Preparation And Application Of Functional Fluorescent Polymers Based On Naphthalene Anhydride Derivatives

In recent years,fluorescent polymer materials have been widely concerned in chemical sensing,photoelectric equipment and cell imaging.Compared with traditional fluorescent small molecules,fluorescent high molecular polymers not only have the same luminescent properties,but also have more excellent properties as new functional materials in recent years,such as good water solubility and biocompatibility,higher fluorescence quantum yield,and simple structure modification to modify them.Generally speaking,the method of synthesizing fluorescent polymers is to directly polymerize small molecules with fluorescent properties as monomers or initiators or to post-modify polymers with non-fluorescent properties.Common synthesis methods,such as free radical polymerization,metathesis polymerization,polycycloaddition and polycoupling,have successfully synthesized fluorescent polymers.At present,scientists have discovered a variety of luminescent monomers with fluorescent properties,such as rhodamine,BODIPY,coumarin,cyanin,1,8-naphthalimide and other fluorophores.Therefore,there is diversity in the selectivity of luminescent monomers.1,8-naphthalimide with D-π-A configuration is widely used in molecular recognition,biological imaging and other fields because of its good photostability,high fluorescence quantum yield and large Stokes/anti-Stokes shift.Based on 1,8-Naiimide fluorophore,a series of lipid drop probes were synthesized in this paper,which broke the traditional synthesis idea of giving polymer materials the same functionality as small molecules through the introduction of functional small molecules,and put forward a new idea of introducing lipid drop probes into polymer materials to make polymer materials have different functionality from small molecules.The main work contents are as follows:（1）A series of oxime group modified fluorescent dyes（NAP-a,NAP-b and NAP-c）and morpholine group modified fluorescent dyes（NAP-OH）were prepared.The structures of NAP-a,NAP-b,NAP-c and NAP-OH probes were determined by the structural characterization methods of ¹H NMR,¹³C NMR and HRMS.In the experiment,the dyes NAP-a,NAP-b,NAP-c and NAP-OH were tested by ultraviolet spectrophotometer and fluorescence spectrophotometer.The experimental results show that these probes are sensitive to polarity and have the advantages of good light stability,excellent anti-interference and large Stokes displacement.The results of cell co-location experiments show that NAP-a,NAP-b and NAP-c can be used as fluorescent probes to label intracellular lipid droplets,and probe NAP-OH can be used as targeting probes for lipid droplets and lysosomes to simultaneously image intracellular lipid droplets and lysosomes.Therefore,NAP-a,NAP-b,NAP-c and NAP-OH have broad application prospects in biological imaging.（2）Based on the lipid droplet probe NAP-OH obtained in the first part,the existence of morpholine group endows NAP-OH with the characteristic of being sensitive to acid gas.NAP-OH was introduced into polyurethane as a blocking agent,and a series of polyurethane emulsions were prepared by improved prepolymer method and changing the mass ratio of NAP-OH,which were spun into films by electrostatic spinning machine.Firstly,SEM and BETSSA experiments were carried out,and the results showed that the prepared spinning film was composed of countless filaments,with small diameter（200～400 nm）and large specific surface area（9.098～9.142 m²/g）.Changing the content of NAP-OH had no effect on the surface properties of the film.The E-NAP_0.1/PU,E-NAP_0.2/PU,E-NAP_0.5/PU,E-NAP_0.8/PU and ENAP_1.0/PU membranes were tested in response to HCl.The experimental results show that the E-NAP_0.5/PU membrane has the advantages of sensitive response and wide detection range.In 6 ppm HCl gas,TFA gas and FA gas,the color of E-NAP_0.5/PU（dark orange red）film changed from dark orange red to green,light green and light orange after 2seconds,20 seconds and 40 seconds respectively.This shows that E-NAP_0.5/PU membrane has great application potential in the identification of acid gases.In addition,in SO₂ gas with a concentration of 360 ppm,E-NAP_0.5/PU changed from orange red to colorless within 30 s..The detection limits of E-NAP_0.5/PU for HCl,TFA,FA and SO²are 996 ppb（0-10 ppm）,660 ppb（0-8 ppm）,724 ppb（0-10 ppm）and 39 ppm（0-360ppm）respectively.More importantly,E-NAP_0.5/PU can be reused for many times.After five times of recycling,the E-NAP_0.5/PU membrane still recovered to its original fluorescence intensity and maintained a good response to acid.Therefore,E-NAP_0.5/PU membrane is expected to have a good application prospect in detecting acid gas and preventing acid gas leakage.（3）Based on the lipid droplet probe NAP-OH obtained in the first part,a lipid droplet probe NAP-SS was obtained by introducing disulfide bonds through esterification reaction.NAP-SS and folic acid were grafted onto pullulan,and a nano fluorescent polymer micelle NPs-NAP-FA-SS was synthesized,which can be used for endoplasmic reticulum imaging and drug delivery.The co-localization cell experiment of NPs-NAP-FA-SS micelle was carried out.The experimental results showed that NPs-NAP-FA-SS micelle targeted endoplasmic reticulum（Pearson coefficient R=0.943）,while small molecule NAP-SS targeted lipid droplets（Pearson coefficient R=0.827）.The He La cells incubated with NPs-NAP-FA-SS micelles were imaged,and then incubated with 10 m M GSH for a period of time,and then imaged again.From the cell images,it can be observed that the red fluorescence signal intensity in the cells increased more than twice before and after GSH was added.Therefore,NPs-NAP-FA-SS micelles can be used to image endoplasmic reticulum and detect GSH in cells.In addition,DOX was encapsulated in NPs-NAP-FA-SS nano-micelle to form NPs-NAP-FA-SS/DOX micelle.Co-localization experiments show that NPs-NAP-FA-SS/DOX micelles also have excellent targeting ability to endoplasmic reticulum（Pearson coefficient R=0.893）,and the fluorescence signal intensity in cells increases continuously after GSH is added.Therefore,NPs-NAP-FA-SS/DOX micelles can not only target the endoplasmic reticulum in cancer cells,but also realize visual drug release through the change of fluorescence signal.To sum up,the preparation of NPs-NAP-FA-SS micelles provides a new strategy for the preparation of endoplasmic reticulum-targeted nano-drug carriers,which has a good application prospect in the field of drug delivery.