β-Galactosidase triggered dual-signal competitive selective recognition of copper ion for diagnosis of urinary tract infection by Escherichia coli

Here, we reported a simple dual-fluorescence homogeneous and binary visualization (color and distance reading) strategy for the analysis of β -galactosidase ( β -Gal) and Escherichia coli ( E. coli ) in clinical urine samples. This system used CdTe quantum dots (QDs) and N-methyl mesoporphyrin IX (NMM) as signal reporters, combining with inkjet printing technology. This work is based on the fact that β -Gal can hydrolyze substrates to generate p -aminophenol (PAP), reducing Cu 2+ to Cu + . Then, QDs and NMM can selectively recognize these two metal ions. Under optimized conditions, the limit of detections (LODs) of the dual fluorescence analysis strategy for E. coli were as low as 0.03 (QDs) colony-forming units (CFU)/mL and 0.04 (NMM) CFU/mL, and the sensitivity was improved by two orders of magnitude compared to the single-signal molecular system. 1 CFU/mL E. coli could be distinguished by reading the color and distance with the naked eye. This method was applied for the quantitative analysis of E. coli in 45 clinical urine samples, whose results were consistent with the results of clinical standard plate colony counting and the matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS). • A homogeneous dual fluorescence and binary visualization (color and distance) strategy for analysis of E. coli was developed. • The developed simple, rapid, low cost and homogeneous visual sensor was present high sensitivity and selectivity. • This system has been successfully used in fluorescence and visualization analysis of E. coli in 45 clinical urine samples.