Smartphone-assisted visual detection of lincomycin hydrochloride based on Cu-BDC@Ag2O with enhanced oxidase-like activity and laccase-like activity

The inappropriate administration of lincomycin hydrochloride (LIN) will lead to severe side effects. It is critically essential to establish LIN effective detection technique. In this work, a new nanozyme Cu-BDC@Ag 2 O was synthesized by hydrothermal method, which was composed of metal organic framework (Cu-BDC, with copper ion as metal center and 2-aminoterephthalic acid as organic ligand) and Ag 2 O, exhibiting enhanced oxidase-like activity (K m  = 0.70 mM, V max  = 42.53 × 10 −8  M s −1 ) and laccase-like activity. This enhanced activity was attributed to the interconversion between Cu + /Cu 2+ valence states and the synergistic effect between Ag and Cu elements. The superoxide anion radical ( O 2 – ) produced during the catalytic process of Cu-BDC@Ag 2 O can swiftly oxidize 3,3′,5,5′-tetramethylbenzidine (TMB) to a blue oxidation product (oxTMB). The methylthio group in LIN molecules reacted with Ag + in the nanozyme, forming a stable complex that inhibited the catalytic activity of Cu-BDC@Ag 2 O, causing discernible fading of the blue coloration. Based on this, a smartphone-assisted chromogenic detection system was established for LIN quantification. The linear range extended from 3.42 to 171 μM, with a detection limit of 3.14 μM. Moreover, the colorimetric sensing platform demonstrated promising results in the analysis of real samples with spiked recoveries in the range of 94.1–100.9 % and relative standard deviations lower than 8.0 %, and validated LIN content compliance with commercial ophthalmic solutions against pharmacopeial specifications. The developed colorimetric sensor demonstrated rapid response (4 min) and superior efficiency, offering a portable tool for LIN detection.