Construction Of A Novel Nanoprobe Based On The NIR-Ⅱ Fluorescent Quantum Dots And Its Application To Imaging Of Hypochlorous Acid

The second near infrared（NIR-II,1000-1700 nm）fluorescence imaging with deep tissue penetration depth,high signal/background ratio and resolution,shows a good application prospect in biological analysis.Among the currently developed NIR-II fluorescent materials,silver chalcogenide quantum dots（QDs）do not contain highly toxic heavy metal elements,and have high luminescence efficiency and photostability,making they are promising NIR-II biological imaging contrast agents and have great potential in the construction of NIR-II fluorescent probes for biological analysis.However,at present,the construction strategy of NIR-II fluorescent probes based on silver chalcogenide QDs is still very scarce.Most of the current probes were constructed using organic small molecules to quench the luminescence of QDs through fluorescence resonance energy transfer or competitive absorption of excitation and response to target analyte.However,there are a few kinds of small molecules that can meet this requirement.Additionally,the hydrophobicity of organic molecules makes them prone to aggregation in physiological environment,thus affecting their regulation of QDs luminescence.Moreover,this construction mechanism of probe makes the excitation wavelength of the QDs probe limited by the absorption wavelength of the organic molecules,which is not conducive to the long-term development and application of the QDs probes.Based on the above background,we proposed a new strategy for the construction of silver chalcogenide QDs probe.A novel NIR-II fluorescence nanoprobe based on silver chalcogenide QDs was developed for imaging analysis of hydrochloric acid（HCl O）in vivo.The nanoprobe can detect HCl O with high specificity and selectivity and be used for imaging analysis of arthritis and peritonitis in vivo.The main research contents include the following two aspects:（1）A strategy for quenching of the NIR-II luminescence of quantum dots was developed.Firstly,the core-shell Ag₂Te@Ag₂S QDs with emission peak located at 1300 nm were synthesized by a thermal injection method,Then,Ag₂Te@Ag₂S QDs were mixed with a gold precursor solution to trigger cation exchange and release silver ions from the QDs.Au-doped QDs（Ag₂Te@Ag₂S/Au）were thus obtained with higher emission intensity and stability.On this basis,the released silver ions were reduced to generate a silver shell on the surface of QDs,which could quench the NIR-Ⅱluminescence of Ag₂Te@Ag₂S QDs.The as-developed strategy can effectively regulate the luminescence of QDs.（2）Based on the above research,the PEG-Ag₂Te@Ag₂S/Au/Ag probe was constructed by modification of Ag₂Te@Ag₂S/Au/Ag QDs with amphiphilic polymer DSPE-m PEG（2000）.The constructed PEG-Ag₂Te@Ag₂S/Au/Ag nanoprobes have good water solubility and biocompatibility.Under the presence of HCl O,the silver shell on the surface of QDs was oxidized and etched by HCl O,resulting in the disappearance of quenching effect and the recovery of fluorescence of QDs.The nanoprobe can be used for highly sensitive and selective detection of HCl O and successful imaging analysis of endogenous HCl O in arthritis and peritonitis mice,providing a promising tool for NIR-II imaging of HCl O in vivo.