Self-propelled supramolecular nanomotors with temperature-responsive speed regulation

Abstract

Self-propelled catalytic micro- and nanomotors have been the subject of intense study over the past few years, but it remains a continuing challenge to build in an effective speed-regulation mechanism. Movement of these motors is generally fully dependent on the concentration of accessible fuel, with propulsive movement only ceasing when the fuel consumption is complete. Here we report a demonstration of control over the movement of self-assembled stomatocyte nanomotors via a molecularly built, stimulus-responsive regulatory mechanism. A temperature-sensitive polymer brush is chemically grown onto the nanomotor, whereby the opening of the stomatocytes is enlarged or narrowed on temperature change, which thus controls the access of hydrogen peroxide fuel and, in turn, regulates movement. To the best of our knowledge, this represents the first nanosized chemically driven motor for which motion can be reversibly controlled by a thermally responsive valve/brake. We envision that such artificial responsive nanosystems could have potential applications in controllable cargo transportation.

Designing Molecular Building Blocks for Functional Polymersomes

“…Methods for the synthesis of PEG azides are reviewed by Sill et al . N 3 −PEG‐ b ‐PS can be synthesized by atom transfer radical polymerization (ATRP) of styrene, providing PS−COOH building blocks, which can be coupled to N 3 −PEG−NH 2 via a amide coupling …”

“…After formation of the stomatocyte from Br−PEG‐ b ‐PS in water/THF/dioxane, the bromide was successively substituted with poly(N‐iso‐propyl acrylamide) (PNIPAM) brushes through surface initiated ATRP, yielding stomatocytes with thermosensitive switches for to control nanomotor movement. The PNIPAM brushes were successfully polymerized at the surface of the stomatocytes via ATRP (Figure ) . Both approaches show the potential of functionalizing Br−PEG−PS with a variety of functional groups.…”

Biohybrid Microtube Swimmers Driven by Single Captured Bacteria

“…This can be followed by “fine” guidance, by disengaging the magnetic field to initiate the bacteria's biological sensing mechanisms (pH, chemical), allowing them to navigate microenvironments or to have their swimming terminated. The presented biohybrid has an advantage over monocomponent micromotors, such as genetically engineered bacteria or catalytically powered motors, as the artificial cargo portion of the biohybrid can be purposed as an external guidance system or chemical trigger while the bacterium is a consistent source of power and environmental sensor. Envisioned clinical use of the bacteria‐tube swimmer would apply to areas where bacteria are already present, such as the gastrointestinal tract and even exploiting the host organism's bacteria to adhere to and then power the biohybrid.…”

“…Biohybrid microsystems are the integration of bioactuators with artificial materials; they exploit the motility and sensing capability of biological cells for generating functional micro‐machines. Unlike other types of catalytic micromotors, biohybrid motors are powered by natural, nontoxic fuel sources found in biological media and operate by converting chemical energy into work . Due to the biocompatibility of their power source, biohybrid microsystems have the potential to operate in in vivo environments for biomedical drug and cargo delivery and micromanipulation of cell tissue .…”

Synthesis and Characterization of Amphiphilic Hairy Nanoparticles with pH and Ionic Dual‐Responsiveness

“…Supramolecular interactions, such as hydrophobic interactions, hydrophilic interactions, hydrogen bonding, acid–base interactions, oppositely charged ionic interactions, and host–guest interactions to fabricate self‐assembly materials, are ubiquitous in biological delivery, chemical sensing, controlled release, microelectronics, and technological processes . Among these intelligent materials, polymeric shell hybrid nanoparticles, called hairy nanoparticles, consisting of a core and a layer of polymeric brushes (e.g., polymeric shell), can be engineered to controllable properties by selecting specific core particles (rigid, soft, optical, and magnetic) and polymeric brushes (environmentally compatible, biodegradable, and responsive) .…”