Construction And Biomedical Application Of "Core-island" Magnetic Gold Nanostar Nanomotors

Gold nanostars have been widely studied by scientists due to their unique structure and electronic optical properties.In recent years,researchers have shown great interest in the application of gold nanostars in the field of biomedical science.Studies have demonstrated their excellent performance in drug delivery,photothermal therapy,SERS sensing,biological imaging,and other aspects.However,these properties are mainly based on the passive diffusion of gold nanostars,which has certain limitations,such as a lack of controllability and targeting.To address the aforementioned issues and further enhance the practical application potential of gold nanostars,this study used gold nanostars as both driving and functional units to surface-functionalize magnetic Fe₃O₄particles.By utilizing the catalytic properties of gold nanostars like glucose oxidase and the magnetic responsiveness of the magnetic substrate,a"core-island"structured magnetic gold nanostar nanomotor was designed and constructed,and the effects of its motion performance on the bio-diagnostic and therapeutic properties of gold nanostars were investigated.First,magnetic Fe₃O₄ nanoparticles were prepared by hydrothermal method,and then chloroauric acid was reduced on the surface to obtain Fe₃O₄nano"core-island"structure with surface distributed gold nanoparticles.Then,using a seed-mediated growth and chemical reduction strategy,branched gold nanostars were grown in situ on the gold nanoparticles on the Fe₃O₄surface to obtain the"core-island"structure of magnetic gold nanostar（MAuNS）nanomotor.By utilizing the near-infrared absorption characteristics of gold nanostars,excellent photothermal conversion performance was imparted to MAuNS nanomotors.The optical properties of MAuNS nanomotors in aqueous solutions were explored,and the experimental results showed that the distribution of gold nanostars on Fe₃O₄cores effectively improved the photothermal conversion efficiency of MAuNS nanomotors.Thus,they can be used as photothermal agents for ex vivo photothermal therapy.The magnetic component allows the nanomotor to be remotely controlled by an external magnetic field.Based on the catalytic properties of gold nanoparticle-conjugated glucose oxidase,this nanomotor is capable of achieving self-diffusiophoresis in the presence of the biological fuel glucose,with an enhanced diffusion effect.By adding glucose to the cell culture medium,the opportunity for mutual contact between the MAuNS nanomotor and the cell membrane is increased,which enhances the cellular uptake of the MAuNS nanomotor,further enhancing the photothermal therapeutic effect.At the same time,thanks to the localized surface plasmon resonance（LSPR）effect of gold nanostars,the nanomotor can serve as a surface-enhanced Raman scattering（SERS）sensing probe.Under the guidance of a gradient magnetic field,nanomotors can move along a predetermined path and reach specific cells.Once the nanomotor is internalized by the cell,it can be controlled to move up and down under an oscillating magnetic field,collecting analytes and achieving enhanced SERS signals.This article explores the design and construction methods of a structurally simple and highly integrated MAuNS nanomotor,and studies the positive effects of its self-propulsion and controllable movement performance on the biomedical functions of nanomotors.It provides new insights for the design and development of biomedical micro/nano carriers.