High‐Resolution SPECT Imaging of Stimuli‐Responsive Soft Microrobots

Abstract

Untethered small‐scale robots have great potential for biomedical applications. However, critical barriers to effective translation of these miniaturized machines into clinical practice exist. High resolution tracking and imaging in vivo is one of the barriers that limit the use of micro‐ and nanorobots in clinical applications. Here, the inclusion of radioactive compounds in soft thermoresponsive magnetic microrobots is investigated to enable their single‐photon emission computed tomography imaging. Four microrobotic platforms differing in hydrogel structure and four 99mTc[Tc]‐based radioactive compounds are investigated in order to achieve optimal contrast agent retention and optimal imaging. Single microrobot imaging of structures as low as 100 µm in diameter, as well as tracking of shape switching from tubular to planar configurations by inclusion of 99mTc[Tc] colloid in the hydrogel structure, is reported.

Development of Magnet‐Driven and Image‐Guided Degradable Microrobots for the Precise Delivery of Engineered Stem Cells for Cancer Therapy

“…[ 28,29 ] The use of radiative imaging technology, such as X‐ray computed tomography, for tracking macrosized structures has been investigated, but its long‐term ionizing irradiation is carcinogenic. [ 30,31 ] Ultrasound (US) imaging suffers from strong interference signal from backgrounds. [ 32 ] Photoacoustic (PA) imaging detects optical absorption contrasts with high resolution [ 33 ] and was recently used to detect the microrobots movement in mouse intestines.…”

Engineering microrobots for targeted cancer therapies from a medical perspective

“…As a next important step, it will be exciting to extend these efforts to whole organisms by integrating for example electromagnetic actuation to small animal bioimaging systems (e.g., fluoroscopy, ultrasound, infra-red coherence tomography and optoacoustic tomography) to assess feasibility for human trials. Notably, the magnetic actuators can be easily scaled-up but then the imaging and feedback control of the untethered microswimmers become more challenging owing to the current spatiotemporal resolution of~150 µm in real time when using cutting-edge ultrasound and optoacoustic imaging systems 28,[172][173][174][175][176] . In this regard, the increased size of individual microrobots over nanomedicines or using microrobot swarms could provide distinct advantages 119,[177][178][179] .…”

Engineering Intelligent Nanosystems for Enhanced Medical Imaging

“…Alternatively, SPECT was used by Iacovacci et al for the tracking of thermoresponsive soft microrobots in vitro and using ex vivo rodent models, through the inclusion of radioactive labeling. [ 152 ] The authors reported not only the visualization of the micromotor but also their configuration, where folding and unfolding in response of a temperature change could be observed (Figure 6B). The use of MRI for the control and guidance of micromotors in vivo also holds a great potential for imaging guided therapy.…”