Antibacterial micro/nanomotors: current research progress, challenges, and opportunities

Abstract

Bacterial infections remain a formidable threat to human health, a situation exacerbated by the escalating problem of antibiotic resistance. While alternative antibacterial strategies such as oxidants, heat treatments, and metal nanoparticles (NPs) have shown potential, they come with significant drawbacks, ranging from non-specificity to potential environmental concerns. In the face of these challenges, the rapid evolution of micro/nanomotors (MNMs) stands out as a revolutionary development in the antimicrobial arena. MNMs harness various forms of energy and convert it into a substantial driving force, offering bright prospects for combating microbial threats. MNMs' mobility allows for swift and targeted interaction with bacteria, which not only improves the carrying potential of therapeutic agents but also narrows the required activation range for non-drug antimicrobial interventions like photothermal and photodynamic therapies, substantially improving their bacterial clearance rates. In this review, we summarized the diverse propulsion mechanisms of MNMs employed in antimicrobial applications and articulated their multiple functions, which include direct bactericidal action, capture and removal of microorganisms, detoxification processes, and the innovative detection of bacteria and associated toxins. Despite MNMs' potential to revolutionize antibacterial research, the translation from laboratory to clinical use remains challenging. Based on the current research status, we summarized the potential challenges and possible solutions and also prospected several key directions for future studies of MNMs for antimicrobial purposes. Collectively, by highlighting the important knowns and unknowns of antimicrobial MNMs, our present review would help to light the way forward for the field of antimicrobial MNMs and prevent unnecessary blindness and detours.

Keywords: bacterial infections; challenges; micro/nanomotors; opportunities.

Figure 1

Schematic diagram of micro/nanomotors based on different antibacterial mechanisms. (A) MNMs for photodynamic therapy. (B) MNMs for photothermal therapy. (C) MNMs for chemodynamic therapy. (D) MNMs for capture microorganisms. (E) MNMs for bacterial detection. (F) MNMs for bactericidal with mental ions. (G) MNMs for drug delivery in vivo, environment remediation and biofilm eradication.

Figure 2

MNMs for drug delivery. (A) In vivo propulsion and drug delivery of the Mg-based micromotors in stomach. Adapted with permission from , copyright 2017 Springer Nature. (B) EMgMs for localized drug delivery to the GI tract. Adapted with permission from , copyright 2016 American Chemical Society. (C) Fabrication of CIP loaded T-Budbots for biofilm eradication. Adapted with permission from , copyright 2020 American Chemical Society. (D) The microneedle patches used for luteolin delivery in wound antibiofilm therapy. Adapted with permission from , copyright 2023 Elsevier.

Figure 3

MNMs for antibacterial with metal ions. (A) Ag/Mg bactericidal micromotor. Adapted with permission from , copyright 2015 Springer Nature. (B) AgNP-coated Janus microbots for killing bacteria in water. Adapted with permission from , copyright 2017 American Chemical Society. (C) The fabrication process of the MOF micromotors and their antibacterial wound therapy. Adapted with permission from , copyright 2022 American Chemical Society.

Figure 4

MNMs for antibacterial photodynamic therapy or photothermal therapy. (A) Light-driven self-propelled tubular B-TiO₂/Ag nanorobots to remove multispecies biofilm from facial titanium miniplates. Adapted with permission from , copyright 2022 WILEY. (B) Enzyme-photocatalyst tandem microrobot for Escherichia coli biofilm eradication. Adapted with permission from , copyright 2022 WILEY. (C) Mesoporous SiO₂/Au nanomotors for biofilm eradication. Adapted with permission from , copyright 2023 WILEY. (D) NIR-II light-driven dual plasmonic (AuNR-SiO2-Cu₇S₄) antimicrobial nanomotors synergistic photothermal and photocatalytic treatment of bacterial infections. Adapted with permission from , copyright 2023 American Chemical Society.

Figure 5

MNMs for antibacterial chemodynamic therapy. (A) Multifunctional motors with enhanced antibacterial activity against refractory biofilm infections. Adapted with permission from , copyright 2022 Elsevier. (B) Janus Ca@PDAFe-CNO nanomotors integrated with biofilm microenvironment for effective sterilization. Adapted with permission from , copyright 2022 WILEY. (C) A self-propelled Prussian blue micromotor combinate with PTT, CDT for achieving physically and chemically disrupt stable biofilm. Adapted with permission from , copyright 2022 Elsevier.

Figure 6

MNMs for detection. (A) Self-propelled Janus microsensors for the detection LPS from Salmonella enterica. Adapted with permission from , copyright 2018 American Chemical Society. (B) Magneto-catalytic graphene QDs based Janus micromotors for bacterial endotoxin detection. Adapted with permission from , copyright 2017 WILEY.

Figure 7

MNMs for capture and isolation. (A) Ultrasound-propelled magnetically-guided receptor-functionalized nanowire motor for selective capture and transport of biological targets. Adapted with permission from , copyright 2013 American Chemical Society. (B) ACE2-algae-microrobot for the binding and removal of spike protein and SARS-CoV-2 virus. Adapted with permission from , copyright 2021 American Chemical Society. (C) Dual magnetic/light-powered hybrid microrobots for removal of yeast cells in beer. Adapted with permission from , copyright 2020 WILEY. (D) PL-motors for binding and isolation of platelet-specific toxins and pathogens. Adapted with permission from , copyright 2017 WILEY. (E) QDs/Fe₃O₄ light driven micromotors for detoxification. Adapted with permission from , copyright 2019 WILEY.