Manipulating the Barrier Function of a Cell Monolayer Using a High-power Miniature Ultrasonic Transducer

Ultrasound (US) and cavitation agents such as microbubbles (MBs) have been demonstrated to decrease the barrier function of endothelial and epithelial layers. However, in vitro experiments that study this effect are often hindered by the inability to deliver buoyant contrast agents in proximity to cell monolayers in order to adequately control the decrease in barrier function whilst insonating a sufficiently large tissue area. We have addressed this by adapting a cell culture system and fabricating a bespoke high-power miniature unfocused US transducer. The setup was used to control the drop in barrier function and to determine how varying the mechanical index (MI) and the duty cycle affected the barrier function. It was found that buffer solution alone and buffer + MBs did not decrease the transepithelial electrical resistance (TEER) of the cell monolayer. Buffer + US decreased the TEER by ~40%, with 10% TEER recovery 9 min after switching US off. Buffer + MBs + US decreased the TEER by 80%, with little or no recovery following treatment. In the presence of MBs, the barrier function was decreased by a duty cycle = [1% - 50%] and by an MI = [0.25 - 0.5], without any recovery following treatment. Detectable amounts of fluorescent dextran were delivered across the Caco-2 monolayer only by a combination of US + MBs. These results suggest that our adapted setup and custom-built miniature transducer permits control of the decrease in barrier function for further therapeutic investigations

Ultrasound mediated delivery of quantum dots from a capsule endoscope to the gastrointestinal wall

Biologic drugs, defined as therapeutic agents produced from or containing components of a living organism, are of growing importance to the pharmaceutical industry. Though oral delivery of medicine is convenient, biologics require invasive injections because of their poor bioavailability via oral routes. Delivery of biologics to the small intestine using electronic delivery with devices that are similar to capsule endoscopes is a promising means of overcoming this limitation and does not require reformulation of the therapeutic agent. The efficacy of such capsule devices for drug delivery could be further improved by increasing the permeability of the intestinal tract lining with an integrated ultrasound transducer to increase uptake. This paper describes a novel proof of concept capsule device capable of electronic application of focused ultrasound and delivery of therapeutic agents. Fluorescent markers, which were chosen as a model drug, were used to demonstrate in-vivo delivery in the porcine small intestine with this capsule. We show that the fluorescent markers can penetrate the mucus layer of the small intestine at low acoustic powers when combining microbubbles with focussed ultrasound. These findings suggest that the use of focused ultrasound together with microbubbles could play a role in the oral delivery of biologic therapeutics

Ultrasound mediated delivery of quantum dots from a proof of concept capsule endoscope to the gastrointestinal wall

Biologic drugs, defined as therapeutic agents produced from or containing components of a living organism, are of growing importance to the pharmaceutical industry. Though oral delivery of medicine is convenient, biologics require invasive injections because of their poor bioavailability via oral routes. Delivery of biologics to the small intestine using electronic delivery with devices that are similar to capsule endoscopes is a promising means of overcoming this limitation and does not require reformulation of the therapeutic agent. The efficacy of such capsule devices for drug delivery could be further improved by increasing the permeability of the intestinal tract lining with an integrated ultrasound transducer to increase uptake. This paper describes a novel proof of concept capsule device capable of electronic application of focused ultrasound and delivery of therapeutic agents. Fluorescent markers, which were chosen as a model drug, were used to demonstrate in vivo delivery in the porcine small intestine with this capsule. We show that the fluorescent markers can penetrate the mucus layer of the small intestine at low acoustic powers when combining microbubbles with focused ultrasound during in vivo experiments using porcine models. This study illustrates how such a device could be potentially used for gastrointestinal drug delivery and the challenges to be overcome before focused ultrasound and microbubbles could be used with this device for the oral delivery of biologic therapeutics

Ultrasound and Microbubbles can Lodge qDots into Murine ex-vivo Small Intestine

Ultrasound (US) and microbubbles (MBs) can deliver drugs to epithelial tissue layers. Previous in vivo work was inconclusive as to whether US + MBs can promote delivery of fluorescent quantum dots (qDots) to intestinal tissue covered by a layer of mucus. The objectives of the present work was (1) to identify a suitable fixative for preserving the mucus layer on the epithelial tissue to enable imaging after US + MB treatment and (2) to verify the depth of penetration of qDots in the small intestine when qDots are delivered in the presence of US + MBs. The mucosa of three murine small intestines were insonated with a 4.18 MHz miniature focused US transducer for 90 s (1 MPa PNP, MI = 0.5) while simultaneously delivering a suspension of qDots and MBs. Fixing tissue with PFA rather than Carnoy was more appropriate for detecting retention of qDots in the mucus layer. Two-photon laser scanning microscopy showed that qDots lodged in mucus, but did not penetrate the underlying intestinal tissue. This indicates that the parameters used for US + MBs were suitable only for delivering qDots into the mucus layer. The finding suggests focused US + MBs + qDots could be used to mark specific intestinal locations which could enable clinicians to target subsequent therapeutic or surgical interventions to the same diseased sites within a short time afterwards.</p

Ultrasound technology for capsule endoscopy

Video capsule endoscopy (VCE), creating optical diagnostic images in the gastrointestinal tract, is now a well-established concept with commercial devices in clinical use. Ultrasound offers an alternative capsule endoscopy imaging modality with the specific additional capability to obtain information from beneath the visible surface of the lumen of the gut and also a means to intervene therapeutically through targeted drug delivery. Research is under way to ideate, develop, and demonstrate ultrasound capsule endoscopy (USCE), with key results already available. Synergy between USCE and robotic control will be at least as great as that between robotic control and VCE, and it is expected that USCE devices will become available for clinical use in the next few years