A Laser‐Driven Microrobot for Thermal Stimulation of Single Cells

Abstract

Here, the study presents a thermally activated cell‐signal imaging (TACSI) microrobot, capable of photothermal actuation, sensing, and light‐driven locomotion. The plasmonic soft microrobot is specifically designed for thermal stimulation of mammalian cells to investigate cell behavior under heat active conditions. Due to the integrated thermosensitive fluorescence probe, Rhodamine B, the system allows dynamic measurement of induced temperature changes. TACSI microrobots show excellent biocompatibility over 72 h in vitro, and they are capable of thermally activating single cells to cell clusters. Locomotion in a 3D workspace is achieved by relying on thermophoretic convection, and the microrobot speed is controlled within a range of 5–65 µm s−1. In addition, light‐driven actuation enables spatiotemporal control of the microrobot temperature up to a maximum of 60 °C. Using TACSI microrobots, this study targets single cells within a large population, and demonstrates thermal cell stimulation using calcium signaling as a biological output. Initial studies with human embryonic kidney 293 cells indicate a dose dependent change in intracellular calcium content within the photothermally controlled temperature range of 37–57 °C.

Multi-Stimuli-Responsive Tadpole-like Polymer/Lipid Janus Microrobots for Advanced Smart Material Applications

“…When a NIR light irradiates the microrobot, the JMs on its surface absorb the light energy and convert it into heat via the NIR light-absorbing agent, and the temperature gradient causes the microrobot to move. This is defined as “Thermophoresis, also known as thermodiffusion or the Ludwig-Soret effect”, which occurs in solutions that cause the microrobot to move through the temperature gradient . Considering that laser irradiation can trigger the photothermal effect of the light-responsive micromotors, leading to the propulsion of the whole structure, , different amounts of PPYNP (50.86 ± 23 nm, Figure S10), which has a photothermal effect, were added to the JP1 and JP2 (see Table S1) to obtain JPPs (PPYNP-loaded JPs).…”

A multiscale approach to assess thermomechanical performance and force generation in nanorobotic microgels

“…35,36 A thermosensitive fluorescent dye, Rhodamine B, was integrated into alginate chains to allow real-time monitoring of light-induced temperature changes. 10…”

“…1–6 Owing to their mobility, small-scale machines have enabled targeting single cells in biological 3D environments, without interfering with cell culture conditions. 7–10 Moreover, force-generating microrobots have demonstrated their potential as effective tools for biomechanical characterization in vitro and tissue regeneration in vivo , further highlighting their versatility. 11–16…”

“…25,26 Specialized imaging methods, such as fluorescence-based thermometry, have allowed photothermal characterization in microsystems, providing indirect control over temperature at the microscale with the precision of direct measurement techniques. 10,31–33 With these approaches, the overall temperature of the optical actuator has been measured, while the photothermal performance of the individual plasmonic building blocks has often been only analyzed with finite element modeling. 1,7,34 Correlating the photothermal performance of the individual plasmonic building blocks and the assembled microactuator with the generated strain and the force could achieve superior mechanical control in active cell culture systems.…”

“…The temperature sensitive fluorescent dye, Rhodamine B, is used as a microthermometer, providing immediate temperature feedback during microgel actuation. 10 We characterize the thermomechanical behavior of both the nanoactuators and the assembled nanorobotic 3D microgels using dynamic light scattering (DLS) and fluorescence-based thermometry via an optical microscope (Fig. 1).…”