Construction And Properties Of Platinum Nanoenzyme Supported By Magnetic Gel Microspheres

At present,with the deterioration of the environment,we find the rate of major diseases is increasing per year and the age distribution become younger.It is urgent to develop some new principles of diagnosis and treatment technology.In recent years,the rapid development of nanomaterials science has provided a new opportunity for the diagnosis and treatment of cancer and other malignant diseases.Among them,nanomaterials mimic enzymes(nanozyme)not only have physical effects such as sound,light,magnetism and heat,but also have biological and chemical effects such as peroxidase(POD),catalase(CAT),oxidase(OXD)and superoxide dismutase(SOD).On the one hand,tumor can be killed by light/magnetothermal therapy,light/acoustic dynamic therapy,etc.;on the other hand,cell death can be induced by the regulation of cellular ROS through the activity of nanozymes(chemodynamic therapy),which has great potential in the application of diagnosis and treatment.In this paper,a novel nanoenzyme structure Fe₃O₄@P(NIP/AA)-Pt with both magnetic response and temperature sensitivity was prepared.Fe₃O₄ provides the nanozyme with magnetic responsiveness,enabling it to conduct magnetic separation and generate heat through the magnetothermal effect.P(NIP/AA)(poly(N isopropyl acrylamide-co-acrylic acid)provides temperature responsiveness and a hydrophobic cavity for the nanoenzyme to regulate the activity of the nanozyme.Pt NPs(platinum nanoparticles)is the enzyme activity center of the nanoenzyme structure,providing redox-like enzyme activity to regulate ROS.In addition,after the Pt active center catalyzed the formation of H₂O₂ into oxygen,it could also be bound in the polymer network by P(NIP/AA),thus obtaining the ultrasound imaging function and oxygen-carrying function.Specific research contents are as follows:The PNIPAm(N-isopropyl acrylamide)and PAA(polyacrylic acid)copolymers were polymerized onto the surface of the magnetic nano-aggregate by emulsion polymerization method to form a typical core-shell structure,and platinum nanoparticles were grown in the magnetic microsphere polymer gel layer by in situreduction method.For synthetic samples by transmission electron microscope(TEM),scanning electron microscope(SEM),scanning electron microscope energy spectrum analysis(SEM,EDS),infrared spectra(FTIR),vibrating sample magnetometer(VSM),alternating magnetic field generator(ACMF),dynamic light scattering particle sizer(DLS)were characterized,suggests that the Fe₃O₄ @P(NIP/AA)-Pt has a typical core-shell structure,controllable and shell thickness,good dispersion,good magnetic responsiveness and temperature sensibility.Subsequently,the enzyme-like activities of Fe₃O₄@P(NIP/AA)-Pt were verified and studied.Compared with ordinary Pt nanases,the activity of Fe₃O₄@P(NIP/AA)-Pt was significantly enhanced in POD,CAT and OXD.This may be due to the fact that the network space structure in the P(NIP/AA)gel layer promotes the interaction between the enzyme activity center and substrate through scoping effect,and effectively enhances the enzymatic activity of the substrate.The results of enzyme homeostasis kinetics also showed that Fe₃O₄@P(NIP/AA)-Pt had a higher reaction rate constant and a significantly increased affinity for H₂O₂ and ABTS compared with ordinary Pt nanozymes.Finally,the capability of Fe₃O₄@P(NIP/AA)-Pt in producing oxygen and carrying oxygen,ultrasound imaging and ROS production was explored.Under neutral conditions,Fe₃O₄@P(NIP/AA)-Pt exerts CAT enzyme activity.On the one hand,it can directly catalyze H₂O₂ to generate O₂ micro-nano bubbles to achieve ultrasonic imaging enhancement.On the other hand,it can also load O₂ in PNIPAm gel network through this catalytic reaction to construct oxygen-carrying ultrasonic imaging agent,which also shows good ultrasonic imaging effect.On the other hand,ultrasonic blasting of O₂ micro-nano bubbles can produce a large number of highly toxic hydroxyl radicals(·OH),and realize the pro-oxidation reaction under neutral conditions.However,under acidic conditions,Fe₃O₄@P(NIP/AA)-Pt can promote oxidation to product hydroxyl radicals by exerting pod-like enzyme activity.To sum up,Fe₃O₄@P(NIP/AA)-Pt has magnetic response,temperature sensitivity and enzymatic-like activity,as well as ultrasonic imaging and oxidation promoting functions,laying a foundation for the development of integrated techniques for the diagnosis and treatment of tumors and other diseases.