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.