Design,Synthesis And Application Of Porphyrin-based Ratiometric Polymer Fluorescent Nanoprobes

Hypochlorous acid（HCl O）and hydrogen sulfide（H₂S）as the active substance in the organism can regulate the normal physiological process of the organism under the condition of normal physiological concentration.However,it will cause many diseases,such as inflammation,cancer,alzheimer’s disease,cirrhosis of the liver and so on,when the concentration is abnormal.Therefore,it is very important to selectively monitor endogenous levels of HCl O and H₂S in organisms.In recent years,ratiometric fluorescent polymer nanoprobes have become popular areas of biosensing due to their good biocompatibility,simple preparation,easy modification,and strong anti-background interference ability.In this work,we successfully prepared porphyrin-based responsive fluorescent polymer nanoprobes and realized the fluorescence detection of HCl O and H₂S.The main contents and the results of this paper are as following:1.The rational design of a zero cross-talk self-referenced ratiometric fluorescent probe for accurate molecular imaging in living cells is still a major challenge.Herein,we report a zero cross-talk fluorescent polymer nanoprobe（named ZC-FPN）with a self-referenced ratiometric effect for lysosomal HCl O imaging using single-wavelength excitation.The newly designed polymer nanoprobe（ZC-FPN）is prepared by using a simple co-precipitation method through self-assembly of two amphiphilic block copolymers,which are covalently linked with a porphyrin fluorophore（HCl O-responsive unit）and a naphthalimide fluorophore（reference unit）,respectively.Remarkably,the ZC-FPN displays an unprecedented separation of two emission peaks（191 nm）,which can avoid the spectral cross-talk problem of the emission-shift type ratiometric probes and is highly favorable for high-resolution bioimaging.In addition,the as-prepared ZC-FPN also shows good water dispersibility,high selectivity,excellent long-term fluorescencestability（>10 weeks）and low cytotoxicity.More importantly,the positive charge of the amino moiety enhances the efficient uptake of the nanoprobe by cancer cells and enables the nanoprobe to selectively accumulate in lysosomes,achieving endogenous HCl O imaging in living cells through fluorescence ratiometric imaging.2.We have designed and prepared a liver-targeted ratiometric fluorescent polymer nanoprobe（LSS-FPN）via co-precipitation method.In this probe,a porphyrin-based compound TPP-（DC）₂ with the response of H₂S as a response group,amphiphilic diblock copolymer gal-b-(PEGMA₃₀-co-AEMH₁₂)-b-PS₇₂ which prepared via combining reversible addition-fragmentation chain transfer radical polymerization（RAFT）and click reaction as a carrier,the conjugated polymer dye with green fluorescence 9,9-dioctyl polyfluorene-benzothiadiazole alternating copolymer（PFBT）as a reference group.When the2,4-diphenylsulfo leaves in the presence of H₂S,the fluorescence intensity of porphyrin was gradually increased at 659 nm,and the fluorescence of PFBT remained stable at 533 nm.LSS-FPN has two emission peaks with zero crosstalk（126 nm）and a large Stokes shift（93nm）,and has excellent stability and water dispersion.In summary,this paper designs and synthesizes two kinds of responsive polymer nanoprobes based on porphyrin to solve some of the shortcomings of current small molecule fluorescent probes and further expand their applications.