Protective coatings for intraocular wirelessly controlled microrobots for implantation: Corrosion, cell culture, and in vivo animal tests

Abstract

Diseases in the ocular posterior segment are a leading cause of blindness. The surgical skills required to treat them are at the limits of human manipulation ability, and involve the risk of permanent retinal damage. Instrument tethering and design limit accessibility within the eye. Wireless microrobots suturelessly injected into the posterior segment, steered using magnetic manipulation are proposed for procedures involving implantation. Biocompatibility is a prerequisite for these procedures. This article investigates the use of polypyrrole- and gold-coated cobalt-nickel microrobots. While gold has been used in ocular implants, no ocular implantation involving polypyrrole is reported, despite its well-established biocompatibility properties. Coated and uncoated microrobots were investigated for their corrosion properties, and solutions that had contained coated and uncoated microrobots for one week were tested for cytotoxicity by monitoring NIH3T3 cell viability. None of the microrobots showed significant corrosion currents and corrosion potentials were as expected in relation to the intrinsic nobility of the materials. NIH3T3 cell viability was not affected by the release medium, in which coated/uncoated microrobots were stored. In vivo tests inside rabbit eyes were performed using coated microrobots. There were no significant inflammatory responses during the first week after injection. An inflammatory response detected after 2 weeks was likely due to a lack of longer-duration biocompatibility. The results provide valuable information for those who work on implant technology and biocompatibility. Coated microrobots have the potential to facilitate a new generation of surgical treatments, diagnostics and drug-delivery techniques, when implantation in the ocular posterior segment will be possible. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 836-845, 2017.

Frontiers of Medical Micro/Nanorobotics: in vivo Applications and Commercialization Perspectives Toward Clinical Uses

“…Additionally, an initial proof of concept based on magnetic microrobots has demonstrated controlled navigation inside the eye of a living rabbit. Although this method has not been demonstrated directly for a surgical procedure, a magnetic coil system enabled the precise navigation of the untethered magnetic microrobots in the posterior eye section (Ullrich et al, 2013 ; Pokki et al, 2016 ). Ultimately, biopsy applications are fertile ground for further micro/nanorobotics research as the success of these applications depends on the ability of the robot to physically manipulate its environment and on the ability of the robot's controller to retrieve the robot.…”

“…Physical robots are supported with the most diverse type of imaging techniques, but only 60% of articles are supported with real-time imaging. Represented techniques include the use of endoscopy and X-rays to detect microgrippers inside the gastrointestinal tract (Gultepe et al, 2012 ), use of optical camera to visualize movement inside the eye (Ullrich et al, 2013 ; Pokki et al, 2016 ), and fluorescence imaging techniques to track the position of magnetically actuated helical microrobots inside the peritoneal cavity of a mouse (Servant et al, 2015 ) or subcutaneously (Li et al, 2018 ). Moreover, a dual imaging approach was used to detect biodegradable magnetic microhelix nanorobots in mice.…”

Trends in Micro‐/Nanorobotics: Materials Development, Actuation, Localization, and System Integration for Biomedical Applications

“…Nelson et al. [ 342–344 ] proposed an invasive, wirelessly steered and powered microrobot for application in ocular medicine. These microrobots are made of magnetic materials such as CoNi with a coating of Au and PPy ( Figure c).…”

“…c–g) Reproduced with permission. [ 342 ] Copyright 2017, Wiley‐VCH. h) Schematic of the targeted delivery process of slippery micropropellers with magnetic field.…”

CANDYBOTS: A New Generation of 3D‐Printed Sugar‐Based Transient Small‐Scale Robots

“…For example, most of reported small-scale robots have been manufactured with materials that are difficult to degrade, resulting in their undesired accumulation in tissues. [2][3][4][5][6][7][8] Accordingly, there is a current upsurge of interest in addressing aspects such as biodegradability and bioresorbability of small-scale robots. [9][10][11] Recently, Wang and co-workers presented transient self-destroyed catalytic magnesium-and zinc-based Janus micromotors for applications in the gastrointestinal track.…”