Evaluation of the feasibility and use of a prototype remote drug delivery capsule (RDDC) for non-invasive regional drug absorption studies in the GI tract of man and beagle dog

State-of-the-art and future perspectives in ingestible remotely controlled smart capsules for drug delivery: A GENEGUT review

An emerging concern globally, particularly in developed countries, is the rising prevalence of Inflammatory Bowel Disease (IBD), such as Crohn's disease. Oral delivery technologies that can release the active therapeutic cargo specifically at selected sites of inflammation offer great promise to maximise treatment outcomes and minimise off-target effects. Therapeutic strategies for IBD have expanded in recent years, with an increasing focus on biologic and nucleic acid-based therapies. Reliable site-specific delivery in the gastrointestinal (GI) tract is particularly crucial for these therapeutics to ensure sufficient concentrations in the targeted cells. Ingestible smart capsules hold great potential for precise drug delivery. Despite previous unsuccessful endeavours to commercialise drug delivery smart capsules, the current rise in demand and recent advancements in component development, manufacturing, and miniaturisation have reignited interest in ingestible devices. Consequently, this review analyses the advancements in various mechanical and electrical components associated with ingestible smart drug delivery capsules. These components include modules for device localisation, actuation and retention within the GI tract, signal transmission, drug release, power supply, and payload storage. Challenges and constraints associated with previous capsule design functionality are presented, followed by a critical outlook on future design considerations to ensure efficient and reliable site-specific delivery for the local treatment of GI disorders.

Review article: Current status and future directions of ingestible electronic devices in gastroenterology

BACKGROUND

Advances in microelectronics have greatly expanded the capabilities and clinical potential of ingestible electronic devices.

AIM

To provide an overview of the structure and potential impact of ingestible devices in development that are relevant to the gastrointestinal tract.

METHODS

We performed a detailed literature search to inform this narrative review.

RESULTS

Technical success of ingestible electronic devices relies on the ability to miniaturise the microelectronic circuits, sensors and components for interventional functions while being sufficiently powered to fulfil the intended function. These devices offer the advantages of being convenient and minimally invasive, with real-time assessment often possible and with minimal interference to normal physiology. Safety has not been a limitation, but defining and controlling device location in the gastrointestinal tract remains challenging. The success of capsule endoscopy has buoyed enthusiasm for the concepts, but few ingestible devices have reached clinical practice to date, partly due to the novelty of the information they provide and also due to the challenges of adding this novel technology to established clinical paradigms. Nonetheless, with ongoing technological advancement and as understanding of their potential impact emerges, acceptance of such technology will grow. These devices have the capacity to provide unique insight into gastrointestinal physiology and pathophysiology. Interventional functions, such as sampling of tissue or luminal contents and delivery of therapies, may further enhance their ability to sharpen gastroenterological diagnoses, monitoring and treatment.

CONCLUSIONS

The development of miniaturised ingestible microelectronic-based devices offers exciting prospects for enhancing gastroenterological research and the delivery of personalised, point-of-care medicine.

Smart pills for gastrointestinal diagnostics and therapy

Ingestible smart pills have the potential to be a powerful clinical tool in the diagnosis and treatment of gastrointestinal disease. Though examples of this technology, such as capsule endoscopy, have been successfully translated from the lab into clinically used products, there are still numerous challenges that need to be overcome. This review gives an overview of the research being done in the area of ingestible smart pills and reports on the technical challenges in this field.

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.

Capsule robot for gut microbiota sampling using shape memory alloy spring

BACKGROUND

Human gut microbiota can provide lifelong health information and even influence mood and behaviour. We currently lack the tools to obtain a microbial sample, directly from the small intestine, without contamination.

METHODS

Shape memory alloy springs are used in concentric configuration to develop an axial actuator. A novel design of sampling mechanism is fabricated for collecting the sample from the gut. Storage chamber (500 µl) is used to protect the sample from downstream contamination.

RESULTS

The developed actuator occupies a small space (5 × Ø5.75 mm) and produces sufficient output force (1.75 N) to operate the sampling mechanism. A non-invasive capsule robot was tested ex vivo on the animal intestine, and it captured an average of 134 µl content which was sufficient for microbiome assessment.

CONCLUSIONS

Laboratory testing revealed that the collected sample had an amino acid signature indicative of microbiota, mucus and digesta, which provided a proof of concept for the proposed design.

Food effect on meal administration time of pharmacokinetic profile of cilostazol, a BCS class II drug

Cilostazol (CLZ) is categorized as a biopharmaceutical classification system (BCS) class II drug. CLZ suspensions of jet-milled particles were orally administered to beagle dogs in fasted and fed states, for which food was given 0.5 h before the experiment.The mean highest concentration of CLZ (C_max) and the area under the serum concentration-time curve (AUC_t) fed/fasted ratios were 2.90 and 2.85, respectively, indicating a large and variable food effect. Additionally, CLZ was administered to the same dogs at 2 and 4 h after food or 0.5 h before food. The serum concentrations of CLZ were similar when dosed 0.5 and 2 h after food; however, they were significantly lower when dosed 4 h after food but still greater compared with the fasted state.Furthermore, the ratio of fed/fasted in AUC_t was better correlated than that in C_max. Additionally, the serum concentrations were similar to the fasted states when CLZ was dosed 0.5 h before food.Therefore, the results of this study showed that the serum concentration-time profile of CLZ was significantly affected by the timing of food administration, and that a good correlation was observed between food administration time and the C_max and AUC_t fed/fasted ratios.

A Prototype Therapeutic Capsule Endoscope for Ultrasound-Mediated Targeted Drug Delivery

The prevalence of gastrointestinal (GI) diseases such as Crohn’s disease, which is chronic and incurable, are increasing worldwide. Treatment often involves potent drugs with unwanted side effects. The technological–pharmacological combination of capsule endoscopy with ultrasound-mediated targeted drug delivery (UmTDD) described in this paper carries new potential for treatment of these diseases throughout the GI tract. We describe a proof-of-concept UmTDD capsule and present preliminary results to demonstrate its promise as an autonomous tool to treat GI diseases.

Medical capsule robots: A renaissance for diagnostics, drug delivery and surgical treatment

The advancements in electronics and the progress in nanotechnology have resulted in path breaking development that will transform the way diagnosis and treatment are carried out currently. This development is Medical Capsule Robots, which has emerged from the science fiction idea of robots travelling inside the body to diagnose and cure disorders. The first marketed capsule robot was a capsule endoscope developed to capture images of the gastrointestinal tract. Today, varieties of capsule endoscopes are available in the market. They are slightly larger than regular oral capsules, made up of a biocompatible case and have electronic circuitry and mechanisms to capture and transmit images. In addition, robots with diagnostic features such as in vivo body temperature detection and pH monitoring have also been launched in the market. However, a multi-functional unit that will diagnose and cure diseases inside the body has not yet been realized. A remote controlled capsule that will undertake drug delivery and surgical treatment has not been successfully launched in the market. High cost, inadequate power supply, lack of control over drug release, limited space for drug storage on the capsule, inadequate safety and no mechanisms for active locomotion and anchoring have prevented their entry in the market. The capsule robots can revolutionize the current way of diagnosis and treatment. This paper discusses in detail the applications of medical capsule robots in diagnostics, drug delivery and surgical treatment. In diagnostics, detailed analysis has been presented on wireless capsule endoscopes, issues associated with the marketed versions and their corresponding solutions in literature. Moreover, an assessment has been made of the existing state of remote controlled capsules for targeted drug delivery and surgical treatment and their future impact is predicted. Besides the need for multi-functional capsule robots and the areas for further research have also been highlighted.

A review of drug delivery systems for capsule endoscopy

The development of a highly controllable drug delivery system (DDS) for capsule endoscopy has become an important field of research due to its promising applications in therapeutic treatment of diseases in the gastrointestinal (GI) tract and drug absorption studies. Several factors need to be considered to establish the minimum requirements for a functional DDS. Environmental factors of the GI tract and also pharmaceutical factors can help determine the requirements to be met by a DDS in an endoscopic capsule. In order to minimize the influence of such factors on the performance of an effective DDS, at least two mechanisms should be incorporated into a capsule endoscope: an anchoring mechanism to control the capsule position and a drug release mechanism to control variables such as the drug release rate, number of doses and amount of drug released. The implementation of such remotely actuated mechanisms is challenging due to several constraints, including the limited space available in a swallowable capsule endoscope and the delicate and complex environment within the GI tract. This paper presents a comprehensive overview of existing DDS. A comparison of such DDS for capsule endoscopy based on the minimum DDS requirements is presented and future work is also discussed.

A novel remote controlled capsule for site-specific drug delivery in human GI tract

Remote controlled capsule (RCC) has been extensively used in the field of site-specific drug delivery. It is a potent tool to study the regional drug absorption of the gastrointestinal (GI) tract that provides pharmaceutical scientists with significant pharmacokinetics data for oral drug formulation development. In present investigations, a patented novel RCC has been devised based on micro-electronic mechanical system (MEMS) technology. Micro-thrusters were for the first time exploited as drug release actuators of RCCs. As the micro-thruster is ignited by a radio frequency (RF) signal, the thrust force generated by the propellants pushes the piston forward and leads to a rapid and complete expulsion of therapeutic agents from the capsule. The micro-thruster merely consumes 120 mW for ignition and the duration time of drug release is decreased to less than 1 s. The feasibility of the novel RCC was evaluated through animal experiments in beagles using aminophylline as the model drug. The novel RCC developed is a promising alternative for site-specific drug delivery in human GI tract.

Assessment of the feasibility of oral controlled release in an exploratory development setting

Controlled release (CR) formulations have generally been considered as follow-ons to conventional immediate release formulations to manage the life cycle of a product. Although significant opportunities exist to use CR as an enabling technology for certain exploratory drug candidates, they have not been fully exploited. However, progress made in assessing CR feasibility based on the physicochemical and biopharmaceutical properties of the drug, together with advances made in understanding the various CR technologies and developing formulations in a fast and efficient manner, have increasingly made it possible to consider CR in an exploratory development setting.

Pharmacoscintigraphic evaluation of riboflavin-containing microballoons for a floating controlled drug delivery system in healthy humans

Hollow microspheres (microballoons) floating on artificial gastric juice were developed as a floating controlled drug delivery system in the stomach. The intragastric behavior of 99mTc labelled microballoons (MB) and nonfloating microspheres (NF) (control) following oral administration in fasted and fed humans was investigated by gamma scintigraphy. Simultaneously, pharmacokinetic examination of riboflavin released from MB and NF was conducted in fasted and fed human subjects. In the fed state, MB were dispersed in the upper portion of the stomach; moreover, MB were retained in the stomach up to 300 min compared with NF, which descended gradually into the lower part of stomach within 90 min. In the fasted state, MB floated for approximately 60 min, after which it was removed rapidly via the cyclic activity referred to as the interdigestive migrating motor complex (IMMC). NF were removed more rapidly, i.e., within 60 min. Pharmacokinetic parameters, e.g., excretion half-life time (t1/2) and total urinary excretion, were well correlated with the gastric residence time (GRT) determined by the gamma scintigraphy analysis. The present investigation suggests that MB are very useful for improving drug bioavailability, resulting in a more sustained pharmacological action.

Feasibility study on the retention of superporous hydrogel composite polymer in the intestinal tract of man using scintigraphy

In recent years, many complex oral drug delivery systems have been developed using various polymers in order to achieve better drug targeting and drug absorption in the intestinal tract. Superporous hydrogel (SPH) and SPH composite (SPHC)-based drug delivery systems were also developed for the targeted delivery of peptide drugs into the intestinal tract. In the present study, the retention time of SPHC polymer is studied in man using the scintigraphy technique. To that purpose, SPHC polymers were radiolabelled with Tc-99m and administered orally in an enteric-coated gelatin capsule. The location of the radiolabelled polymer was monitored in five healthy volunteers while the subjects were sitting in front of a large field of view gamma camera. The results showed that enteric-coated gelatin capsules remained in the stomach for 75 to 150 min after oral administration to fasted volunteers and that the SPHC polymers thereafter attached to the upper part of the small intestine for at least 45 to 60 min due to their mechanical fixation properties. No discomfort was observed in any of the volunteers after oral administration of these polymers, which indicates that they are safe to be applied for oral drug delivery systems in man.

[Remote controlled drug release in the alimentary tract by local power deposition in alternating magnetic fields]

Remote controlled release of agents in the alimentary tract is an important task of gastroenterology and pharmacy. We investigated two different methods of drug release by heating locally restricted parts in medical capsules: hysteresis losses of magnetite powder and eddy current losses of metals in alternating magnetic fields. The comparison of our experimental results with theoretically derived expectations show that both methods are suitable techniques if special technical conditions are met. In order to demonstrate the feasibility of simple constructions, we used a gelatin capsule, consisting of two parts which were kept together by a belt of wax and a small copper coil. This capsule was placed in water and the belt was heated in an alternating magnetic field until melting and releasing a test fluid after about 60 s.

Peroral absorption of octreotide in pigs formulated in delivery systems on the basis of superporous hydrogel polymers

PURPOSE

The aim of this study was to investigate the enhancement of peroral octreotide absorption using delivery systems based on superporous hydrogel (SPH) and SPH composite (SPHC) polymers.

METHODS

Six female pigs (BW of 23.5 kg) were used in this study. SPH-based delivery systems were made of two components: 1) a conveyor system made of SPH and SPHC; 2) a core that contained octreotide. The core was inserted into the conveyor system (core inside, c.i.) or attached to the surface of the conveyor system (core outside, c.o.). Four different peroral formulations were investigated: c.i., c.o., core outside including trimethyl chitosan chloride (c.o.t.), and octreotide only in the absence of any polymer (o.o.). All formulations were placed in enteric-coated gelatin capsules (size 000) and administered perorally. Intravenous administration was used to determine bioavailability (F) values. Blood samples taken from the cannulated jugular vein were analyzed by radioimmunoassay.

RESULTS

Peroral administration of 15 mg o.o. resulted in low F values of 1.0 +/- 0.6% (mean +/- SEM) whereas c.i. and c.o. administrations resulted in remarkably higher F values of 12.7 +/- 3.6% and 8.7 +/- 2.4%, respectively. By the addition of trimethyl chitosan chloride as an extra absorption enhancer to c.o.t., the highest bioavailability (16.1 +/- 3.3%) was achieved.

CONCLUSIONS

These novel delivery systems based on SPH and SPHC polymers are able to increase the peroral bioavailability of octreotide by mechanical fixation and increasing the retention of the dosage form at the absorption site.

Evaluation of Pulsincap to provide regional delivery of dofetilide to the human GI tract

Pulsincap formulations designed to deliver a dose of drug following a 5-h delay were prepared to evaluate the capability of the formulation to deliver dofetilide to the lower gastrointestinal (GI) tract. By the expected 5-h release time, the preparations were well dispersed throughout the GI tract, from stomach to colon. Plasma analysis permitted drug absorption to be determined as a function of GI tract site of release. Dofetilide is a well-absorbed drug, but showed a reduction in observed bioavailability when delivered from the Pulsincap formulations, particularly at more distal GI tract sites. Dispersion of the drug from the soluble excipient used in this prototype formulation relies on a passive diffusion mechanism and the relevance of this factor to the reduced extent and consistency of absorption from the colon is discussed. In these studies the effects of the degree of dispersion versus the site of dispersion could not be ascertained; nevertheless the scintigraphic analysis demonstrated good in vitro-in vivo correlation for time of release from Pulsincap preparations. The combination of scintigraphic and pharmacokinetic analysis permits identification of the site of drug release from the dosage form and pharmacokinetic parameters to be studied in man in a non-invasive manner.

Evaluation of the feasibility and use of a prototype remote drug delivery capsule (RDDC) for non-invasive regional drug absorption studies in the GI tract of man and beagle dog

PURPOSE

Evaluate a prototype Remote Drug Delivery Capsule (RDDC) for use in beagle dogs and human volunteers for non-invasive drug absorption studies in different regions of the gastrointestinal tract.

METHODS

The device was dual radiolabeled and GI transit of the RDDC was monitored by gamma scintigraphy. Beagles were used initially to demonstrate the functional utility of the device where a solution of ranitidine hydrochloride (150 mg) was non-invasively delivered to the stomach, proximal small intestine and distal small intestine. A subsequent first time in human study enrolled twelve healthy male volunteers where the intended site of release was the stomach, early small bowel, distal small bowel or colon.

RESULTS

Preliminary studies conducted in beagles indicated that the RDDC operated successfully and the onset of ranitidine serum levels were dependent on the time of capsule activation and site of drug release. Results from the human study showed that all twelve subjects swallowed the device with no discomfort. Mean gastric emptying of the RDDC was 1.50 +/- 1.28 h (range = 0.25 to 4.25 h), and total small intestine transit was 4.79 +/- 1.82 h (range = 2.00 to 8.25 h). The capsule was retrieved from the feces at 30.25 +/- 15.21 h (range = 14.12 to 74.25 h) and there were no reported adverse events. The prototype RDDC operated successfully in nine of the twelve human volunteers and the cause for the three failures was attributed to mechanical failure while the electronics assembly performed favorably.

CONCLUSIONS

This prototype remote control capsule was shown to be well tolerated and functional to use in human volunteers as well as beagles. The application of the device coupled with gamma scintigraphy has the potential to be a valuable and rapid method to non-invasively evaluate regional drug absorption in the gastrointestinal tract under conditions that are both pharmaceutically and physiologically meaningful.