Preparation Of Fluorescent Carbon Nanozyme And Its Application In Disease Diagnosis And Therapy

Nanozymes are nanomaterials with properties similar to natural enzymes,which have attracted great interest due to their high stability,easy preparation and excellent catalytic properties.Since the first report of the intrinsic peroxidase activity of Fe₃O₄ nanoparticles in 2007,with the rapid development of nanoscience and nanotechnology and the continuous in-depth research,the development and application of nanozymes are irresistible.Carbon-based nanomaterials have been widely developed as nanomaterials due to their definite electronic and geometric structures.Carbon nanomaterials have shown great application potential in biological analysis,disease diagnosis and treatment and other biomedical fields.Nanozymes based on carbon nanomaterials include carbon dots,graphene,graphene quantum dots,carbon nanospheres,carbon nanotubes and et al.Recently,carbon dots（CDs）,a new star in carbon materials,have good biocompatibility,photostability and long Stokes shift.As a result,CDs are expected to be ideal materials for biosensing,disease diagnosis and treatment.Therefore,simple,rapid,sensitive,high selectivity and real-time analysis of biomarkers has important research value.Fluorescence analysis has the advantages of high sensitivity and high temporal and spatial resolution imaging.At the same time,because there are abundant functional groups in the core-shell structure of sp² hybrid carbon nucleus,CDs have the enzymatic catalytic property of selective activation.In recent years,in order to obtain more superior CDs,surface functionalization research has been carried out.However,the subsequent functionalization of CDs is not only difficult,but also time-consuming and costly.Therefore,there is an urgent need to develop a simple CDs synthesis method,which simultaneously realizes the functions of analytical detection,targeted imaging and disease treatment.In this paper,multifunctional CDs were used as the main tool to study the diagnosis and treatment of diseases.The main contents are as follows:1.β-glucosidase is an important component in the body of organisms,maintaining the basic life process of organisms,and abnormal content in the body of organisms can be an important signal of the occurrence of some diseases.Energy transfer engineering based on the fluorescent probes for directly sensing enzyme activities are in great demand as the enzyme mediated transformations,which are central to all biological processes.Herein,a fluorescent carbon dots（CDs）-based assay exhibiting selective responses to the quantitation of theβ-glucosidase and the inhibitory effect of its inhibitor has been developed.The most common substrate,para-nitrophenyl-β-D-glucopyranoside（p NPG）,are hydrolyzed byβ-glucosidase to release p-nitrophenol（p NP）,which can efficiently quench the fluorescence（FL）of CDs via inner filter effect and electron transfer.However,in the presence of inhibitors ofβ-glucosidase,the fluorescence intensity gradually recovers as the concentration of inhibitors increases.Therefore,the enzyme-triggered FL turn-off/on of specific CDs successfully gets the sensitive detection ofβ-glucosidase and monitors the inhibitory effect of its inhibitors.Furthermore,the new strategy has been applied to detect theβ-glucosidase and monitor the inhibitor ofβ-glucosidase in hepatoma cells by cell imaging.All results suggest that the new method is sensitive and promising to be used in the further cancer diagnosis and treatment.2.Excess reactive oxygen species（ROS）cause oxidative stress with pathobiological consequences such as inflammatory illness.New agents with intrinsic ROS-scavenging capabilities are promising for treatment of inflammation.Herein,we report a new biocompatible metal free carbon nanozyme（C-nzyme）which simultaneously has the antioxidant activities of peroxidase（POD）and catalase（CAT）for H₂O₂,superoxide dismutase（SOD）for O₂^·-,and the depletion properties of·OH.It was found that the C-nzyme has the capability to efficiently deplete the excessive ROS owing to its abundant functional groups acting as the efficient electron transporters.To study the ROS detecting and scavenging ability of C-nzyme,a ROS-generating model was established using Lipopolysaccharide（LPS）for in vitro monitoring and cell imaging.In addition,the liver tissues were found to be protected with the prevention efficiency of 87%through intrinsic passive targeting capability after the tail injection of the C-nzyme in an LPS-induced mice liver inflammation model,showing that this metal free C-nzyme has great potential in anti-inflammation therapy.In general,we focused our investigation on multi-functional CDs and the application of the CDs in analytical detection and disease diagnosis and treatment.The innovation of this paper is reflected in two aspects:one is to develop a sensitive detection and imaging strategy for the inhibitory effect ofβ-glucosidase and its inhibitors,another is the CDs with ROS scavenging capacity,which can be passively targeted and accumulated into inflammatory liver tissue,and has a good therapeutic effect in the mice model of inflammatory liver disease.