Entrapment of horseradish peroxidase into nanometer-scale metal-organic frameworks: a new nanocarrier for signal amplification in enzyme-linked immunosorbent assay.

Horseradish peroxidase (HRP) was highly loaded into large holes of nanometer-scale metal-organic frameworks (i.e., PCN-333(Al)) for signal amplification in enzyme-linked immunosorbent assay (ELISA). The enzyme-labeled antibody complex prepared using nanometer-scale PCN-333(Al) maintained a high catalytic efficiency. Its Vm and Kcat values with 3,3',5,5'-Tetramethylbenzidine (TMB)-H2O2 as substrates were 4.84 × 10-5 mM/s and 4.84 × 104 min-1, respectively. We demonstrated an HRP@PCN-333 signal amplification strategy for colorimetric assay of human prostate-specific antigen (PSA). The linear range of PSA detection by using this method was 15-165 pg/mL, and the limit of detection was 6 pg/mL (S/N = 3), indicating the potential application of this method in detecting disease markers under clinical conditions. The presented strategy exhibited the characteristics of significantly increased amount of labeled enzymes, improved stability and utilization of enzymes, simple preparation process of enzyme-labeled antibodies, and low cost.