Self‐propelled micro‐ and nanomotors (MNMs) have shown great potential for applications in the biomedical field, such as active targeted delivery, detoxification, minimally invasive diagnostics, and nanosurgery, owing to their tiny size, autonomous motion, and navigation capacities. To enter the clinic, biomedical MNMs request the biodegradability of their manufacturing materials, the biocompatibility of chemical fuels or externally physical fields, the capability of overcoming various biological barriers (e.g., biofouling, blood flow, blood–brain barrier, cell membrane), and the in vivo visual positioning for autonomous navigation. Herein, the recent advances of synthetic MNMs in overcoming biological barriers and in vivo motion‐tracking imaging techniques are highlighted. The challenges and future research priorities are also addressed. With continued attention and innovation, it is believed that, in the future, biomedical MNMs will pave the way to improve the targeted drug delivery efficiency.
The delivery of probiotics to the microbiota is a promising method to prevent and treat diseases. However, oral probiotics will suffer from gastrointestinal insults, especially the pathological microenvironment of inflammatory diseases such as reactive oxygen species (ROS) and the exhausted mucus layer, which can limit their survival and colonization in the intestinal tract. Inspired by the fact that probiotics colonized and grew in the mucus layer under physiological conditions, we developed a strategy for a super probiotic (EcN@TA-Ca 2+ @Mucin) coated with tannic acid and mucin via layer-by-layer technology. We demonstrated that mucin endows probiotics with superior resistance to the harsh environment of the gastrointestinal tract and with strong adhesiveness to the intestine through its interaction with mucus, which enhanced colonization and growth of probiotics in the mucus layer without removing the coating. Moreover, EcN@TA-Ca 2+ @Mucin can distinctly down-regulate inflammation with ROS scavenging and reduce the side effects of bacterial translocation in inflammatory bowel diseases, increasing the abundance and diversity of the gut microflora. We envision that it is a powerful platform to improve the colonization of probiotics by regulating the pathological microenvironment, which is expected to provide an important perspective for applying the intestinal colonization of probiotics to treat a variety of diseases.
Micro/nanomotors (MNMs) are miniaturized devices capable of performing self-propelled motion and ondemand tasks, which have brought revolutionary renovations in nanomedicine, environmental remediation, biochemical sensing, etc. Numerous methods of either chemical synthesis or physical fabrications have been extensively investigated to prepare MNMs of various shapes and functions. However, MNMs with replaceable engines that can be flexibly assembled and disassembled, resembling that of a macroscopic machine, have not been achieved. Here, for the first time, we report a demonstration of control over the engine replacement of self-propelled nanomotors based on hollow mesoporous silica nanoparticles (HMSNPs) via supramolecular machine-based host−guest assembly and disassembly between azobenzene (Azo) and β-cyclodextrin (β-CD). Nanomotors with different driving mechanisms can be rapidly constructed by selecting corresponding β-CD-modified nanoengines of urease, Pt, or Fe 3 O 4 , to assemble with the azobenzenemodified HMSNPs (HMSNPs-Azo). In virtue of photoresponsive cis/trans isomer conversion of azobenzene molecules, engine switching can be accomplished by remote light triggered host−guest assembly or disassembly between HMSNPs-Azo and β-CDmodified engines. Moreover, this method can quickly include multiple engines on the surface of the HMSNPs-Azo to prepare a hybrid MNM with enhanced motion capability. This strategy not only is cost-effective for the rapid and convenient preparation of nanomotors with different propulsion mechanism but also paves a new path to future multiple functionalization of MNMs for ondemand task assignment.
Traditionally, containers made from steel or other metals are not good for making tea, probably due to the fact that polyphenol components in tea can chelate with metal ions. A similar reason might stand behind the observations as reported herein. During the coating of well-defined metal-organic framework (MOF) crystalline particles with polydopamine (PDA) via pH-induced self-polymerization of dopamine, we found that MOF templates automatically etch off during the coating, giving rise to nonspherical PDA capsules that inherit the morphologies of the templates. Such self-etching of MOF templates is ascribed to the chelation of the metal nodes of the MOFs by the catechol moieties in the PDA layer. In addition, the self-etching of the zeolitic imidazolate framework-8 (ZIF-8) with a truncated cubic shape probably follows a crystalline facet-dependent fashion, resulting in intermediate yolk-shell structures with ZIF-8 cargos of various shapes inside a highly biocompatible PDA shell. Incubation of such intermediate hybrid particles with the cancerous HeLa cell line leads to pronounced cytotoxicity, which is tentatively connected with the cellular internalization of the ZIF@PDA nanoparticles because of the cell affinity of the PDA layer. Subsequently, the continuous release of Zn by the self-etching of the encapsulated ZIF-8 inside the cell increases intracellular Zn to a harmful level. Therefore, intracellular delivery of metal ions is probably realized, which might offer a novel way for cancer therapy.
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