Microrobots for Targeted Delivery and Therapy in Digestive System

Abstract

Untethered miniature robots enable targeted delivery and therapy deep inside the gastrointestinal tract in a minimally invasive manner. By combining actuation systems and imaging tools, significant progress has been made toward the development of functional microrobots. These robots can be actuated by external fields and fuels while featuring real-time tracking feedback toward certain regions and can perform the therapeutic process by rational exertion of the local environment of the gastrointestinal tract (e.g., pH, enzyme). Compared with conventional surgical tools, such as endoscopic devices and catheters, miniature robots feature minimally invasive diagnosis and treatment, multifunctionality, high safety and adaptivity, embodied intelligence, and easy access to tortuous and narrow lumens. In addition, the active motion of microrobots enhances local penetration and retention of drugs in tissues compared to common passive oral drug delivery. Based on the dissimilar microenvironments in the various sections of the gastrointestinal tract, this review introduces the advances of miniature robots for minimally invasive targeted delivery and therapy of diseases along the gastrointestinal tract. The imaging modalities for the tracking and their application scenarios are also discussed. We finally evaluate the challenges and barriers that retard their applications and hint on future research directions in this field.

Tracking and navigation of a microswarm under laser speckle contrast imaging for targeted delivery

“…Precise tracking and navigation improve the delivery efficiency of micro/nanorobots and thus are essential for imagingguided safe and efficacious biomedical applications (45)(46)(47)(48). Although challenging, these goals may be achieved by accurate real-time imaging guidance under biological environments, especially in the endovascular system.…”

Response and Regulation of the Microenvironment Based on Hollow Structured Drug Delivery Systems

“…The pH varies rapidly from acid in the stomach (pH 1–4) to neutral in the small intestine (pH 6.5–7), which could serve as a trigger for the drug delivery in the gastrointestinal tract. [ 81 ] Numerous drug carriers cannot withstand the harshly acidic environment in the stomach and remain structurally intact when they reach the gut, which limits the absorption of drugs. In addition, near‐neutral pH in the small intestine also comes with drawbacks.…”

Stimuli-Responsive Functional Micro-/Nanorobots: A Review

“…Micro-/nanorobots, which are mobile robotic devices with microscale or nanoscale sizes, have currently drawn the attention of scientists. − They have tremendous benefits, including tiny size, wireless controllability, minimal invasiveness to the body, ability to target difficult-to-reach regions, good mobility in environments with low Reynolds numbers, and ease of transferring external energy to locomotion. Thus, they have been widely utilized in activities including drug delivery, − disease diagnosis, tissue regeneration, sensors, and environmental remediation. − …”