Cytotoxicity Of AgInS₂ Quantum Dots And Their Application In Cell Imaging As Well As Pb²⁺ Detection

Background:As a typical representative of new materials,AgInS₂ quantum dots（AIS QDs）show a good application prospect in biomedicine field due to the economical and environment-friendly synthetic method,easy surface modification,good biocompatibility and excellent optical properties.In this work,AIS QDs was selected as the research objective,and their applications in biological field were explored.Objectives:The purpose of this study was to synthesize the water-soluble AIS QDs,evaluate their cytotoxicity,and analyze the possible causes of their toxic effects.Based on the fluorescence properties of AIS QDs,the applications of AIS QDs in cell imaging and Pb²⁺detection were studied.Methods:1.AIS QDs were synthesized by a one-pot aqueous method.The crystal structure,surface element composition,element valence,morphology,particle size and optical properties of synthesized AIS QDs were characterized by X-ray diffractometer（XRD）,X-ray photoelectron spectroscopy（XPS）,transmission electron microscope（TEM）,ultraviolet-visible spectrophotometer（UV-vis）,fluorescence spectrophotometer and nano-laser particle sizer（DLS）.2.MFC cells,HT-29 cells and PC12 nerve cells were cocultured with AIS QDs for a period of time,respectively.CCK-8 reagent was added into well.The absorbance of each well in the96-well plate was detected by a microplate reader.The viability of cell was calculated according to the corresponding formula,thus the toxic effect of AIS QDs on cancer cells was evaluated accordingly.3.MFC cells,HT-29 cells and PC12 cells were incubated with AIS QDs for a certain period of time,then DAPI or Hoechst 33258 was added to observe the labeling of cancer cells with organic dyes and AIS QDs by scanning laser confocal microscopy.4.Based on the quenching effect of Pb²⁺on the fluorescence of AIS QDs,the detection conditions were optimized,and a fluorescence method was established to detect Pb²⁺content in water.Results:1.AIS QDs with good water-soluble and excellent fluorescence properties was prepared by one-pot water phase method.As-prepared sample was of tetragonal phase structure.The valence of Ag,In and S elements in AIS QDs were+1,+3 and-2,respectively.The morphology of AIS QDs was approximately spherical,and AIS QDs showed good dispersion,crystallinity and stability.2.After MFC cells,HT-29 cells and PC12 cells were cocultured with AIS QDs dispersions of different concentrations in complete medium for 12 h and 24 h,the viability of three cells decreased with the increase of AIS QDs dose and the extension of acting time.3.AIS QDs was an excellent fluorescent probe,which could enter into the cytoplasm of MFC cells,HT-29 and PC12 cells and display green fluorescence signal under visible light excitation.4.AIS QDs were n-type semiconductors,and their conduction band potential and valence band potential were-0.79 e V and 1.15 e V,respectively.When test temperature was 22°C,the interaction time between Pb²⁺and AIS QDs dispersion was 60 min,the standard curve was drawn with the relative fluorescence quenching amount of AIS QDs as the ordinate and the concentration of Pb²⁺as the abscissa.The detection range was 0.002-0.11μg/m L,the detection limit was 4 n M,and the spiked recoveries were between 94.9%and 99.7%.Conclusions:AIS QDs as-prepared had strong fluorescence,high stability,and good dispersibility in water,which could be applied to biological field.The reason why AIS QDs interfered with the viability of cancer cells might be related to their chemical constitution.AIS QDs could be taken up by cells and mark cytoplasm through cell membrane.The detection of Pb²⁺in water could be realized based on the effect that Pb²⁺could reduce or even quench the fluorescence generated by AIS QDs.The method had a wide detection range,a low detection limit,and simple operability.This study provides data support and new ideas for the application of AIS QDs in fluorescence labeling and fluorescence analysis sensing.