Swarming Responsive Photonic Nanorobots for Motile-Targeting Microenvironmental Mapping and Mapping-Guided Photothermal Treatment

Micro/nanorobots can propel and navigate in many hard-to-reach biological environments,and thus may bring revolutionary changes to biomedical research and applications.However,current MNRs lack the capability to collectively perceive and report physicochemical changes in unknown microenvironments.Here we propose to develop swarming responsive photonic nanorobots that can map local physicochemical conditions on the fly and further guide localized photothermal treatment.The RPNRs consist of a photonic nanochain of periodically-assembled magnetic Fe_(3)O_(4)nanoparticles encapsulated in a responsive hydrogel shell,and show multiple integrated functions,including energetic magnetically-driven swarming motions,bright stimuli-responsive structural colors,and photothermal conversion.Thus,they can actively navigate in complex environments utilizing their controllable swarming motions,then visualize unknown targets(e.g.,tumor lesion)by collectively mapping out local abnormal physicochemical conditions(e.g.,pH,temperature,or glucose concentra-tion)via their responsive structural colors,and further guide external light irradiation to initiate localized photothermal treatment.This work facilitates the development of intelligent motile nanosensors and versatile multifunctional nanotheranostics for cancer and inflam-matory diseases.

Swarming magnetic photonic-crystal microrobots withon-the-fly visual pH detection and self-regulated drug delivery

Swarming magnetic micro/nanorobots hold great promise for biomedical applications,but at present suffer from inferior capabilities to perceive and respond to chemical signals in local microenvironments.Here we demonstrate swarming magnetic photonic crystal microrobots(PC-bots)capable of sponta-neously performing on-the-fly visual pH detection and self regulated drug delivery by perceiving local pH changes.The magnetic PC-bots consist of pH-responsive hydrogel microspheres with encapsulated one-dimensional periodic assemblies of Fe3O4 nanoparticles.By programming extemnal rotating magnetic fields,they can self-organize into large swarms with much-enhanced collective velocity to actively find targets while shining bright“blinking”structural colors.When approaching the target with abnormal pH conditions(e.g.an ulcerated superficial tumor lesion),the PC-bots can visualize local pH changes on the fly via pH-responsive structural colors,and realize self-regulated release of the loaded drugs by recognizing local pH.This work facilita tes the develop-ment of intelligent micro/nanorobots for active“motile-targeting”tumor diag-nosis and treatment.

Mg-Based Micromotors with Motion Responsive to Dual Stimuli

Mg-based micromotors have emerged as an extremely attractive artificial micro/nanodevice,but suffered from uncontrollable propulsion and limited motion lifetime,restricting the fulfillment of complex tasks.Here,we have demonstrated Mg-based micromotors composed of Mg microspheres asymmetrically coated with Pt and temperature-sensitive poly(N-isopropylacrylamide)(PNIPAM)hydrogel layers in sequence.They can implement different motion behaviors stemming from the driving mechanism transformation when encountering catalyzed substrates such as H_(2)O_(2) and respond to both H_(2)O_(2) concentration and temperature in aqueous environment.The as-constructed Mg-based micromotors are self-propelled by Pt-catalyzed H_(2)O_(2) decomposition following the self-consuming Mg-H_(2)O reaction.In this case,they could further generate bilateral bubbles and thus demonstrate unique self-limitation motion like hovering when the phase transformation of PNIPAM is triggered by decreasing temperature or when the H_(2)O_(2) concentration after permeating across the PNIPAM hydrogel layer is high enough to facilitate bubble nucleation.Our work for the first time provides a stimuli-induced“hovering”strategy for self-propelled micromotors,which endows Mg-based micromotors with an intelligent response to the surroundings besides the significant extension of their motion lifetime.

Light-Programmable Assemblies of Isotropic Micromotors

“Life-like”nonequilibrium assemblies are of increasing significance,but suffering from limited steerability as they are generally based on micro/nanomotors with inherent asymmetry in chemical composition or geometry,of which the vigorous random Brownian rotations disturb the local interactions.Here,we demonstrate that isotropic photocatalytic micromotors,due to the persistent phoretic flow from the lluminated to shadowed side rrespective of their Brownian rotations,experience lightprogrammable local interactions(reversibly from atraction to repulsion and/or alignment)depending on the direction of the incident lights.Thus,they can be organized into a variety of tunable nonequilibrium assemblies,such as apolar solids(i.e.,immobile colloidal crystal),polar liquids(ie.,phototactic colloidal stream),and polar solids(i.e.,phototactic colloidal crystal),which can further be“cut”into a predesigned pattern by utilizing the switching motor-motor interactions at superimposedlight edges.This work facilitates the development of active matters and motile functional microdevices.