Preparation And Properties Of Nanocomposites Of Gold And Rare Earth Coordination Polymer

Owing to the strong Localized surface plasmon resonance effect?LSPR?,gold nanoparticles can induce localized electric field enhancement,leading to many novel physical phenomena such as surface-enhanced raman scattering?SERS?and metal-enhanced fluorescence.On the basis of unique optical and physical properties,coupled with high degree of anti-oxidation,anti-corrosion properties and simple preparation method,gold nanoparticles have a wide range of application prospects in the fields of biomedicine,optical sensing and catalysis.In particular,extensive research has been conducted on gold nanocomposites.The rare earth coordination polymers have large Stokes and anti-Stokes shifts,sharp peaks,long fluorescence lifetime and excellent light stability.At the same time,the luminescent properties are flexible,upconversion light emission and down-conversion light emission can be realized according to actual application needs.Therefore,they have a wide range of applications in lighting,fiber optic communications,organic electroluminescence and biomedical.Meanwhile,rare earth ions have multiple coordination sites,they can coordinate with organic ligands containing different functional groups,using the“antenna effect”to improve the luminous efficiency of rare earth ions and a variety of structure-functionalized rare earth nanomaterials were prepared.Furthermore,some functional groups such as carboxyl?-COOH?and amino?-NH2?groups are always presents on the surface of coordination polymers,which provides convenience for their bioapplications.To date,most of the researches are focused on the composite materials of gold nanoparticles with inorganic rare earth compouds,while the study of gold nanoparticles and rare earth coordination polymers is at the early stage.Based on the excellent properties of gold nanoparticle and rare earth coordination polymer,with the aim to explore their photothermal performance and magnetic imaging performance,guided by their biomedical function,three kinds of Au@rare earth coordination polymer nanocomposites?Au@RECP?were designed and prepared.The properties and the interaction mechanism of each component were investigated,which provides reference for their medical application.The main research contents include:?1?AuNPs,AuNRs and Au@PdNPs were synthesized by liquid phase reduction method,seed-mediated method and one-pot reduction method,exploying gold chloride trihydrate?HAuCl4?3H2O?and potassium tetrachloropalladate?K2PdCl4?were chosen as raw matrial.Meanwhile,the reaction time and temperature were optimized for the synthesis.Results show that the size of AuNPs is 20 nm with LSPR peaks at 527 nm;the AuNRs with an average length of 30 nm and width of 9.5 nm?aspect ratio=3.16?and the LSPR peaks at 605 nm and 763 nm,respectivly;Au@PdNPs is hexagonal with edge of 60 nm and 547 nm LSPR peak.The above gold nanopartilces provide a material for the preparation of Au@RECP nanocomposites in the next step.?2?Meso-?2,3-mercaptosuccinic?acid?DMSA?was chosen as organic ligand,Eu?NO3?3?6H2O and AuNPs were chosen as raw materials,Au@EuCP core-shell nanoparticles has been prepared via a facie solvothermal method.The material was characterized by XRD,TEM,FT-IR and Mapping,the photothermal transduction properties and biocompatibility of Au@EuCP were observed also.The results show that Au@EuCP is spherical with an averge diameter of 100 nm,which has a good biocompatibility,and its photothermal effect is obvious.After light irradiation,the temperature increased by 18.4°C to 52.4°C.After 5 cycles,the temperature can still reach 50°C or more.The photothermal conversion performance of Au@EuCP is due to the strong dissipative loss and the radiation resorption process with the introduction of AuNPs.In addition,the formation mechanism of Au@RECP core-shell nanoparticles have been discussion,the AuNPs play the roles of raw matrials and tempelates.Therefore,Au@RECP provides a well idea for design of Au@RECP to development the application of biomedicine.?3?To improve the effect of photothermal conversion,on the basis of the previous work,we selected DMSA as ognic ligand,the AuNPs and Tb³⁺which was overlapped well with the spectral absorb of AuNPs as raw materials.The Au@TbCP was obtained through solvothermal method.The material was characterized by XRD,SEM,TEM and Mapping,the photothermal transduction properties and biocompatibility of Au@TbCP were observed also.The Au@TbCP has good biocompatibility under dark vision,and the cell survival rate is only 19%under light,which has the ability of killing cells.The solution reached 72°C,and improved effect of photothermal conversion was realized.The fluorescence resonance energy transfer?FRET?proess provides an excellent photothermal conversion,the emission of TbCP is well overlap with the absorb of AuNPs,while the TbCP was used as energy donor and AuNPs was used as energy receptor.This work shows a design idea for photothermal therapy?PTT?application of Au@RECP.?4?Base on Gd³⁺ion contains seven isolated pairs of electrons in the 4f electron layer,a large magnetic distance and good paramagnetism,the Au@GdCP nanocomposite were synthesis by hydrothermal method with AuNPs,Allantoin?ALLA?and Gd³⁺ion.The material was characterized by XRD,TEM,FT-IR and Mapping,the T1-MRI properties and biocompatibility of Au@GdCP were investigated also.It was turn out that LSPR of AuNPs influence the radiation attenuation rate and the magnetic field intensity of the luminescence center,the improved luminescence intensity and enhanced magnetic contrast effect were achieved with the introduction of AuNPs.The enhancement of the longitudinal relaxation rate?r1?and transverse relaxation?r2?of the Au@GdCP were 11.5 times and10.7 times of GdCP,respectively.Additionally,the T1-MRI results show that the MRI contrast of Au@GdCP is much better than GdCP.Au@GdCP exhibits excellent biocompatibility simultaneously.Au@GdCP is expected to play a positive role in enhancing the MRI signal and reducing the dosage and toxicity of contrast agent.?5?On the base of above successful study and excellent drug delivery ability of coordination polymer,Au@GdCP with upconversion luminescence properties were chosen and three different drug carriers were explored.The possibility of drug loading was explored and the drug release capacity under different pH environments was studied.The drug release ability under acidic conditions is stronger than neutral conditions,which is benificial for Au@GdCP to apply in targeted therapy and controlled release of drug delivery system because of the tumor tissue is mostly weakly acidic.In addition,the drug-carrying capacity and release capacity are closely related to the binding ability of the material surface to the drug,hydrogen bonding,and?-?bond interaction.The above results provide further design ideas for the study of Au@RECP multifunctional nanocomposites.