Radiopaque Nanorobots as Magnetically Navigable Contrast Agents for Localized In Vivo Imaging of the Gastrointestinal Tract

Abstract

Magnetic nanorobots offer wireless navigation capability in hard-to-reach areas of the human body for targeted therapy and diagnosis. Though in vivo imaging is required for guidance of the magnetic nanorobots toward the target areas, most of the imaging techniques are inadequate to reveal the potential locomotion routes. This work proposes the use of radiopaque magnetic nanorobots along with microcomputed tomography (microCT) for localized in vivo imaging applications. The nanorobots consist of a contrast agent, barium sulfate (BaSO 4 ), magnetized by the decoration of magnetite (Fe 3 O 4 ) particles. The magnetic features lead to actuation under rotating magnetic fields and enable precise navigation in a microfluidic channel used to simulate confined spaces of the body. In this channel, the intrinsic radiopacity of the nanorobots also provides the possibility to reveal the internal structures by X-ray contrast. Furthermore, in vitro analysis indicates nontoxicity of the nanorobots. In vivo experiments demonstrate localization of the nanorobots in a specific part of the gastrointestinal (GI) tract upon the influence of the magnetic field, indicating the efficient control even in the presence of natural peristaltic movements. The nanorobots reported here highlight that smart nanorobotic contrast agents can improve the current imaging-based diagnosis techniques by providing untethered controllability in vivo.

In vivoapplications of micro/nanorobots

“…154 However, most of the micro/nanorobots do not hold this functionality, and this situation can lead to the need of specific contrast agents, e.g., iodine-and barium-based compounds, and/or swarming behavior to more easily discriminate them from the surrounding environment. [155][156][157] Additionally, combining different imaging modalities can be an attractive approach to overcome limitations of the currently used modalities, e.g., CT, MRI, US, PET, and SPECT. 135,158 Considering that most of the externally driven micro/nanorobots would be "blind" in the body without convenient imaging modalities, an effective approach for in vivo tracking should be an integral part of the micro/nanorobot design to enable the successful completion of their intended use.…”

“…, iodine- and barium-based compounds, and/or swarming behavior to more easily discriminate them from the surrounding environment. 155–157 Additionally, combining different imaging modalities can be an attractive approach to overcome limitations of the currently used modalities, e.g. , CT, MRI, US, PET, and SPECT.…”

A novel magnetically guided, oxygen propelled CoPt/Au nanosheet motor in conjugation with a multilayer hollow microcapsule for effective drug delivery and light triggered drug release

“…1 In recent years, synthetic nanomotors capable of converting chemical or external energy into mechanical motion were shown to have considerable potential for different functions, including water purification, [2][3][4] biosensing, [5][6][7] drug delivery, [8][9][10] nano-surgery 11 and imaging. 12,13 Among these, the significant advancements in targeted drug delivery have been very promising. In fact, nanomotors as self-propelled platforms are essential for the design of drug delivery systems.…”

A drug co-delivery platform made of magnesium-based micromotors enhances combination therapy for hepatoma carcinoma cells

“…Among them, chemical-propelled micro/nanomotors offer greater driving forces and avoid the installation of complex external fields. [25][26][27][28] Recently, magnesium (Mg)-based micromotors have been synthesized to deliver drugs in vivo as they can react with biofluids to produce hydrogen for propulsion. [29][30][31] Being a necessary trace element for human body, Mg is biocompatible, and its degradation product in the physiological environment is harmless to tissues and cells.…”