Preparation And Application Of MOF-based Microwave Responsive Materials

Microwave is an electromagnetic wave with a frequency between 300 MHz-300GHz,which has the characteristics of high frequency and wide bandwidth,making microwave widely used in various fields.Microwave thermotherapy is one of the applications of microwave in the field of biomedical treatment,and its main principle is that when microwave penetrates into the biological tissues,the biological tissues will absorb the energy of microwave,which will be converted into thermal effect,warming up the tissues and achieving the purpose of treating diseases.At present,microwave thermotherapy technology has been widely used in the treatment of primary liver cancer,liver metastatic tumours,thyroid tumours and renal tumours,etc.,and has achieved more outstanding results.However,with the deepening of medical research and clinical application,the medical problems faced by microwave thermotherapy technology have gradually come to the fore.For example,microwaves cannot specifically identify tumors.There is a temperature gradient in the microwave thermal field,and the temperature in the warm zone is low,resulting in the cells in the region being in a sub-lethal state,while the residual tumor cells are prone to recurrence and metastasis.In addition,the heat generated by microwaves is not easy to regulate,and it is difficult to eliminate completely larger tumors with a single therapy.To solve these problems,the research of microwave-responsive materials has become an important development direction,i.e.,the use of materials with high microwave-thermal conversion efficiency to improve the heating selectivity of microwaves on tumors.Currently,there are two main development directions for the design of microwave-responsive materials:one is to design materials with micro-nanostructures and utilize the ion-limited domain effect to improve the microwave-thermal conversion efficiency of the materials.The ion confinement effect refers to when the ions are confined in the narrow space of the micro-nano structure,microwave irradiation-induced ion movement is limited,the frequency of collision friction between the ions increases dramatically,so that the system has a higher warming capacity.The second is to design nanomaterials with direct microwave absorption,i.e.,microwaves are incident to the interior of the material,and the microwave energy is converted into heat energy through dielectric loss or magnetic loss,etc.,thus producing a good thermal effect.Unfortunately,most direct microwave-absorbing materials have absorption frequencies mainly in the mid-and high-frequency bands,while few materials have microwave-absorbing properties in the medical low-frequency bands（433 MHz,915 MHz,and 2450MHz）.Based on this,this thesis designs several microwave-responsive materials corresponding to the above two types of studies and further explores their microwave-responsive properties,and the main research contents are as follows:1.Amino-bonded zirconium-based metal-organic framework（MOF）nanomaterials（Zr MOF-NH₂）have been synthesized by hydrothermal self-assembly method,and GGA/CSNO@Zr MOF-NH₂-LM-TPP（GCZMT）nanoamplifiers have been obtained by several methods,including stirring,pumping,and coupling.Due to the ionic domain-limiting effect conferred by the porous structure of the MOF material,the GCZMT nanoamplifier has excellent microwave thermal sensitivity.The GCZMT nanoamplifiers at a concentration of 10 mg m L^-1 increased 8.1°C compared to the control,and the microwave thermal conversion efficiency was up to 20.1%.Moreover,microwave combined with GCZMT nanoamplifier achieved programmed up-regulation of heat shock protein 70（HSP70）expression in response to microwave,which improved the systemic immune response after microwave hyperthermia,and enhanced the therapeutic efficacy of microwave hyperthermia.2.Gallium-based metal-organic framework（MOF）nanomaterials with arginine（GaMOF-Arg,GA）were synthesized by hydrothermal self-assembly,and this microwave sensitizer can significantly enhance the efficacy of microwave thermotherapy.The concentration of GAT nanocomposites at 10 mg m L^-1 increased 6.9°C compared to the control and microwave thermal conversion efficiency up to 38.22%.And GAT nanocomposites enable the release of nitric oxide gas in the presence of microwaves,and then activate the immune response of the body under the combined effect of microwave thermotherapy and gas therapy,triggering strong immune response and memory effect,so as to counteract the metastasis and recurrence of tumors after microwave thermotherapy.Then,under the joint action of microwave thermotherapy and gas therapy,it activates the body’s immune response and triggers a strong immune response and memory effect,thus combating the metastasis and recurrence of tumor after microwave thermotherapy.3.GaMOF was synthesised by stirring method and then Co ions and Ni ions were loaded into GaMOF.This was later reduced to metal monomers by sodium borohydride to obtain GaMOF-Co/Ni（GCN）nanomaterials.The nanomaterials formed multiple heterogeneous interfaces compared to GaMOF,which improved the dielectric loss of the material at medical frequencies by increasing the interfacial polarisation and dipole polarisation.It also enhanced its own magnetism,which induced natural resonance and eddy current losses,and improved the magnetic loss of the material at medical frequencies.The increased of dielectric loss and magnetic loss made the GCN nanomaterials have a good microwave absorption effect at the medical frequency with a minimum reflection loss of-18.09 d B.Moreover,the in vitro microwave heating experiment proved that the GCN nanomaterials have good microwave thermal conversion effect.The GCN composite at a concentration of 4 mg m L^-1 was elevated by 9.7°C compared to the control.4.Similarly,GaMOF nanomaterials were used as the substrate,and the GaMOF-Ni/Ni（RGNR）nanomaterials were obtained by adsorption of monomers Ru and Ni through pumping and stirring,and then the THRGNR nanomaterials were obtained by high-temperature calcination.The synthesised RGNR and THRGNR nanomaterials also formed a variety of heterogeneous interfaces,which enhanced the magnetic properties of the materials,thus improving their dielectric loss and magnetic loss at medical frequencies,resulting in excellent microwave absorption at medical frequencies with a minimum reflection loss of-14.03 d B and-12.63 d B.Moreover,compared with the previous work,the thickness of the material with absorption effect at medical frequencies is significantly reduced,which is more favourable for the application of the wave-absorbing material.The concentration of RGNR and THRGNR nanomaterials at 4 mg m L^-1 increased 8.7°C and 8.9°C,respectively,compared to the control.