarose hydrogel with dual-emission coordination polymers (CPs) nanocomposite comprised of Ru(bpy)32+ and zinc (II)-based CPs (ZnCPs) loaded with thioflavin T (ThT). Different from Ru(bpy)32+ with stable fluorescence in acidic environment, ThT@ZnCPs is highly sensitive to H+, which destroys the structure of ZnCPs as a host and quenches ThT@ZnCPs fluorescence. The distinct fluorescence behaviors of Ru(bpy)32+ and ThT@ZnCPs in acidic environment enable the hydrogel test kit to exhibit ratiometric fluorescence responses to acetylcholinesterase (AChE), which hydrolyzes acetylcholine to acetic acid and provides H+. On this basis, combining the inhibition effect of OPs to AChE activity, a ratiometric fluorescence method for OPs detection was established with the hydrogel test kit, and satisfactory results have been achieved in buffered aqueous solutions and apple juice samples. Attractively, by employing smartphone as a signal readout, on-site quantitation of OPs was accomplished with the features of easy to use, portability and low cost, demonstrating a great promising for point-of-care testing in food safety monitoring.

Integrated enzyme with stimuli-responsive coordination polymer for personal glucose meter-based portable immunoassay.

Coordination polymers (CPs) with tunable structures and properties have been extensively explored in a variety of fields. In this work, we demonstrated the potential of stimuli-responsive CPs as a host of integrating enzymes to construct a portable immunoassay. By employing terbium ion (Tb3+) as a metal node and guanine monophosphate (GMP) as a bridge ligand, an alkaline phosphatase (ALP)-responsive Tb/GMP CPs was fabricated, which allows amyloglucosidase (GA) to be integrated to form GA@Tb/GMP composite. Owing to the size-selectivity of Tb/GMP CPs as a host, the loaded GA was physically isolated from its substrate starch. However, Tb/GMP CPs is highly sensitive to ALP, which can hydrolyze the phosphate group of GMP to destroy the structure of Tb/GMP CPs, leading to the release of GA from GA@Tb/GMP composite. The released GA can digest starch to produce glucoses and give a measured signal by personal glucose meter (PGM). This finding leads to a PGM-based portable immunoassay for the quantitative analysis of carcinoembryonic antigen (CEA), and satisfactory results with a detection limit of 0.28 ng/mL have been achieved. The successful determination of CEA in serum samples demonstrates its potential in practical application. We believe that this work can provide a remarkable insight for the rational design of stimuli-responsive CPs for a wide of applications.