Construction Of Activatable Photoacoustic Imaging Nanoprobes And Their Applications In Disease Diagnosis And Treatment

Improving the resolution,sensitivity,accuracy and tissue penetration depth of biological imaging is a major scientific problem that is urgently needed to be solved in the field of biological imaging.Photoacoustic imaging combines the advantages of optical imaging and ultrasound imaging to display high-resolution,high-contrast imaging capabilities of deep tissues in living organisms.In this study,the objective is to obtain in situ,specific and real-time imaging information of active small molecules in the deep tissues in vivo.At the same time,modern treatment techniques such as photodynamic,chemodynamic and photothermal are combined to achieve accurate diagnosis and treatment of major diseases guided by photoacoustic imaging.Therefore,in this thesis we designed and synthesized a series of photoacoustic imaging nano-probes with good bio-compatibility,high stability and low toxic side effects for the precise imaging of bioactive small molecules in vivo and the diagnosis and treatment of related diseases.The main results were as follows:1.An iron and copper co-doped polyaniline nanoparticle（Fe-Cu@PANI）was designed and synthesized as a photoacoustic nanoprobe for tumor microenvironment activation,as the absorption spectrum of this nanoparticle can be red-shifted to the near-infrared region in the tumor microenvironment.The Cu（II）in this nanoprobe can undergo redox reaction with the highly expressed GSH in tumor.The redox reaction induces a red shift in the absorption spectrum of the Fe-Cu@PANI nanoparticles from the visible to the near-infrared region accompanying with the etching of this nanoparticle,which simultaneously activates tumor photoacoustic imaging and photothermal therapy,thereby improving the accuracy of in vivo tumor imaging and the efficiency of photothermal therapy,and this probe can be used to dynamically monitor the tumor development process and achieve precise diagnosis and treatment of tumors.2.A circular dichroism（CD）and photoacoustic（PA）dual-mode probe was designed and synthesized for precision theranostics of drug-induced liver injury（DILI）.This probe uses chiral D/L-cysteine and molybdate as raw materials to form nanocomplexes with chiral features based on the interaction of metal ions inOx-POM with sulfhydryl groups in amino acids（Ox-POM@D/L-Cys）.The nanocomplex can undergo specific REDOX reactions with·OH,resulting in changes in its circular dichroism and photoacoustic spectra.Therefore,it was used as a circular dichroism and photoacoustic dual-mode probe to monitor the autoxidation process of Fe²⁺ions by circular dichroism spectral changes in vitro,and to perform in situ PA imaging of the liver region in DILI mice by photoacoustic spectral changes in vivo.DILI mice were treated based on the fact that the probe consumed body·OH in vivo,and the recovery of liver function in mice could be tracked based on photoacoustic imaging.3.A photoacoustic imaging nanoprobe for monitoring diabetes-induced liver injury and its complications was designed and synthesized.The nanoprobe consists of Fe MoO_x nanoparticles with catalase activity,and combined it to 2,2’-azino-bis（3-ethylbenzothiazoline-6-sulfonic acid）diammonium salt（ABTS）and distearoyl phosphoethanola-mine-polyethylene-glycol（DSPE-PEG）to engineer a biomimetic nanoenzyme-triggered photoacoustic（PA）probe（Fe MoO_x@ABTS@DSPE-PEG（FADP））.The nanoprobe was able to react specifically with H₂O₂,causing the ABTS in the structure to be converted to the oxidized state of ABTS·⁺.While ABTS·⁺has a strong absorption in the near-infrared region,which can be used as an ideal contrast agent for PA imaging.H₂O₂ as a biomarker of oxidative stress response is closely related to the occurrence and development of diabetes mellitus and its complications.The results demonstrate that the synthesized FADP nanoprobe can sensitively monitor the pathogenesis of diabetes induced by streptozotocin（STZ）and the photoacoustic signal changes in liver tissue during metformin-mediated treatment of diabetes.4.An oxidized molybdenum polyoxometalate-copper nanocomposite（Ox-POM@Cu）was designed and synthesized.The doping with Cu determines the formation of oxygen vacancies,which can increase the carrier concentration inOx-POM@Cu,accelerate electron transfer,and enhance the redox activity,thus playing an efficient catalytic role.The nanocomposite presents unique enzymatic functions characterized by a multielement catalytic activity in the tumor microenvironment（TME）.In addition,it can be employed as an NIR-Ⅱ photoacoustic imaging（PAI）probe and cancer therapy agent.Firstly,it participates in the redox reaction with glutathione（GSH）in tumor tissues,activates the PAI and photothermal therapy functions via NIR-Ⅱ laser irradiation,and depletes the GSH supply in cancerous cells.Subsequently,it catalyzes a Fenton-like reaction with H₂O₂ in tumor tissues to form·OH,thereby performing a chemodynamic therapy function.The results showed that the synthesized nanoenzymes were effective in NIR-Ⅱ for diagnosis and combination therapy of tumors.5.A water-soluble MoO₃ nanoprobe was designed and synthesized.The nanoprobe can reacts specifically with H₂S molecules and can activate the probe for PA imaging and photothermal therapy（PTT）in the first near-infrared（NIR-Ⅰ）and second near-infrared（NIR-Ⅱ）regions.The PA imaging and photothermal therapy（PTT）of the present invention can perform photoacoustic imaging detection of H₂S molecules in colon cancer tissue.Through experimental comparison,we found that in the NIR-Ⅱ window,the background of biological tissues would cause less interference with PA imaging,and the photothermal conversion efficiency of NIR-Ⅱ would be higher and the therapeutic efficacy would be better.Thus the prepared MoO₃nanoprobe can thus be used for NIR-Ⅱ photoacoustic imaging and photothermal therapy of colon cancer.6.A CuO_xNPs@MOF biomimetic MOFs bionanoreactor was designed and synthesized.The bionanoreactor was coated with imidazole framework-8（ZIF-8）as a probe molecule with a specific response of the metastable metal oxide Cu₂O.The pore size of MOF（ZIF-8）was used to improve the selectivity of the reactor to H₂S.The CuO_xNPs@MOF bionanoreactor can specifically react with H₂S in situ sulfidation to turn on the photoacoustic signal of NIR-Ⅱ.However,metformin is currently the most commonly used oral drug for the treatment of diabetes mellitus,and excessive ingestion may cause upregulation of H₂S levels in the liver,resulting in severe liver injury and hepatotoxicity.Therefore,using endogenous H₂S as the target molecule of the intelligent triggering probe,the CuO_xNPs@MOF bioreactor can perform noninvasive,highly specific in-situ photoacoustic imaging monitoring of hepatotoxicity induced by metformin.The observation of photoacoustic signal changes in mouse liver allows for accurate diagnosis of liver injury in real time,non-invasively and with high sensitivity.