Preparation And Properties Of Poly(p-phenylene Vinylene) Chemiluminescence Nanoprobes

Chemiluminescence(CL)imaging does not require an external excitation source,has no light damage and photobleaching,and has an optical-signal readout with a high signal-to noise ratio.Thus,CL is an advantageous detection tool for in vivo imaging.CL imaging has been widely used in biological analyses and disease diagnoses.The fluorescent conjugated polymers(CPs)are fluorescent material with excellent optical properties.CPs are used as energy acceptor in CL conjugated polymer nanoparticles(CPNs)to enhance CL signals via chemiluminescence resonance energy transfer(CRET)using their excellent light-harvsting ability.The introduction of small molecule CL donors leads to the possibility of leakage of small molecule and reduction of stability of CL nanoparticles.Therefore,CL nanoparticles with simple preparation and without the involvement of small molecule CL donor have good prospects for the application in vivo CL imaging.In this thesis,CPs/nonionic surfactant nanoparticles and CPs/mesoporous silica nanoparticles(MSN)composites were designed and synthesized.The CL phenomenon based on the conjugated polymer backbone was studied as well as its bioassay applications.Possible mechanism of CL of CPs was proposed.The study was carried out through the following two aspects:1.CL of CPNs by direct oxidation with hypochloriteWe used five CPs,(Poly(9,9-di-n-dodecylfluorenyl-2,7-diyl),PFD),(Poly[[[(2-ethylhexyl)oxy]methoxy-1,4-phenylene]-1,2ethenediyl],MEH-PPV),(Poly[(9,9-dioctyl-9H-fluorene-2,7-diyl)-(1 E)-1,2-ethenediyl],PFV),(Poly[(9,9-dioctyl-2,7-divinylenefluorenylene)-alt-{2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene},PFV-alt-MEHPV],and(Poly[(9,9-di-(2-ethylhexyl)-9H-fluorene-2,7-vinylene)-co-(1-methoxy-4-(2-ethylhexyloxy)-2,5-phenylenevinylene)],PFV-co-MEHPV)were mixed with the nonionic surfactant Pluronic F-127 to prepare five CPNs.These five CPs contain carbon double bonds except PFD.We demonstrated CL from the direct oxidation of CPs backbones in CPNs by hypochlorite.The dioxetane intermediate formation was confirmed by UV-Vis absorption,fluorescence,nuclear magnetic resonance spectroscopy(1H NMR),and Fourier-transform infrared spectroscopy(FT-IR)spectroscopy.The possible CL mechanism is:Hypochlorite can oxidize the vinylene bond(C=C)in polyfluorene-vinylene(PFV)/polyphenylene vinylene(PPV)via ?2-?2 cycloaddition to form a PFV/PPV-dioxetane intermediate that are unstable and can spontaneously degrade into a PFV/PPV-aldehyde and generate photons.Further oxidation of the PFV-or PPV-aldehyde yields PPV-carboxyl as the final product of the oxidation reaction.The CL CPNs completely avoided the involvement of small molecules CL donors.The strategy greatly simplified the CL probes preparation and increased the stability of CL nanoprobes by overcame the leakage problem of CL donors in nanoparticles.The CL quantum yield(QY)of brightest CL probe CPN-PFV-co-MEHPV was 17.79 einsteins/mol(based on the molar particle concentration of nanoparticles).CPN-PFV-co-MEHPV was size-stable,non-cytotoxic,selective,and sensitive for hypochlorite detection.Thus,the CPN-PFV-co-MEHPV was successfully applied for in vivo imaging of endogenously produced CIO-in the living animals,and has achieved good results.2.Study on CL properties of Poly(p-phenylenevinylene)/Mesoporous silica nanoparticles(PPV@MSN)The composite material PPV@MSN were prepared by encapsulating CPs Poly(p-phenylenevinylene)(PPV)in MSN which avoids the aggregation of polymer chains,has the advantages of high fluorescence quantum yield and strong anti-oxidative photobleaching ability.Thus,PPV@MSN would be an ideal fluorescent material.PPV@MSN should have better CL properties than the CPNs that were encapsulted by Pluronic F-127.Therefore,we prepared PPV@MSN and studied its CL properties.Due to the high fluorescence quantum yield of PPV@MSN and existence of the vinylidene bond(C=C)in PPV,we tested the CL ability by directly oxidizing PPV@MSN with sodium hypochlorite and hydrogen peroxide.We found that sodium hypochlorite can oxidizes PPV@MSN to produce CL but hydrogen peroxide does not.The oxidation of PPV@MSN by hypochlorite produces CL with a higher intensity than CPNs/Pluronic F-127.In addition,we explored the CL of PPV@MSN as an energy acceptor.We modified the PPV@MSN to get PPV@MSN-NH2.The CPPO is then doped into the mesopores of PPV@MSN-NH2 to form PPV@MSN-NH2@CPPO.Then we studied the CL response of PPV@MSN-NH2@CPPO to hydrogen peroxide.We found that the energy produced by the reaction of CPPO with hydrogen peroxide can stimulate PPV@MSN to produce CL.It was demonstrated that PPV@MSN can act as an energy acceptor and can also produce strong CL signals.