Dual Ultrasound and Photoacoustic Tracking of Magnetically Driven Micromotors: From In Vitro to In Vivo

• Published in: Advanced healthcare materials 2021-11, Vol.10 (22), p.e2101077-n/a
• Main Authors: Aziz, Azaam, Holthof, Joost, Meyer, Sandra, Schmidt, Oliver G., Medina‐Sánchez, Mariana
• Format: Article
• Language: English
• Subjects: Animals; Chromophores; Diagnostic Imaging; dual in vivo imaging; Imaging techniques; Medical imaging; medical tracking; Mice; Micromotors; Multispectral analysis; Optics; Penetration depth; Photoacoustic Techniques; photoacoustics; Ultrasonic imaging; Ultrasonography; Ultrasound; Uterus
• ISSN: 2192-2640; 2192-2659; 2192-2659
• DOI: 10.1002/adhm.202101077

The fast evolution of medical micro‐ and nanorobots in the endeavor to perform non‐invasive medical operations in living organisms has boosted the use of diverse medical imaging techniques in the last years. Among those techniques, photoacoustic imaging (PAI), considered a functional technique, has shown to be promising for the visualization of micromotors in deep tissue with high spatiotemporal resolution as it possesses the molecular specificity of optical methods and the penetration depth of ultrasound. However, the precise maneuvering and function's control of medical micromotors, in particular in living organisms, require both anatomical and functional imaging feedback. Therefore, herein, the use of high‐frequency ultrasound and PAI is reported to obtain anatomical and molecular information, respectively, of magnetically‐driven micromotors in vitro and under ex vivo tissues. Furthermore, the steerability of the micromotors is demonstrated by the action of an external magnetic field into the uterus and bladder of living mice in real‐time, being able to discriminate the micromotors’ signal from one of the endogenous chromophores by multispectral analysis. Finally, the successful loading and release of a model cargo by the micromotors toward non‐invasive in vivo medical interventions is demonstrated. Dual ultrasound and photoacoustic imaging enables the tracking of micromotors ex vivo and in vivo with precise localization and high spatiotemporal resolution, being a key step toward noninvasive in vivo medical operations.