Intracellular Proteolytic Disassembly Of Self-Quenched Near-Infrared Nanoparticles Turning Fluorescence On For Tumor-Targeted Imaging

Cellulose, consists of glucose molecules, is the most abundant biological polymer in nature. Cellulose is the main component of plant cell wall, which plays a mechanical support role in the process of plant growth. Cellulose is widely used in agriculture and in industry, and cellulose is widely used in the application of paper making, textile and renewable energy. Cellulose content is a very important parameter in the application of cellulose. Cellulose is associated with hemicellulose, lignin and pectin to form a very complex crystal morphology, resulting in difficult to separate.The mode of binding and content of cellulose has a greater impact on the quality of plant. Therefore, quantitative analysis of cellulose is a very meaningful work. At present, the method for determining cellulose in industry is chemical method, which determining cellulose by destructive degradation of cellulose. Chemical methods involve cumbersome extraction and separation processes, which are time-consuming and environmental pollution. Therefore, a spectroscopic method for determining cellulose is highly expected.13C CP/MAS NMR is a very important tool to characterize the structure and sequence of polysaccharides. The application of cross-polarization and magic angle rotation technology effectively eliminates the effects of chemical displacement anisotropy and dipole interactions on NMR peaks, and greatly improved resolution and sensitivity. The spectral deconvolution technique can effectively isolate the interference of overlapping peaks by curve fitting. We developed a fast, efficient,accurate and environmentally friendly method for quantitative analysis of cellulose by combining 13C CPMAS NMR with spectral deconvolution technology. The method was successfully applied to the quantitative analysis of different cellulose content samples.In clinical studies, the development of effective tumor detection and imaging techniques is particularly critical for the discovery and treatment of cancers, which can effectively improve the survival rate of cancer treatments. Near-infrared fluorescence imaging technology has attracted widespread attention and research due to its effective reduction of tissue absorption, scattering and spontaneous fluorescence in 700-900nm. Organic fluorescence probes have been used extensively in tumor imaging study due to their good biocompatibility. Due to the large surface area and easily modify a series of fluorescent groups, functional nanoparticles were applied to the tumor imaging study, and achieved good result. Moreover, NPs can use enhanced permeability and retention(EPR) effect to realize passive transport tumor-targeted imaging. Tumor cells also have a higher expression of special enzymes compared to normal cells due to the need of proliferation, development and invasion. It is a wise strategy to target these enzymes when designing probes for tumor imaging. Many studies have shown that a large number of tumor cells show high expression of biotin receptors, so it will beneficial to target tumor cells when probes connect biotin.Compared with fluorescence "Turn-Off’,fluorescence "Turn-On" has higher signal-to-noise ratio and thus has higher sensitivity. Most of the fluorescence"Turn-On" probes use the fluorescence resonance energy transfer (FRET) effect to turn "On" their fluorescence. For instance,upon the cleavage of the linker by an enzyme, the quencher(acceptor) is separated from the fluorophore(donor) or the fluorophore is separated from the fluorophore(Self-Quenching),thus turning "On"the fluorescence of the probe. In the last decade, there is also use enzyme-instructed aggregation-induced emission (AIE) to realize florescence "Turn On".Based on the CBT-Cys click reaction, we developed a biotinylated nanoparticle probe for tumor-targeted imaging. These probes have the ability to identify biotin receptor-positive tumor cells, thus realize active targeting for tumor imaging. After being uptake by targeted tumor cells, the disassembly of 1-NPs by robust proteases turned the NIR fluorescence on in tumor cells, so as to achieve NIR fluorescence tumor-targeted imaging with high specificity and sensitivity. The probe was successfully applied in vitro imaging and imaging study of mouse tumors in vitro.