Biodegradable Caramelized Carbonaceous Nanospheres Supported Manganese For Magnetic Resonance Imaging And Photothermal Therapy

Cancer is a malignant disease threatening human health.It is very important to realize the accurate diagnosis and treatment of cancer.MRI can provide excellent resolution,high in vivo accuracy and multi-parameter imaging under the absence of radiation,which made it one of the most useful diagnostic methods.In order to enhance contrast in clinical application,contrast agents were developed to enhance the performance of MRI.Photothermal therapy（PTT）is a new method for the treatment of cancer,which has the advantages of high precision and low damage,and it is important to have a high photothermal conversion efficiency.With the development of nanomaterials,they have been widely used in biomedicine because of their unique optical,magnetic and electronic properties.Contrast agents can be divided into two categories,including T1 group and T2 group,manganese-based nanomaterials can improve the performance of T1 imaging.Photothermal therapy agents include the dye nanomaterials,gold-based nanomaterials,carbon nanomaterials and semiconductor nanomaterials.The diagnosis and treatment of multifunctional nanomaterials have been extensively studied,the toxicity and metabolism of nanomaterials in vivo is a major obstacle to the use of nanomaterials in clinical practice,which have been the focus of attention.In this paper,Caramelization reaction is a general type of non-enzymatic browning reactions to food caramels,caramelized carbonaceous nanospheres（CNPs）with good biocompatibility and biodegradability were synthesized by glucose.CNPs have functional groups and can form manganese carbon nanomaterials for MRI and PTT.The contents are summarized as follows:1.we report a biocompatible caramelized carbonaceous nanospheres supported paramagnetic ultrathin manganese oxide nanosheets via self-sacrificing reduction as a liver MRI contrast agent and for T,-weighted MR imaging,which are taken up by Kupffer cells resulting in a high relaxivity rate.Mn3O4-caramelized nanoparticles（Mn3O4-CNPs）were synthesized and their characteristics as MR contrast agents were investigated.The relaxation rate（r1）of Mn3O4-CNPs is calculated to 11.6 mM-1 s-1 by Mn concentrations and is nearly three times commercial GdⅢ-based complex agents at a 3.0 T clinical MR scanner,and the in vivo experiment shows that the signals of mouse liver increase by 50.1%under T1-weighted imaging in 4 h post-injection of Mn3O4-CNPs.The in vivo bio-distribution reveals that the concentrations of Mn are equal to the pre-injection after post-injection of Mn3O4-CNPs 48 h.Therefore,the Mn3O4-CNPs can be used as biocompatible liver MR contrast agents.2.Biodegradable and pH responsitive of Mn2-CNPs were synthesized by ion adsorption and coordination for magnetic resonance imaging（MRI）and photothermal therapy（PTT）.Mn²⁺-CNPs were demonstrated that they have outstanding photothermal performance under near-infrared laser irradiation.The release of Mn²⁺from Mn2-CNPs is calculated 45%at pH = 5.0.The cytotoxicity study show excellent biocompatibility.The in vivo experiment indicates that after injecting 15 min Mn²⁺-CNPs,the signals of tumour increase by 64%under T1-weighted imaging mode,which show excellent tumor imaging ability.The blood plasma experiment and intracellular biodegradation behavior indicate that Mn²⁺-CNPs can be biodegraded.Therefore,Mn²⁺-CNPs have great potential in clinical diagnosis and treatment of tumors.