Switchable chemotaxis is vital for motile microorganisms seeking benefits or to avoid harm. Inspired by nature, and for the first time, we demonstrate an artificial enzyme-powered micromotor that can autonomously regulate the propulsion mechanism, as well as motion directionality, by solely sensing the change of fuel concentration (Cf) in its surroundings. The as-designed micromotors have a pot-like microstructure with ureases immobilized on the inner surface. With the confined effect of the pot-like microstructure and unique features of the urease catalytic reaction, the molecular products are further reacted into ions, and their propulsion mechanism can be reversibly adjusted between ionic diffusiophoresis and microbubble recoils when Cf changes. Consequently, the as-developed micromotors under magnetic field are able to self-turn back if the local Cf differs greatly in their surroundings, indicating the achievement of positive and negative chemotaxis by sensing local Cf. Meanwhile, the micromotors also show highly enhanced migration speed by microbubble ejection, up to 60 μm/s, around 30 body lengths per second at physiological urea concentrations. Furthermore, they have an outer surface of mesoporous silica which is easily functionalized for applications such as stimuli-responsive delivery-associated therapies. This work will promote “smart” artificial micro/nanomotors for in vivo biomedical applications.

Injectable chemically powered nanomotors may revolutionize biomedical technologies, but to date, it is a challenge for them to move autonomously in the blood circulation system and they are too large in size to break through the biological barriers therein. Herein, we report a general scalable colloidal chemistry synthesis approach for the fabrication of ultrasmall urease-powered Janus nanomotors (UPJNMs) that have a size (100–30 nm) meeting the requirement to break through the biological barriers in the blood circulation system and can efficiently move in body fluids with only endogenous urea as fuel. In our protocol, the two hemispheroid surfaces of eccentric Au−polystyrene nanoparticles are stepwise grafted with poly(ethylene glycol) brushes and ureases via selective etching and chemical coupling, respectively, forming the UPJNMs. The UPJNMs have lasting powerful mobility with ionic tolerance and positive chemotaxis, while they are able to be dispersed steadily and self-propelled in real body fluids, as well as demonstrate good biosafety and a long circulation time in the blood circulation system of mice. Thus, the as-prepared UPJNMs are promising as an active theranostics nanosystem for future biomedical applications.

Artificial nanomotors are nanoscale machines capable of converting surrounding other energy into mechanical motion and thus entering the tissues and cells of organisms. They hold great potential to revolutionize the diagnosis and treatment of diseases by actively targeting the lesion location, though there are many new challenges that arise with decreasing the size to nanoscale. This review summarizes and comments on the state-of-the-art artificial nanomotors with advantages and limitations. It starts with the fabrication methods, including common physical vapor deposition and colloidal chemistry methods, followed by the locomotion characterization and motion manipulation. Then, the in vitro and in vivo biomedical applications are introduced in detail. The challenges and future prospects are discussed at the end.

Background and Objective:The aim of this study was to compare the outcome of using tibial nails inserted by the suprapatellar approach with tibial nails inserted by the infrapatellar approach in a meta-analysis of randomized controlled trials (RCTs).Methods:The following electronic databases were searched: PubMed (1966 to January 2018), EMBASE (1974 to January 2018), Cochrane Library (January 2018), Web of Science (1990 to January 2018). We also used Google Search Engine to search more potentially eligible studies until January 2018. The methodological qualities of included studies were assessed in accordance with the guidelines provided by the Cochrane Collaboration for Systematic Reviews. The statistical analysis all of included studies were performed by STATA 13.0 software. The outcomes were total blood loss, postoperative pain, range of motion (ROM), Lysholm knee score, fluoroscopy time, operation time, and postoperative complications.Results:Four RCTs published between 2015 and 2017 were selected in the meta-analysis. There was a significant difference between suprapatellar and infrapatellar approach surgery in total blood loss, postoperative pain, ROM, Lysholm knee scores, and fluoroscopy times.Conclusions:The suprapatellar approach for intramedullary nailing appears superior to the infrapatellar approach, with a reduction in total blood loss, improved postoperative pain, shorter fluoroscopy time, and better knee functionality outcomes. There was no increased incidence of postoperative complications between the 2 groups. Further research remains necessary.