Biofriendly micro/nanomotors operating on biocatalysis: from natural to biological environments

Abstract

Micro/nanomotors (MNMs) are tiny motorized objects that can autonomously navigate in complex fluidic environments under the influence of an appropriate source of energy. Internal energy driven MNMs are composed of certain reactive materials that are capable of converting chemical energy from the surroundings into kinetic energy. Recent advances in smart nanomaterials design and processing have endowed the internal energy driven MNMs with different geometrical designs and various mechanisms of locomotion, with remarkable travelling speed in diverse environments ranging from environmental water to complex body fluids. Among the different design principals, MNM systems that operate from biocatalysis possess biofriendly components, efficient energy conversion, and mild working condition, exhibiting a potential of stepping out of the proof-of-concept phase for addressing many real-life environmental and biotechnological challenges. The biofriendliness of MNMs should not only be considered for in vivo drug delivery but also for environmental remediation and chemical sensing that only environmentally friendly intermediates and degraded products are generated. This review aims to provide an overview of the recent advances in biofriendly MNM design using biocatalysis as the predominant driving force, towards practical applications in biotechnology and environmental technology.

Keywords: Biocatalysis; Biofriendly MNM design; Micro/nanomotors (MNMs).

Figure 1

Overview of biofriendly MNMs driven by biocatalysis for environmental and biotechnological applications. Reproduced with permission: A WILEY-VCH (Gao et al. 2019); B American Chemical Society (Kiristi et al. 2015); C WILEY-VCH (Mayorga‐Martinez and Pumera 2019); D Springer Nature (de Ávila et al. 2017); E Elsevier (Zhao et al. 2020)

Figure 2

Micromotor systems for motion control and cargo delivery. A Open view of the hybrid biocatalytic micro-engine with surface modification of inner Au layer and enzymatic decomposition of peroxide fuel. Reproduced with permission of American Chemical Society (Sanchez et al. 2010). B Schematic illustration of enzymatic hollow mesoporous silica Janus nanomotors. Reproduced with permission of Springer Nature (Kumar et al. 2018). C Schematic illustration of preparation of avidin/ biotinylated urease (Avi/bUre) microtube and swimming Avi/bUre microtube with non-bubble propulsion and self-rotation. Reproduced with permission of Wiley‐VCH (Sugai et al. 2019). D Schematic of the reactive inkjet printing process for manufacturing biocatalytic micro-rockets. Reproduced with permission of WILEY‐VCH (Gregory et al. 2016)

Figure 3

Micromotor systems working in the natural environment. A Schematic illustration of the concept of motor-based biocatalytic pollutant remediation involving gradual release and mixing of an enzyme. Reproduced with permission of WILEY-VCH (Orozco et al. 2014). B Schematic illustration of the dual-function plant (radish) motors. Reproduced with permission of the Royal Society of Chemistry (Sattayasamitsathit et al. 2014). C Schematic illustration of the pollutant effect on the microfish locomotion speed. Reproduced with permission of American Chemical Society (Orozco et al. 2013). D Schematic representation of self-propelled all-polymer micromotor and the gas sensing behavior. Reproduced with permission of the Royal Society of Chemistry (Liu et al. 2016)

Figure 4

Micromotor systems for drug delivery. A MOFs-based micromotors with reversible pH-speed regulation. Reproduced with permission of WILEY-VCH (Gao et al. 2019). B Vertical directionally propelled micromotors with pH-controlled hydrophilicity/hydrophobicity switch. Reproduced with permission of Elsevier (Guo et al. 2019). C PLL/BSA-Based rockets for drug transportation and light-triggered release. Reproduced with permission of American Chemical Society (Wu et al. 2015). D Schematic illustration of intravesical delivery using urease-powered nanomotors. Reproduced with permission of American Chemical Society (Choi et al. 2020)

Figure 5

Micromotor systems for biosensing. A Schematic illustration of ultrasound-based visualization of oxygen microbubbles formed by micromotor converters. Reproduced with permission of Elsevier (Olson et al. 2013). B Schematic illustration of micromotors used for specific DNA sensing. Reproduced with permission of American Chemical Society (Zhang et al. 2019). C Schematic representation of the micromotors fabrication, where a silicon dioxide layer is grown onto a commercial polystyrene template. Reproduced with permission of American Chemical Society (Patino et al. 2019). D Schematic illustration of ratiometric fluorescence response of Janus micromotors after capture of tumor cells. Reproduced with permission of Elsevier (Zhao et al. 2020)