Design of a Sensing System for Turn-on Fluorescence Assay for Norfloxacin Based on Inner-filter Effect

KeyWord:Inner-filter effect  norfloxacin  alizarin red  turn-on fluorescence assay

Abstract:

      A highly selective sensing system for turn-on fluorescence assay of norfloxacin(NOR) was proposed based on UV-visible absorption of alizarin red S(ARS) coupled with the use of meso-tetra(N-methyl-4-pyridyl)porphine tetratosylate salt(TMPyP) operative on the fluorescence inner-filter effect(IFE)£¬in which the combination of two signaling mechanisms allows molecular recoginition event and the signal read-out£¬independently.The viability of converting the absorption signal of ARS into a fluorescence signal was explored.In the absence of NOR£¬the absorption spectrum of the ARS has a strong peak at 420 nm£¬significantly overlapping with the excitation of TMPyP.The formation of NOR-ARS complex shifts the maximum absorbance from 420 nm to 523 nm£¬which overlap negligibly with the excitation of TMPyP and turn on the proper emission spectrum for TMPyP.Under the optimum conditions£¬there is a good linear relationship(r2=0.987 8) between relative fluorescence intensity ratio(IF/I0F) of TMPyP and NOR concentration of 10-450 mg?L-1.The limit of detection(S/N=3) was 5 mg?L-1.At the same time£¬the fluorescence response is highly selective for NOR detection over other metal ions and the common auxiliary materials.The proposed fluorescent NOR assay improved the sensitivity of the UV-Vis method for NOR detection based on the IFE which convert the absorption signal into fluorescent signal.The fluorescent method based on IFE does not require the establishing of any covalent linking between the receptor and the fluorophore.The proposed study offers a novel design to detect drug based on the fluorescence spectroscopy.