Gear-like MOF microrobots for single cell mechanotransduction of microvilli

Figures

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  Fig. 1. Fabrication and characterization of the gear-like MOFbots. a Schematic illustration of the preparation process for the gear-like MOFbots. SEM images of (b) MIL-125, (c) MIL-125@ZIF-8 particles. d FT-IR spectra of the as-prepared MIL-125, ZIF-8 and MIL-125@ZIF-8 microparticles. e N2 absorption/desorption isotherms of the as-prepared MIL-125, ZIF-8, and MIL-125@ZIF-8 microparticles. P: the abbreviation of pressure. f, g Powder XRD patterns and the enlarged XRD patterns of the as-prepared MIL-125, ZIF-8 and MIL-125@ZIF-8 microparticles. h, i SEM image and EDX mapping of gear-like MOFbots. In (b, c, h), the experiments were repeated independently three times with similar results, and a representative result is shown for each.

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  Fig. 2. Magnetically controlled motion behaviors of the gear-like MOFbot. a Schematic illustration of microrobot motion manipulation by the horizontally and vertically rotating magnetic fields. b Rotating and rolling motion of gear-like MOFbot at different time intervals. The frequency of horizontally and vertically rotating magnetic fields are 7 and 6 Hz, respectively. c, d Average rotational rate and translational velocity of the gear-like MOFbot under the actuation of magnetic field (6 mT) at different frequencies (N = 10 independent samples). e Simulation of the flow field and fluid pressure distribution induced by the rotation of gear-like MOFbot with different frequencies. f Quantitative analysis of the maximum fluid pressure induced by the rotation of gear-like MOFbot with different frequencies. g–i Optical images and surface topography of the patterned substrate using a 3D surface profiler. j Superimposed image of the sequential frames of a gear-like MOFbot overcoming obstacles on the patterned substrate. k The instantaneous velocity of gear-like MOFbot when moving across the patterned substrate. l Time-lapse images of a moving PS@Ni@Au spherical microrobot on the patterned…

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  Fig. 3. Interaction between cell microvilli and gear-like MOFbots. Representative CLSM views and SEM images illustrating the distribution of MOFbots on HeLa cells. a Gear-like MOFbots under external magnetic field actuation. b Gear-like MOFbots in the absence of magnetic field. c Spherical microrobots under external magnetic field actuation. MF: the abbreviation of magnetic field. In pseudo-colored SEM images, microrobots and microvilli were marked with yellow and red colors, respectively. d The U-Net + + network model used for semantic segmentation of cellular images, enabling precise extraction of target cell regions and voxel-level identification, effectively distinguishing cells from background. Each experiment was repeated independently for 3 times with similar results. Segmentation results from 3D reconstructions illustrating the distribution of each voxel type (red and green) in stained cells treated under different conditions: (e) gear-like MOFbots with a magnetic field, (f) gear-like MOFbots without a magnetic field, and (g) Spherical microrobots with a magnetic field.

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  Fig. 4. Analysis of mechanical forces generated by the gear-like MOFbots on cell through microvilli. a Schematic illustration of the traction force microscopy method. In this approach, cells are cultured on a PA gel substrate. Fluorescent beads are embedded on the surface of the PA gel to precisely track and quantify lateral deformations caused by cellular forces. b Representative displacement and traction stress maps of MOFbot-induced substrate deformation in normal and microvilli-deficient HeLa cells (without/with the actuation of magnetic field), derived from PA-induced lateral deformation. c, d Quantitative analysis of displacement and traction stress (N = 22 cells). Statistical differences were calculated using two-tailed Student’s t test, **P < 0.01, ****P < 0.0001. e Schematic illustration of the FRET-based actin force probe. f, g Representative time-lapse images displaying the change of FRET signals in normal and microvilli-deficient HeLa cells under the influence of MOFbots. h Quantitative analysis of the FRET signal intensity changes in different HeLa cells over time, shaded areas represent SD for N = 22 cells. i Average FRET signal in normal and microvilli-deficient HeLa cells…

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  Fig. 5. The levels of Ca²⁺ influx and phosphorylated FAK (pFAK) in HeLa cells induced by the mechanical forces exerted by the gear-like MOFbots. a Schematic illustration showing that the active motion of the gear-like MOFbots induces the Ca²⁺ influx and phosphorylation of FAK. b, c Fluorescence images and normalized fluorescence intensity of intracellular Ca2+ in response to gear-like MOFbot treatment under three conditions: untreated control cells, cells pre-incubated with 1 μM GsMTx4 (Piezo1 inhibitor), and cells pre-incubated with HC-067047 (TRPV4 antagonist, 1 μM). In Fig. 5b, the experiments were repeated independently three times with similar results, and a representative result is shown for each. F the abbreviation of fluorescence. d–f Color-scaled heat map depicting the Ca2+ response in HeLa cells under three conditions: untreated control, cells incubated with Piezo1 inhibitor GsMTx4, and cells incubated with TRPV4 antagonist HC-067047, upon treatment with gear-like MOFbots (N = 50 cells). g, h Representative fluorescence images and average intensities of pFAK in HeLa cells exposed to the gear-like MOFbots, analyzed under conditions with and without the application of a magnetic…

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  Fig. 6. Mechanical stimulation induced change of membrane permeability and enhanced intracellular drug delivery by the gear-like MOFbots. a Schematic illustration depicting the active targeting of a cell and active motion enabled regulation of membrane permeabilization for transmembrane delivery. b Simulation result of the interaction between the gear-like MOFbot and cellular microvilli. c, d Superimposed images of sequential frames and instantaneous velocity illustrating the targeting, approaching, and interaction processes between the HeLa cell and the gear-like MOFbot. e, f Time-lapse fluorescence images and corresponding intensity analysis depicting the dynamic intracellular distribution of PI following treatment with gear-like MOFbots. PI: the abbreviation of propidium iodide. g The average fluorescence intensities of DOX in HeLa cells exposed to the gear-like MOFbots under conditions with and without the application of a magnetic field (N = 25 cells). MF: the abbreviation of magnetic field. Statistical differences were calculated using two-tailed Student’s t test, ****P < 0.0001. h Viability of HeLa cells treated with the different concentrations of DOX-loaded gear-like MOFbots (N…