| In vivo imaging analysis plays an indispensable role in the field of biomedicine.Traditional imaging methods such as magnetic resonance imaging(MRI)and positron emission tomography(PET)have some defects such as long time-consuming,low spatio-temporal resolution and great damage to human body.Optical imaging,especially fluorescence imaging,has attracted wide attention in the medical field because of its high temporal and spatial resolution,sensitivity,convenience and speed.The light wave(1000–1700 nm)in the second near infrared region(NIR-II),with its high tissue penetration,opens a biological"transparent"window and encourages researchers to develop more NIR-II fluorescent materials.Among them,organic fluorescent dyes have good application potential in biomedical field because of their excellent biocompatibility.However,at present,the available NIR-II organic fluorescent materials are still faced with relatively few problems,difficult to design and synthesis and poor photophysical properties.Therefore,the development of NIR-II organic dyes with excellent photophysical properties is still one of the challenging topics in this field.In view of this research status,NIR-II molecules with excellent photophysical properties have been designed and synthesized by molecular engineering and J-aggregation strategy using BODIPY dimer bridged by 1,4-bisvinylbenzene,and have been successfully applied in the field of biological non-invasive imaging.The specific research content includes the following two parts:In the second chapter,we designed and synthesized 1,4-divinylbenzene bridged BODIPY dimer BVB-BDP1–7 through molecular engineering strategy,and realized the regulation of molecular second near infrared region emission performance.The maximum absorption and emission of the obtained dimer are 780–882 nm and 965–1050 nm,respectively.Among them,the water-soluble and cancer cell-targeting groups of BVB-BDP5 are modified.The maximum absorption wavelength of BVB-BDP6–7 in water is at 882 nm,and the maximum emission wavelength is at 1050 nm,and maintain a high fluorescence quantum yield(Φ_f=1.2%).The above studies provide a new molecular platform and theoretical research for the development of organic fluorescent materials with NIR-II emission.In the third chapter,we further realize the regulation of molecular NIR-II absorption and emission properties through molecular binding engineering and molecular aggregation strategy.On the basis of BVB-BDP series molecules,a series of molecules A-BVB-BDP1–6 were designed and synthesized by replacing water-soluble polyether chains with fat-soluble alkyl chains.Some molecules show excellent J-aggregation properties in large polar solvents.The maximum absorption distribution of J-aggregates is 855–1033 nm and the maximum emission is about 1100nm.Among them,A-BVB-BDP4 J-aggregates were coated by pluronic F-127 into water-soluble nanoparticles J-NPs.Compared with the order molecule A-BVB-BDP4(Φ_f=2.1%)in the solution state,the maximum absorption of J-NPs in water was red-shifted to 1033 nm,the maximum emission red-shifted to 1105 nm,and the fluorescence quantum yield was increased(Φ_f=2.9%),which achieved the effect of aggregation-induced emission enhancement(AIEE).The above studies provide a new molecular basis and theoretical support for the development of organic fluorescent materials with both NIR-II absorption and emission. |
