Breaking pH limitation of POD-like Cu-NC NP by ATP modulation and construction of colorimetric and ratiometric fluorescence-scattering dual-mode detection method for tetracycline

Abstract

In this work, a novel POD-like nanozyme Cu-NC NP was synthesized, and the pH limitation was broken by ATP modification. The formed ATP@Cu-NC NP could oxidize TMB into oxTMB in the presence of H₂O₂ under pH 7. Furthermore, a novel dual-mode detection method for antibiotic tetracycline (TC) was proposed based on the second order scatter (SOS) of ZIF-90 and its inhibition of the POD-like activity of ATP@Cu-NC NP. When TC was present, Zn (ІІ) node of ZIF-90 coordinated with TC to form fluorescent compound TC-Zn and ZIF-90 was therefore decomposed. Thus, the fluorescence of TC-Zn compound at 541 nm increased while the SOS of ZIF-90 at 741 nm decreased, the ratio signal I₅₄₁/S₇₄₁ was linearly related to the TC concentration. Meanwhile, the inhibition of the POD-like activity of ATP@Cu-NC NP from ZIF-90 due to the aldehyde group on the surface was reduced after corrosion by TC, the absorbance of oxTMB at 652 nm then recovered, thus colorimetric detection was also achieved. The fluorescence-scattering (FL-SOS) and colorimetric dual-mode detection of TC was sensitive with LODs of 11.556 nM and 0.244 µM, respectively. Successful application in milk, egg and human serum was achieved, proving the applicability of the proposed TC sensing method. A portable kit for visual TC detection was also constructed using agarose hydrogel, which was instrument-free, time-saving and sensitive for the detection of TC.