Biomembrane-inspired design of medical micro/nanorobots:From cytomembrane stealth cloaks to cellularized Trojan horses

Micro/nanorobots are promising for a wide range of biomedical applications(such as targeted tumor,thrombus,and infection therapies in hard-to-reach body sites)because of their tiny size and high maneuverability through the actuation of external fields(e.g.,magnetic field,light,ultrasound,electric field,and/or heat).However,fully synthetic micro/nanorobots as foreign objects are susceptible to phagocytosis and clearance by diverse phagocytes.To address this issue,researchers have attempted to develop various cytomembrane-camouflaged micro/nanorobots by two means:(1)direct coating of micro/nanorobots with cytomembranes derived from living cells and(2)the swallowing of micro/nanorobots by living immunocytes via phagocytosis.The camouflaging with cytomembranes or living immunocytes not only protects micro/nanorobots from phagocytosis,but also endows them with new characteristics or functionalities,such as prolonging propulsion in biofluids,targeting diseased areas,or neutralizing bacterial toxins.In this review,we comprehensively summarize the recent advances and developments of cytomembrane-camouflaged medical micro/nanorobots.We first discuss how cytomembrane coating nanotechnology has been employed to engineer synthetic nanomaterials,and then we review in detail how cytomembrane camouflage tactic can be exploited to functionalize micro/nanorobots.We aim to bridge the gap between cytomembrane-cloaked micro/nanorobots and nanomaterials and to provide design guidance for developing cytomembrane-camouflaged micro/nanorobots.

Preparation of microstructure-controllable superhydrophobic polytetrafluoroethylene porous thin film by vacuum thermal-evaporation

The three-dimensional porous network polytetrafluoroethylene （PTFE） thin films were achieved by a vacuum technique through evaporating the pure PTFE powders. The surfaces of PTFE thin films showed various morphologies by adjusting the evaporation temperature and the corresponding contact angle ranging from 133° to 155°. Further analyses of surface chemical composition and morphology by FTIR and FE-SEM revealed that the origin of hydrophobicity for the PTFE thin films could be ascribed to the fluorine-containing groups and the surface morphologies, indicating that abundant -CF2 groups and network structures with appropriate pore sizes played a vital role in superhydrophobicity. By characterization of UV-Vis, the films also showed high transmittance and antireflection effect. The films prepared by this simple method have potential applications such as waterproof membrane and self-cleaning coating.

Biohybrid Micro-and Nanorobots for Intelligent Drug Delivery

Biohybrid mico-and nanorobots are integrated tiny machines from biological components and artificial components.They can poss ess the advantages of onboard actuation,sensing,control,and implementation of multiple medical tasks such as targeted drug delivery,single-cell manipulation,and cell microsurgery.This review paper is to give an overview of biohybrid micro-and nanorobots for smart drug delivery applications.First,a wide range of biohybrid micro-and nanorobots comprising different biological components are reviewed in detail.Subsequently,the applications of biohybrid mico-and nanorobots for active drug delivery are introduced to demonstrate how such biohybrid micro-and nanorobots are being exploited in the field of medicine and healthcare.Lastly,key challenges to be overcome are discussed to pave the way for the clinical translation and application of the biohybrid micro-and nanorobots.

Hydrogel-Based Stimuli-Responsive Micromotors for Biomedicine

The rapid development of medical micromotors draws a beautiful blueprint for the noninvasive or minimally invasive diagnosis and therapy.By combining stimuli-sensitive hydrogel materials,micromotors are bestowed with new characteristics such as stimuli-responsive shape transformation/morphing.excellent biocompatibility and biodegradability,and drug loading ability.Actuated by chemical fuels or external fields(eg,magnetic field,ultrasound,light,and electric field),hydrogel-based stimuli-responsive(HBSR)micromotors can be utilized to load therapeutic agents into the hydrogel networks or directly grip the target cargos(eg.,drug-loaded partides,cells,and thrombus),transport them to sites of interest(e.g.,tumor area and diseased tissues),and unload the cargos or execute a specific task(e.g.,cell capture,targeted sampling,and removal of blood dots)in response to a stimulus(eg.,change of temperature,pH,ion strength,and chemicals)in the physiological environment.The high flexibility,adaptive capacity,and shape morphing property enable the H BSR micromotors to complete specific medical tasks in complex physiological scenarios,especially in confined,hard to-reach tissues,and vessels of the body.Herein,this review summarizes the current progress in hydrogel-based medical micromotors with stimuli responsiveness.The thermo-responsive,photothermal-responsive,magnetocaloric-responsive,pH-responsive,ionic strength-responsive,and chemoresponsive micromotors are discussed in detail.Finally,curent challenges and future perspectives for the development of HBSR micromotors in the biomedical field are discussed.