Rare Earth Hybrid Nanomaterials And Their Applications In Bioimaging And Therapy

The rare earth elements include lanthanoid elements,yttrium and scandium.When the rare earth elements lose the outer electrons becomeing trivalent ions,electronic transition will occurs inside the rare earth ions,under the protection of the 5s²5p⁶ electron layer.Due to its unique electronic structure,rare earth doped upconversion luminescent materials?UCNPs?have some advantages,such as absorption and emission wavelength ranging infrared to ultraviolet region,narrow emission spectrum,and high color purity.UCNPs can be used for upconversion luminescence?UCL?imaging and magnetic resonance imaging?MRI?.Meanwhile,UCNPs utilizing near-infrared light as the excitation light source can result in a deep tissue penetration depth.Through the combination of other nanomaterials,integrating imaging and therapeutic for treating cancer can be constructed.These advantages make UCNPs a wide range application in biomedical.In this thesis,we focus on the construction of rare earth doped nanocomposites in the diagnosis and treatment of tumors.1.As the study of drug carriers has gradually increased,various encapsulated molecules that activate light,pH,redox potential,and temperature to achieve selective release at the tumor site have also been reported.Manganese dioxide nanosheets exhibit many unique advantages in these encapsulated molecules,such as large surface area and broad absorption.Based on the features above,MnO₂ nanosheets can achieve a sufficient encapsulation effect to prevent the release of drug,and UCL imaging at tumor site.The MnO₂ nanosheets can be reduced by glutathione?GSH?in the acidic environment of the tumor site.The generated Mn²⁺ions can enhance the magnetic resonance signals at the tumor site.MnO₂ nanosheets as a novel GSH and pH-responsive nanomaterial can be effectively applied to selective drug release at tumor site.We report UCNPs@mSiO₂?DOX?-MnO₂nanostructures?UCDMs?based on MnO₂ nanosheets for selective drug release,UCL imaging,and enhanced MRI.The response of MnO₂ nanosheets to pH/GSH was studied to determine their potential application as drug carriers.In vitro study using HeLa cells was performed to achieve the controlled drug release of UCDMs.The results show that UCDMs have potential applications as drug carriers.In addition,the application of intracellular UCL imaging and enhanced MRI was achieved,demonstrating the potential multimodal bioimaging guided chemotherapy.2.At present,the combination of imaging and therapeutic is particularly important in order to achieve more extensive and accurate diagnosis and treatment of cancer.MRI can provide high spatial resolution,high sensitivity of 3D and angiography information,and is widely used in the diagnosis of cancer.In part,we used a simple and gentle method to synthesize a novel double mesoporous nanosystem for photothermal therapy and MRI.Firstly,the mesoporous platinum nanoparticles coated with mesoporous silica,and after amino modification,the final mPt@mSiO₂-GdDTPA nanosystem is obtained by linking with the Gd-DTPA complexes.Mesoporous platinum nanoparticles?mPt?act as nuclei and exhibit excellent photothermal properties under excitation at808 nm.The mesoporous silica shell connected with Gd-DTPA complexes which can be used as contrast agents for MRI.In addition,the mPt@mSiO₂-GdDTPA nanosystem using the methylthiazolyl tetrazole?MTT?method and histological and hematological analysis showed that the nanosystem has low bio-toxicity.And the nanosystem has been successfully applied to in vivo MRI and photothermal therapy of Kunming mice.