Micromotor-enabled active drug delivery for in vivo treatment of stomach infection

Abstract

Advances in bioinspired design principles and nanomaterials have led to tremendous progress in autonomously moving synthetic nano/micromotors with diverse functionalities in different environments. However, a significant gap remains in moving nano/micromotors from test tubes to living organisms for treating diseases with high efficacy. Here we present the first, to our knowledge, in vivo therapeutic micromotors application for active drug delivery to treat gastric bacterial infection in a mouse model using clarithromycin as a model antibiotic and Helicobacter pylori infection as a model disease. The propulsion of drug-loaded magnesium micromotors in gastric media enables effective antibiotic delivery, leading to significant bacteria burden reduction in the mouse stomach compared with passive drug carriers, with no apparent toxicity. Moreover, while the drug-loaded micromotors reach similar therapeutic efficacy as the positive control of free drug plus proton pump inhibitor, the micromotors can function without proton pump inhibitors because of their built-in proton depletion function associated with their locomotion.Nano- and micromotors have been demonstrated in vitro for a range of applications. Here the authors demonstrate the in-vivo therapeutic use of micromotors to treat H. pylori infection.

Fig. 1

Synthesis and characterization of drug-loaded Mg-based micromotors. a Schematic preparation of the micromotors: Mg microparticles dispersion over a glass slide, TiO₂ atomic layer deposition (ALD) over the Mg microparticles, drug-loaded PLGA deposition over the Mg-TiO₂ microparticles, and Chitosan polymer deposition over the Mg-TiO₂-PLGA microparticles. b Schematic of in vivo propulsion and drug delivery of the Mg-based micromotors in a mouse stomach. c Time-lapse images (2 min intervals, taken from Supplementary Movie 3) of the propulsion of the drug-loaded Mg-based micromotors in simulated gastric fluid (pH ~1.3). d Schematic dissection of a drug-loaded micromotor consisting of a Mg core, a TiO₂ shell coating, a drug-loaded PLGA layer, and a chitosan layer. e Scanning electron microscopy (SEM) image of a drug-loaded Mg-based micromotor. f, g Energy-dispersive X-ray spectroscopy (EDX) images illustrating the distribution of f magnesium and g titanium in the micromotor. h–k Microscopy images of dye-loaded Mg-based micromotor: h optical image and fluorescence images showing the dye-loaded Mg-based micromotors in the i DiD channel (PLGA layer), j FITC channel (chitosan layer), along with an overlay of the two channels k

Fig. 2

Antibiotic drug loading of the Mg-based micromotors and in vitro bactericidal activity. a Schematic displaying the loading clarithromycin (CLR) onto the Mg-based micromotors. PLGA polymer dissolved in ethyl acetate is mixed with CLR, and the solution is deposited over the Mg-TiO₂ microparticles resulting in the formation of a thin PLGA-CLR coating. b Microscope images showing the PLGA-CLR film over the Mg-based micromotors. Scale bars 100 µm and 40 µm, respectively. c Quantification of CLR-loading amount and yield of the micromotors prepared with different CLR solutions: (I) 100 µL of 40 mg mL⁻¹ CLR solution, (II) 120 µL of 40 mg mL⁻¹ CLR solution, and (III) 200 µL of 30 mg mL⁻¹ CLR solution. All the CLR-loaded Mg-based micromotors were coated with a thin chitosan layer; all samples were dissolved in acid for 24 h before the drug-loading measurement. d In vitro bactericidal activity of free CLR, CLR-loaded Mg-based micromotors, and blank Mg-based micromotors (without CLR drug) against H. pylori bacteria. Error bars estimated as a triple of s.d. (n = 3)

Fig. 3

Retention of the Mg-based micromotors in mouse stomachs. a Bright-field and fluorescence images of the luminal lining of freshly excised mouse stomachs at 0 min after oral gavage of deionized (DI) water (control), and at 30 min and 2 h after oral gavage of the Mg-based micromotors. Scale bar 500 mm. b Corresponding fluorescence quantification of all the images shown in a. Error bars estimated as a triple of s.d. (n = 3)

Fig. 4

In vivo anti-H. pylori therapeutic efficacy. a The study protocol including H. pylori inoculation and infection development in C57BL/6 mice, followed by the treatments. b Quantification of bacterial burden in the stomach of H. pylori-infected mice treated with DI water (black color), bare Mg-based micromotors (orange color), free CLR+PPI (green color), CLR-loaded silica microparticles (blue color), and CLR-loaded Mg-based micromotors (red color), respectively (n = 6 per group). Bars represent median values. *P < 0.05, **P < 0.01, ns no statistical significance

Fig. 5

In vivo toxicity evaluation of the Mg-based micromotors. Uninfected mice were orally administered with the Mg-based micromotors or DI water once daily for five consecutive days. a Mouse body weight log from day 0 to day 6 of the toxicity study. Error bars represent the s.d. of the mean (n = 6). On day 6, mice were killed and sections of the mouse stomach b, small c–e and large f, g intestine tissues were processed for histological staining with hematoxylin and eosin (H&E). Scale bars Mg-motor, 250 and 100 μm (left and right column, respectively); DI water, 250 and 100 μm (left and right column, respectively)