A Microstirring Oral Pill for Improving the Glucose-Lowering Effect of Metformin

Robotic micromotors transforming oral drug administration

Oral medication is preferred for its convenience; however, efficient drug delivery remains challenging due to issues such as poor solubility, and absorption caused by mucosal barriers, which result in low bioavailability. In this review, we discuss new strategies integrating robotic capabilities into oral formulations to enhance drug delivery. Such robotic pill systems leverage the efficient propulsion of biological and synthetic micromotors to accelerate pill disintegration and overcome mucosal barriers, increasing bioavailability with lower doses and fewer side effects. In addition, advanced bioinspired robotic capsules, including microneedles, microinjectors, and microjet systems, offer enhanced macromolecule bioavailability comparable with that achieved with subcutaneous injections. The future of precision medicine lies in encapsulating diverse micromotors (with unique capabilities) within pharmaceutical carriers, offering groundbreaking opportunities for enhanced therapeutic interventions.

Determination of insulin with ultra-performance liquid chromatography tandem mass spectrometry enhanced by Mg-based micromotors

An active drug delivery vector of Mg-based micromotor is proposed for enhanced intestinal drug mass spectrometry (MS) detection from proof of concept. Taking diabetes as a disease model, insulin nanoparticles (Ins-NPs) were successfully loaded in chitosan (CHI) layer of Mg-based micromotor (Mg/Au/PLGA/CHI@Ins-NPs) due to electrostatic adsorption with PLGA. The penetration ability of micromotors was evaluated on artificial mucin, which is distributed within about 300 μm of the mucus. In addition, in vitro drug delivery and retention was carried out on the isolated small intestine of mice; then, the insulin molecule was determined by ultra-performance liquid chromatography-mass spectrometry (UPLC-MS). By overcoming the mucus barrier and enhancing retention in intestine through active transport of micromotor, insulin ions at m/z 963.9443, 1156.3287, and 1445.1592 were detected by UPLC-MS and classified as [Insulin + 6H]6+, [Insulin + 5H]5+, and [Insulin + 4H]4+. Notably, the mass-to-charge ratio of insulin ions was detected only in micromotor drug delivery systems compared to drug-loaded inert particles in the isolated small intestine, attributed to the intensive penetration and retention capability of micromotors. Meanwhile, this Mg-based micromotor exhibited good biocompatibility and was easy to be removed for the UPLC-MS detection sample preparation. Overall, we provide a potential strategy to detect the low content of drugs with UPLC-MS technique by combining with active micromotor and further broadening the sensing application for untethered micromotor.

Towards multifunctional robotic pills

Robotic pills leverage the advantages of oral pharmaceutical formulations-in particular, convenient encapsulation, high loading capacity, ease of manufacturing and high patient compliance-as well as the multifunctionality, increasing miniaturization and sophistication of microrobotic systems. In this Perspective, we provide an overview of major innovations in the development of robotic pills-specifically, oral pills embedded with robotic capabilities based on microneedles, microinjectors, microstirrers or microrockets-summarize current progress and applicational gaps of the technology, and discuss its prospects. We argue that the integration of multiple microrobotic functions within oral delivery systems alongside accurate control of the release characteristics of their payload provides a basis for realizing sophisticated multifunctional robotic pills that operate as closed-loop systems.

Low efficiency of Janus microswimmers as hydrodynamic mixers

The generation of fluid flows by autophoretic microswimmers has been proposed as a mechanism to enhance mass transport and mixing at the micro- and nanoscale. Here, we experimentally investigate the ability of model 2D active baths of photocatalytic silica-titania Janus microspheres to enhance the diffusivity of tracer particles at different microswimmer densities below the onset of collective behavior. Inspired by the similarities between our experimental findings and previous results for biological microorganisms, we then model our Janus microswimmers using a general squirmer framework, specifically treating them as neutral squirmers. The numerical simulations faithfully capture our observations, offer an insight into the microscopic mechanism underpinning tracer transport, and allow us to expand the parameter space beyond our experimental system. We find strong evidence that near-field interactions dominate enhancements in tracer diffusivity in active Janus baths, leading to the identification of an operating window for enhanced tracer transport by chemical microswimmers based on scaling arguments. Based on this argumentation, we suggest that for many chemically active colloidal systems, hydrodynamics alone is likely to be insufficient to induce appreciable mixing of passive components with large diffusion coefficients.

Oral administration microrobots for drug delivery

Oral administration is the most simple, noninvasive, convenient treatment. With the increasing demands on the targeted drug delivery, the traditional oral treatment now is facing some challenges: 1) biologics how to implement the oral treatment and ensure the bioavailability is not lower than the subcutaneous injections; 2) How to achieve targeted therapy of some drugs in the gastrointestinal tract? Based on these two issues, drug delivery microrobots have shown great application prospect in oral drug delivery due to their characteristics of flexible locomotion or driven ability. Therefore, this paper summarizes various drug delivery microrobots developed in recent years and divides them into four categories according to different driving modes: magnetic-controlled drug delivery microrobots, anchored drug delivery microrobots, self-propelled drug delivery microrobots and biohybrid drug delivery microrobots. As oral drug delivery microrobots involve disciplines such as materials science, mechanical engineering, medicine, and control systems, this paper begins by introducing the gastrointestinal barriers that oral drug delivery must overcome. Subsequently, it provides an overview of typical materials involved in the design process of oral drug delivery microrobots. To enhance readers' understanding of the working principles and design process of oral drug delivery microrobots, we present a guideline for designing such microrobots. Furthermore, the current development status of various types of oral drug delivery microrobots is reviewed, summarizing their respective advantages and limitations. Finally, considering the significant concerns regarding safety and clinical translation, we discuss the challenges and prospections of clinical translation for various oral drug delivery microrobots presented in this paper, providing corresponding suggestions for addressing some existing challenges.

A temperature-responsive dual-hormone foam nanoengine improves rectal absorptivity of insulin-pramlintide for diabetes treatment

Despite the therapeutic benefits of insulin-pramlintide dual-hormone therapy in diabetes, its application potential has been limited due to a lack of efficient delivery routes. Here, we developed a temperature-responsive dual-hormone foam nanoengine (HormFoam) and combined it with a customized spraying device to further construct an in situ foam-generating system for improving the rectal bioavailability of dual-hormone therapy. To support rapid clinical translation, a continuous microfluidic preparation for HormFoam was proposed, including the power unit of perfluorocarbon nanodroplets and the pharmaceutical components Pluronic F127-functionalized liposomal insulin and pramlintide. We found that HormFoam could consistently generate foams to drive drugs forward after rectal administration, which enhanced intestinal distribution and mucosa absorption, leading to systemic codelivery of insulin-pramlintide. HormFoam reproduced the physiology of endocrine pancreas for glycemic control and induced body weight loss while reversing metabolic disorders in diabetic mice with good biosafety. Therefore, HormFoam represents a state-of-the-art dual-hormone regimen with the potential to address unmet needs in diabetes management.

Overview of growth differentiation factor 15 (GDF15) in metabolic diseases

GDF15 is a stress response cytokine and a distant member of the transforming growth factor beta (TGFβ) superfamily, its levels increase in response to cell stress and certain diseases in the serum. To exert its effects, GDF15 binds to glial-derived neurotrophic factor (GDNF) receptor alpha-like (GFRAL), which was firstly identified in 2017 and highly expressed in the brain stem. Many studies have demonstrated that elevated serum GDF15 is associated with anorexia and weight loss. Herein, we focus on the biology of GDF15, specifically how this circulating protein regulates appetite and metabolism in influencing energy homeostasis through its actions on hindbrain neurons to shed light on its impact on diseases such as obesity and anorexia/cachexia syndromes. It works as an endocrine factor and transmits metabolic signals leading to weight reduction effects by directly reducing appetite and indirectly affecting food intake through complex mechanisms, which could be a promising target for the treatment of energy-intake disorders.

Separable Microneedle for Integrated Hyperglycemia Sensing and Photothermal Responsive Metformin Release

Microdevices that offer hyperglycemia monitoring and controllable drug delivery are urgently needed for daily diabetes management. Herein, a theranostic separable double-layer microneedle (DLMN) patch consisting of a swellable GelMA supporting base layer for glycemia sensing and a phase-change material (PCM) arrowhead layer for hyperglycemia regulation has been fabricated. The Cu-TCPP(Fe)/glucose oxidase composite and 3,3',5,5'-tetramethylbenzidine coembedded in the supporting base layer permit a visible color shift at the base surface in the presence of glucose via a cascade reaction, allowing for the in situ detection of glucose in interstitial fluid. The PCM arrowhead layer is encapsulated with water monodispersity melanin nanoparticles from Sepia officinalis and metformin that is imparted with a near-infrared ray photothermal response feature, which is beneficial to the controllable release of metformin for suppression of hyperglycemia. By applying the DLMN patch to the streptozotocin-induced type 2 diabetic Sprague-Dawley rat model, the results demonstrated that it can effectively extract dermal interstitial fluid, read out glucose levels, and regulate hyperglycemia. This DLMN-integrated portable colorimetric sensor and self-regulated glucose level hold great promise for daily diabetes management.

Recent advancements in Mg-based micromotors for biomedical and environmental applications

Synthetic micro/nanomotors have attracted considerable attention due to their promising potential in the field of biomedicine. Despite their great potential, major micromotors require chemical fuels or complex devices to generate external physical fields for propulsion. Therefore, for future practical medical and environmental applications, Mg-based micromotors that exhibit water-powered movement and thus eliminate the need for toxic fuels, and that display optimal biocompatibility and biodegradability, are attracting attention. In this review, we summarized the recent microarchitectural design of Mg-based micromotors for biomedical applications. We also highlight the mechanism for realizing their water-powered motility. Furthermore, recent biomedical and environmental applications of Mg-based micromotors are introduced. We envision that advanced Mg-based micromotors will have a profound impact in biomedicine.

Biocompatible smart micro/nanorobots for active gastrointestinal tract drug delivery

INTRODUCTION

Oral delivery is the most commonly used route of drug administration owing to good patient compliance. However, the gastrointestinal (GI) tract contains multiple physiological barriers that limit the absorption efficiency of conventional passive delivery systems resulting in a low drug concentration reaching the diseased sites. Micro/nanorobots can convert energy to self-propulsive force, providing a novel platform to actively overcome GI tract barriers for noninvasive drug delivery and treatment.

AREAS COVERED

In this review, we first describe the microenvironments and barriers in the different compartments of the GI tract. Afterward, the applications of micro/nanorobots to overcome GI tract barriers for active drug delivery are highlighted and discussed. Finally, we summarize and discuss the challenges and future prospects of micro/nanorobots for further clinical applications.

EXPERT OPINION

Micro/nanorobots with the ability to autonomously propel themselves and to load, transport, and release payloads on demand are ideal carriers for active oral drug delivery. Although there are many challenges to be addressed, micro/nanorobots have great potential to introduce a new era of drug delivery for precision therapy.