RESUMEN

Pancreatic ß cells secrete insulin in response to elevated levels of glucose. Stem cell derived ß (SCß) cells aim to replicate this glucose-stimulated insulin secretion (GSIS) function, but current preparations cannot provide the same level of insulin as natural ß cells. Here, we develop an assay to measure GSIS at the single cell level to investigate the functional heterogeneity of SCß cells and donor-derived islet cells. Our assay involves randomly depositing single cells and insulin capture microbeads in open-top nanowells (40 × 40 × 55 µm3) fabricated on glass-bottom imaging microwell plates. Insulin secreted from single cells is captured on microbeads and then stained using a detection antibody. The nanowell microstructure limits diffusion of secreted insulin. The glass substrate provides an optically flat surface for quantitative microscopy to measure the concentration of secreted insulin. We used this approach to measure GSIS from SCß cells and donor-derived islet cells after 15 minutes exposure to 3.3 mM and 16.7 mM glucose. Both cell types exhibited significant GSIS heterogeneity, where elite cells (<20%) produced the majority of the secreted insulin (55-78%). This assay provides an immediate readout of single cell glucose-stimulated insulin secretion in a flexible well plate-based format.

Asunto(s)

Glucosa , Secreción de Insulina , Células Secretoras de Insulina , Insulina , Análisis de la Célula Individual , Glucosa/metabolismo , Secreción de Insulina/efectos de los fármacos , Insulina/metabolismo , Células Secretoras de Insulina/metabolismo , Células Secretoras de Insulina/citología , Células Secretoras de Insulina/efectos de los fármacos , Animales , Análisis de la Célula Individual/instrumentación , Ratones , Humanos

RESUMEN

This paper proposes an acoustic bubble and magnetic actuation-based microrobot for enhancing multiphase drug delivery efficiency. The proposed device can encapsulate multiphase drugs, including liquids, using the two bubbles embedded within the microtube. Additionally, using the magnetic actuation of the loaded magnetic liquid metal, it can deliver drugs to target cells. This study visualized the flow patterns generated by the oscillating bubble within the tube to validate the drug release principle. In addition, to investigate the effect of the oscillation properties of the inner bubble on drug release, the oscillation amplitude of the inner bubble was measured under various experimental variables using a high-speed camera. Subsequently, we designed a microrobot capable of encapsulating bubbles, drugs, and magnetic liquid metal and fabricated it using microfabrication technology based on ultra-precision 3D printing. As a proof of concept, we demonstrated the transport and drug release of the microrobot encapsulating the drug in a Y-shaped channel simulating a blood vessel. The proposed device is anticipated to enhance the efficiency of drug therapy by minimizing drug side effects, reducing drug administration frequency, and improving the stability of the drug within the body. This paper is expected to be applicable not only to targeted drug delivery but also to various biomedical fields, such as minimally invasive surgery and cell manipulation, by effectively delivering multiphase drugs using the simple structure of a microrobot.

RESUMEN

This paper presents a new type of switchable liquid shutter for the security and design of mobile electronic devices. The operation test of the liquid shutter is conducted using a prototype sample prepared by standard microfabrication processes. The liquid shutter consists of an opaque liquid for absorbing light and a transparent oil for transmitting light on two parallel plates with patterned indium titanium oxide electrodes. The liquid shutter can be opened and closed by sequentially applying an electrical voltage to the patterned electrodes owing to an electrowetting principle. The switching time of the liquid shutter is measured using a high-speed camera and is found to take about 550 ms to open the shutter and 240 ms to close the shutter at 70 Vrms (1 kHz). To validate the applicability of the liquid shutter, the operation of liquid shutters with different colored liquids mounted on a smartphone is successfully demonstrated. The proposed liquid shutter not only allows a simple design to be easily miniaturized and integrated with electronic devices but also provides a robust and fast switching operation.

RESUMEN

Despite the considerable research interest due to practical importance of pervasive wireless sensing systems in a wide range of engineering fields, power management remains an arduous task for further development of pervasive wireless sensing systems due to inherent needs for self-reliant functionality and portability during their operations. To this end, we here propose a new type of energy harvesting strategy in which an optothermally pulsating microbubble is submerged in an underwater medium. The pulsating microbubble gives rise to the periodic vibration of piezocantilevers in contact, which resultantly can produce electrical outputs. On the basis of this simple idea, mechanical power can be extracted from light energy through optothermally pulsating microbubbles in an aqueous medium and subsequently the mechanical power can be converted to electrical power for wireless devices. To elucidate physical factors affecting the performance of the proposed strategy, we thoroughly explore the effect of the intensity and frequency of the laser beam on the pulsation amplitude of optothermally pulsating bubbles and subsequent electrical outputs (e.g., electrical voltage and power). The dependence of electrical output on wetting property of piezocantilevers and electrical resistance is also established. The present work would provide a new framework for fundamental design of bubble-based microactuators as energy harvesters and microsensors in the near future.