From concept to in vivo testing: Microcontainers for oral drug delivery

Flexible Coatings Facilitate pH-Targeted Drug Release via Self-Unfolding Foils: Applications for Oral Drug Delivery

Ingestible self-configurable proximity-enabling devices have been developed as a non-invasive platform to improve the bioavailability of drug compounds via swellable or self-unfolding devices. Self-unfolding foils support unidirectional drug release in close proximity to the intestinal epithelium, the main drug absorption site following oral administration. The foils are loaded with a solid-state formulation containing the active pharmaceutical ingredient and then coated and rolled into enteric capsules. The coated lid must remain intact to ensure drug protection in the rolled state until targeted release in the small intestine after capsule disintegration. Despite promising results in previous studies, the deposition of an enteric top coating that remains intact after rolling is still challenging. In this study, we compare different mixtures of enteric polymers and a plasticizer, PEG 6000, as potential coating materials. We evaluate mechanical properties as well as drug protection and targeted release in gastric and intestinal media, respectively. Commercially available Eudragit® FL30D-55 appears to be the most suitable material due to its high strain at failure and integrity after capsule fitting. In vitro studies of coated foils in gastric and intestinal media confirm successful pH-triggered drug release. This indicates the potential advantage of the selected material in the development of self-unfolding foils for oral drug delivery.

Intestinal retentive systems - recent advances and emerging approaches

Intestinal retentive devices (IRDs) are devices designed to anchor within the lumen of the intestines for long-term residence in the gastrointestinal tract. IRDs can enable impactful medical device technologies including sustained oral drug delivery systems, indwelling sensors, or real-time diagnostics. The design and testing of IRDs present a myriad of challenges, including precise deployment of the device at desired intestinal locations, secure anchoring within the gastrointestinal tract to allow for natural function, and safe removal of the IRD at user-defined times. Advancing the state-of-the-art of IRD is an interdisciplinary effort that requires innovations such as new materials, novel anchoring mechanisms, and medical device design with consistent input from clinical practitioners and end-users. This perspective briefly reviews the current state-of-the-art for IRDs and charts a path forward to inform the design of future concepts. Specifically, this article will highlight materials, retention mechanisms, and test beds to measure the efficacy of IRDs and their mechanisms. Finally, potential synergies between IRD and other medical device technologies are presented to identify future opportunities.

A self-unfolding proximity enabling device for oral delivery of macromolecules

Oral delivery of macromolecules remains highly challenging due to their rapid degradation in the gastrointestinal tract and poor absorption across the tight junctions of the epithelium. In the last decade, researchers have investigated several medical devices to overcome these challenges using various approaches, some of which involve piercing through the intestine using micro and macro needles. We have developed a new generation of medical devices called self-unfolding proximity enabling devices, which makes it possible to orally deliver macromolecules without perforating the intestine. These devices protect macromolecules from the harsh conditions in the stomach and release their active pharmaceutical ingredients in the vicinity of the intestinal epithelium. One device version is a self-unfolding foil that we have used to deliver insulin and nisin to rats and pigs respectively. In our study, this device has shown a great potential for delivering peptides, with a significant increase in the absorption of solid dosage of insulin by ∼12 times and nisin by ∼4 times in rats and pigs, respectively. With the ability to load solid dosage forms, our devices can facilitate enhanced absorption of minimally invasive oral macromolecule formulations.

Microscopic Cascading Devices for Boosting Mucus Penetration in Oral Drug Delivery-Micromotors Nesting Inside Microcontainers

In the case of macromolecules and poorly permeable drugs, oral drug delivery features low bioavailability and low absorption across the intestinal wall. Intestinal absorption can be improved if the drug formulation could be transported close to the epithelium. To achieve this, a cascade delivery device comprising Magnesium-based Janus micromotors (MMs) nesting inside a microscale containers (MCs) has been conceptualized. The device aims at facilitating targeted drug delivery mediated by MMs that can lodge inside the intestinal mucosa. Loading MMs into MCs can potentially enhance drug absorption through increased proximity and unidirectional release. The MMs will be provided with optimal conditions for ejection into any residual mucus layer that the MCs have not penetrated. MMS confined inside MCs propel faster in the mucus environment as compared to non-confined MMs. Upon contact with a suitable fuel, the MM-loaded MC itself can also move. An in vitro study shows fast release profiles and linear motion properties in porcine intestinal mucus compared to more complex motion in aqueous media. The concept of dual-acting cascade devices holds great potential in applications where proximity to epithelium and deep mucus penetration are needed.

Assembly of Fillable Microrobotic Systems by Microfluidic Loading with Dip Sealing

Microrobots can provide spatiotemporally well-controlled cargo delivery that can improve therapeutic efficiency compared to conventional drug delivery strategies. Robust microfabrication methods to expand the variety of materials or cargoes that can be incorporated into microrobots can greatly broaden the scope of their functions. However, current surface coating or direct blending techniques used for cargo loading result in inefficient loading and poor cargo protection during transportation, which leads to cargo waste, degradation and non-specific release. Herein, a versatile platform to fabricate fillable microrobots using microfluidic loading and dip sealing (MLDS) is presented. MLDS enables the encapsulation of different types of cargoes within hollow microrobots and protection of cargo integrity. The technique is supported by high-resolution 3D printing with an integrated microfluidic loading system, which realizes a highly precise loading process and improves cargo loading capacity. A corresponding dip sealing strategy is developed to encase and protect the loaded cargo whilst maintaining the geometric and structural integrity of the loaded microrobots. This dip sealing technique is suitable for different materials, including thermal and light-responsive materials. The MLDS platform provides new opportunities for microrobotic systems in targeted drug delivery, environmental sensing, and chemically powered micromotor applications.

Advances in Oral Drug Delivery Systems: Challenges and Opportunities

The oral route is the most preferred route for systemic and local drug delivery. However, the oral drug delivery system faces the harsh physiological and physicochemical environment of the gastrointestinal tract, which limits the bioavailability and targeted design of oral drug delivery system. Innovative pharmaceutical approaches including nanoparticulate formulations, biomimetic drug formulations, and microfabricated devices have been explored to optimize drug targeting and bioavailability. In this review, the anatomical factors, biochemical factors, and physiology factors that influence delivering drug via oral route are discussed and recent advance in conventional and novel oral drug delivery approaches for improving drug bioavailability and targeting ability are highlighted. We also address the challenges and opportunities of oral drug delivery systems in future.

3D-Printed Radiopaque Microdevices with Enhanced Mucoadhesive Geometry for Oral Drug Delivery

During the past decades, microdevices have been evaluated as a means to overcome challenges within oral drug delivery, thus improving bioavailability. Fabrication of microdevices is often limited to planar or simple 3D designs. Therefore, this work explores how microscale stereolithography 3D printing can be used to fabricate radiopaque microcontainers with enhanced mucoadhesive geometries, which can enhance bioavailability by increasing gastrointestinal retention. Ex vivo force measurements suggest increased mucoadhesion of microcontainers with adhering features, such as pillars and arrows, compared to a neutral design. In vivo studies, utilizing planar X-ray imaging, show the time-dependent gastrointestinal location of microcontainers, whereas computed tomography scanning and cryogenic scanning electron microscopy reveal information about their spatial dynamics and mucosal interactions, respectively. For the first time, the effect of 3D microdevice modifications on gastrointestinal retention is traced in vivo, and the applied methods provide a much-needed approach for investigating the impact of device design on gastrointestinal retention.

Delivery of E. coli Nissle to the mouse gut by mucoadhesive microcontainers does not improve its competitive ability against strains linked to ulcerative colitis

For patients with ulcerative colitis (UC), administration of the probiotic E. coli Nissle (EcN) holds promise for alleviation of disease symptoms. The mechanisms are unclear, but it has been hypothesised that a capacity of the probiotic to outcompete potentially detrimental UC-associated E. coli strains plays an important role. However, this could previously not be confirmed in a mouse model of competition between EcN and two UC-associated strains, as reported by Petersen et al. 2011. In the present study, we re-evaluated the idea, hypothesising that delivery of EcN by a micro device dosing system (microcontainers), designed for delivery into the intestinal mucus, could support colonisation and confer a competition advantage compared to classical oral dosing. Six groups of mice were pre-colonised with one of two UC-associated E. coli strains followed by oral delivery of EcN, either in capsules containing microcontainers with freeze-dried EcN powder, capsules containing freeze-dried EcN powder, or as a fresh sucrose suspension. Co-colonisation between the probiotic and the disease-associated strains was observed regardless of dosing method, and no competition advantages linked to microcontainer delivery were identified within this setup. Other approaches are thus needed if the competitive capacity of EcN in the gut should be improved.

Bioadhesive Tannic-Acid-Functionalized Zein Coating Achieves Engineered Colonic Delivery of IBD Therapeutics via Reservoir Microdevices

The biggest challenge in oral delivery of anti-inflammatory drugs such as 5-aminosalicylic acid (5-ASA) is to (i) prevent rapid absorption in the small intestine and (ii) achieve localized release at the site of inflammation in the lower gut, i.e., the colon. Here, we present an advanced biopolymeric coating comprising of tannic-acid-functionalized zein protein to provide a sustained, colon-targeted release profile for 5-ASA and enhance the mucoadhesion of the dosage form via a mussel-inspired mechanism. To enable localized delivery and provide high local concentration, 5-ASA is loaded into the microfabricated drug carriers (microcontainers) and sealed with the developed coating. The functionality and drug release profile of the coating are characterized and optimized in vitro, showing great tunability, scalability, and stability toward proteases. Further, ex vivo experiments demonstrate that the tannic acid functionalization can significantly enhance the mucoadhesion of the coating, which is followed up by in vivo investigations on the intestinal retention, and pharmacokinetic evaluation of the 5-ASA delivery system. Results indicate that the developed coating can provide prolonged colonic delivery of 5-ASA. Therefore, the here-developed biodegradable coating can be an eco-friendly substitute to the state-of-the-art commercial counterparts for targeted delivery of 5-ASA and other small molecule drugs.

Open-source force analyzer with broad sensing range based on an optical pickup unit

In the pharmaceutical field, oral drug delivery devices continue to shrink down to the micrometer scale, driving a trending demand to investigate ex vivo mucoadhesive force down to the micro-Newton scale. However, owing to the limitation of measuring sensitivity, conventional methods (e.g., a texture analyzer) lack reliability while measuring forces in this range. Herein, we report on an open-source force analyzer that utilizes an optical-pickup-unit (from a DVD player) to detect cantilever-based force transducers and thereby, achieves a wide force-sensing range from 1.1 N to 0.99 nN. The cantilever force transducers can easily be adjusted to fit different force ranges by adjusting the steel shim, magnets, and 3D printed components. To validate the analyzer, we conducted a preliminary study to investigate the effect of time and humidity of mucoadhesion of porcine intestinal tissues. Besides, we measured the mucoadhesive force of a single oral drug delivery microdevice with an average force of 93.7 µN on the top sides of the device. This analyzer offers the possibility of measuring e.g. mucoadhesion of individual microdevices in the micro-Newton range. Hence, the analyzer can assist in the development of miniaturized oral drug delivery devices but has a much wider field of potential force sensing applications.

Open source anaerobic and temperature-controlled in vitro model enabling real-time release studies with live bacteria

In vitro release and dissolution models are widely used in the development phases of oral drug delivery systems to measure how an active pharmaceutical ingredient (API) is released from a dosage form. However, additional requirements for these models arise when evaluating probiotic dosage forms since they are often sensitive to temperature and oxygen levels. As a solution to this, we propose a custom-designed anaerobic in vitro release setup, made mainly by 3D printing and laser cutting, to function together with state-of-the-art pharmaceutical dissolution equipment - in this case, a microDISS Profiler™. The in vitro release model makes it possible to study the release rate of oxygen-sensitive probiotics in simulated intestinal conditions, while ensuring their survival due to the anaerobic conditions. This has not been possible so far since the available in vitro dissolution models have not been compatible with anaerobic conditions. With two different case studies, the developed model combined with a microDISS Profiler™ has proven capable of measuring the release of a probiotic and a small-molecule API from microdevices for oral drug delivery. Further, the model facilitated the survival of anaerobic bacteria present in the release medium.

Impact of oral gavage technique of drug-containing microcontainers on the gastrointestinal transit and absorption in rats

Oral gavage is the most common way to administer drug formulations orally to rats. Yet, the technique applied and its influence on gastrointestinal (GI) transit receive little attention. This study aims to investigate the impact of three oral gavage techniques on GI transit and drug absorption utilizing microcontainers (MCs). The MCs were filled with paracetamol and BaSO₄ (1:1 w/w ratio), coated with Eudragit S100, and filled into size-9 gelatin capsules. An in vitro study confirmed the intactness of the coating, and the capsules were administered to rats with air, water, or a piston. X-ray imaging determined the locations of the MCs, and the corresponding plasma concentration of paracetamol established a correlation with the location. The fastest GI transit occurred with air-dosing, while water-dosing caused delayed gastric emptying for 3h with non-quantifiable paracetamol absorption. Piston-dosed MCs were retained in the stomach for up to 1h, though for 3h in one rat. Air-dosing caused discomfort and stress in rats, thus limiting its ethical and physiological relevance. Water-dosing confined its use due to delayed gastric emptying. In conclusion, the oral gavage technique affected the GI transit of MCs and, consequently, drug absorption. Piston-dosing appeared to be the superior dosing technique.

Formulation strategies to improve the efficacy of intestinal permeation enhancers. Adv Drug Deliv Rev 2021;177:113925. [PMID: 34418495 DOI: 10.1016/j.addr.2021.113925]

The use of chemical permeation enhancers (PEs) is the most widely tested approach to improve oral absorption of low permeability active agents, as represented by peptides. Several hundred PEs increase intestinal permeability in preclinical bioassays, yet few have progressed to clinical testing and, of those, only incremental increases in oral bioavailability (BA) have been observed. Still, average BA values of ~1% were sufficient for two recent FDA approvals of semaglutide and octreotide oral formulations. PEs are typically screened in static in vitro and ex-vivo models where co-presentation of active agent and PE in high concentrations allows the PE to alter barrier integrity with sufficient contact time to promote flux across the intestinal epithelium. The capacity to maintain high concentrations of co-presented agents at the epithelium is not reached by standard oral dosage forms in the upper GI tract in vivo due to dilution, interference from luminal components, fast intestinal transit, and possible absorption of the PE per se. The PE-based formulations that have been assessed in clinical trials in either immediate-release or enteric-coated solid dosage forms produce low and variable oral BA due to these uncontrollable physiological factors. For PEs to appreciably increase intestinal permeability from oral dosage forms in vivo, strategies must facilitate co-presentation of PE and active agent at the epithelium for a sustained period at the required concentrations. Focusing on peptides as examples of a macromolecule class, we review physiological impediments to optimal luminal presentation, discuss the efficacy of current PE-based oral dosage forms, and suggest strategies that might be used to improve them.

Sensing technologies and experimental platforms for the characterization of advanced oral drug delivery systems

Complex and miniaturized oral drug delivery systems are being developed rapidly for targeted, controlled drug release and improved bioavailability. Standard analytical techniques are widely used to characterize i) drug carrier and active pharmaceutical ingredients before loading into a delivery device (to ensure the solid form), and ii) the entire drug delivery system during the development process. However, in light of the complexity and the size of some of these systems, standard techniques as well as novel sensing technologies and experimental platforms need to be used in tandem. These technologies and platforms are discussed in this review, with a special focus on passive delivery systems in size range from a few 100 µm to a few mm. Challenges associated with characterizing these systems and evaluating their effect on oral drug delivery in the preclinical phase are also discussed.

Physical methods for enhancing drug absorption from the gastrointestinal tract

Overcoming the gastrointestinal (GI) barriers is a formidable challenge in the oral delivery of active macromolecules such as peptide- and protein- based drugs. In the past four decades, a plethora of formulation strategies ranging from permeation enhancers, nanosized carriers, and chemical modifications of the drug's structure has been investigated to increase the oral absorption of these macromolecular compounds. However, only limited successes have been achieved so far, with the bioavailability of marketed oral peptide drugs remaining generally very low. Recently, a few approaches that are based on physical interactions, such as magnetic, acoustic, and mechanical forces, have been explored in order to control and improve the drug permeability across the GI mucosa. Although in the early stages, some of these methods have shown great potential both in terms of improved bioavailability and spatiotemporal delivery of drugs. Here, we offer a concise, yet critical overview of these rather unconventional technologies with a particular focus on their potential and possible challenges for further clinical translation.

Hot punching for loading of biodegradable microcontainers with budesonide-Soluplus film

Micro-reservoir based drug delivery systems have the potential to provide targeted drug release locally in the intestine, i.e. at the inflamed areas of the intestine of patients with inflammatory bowel disease (IBD). In this study, microcontainers with a diameter of 300 µm and a height of 100 µm, asymmetrical geometry and the possibility to provide unidirectional release, are fabricated in the biodegradable polymer poly-ɛ-caprolactone (PCL) using hot punching. As a first step towards local treatment of IBD, a novel method for loading of microcontainers with the corticosteroid budesonide is developed. For this purpose, a budesonide-Soluplus drug-polymer film is prepared by spin coating and loaded into the microcontainer reservoirs using hot punching. The processing parameters are optimized to achieve a complete loading of a large number of containers in a single step. A poly(lactic-co-glycolic acid) (PLGA) 50:50 lid is subsequently applied by spray coating. Solid-state characterization indicates that the drug is in an amorphous state in the drug-polymer films and the in vitro drug release profile showed a 68% release over 10 h. The results demonstrate that hot punching can be employed both as a production and loading method for PCL microcontainers with the perspective of local treatment of IBD.

Polymeric nano- and microparticulate drug delivery systems for treatment of biofilms

Now-a-days healthcare systems face great challenges with antibiotic resistance and low efficacy of antibiotics when combating pathogenic bacteria and bacterial biofilms. Administration of an antibiotic in its free form is often ineffective due to lack of selectivity to the infectious site and breakdown of the antibiotic before it exerts its effect. Therefore, polymeric delivery systems, where the antibiotic is encapsulated into a formulation, have shown great promise, facilitating a high local drug concentration at the site of infection, a controlled drug release and less drug degradation. All this leads to improved therapeutic effects and fewer systemic side effects together with a lower risk of developing antibiotic resistance. Here, we review and provide a comprehensive overview of polymer-based nano- and microparticles as carriers for antimicrobial agents and their effect on eradicating bacterial biofilms. We have a main focus on polymeric particulates containing poly(lactic-co-glycolic acid), chitosan and polycaprolactone, but also strategies involving combinations of these polymers are included. Different production techniques are reviewed and important parameters for biofilm treatment are discussed such as drug loading capacity, control of drug release, influence of particle size and mobility in biofilms. Additionally, we reflect on other promising future strategies for combating biofilms such as lipid-polymer hybrid particles, enzymatic biofilm degradation, targeted/triggered antibiotic delivery and future alternatives to the conventional particles.

Enhanced Eradication of Mucin-Embedded Bacterial Biofilm by Locally Delivered Antibiotics in Functionalized Microcontainers

Bacterial biofilm-related infections are difficult to eradicate and require repeated treatments with high doses of antibiotics. Thus, there is an urgent need for new treatment strategies that minimize the use of antibiotics while enhancing biofilm eradication. Functionalized reservoir-based microdevices, such as, microcontainers (MCs), offer, high drug loading capacity, mucus embedment, and tuneable drug release. Here, MCs are loaded with the antibiotic ciprofloxacin (CIP), and sealed with a lid consisting of chitosan (CHI) and a mucolytic agent, N-acetylcysteine (NAC). It is found that CHI and NAC work synergistically, showing improved mucoadhesive and mucolytic properties. To better mimic the in vivo habitat of Pseudomonas aeruginosa (P. aeruginosa), the biofilm is grown in a mucin-containing medium on a newly developed centrifugal microfluidic system. The CHI/NAC coated MCs improve eradication of biofilm (88.22 ± 2.89%) compared to CHI-coated MCs (72.68 ± 3.73%) or bolus injection (39.86 ± 13.28%). The findings suggest that MCs are significantly more efficient than a bolus treatment. Furthermore, CHI/NAC functionalized MCs kill most of the biomass already after 5 h (80.75 ± 3.50%), mainly due to a fast drug release. This is the first time that CHI/NAC has been combined as a coating to explore mucolytic properties on bacterial biofilms.

X-ray Imaging for Gastrointestinal Tracking of Microscale Oral Drug Delivery Devices

Microscale devices are promising tools to overcome specific challenges within oral drug delivery. Despite the availability of advanced high-quality imaging techniques, visualization and tracking of microscale devices in the gastrointestinal (GI) tract is still a challenge. This work explores the possibilities of applying planar X-ray imaging and computed tomography (CT) scanning for visualization and tracking of microscale devices in the GI tract of rats. Microcontainers (MCs) are an example of microscale devices that have shown great potential as an oral drug delivery system. Barium sulfate (BaSO₄) loaded into the cavity of the MCs increases their overall X-ray contrast, which allows them to be easily tracked. The BaSO₄-loaded MCs are quantitatively tracked throughout the entire GI tract of rats by planar X-ray imaging and visualized in 3D by CT scanning. The majority of the BaSO₄-loaded MCs are observed to retain in the stomach for 0.5-2 h, enter the cecum after 3-4 h, and leave the cecum and colon 8-10 h post-administration. The imaging approaches can be adopted and used with other types of microscale devices when investigating GI behavior in, for example, preclinical trials and potential clinical studies.

In vitro and in vivo comparison of microcontainers and microspheres for oral drug delivery

Microcontainers, which are microfabricated cylindrical devices with a reservoir function, have shown promise as an oral drug delivery system for small molecular drug compounds. However, they have never been evaluated against a relevant control formulation. In the current study, we prepared microcrystalline cellulose (MCC) microspheres as a control for in vitro and in vivo testing of SU-8 microcontainers as an oral drug delivery system. Both dosage forms were loaded with paracetamol and coated with chitosan or polyethylene glycol (PEG) (12 kDa). These coatings were followed by an additional enteric coating of Eudragit® S100. In addition, a control dosage form was coated with Eudragit® alone. The dosage forms were evaluated in vitro, in a physiologically relevant two-step model simulating rat gastrointestinal fluids, and in vivo by oral administration to rats. In vitro, the microcontainers coated with PEG/Eudragit® resulted in a prolonged release of paracetamol compared to the respective microspheres, which was consistent with in vivo observations of a later time (T_max) for maximum plasma concentration (C_max) for the microcontainers. For microspheres and microcontainers coated with chitosan/Eudragit®, the time for complete in vitro release of paracetamol was very similar, due to an earlier release from the microcontainers. This trend was supported by very similar T_max values in vivo. The in vitro in vivo relation was confirmed by a linear regression with R² = 0.9, when T_max for each dosage form was plotted as a function of time for 90% paracetamol release in vitro. From the in vivo study, the average plasma concentration of paracetamol 120 min after dosing was significantly higher for microcontainers than for microspheres (0.3 ± 0.1 µg/mL and 0.1 ± <0.1 µg/mL, respectively) - regardless of the coating applied.

Co-delivery of ciprofloxacin and colistin using microcontainers for bacterial biofilm treatment

In many infected patients, bacterial biofilms represent a mode of growth that significantly enhances the tolerance to antimicrobials, leaving the patients with difficult-to-cure infections. Therefore, there is a growing need for effective treatment strategies to combat biofilm infections. In this work, reservoir-based microdevices, also known as microcontainers (MCs), are co-loaded with two antibiotics: ciprofloxacin hydrochloride (CIP) and colistin sulfate (COL), targeting both metabolically active and dormant subpopulations of the biofilm. We assess the effect of the two drugs in a time-kill study of planktonic P. aeruginosa and find that co-loaded MCs are superior to monotherapy, resulting in complete killing of the entire population. Biofilm consortia of P. aeruginosa grown in flow chambers were not fully eradicated. However, antibiotics in MCs work significantly faster than simple perfusion of antibiotics (62.5 ± 8.3% versus 10.6 ± 10.1% after 5 h) in biofilm consortia, showing the potential of the MC-based treatment to minimize the use of antimicrobials in future therapies.

Tissue-based biosensor for monitoring the antioxidant effect of orally administered drugs in the intestine

For a better understanding of the effect of drugs and their interaction with cells and tissues, there is a need for in vitro and ex vivo model systems which enables studying these events. There are several in vitro methods available to evaluate the antioxidant activity; however, these methods do not factor in the complex in vivo physiology. Here we present an intestinal tissue modified oxygen electrode, used for the detection of the antioxidant effect of orally administered drugs in the presence of H₂O₂. Antioxidants are essential in the defense against oxidative stress, more specifically against reactive oxygen species such as H₂O_2. Due to the presence of native catalase in the intestine, with the tissue-based biosensor we were able to detect H₂O₂ in the range between 50 and 500 µM. The reproducibility of the sensor based on the calculated relative standard deviations was 15 ± 6%. We found that the O₂ production by catalase from H₂O₂ was reduced in the presence of a well-known antioxidant, quinol. This indirectly detected antioxidant activity was also observed in the case of orally administered drugs with a reported anti-inflammatory effect such as mesalazine and paracetamol, while no antioxidant activity was recorded with aspirin and metformin.

Controlled Drug Release from Biodegradable Polymer Matrix Loaded in Microcontainers Using Hot Punching

Microcontainers are reservoir-based advanced drug delivery systems (DDS) that have proven to increase the bioavailibity of the small-molecule drugs, targeting of biomolecules, protection of vaccines and improved treatment of Pseudomonas aeruginosa. However, high-throughput loading of these micron-sized devices with drug has been challenging. Hot punching is a new technique that is a fast, simple and single-step process where the microdevices are themselves used as mold to punch biocompatible and biodegradable drug-polymer films, thereby loading the containers. Here, we investigate the effect of hot punching on the drug distribution as well as drug release from the loaded drug-polymer matrices. Zero-order sustained drug release is observed for the model drug Furosemide embedded in biodegradable polymer, Poly-ε-caprolactone, which is attributed to the unique spatial distribution of Furosemide during the loading process.

Gastrointestinal-resident, shape-changing microdevices extend drug release in vivo

Extended-release gastrointestinal (GI) luminal delivery substantially increases the ease of administration of drugs and consequently the adherence to therapeutic regimens. However, because of clearance by intrinsic GI motility, device gastroretention and extended drug release over a prolonged duration are very challenging. Here, we report that GI parasite-inspired active mechanochemical therapeutic grippers, or theragrippers, can reside within the GI tract of live animals for 24 hours by autonomously latching onto the mucosal tissue. We also observe a notable sixfold increase in the elimination half-life using theragripper-mediated delivery of a model analgesic ketorolac tromethamine. These results provide first-in-class evidence that shape-changing and self-latching microdevices enhance the efficacy of extended drug delivery.

Intestinal permeation enhancers to improve oral bioavailability of macromolecules: reasons for low efficacy in humans

INTRODUCTION

Intestinal permeation enhancers (PEs) are substances that transiently alter the intestinal epithelial barrier to facilitate permeation of macromolecules with low oral bioavailability (BA). While a number of PEs have progressed to clinical testing in conventional formulations with macromolecules, there has been only low single digit increases in oral BA, irrespective of whether the drug met primary or secondary clinical endpoints.

AREAS COVERED

This article considers the causes of sub-optimal BA of macromolecules from PE dosage forms and suggests approaches that may improve performance in humans.

EXPERT OPINION

Permeation enhancement is most effective when the PE is co-localized with the macromolecule at the epithelial surface. Conditions in the GI tract impede optimal co-localization. Novel delivery systems that limit dilution and spreading of the PE and macromolecule in the small intestine have attempted to replicate promising enhancement efficacy observed in static drug delivery models.

Systemic delivery of peptides by the oral route: Formulation and medicinal chemistry approaches

In its 33 years, ADDR has published regularly on the po5tential of oral delivery of biologics especially peptides and proteins. In the intervening period, analysis of the preclinical and clinical trial failures of many purported platform technologies has led to reflection on the true status of the field and reigning in of expectations. Oral formulations of semaglutide, octreotide, and salmon calcitonin have completed Phase III trials, with oral semaglutide being approved by the FDA in 2019. The progress made with oral peptide formulations based on traditional permeation enhancers is against a background of low and variable oral bioavailability values of ~1%, leading to a current perception that only potent peptides with a viable cost of synthesis can be realistically considered. Desirable features of candidates should include a large therapeutic index, some stability in the GI tract, a long elimination half-life, and a relatively low clearance rate. Administration in nanoparticle formats have largely disappointed, with few prototypes reaching clinical trials: insufficient particle loading, lack of controlled release, low epithelial particle uptake, and lack of scalable synthesis being the main reasons for discontinuation. Disruptive technologies based on engineered devices promise improvements, but scale-up and toxicology aspects are issues to address. In parallel, medicinal chemists are synthesizing stable hydrophobic macrocyclic candidate peptides of lower molecular weight and with potential for greater oral bioavailability than linear peptides, but perhaps without the same requirement for elaborate drug delivery systems. In summary, while there have been advances in understanding the limitations of peptides for oral delivery, low membrane permeability, metabolism, and high clearance rates continue to hamper progress.

Orally ingestible medical devices for gut engineering

Orally ingestible medical devices provide significant advancement for diagnosis and treatment of gastrointestinal (GI) tract-related conditions. From micro- to macroscale devices, with designs ranging from very simple to complex, these medical devices can be used for site-directed drug delivery in the GI tract, real-time imaging and sensing of gut biomarkers. Equipped with uni-direction release, or self-propulsion, or origami design, these microdevices are breaking the barriers associated with drug delivery, including biologics, across the GI tract. Further, on-board microelectronics allow imaging and sensing of gut tissue and biomarkers, providing a more comprehensive understanding of underlying pathophysiological conditions. We provide an overview of recent advances in orally ingestible medical devices towards drug delivery, imaging and sensing. Challenges associated with gut microenvironment, together with various activation/actuation modalities of medical devices for micromanipulation of the gut are discussed. We have critically examined the relationship between materials–device design–pharmacological responses with respect to existing regulatory guidelines and provided a clear roadmap for the future.

Microcontainer Delivery of Antibiotic Improves Treatment of Pseudomonas aeruginosa Biofilms

Biofilm-associated infections are difficult to treat effectively with antibiotics despite repeated treatments. Polymeric microdevices (microcontainers) have previously been shown to engulf in mucus layers and to provide tunable release. Such devices may overcome the challenge of delivering antibiotics into the biofilm, increasing the local drug concentration and hence improve local bacterial killing. In this work, microcontainers are loaded with the antibiotic, ciprofloxacin hydrochloride, and functionalized with polymeric lids of polyethylene glycol (PEG), chitosan, or Eudragit S100. The PEG lid gives rise to a drug release comparable to uncoated microcontainers showing complete release after 8 h, whereas chitosan and Eudragit S100 lids result in continuous release during the course of 24 h. All antibiotic-containing microcontainers inhibit planktonic growth of Pseudomonas aeruginosa (PAO1) cells, but the degree of inhibition depends on the coating. Microcontainers with ciprofloxacin hydrochloride kill about three times more biofilm-associated PAO1 cells compared with a single standard bolus. Moreover, the use of microcontainers in biofilm result in bacterial killing equal to a constant flow of a three times higher concentration of solubilized antibiotics. These studies suggest that microcontainers can be useful for antibiotic delivery in treatment of biofilm-associated infections, resulting in more effective treatment and reduced use of antibiotics.

Cubic Microcontainers Improve In Situ Colonic Mucoadhesion and Absorption of Amoxicillin in Rats

An increased interest in colonic drug delivery has led to a higher focus on the design of delivery devices targeting this part of the gastrointestinal tract. Microcontainers have previously facilitated an increase in oral bioavailability of drugs. The surface texture and shape of microcontainers have proven to influence the mucoadhesion ex vivo. In the present work, these findings were further investigated using an in situ closed-loop perfusion technique in the rat colon, which allowed for simultaneous evaluation of mucoadhesion of the microcontainers as well as drug absorption. Cylindrical, triangular and cubic microcontainers, with the same exterior surface area, were evaluated based on in vitro release, in situ mucoadhesion and in situ absorption of amoxicillin. Additionally, the mucoadhesion of empty cylindrical microcontainers with and without pillars on the top surface was investigated. From the microscopy analysis of the colon sections after the in situ study, it was evident that a significantly higher percentage of cubic microcontainers than cylindrical microcontainers adhered to the intestinal mucus. Furthermore, the absorption rate constants and blood samples indicated that amoxicillin in cubic microcontainers was absorbed more readily than when cylindrical or triangular microcontainers were dosed. This could be due to a higher degree of mucoadhesion for these particular microcontainers.

Long lasting mucoadhesive membrane based on alginate and chitosan for intravaginal drug delivery

The intravaginal route of administration can be exploited to treat local diseases and for systemic delivery. In this work, we developed an alginate/chitosan membrane sufficiently stable in a simulated vaginal fluid and able to dissolve over time at a very slow and linear rate. The membrane demonstrated good mechanical properties both in its swollen and dry form. As a study case, we evaluated the viability of this potential drug delivery system for the treatment of bacterial vaginosis, a common disease affecting women in their reproductive age. Metronidazole was effectively included in the alginate/chitosan membrane and its bactericide effect was demonstrated against Staphylococcus aureus and Gardnerella vaginalis, simultaneously showing good biocompatibility with a cervix epithelial cell line. Since this alginate/chitosan membrane is stable in a simulated vaginal environment, is easy to fabricate and can be used for the controlled release of a model drug, it represents a promising drug delivery system for local intravaginal applications.

Gastrointestinal Tracking and Gastric Emptying of Coated Capsules in Rats with or without Sedation Using CT imaging

Following oral administration, gastric emptying is often a rate-limiting step in the absorption of drugs and is dependent on both physiological and pharmaceutical factors. To guide translation into humans, small animal imaging during pre-clinical studies has been increasingly used to localise the gastrointestinal transit of solid dosage forms. In contrast to humans, however, anaesthesia is usually required for effective imaging in animals which may have unintended effects on intestinal physiology. This study evaluated the effect of anaesthesia and capsule size on the gastric emptying rate of coated capsules in rats. Computed tomography (CT) imaging was used to track and locate the capsules through the gastrointestinal tract. Two commercial gelatine mini-capsules (size 9 and 9h) were filled with barium sulphate (contrast agent) and coated using Eudragit L. Under the effect of anaesthesia, none of the capsules emptied from the stomach. In non-anaesthetised rats, most of the size 9 capsules did not empty from the stomach, whereas the majority of the smaller size 9h capsules successfully emptied from the stomach and moved into the intestine. This study demonstrates that even with capsules designed to empty from the stomach in rats, the gastric emptying of such solid oral dosage forms is not guaranteed. In addition, the use of anaesthesia was found to abolish gastric emptying of both capsule sizes. The work herein further highlights the utility of CT imaging for the effective visualisation and location of solid dosage forms in the intestinal tract of rats without the use of anaesthesia.

Micro and nanoscale technologies in oral drug delivery

Oral administration is a pillar of the pharmaceutical industry and yet it remains challenging to administer hydrophilic therapeutics by the oral route. Smart and controlled oral drug delivery could bypass the physiological barriers that limit the oral delivery of these therapeutics. Micro- and nanoscale technologies, with an unprecedented ability to create, control, and measure micro- or nanoenvironments, have found tremendous applications in biology and medicine. In particular, significant advances have been made in using these technologies for oral drug delivery. In this review, we briefly describe biological barriers to oral drug delivery and micro and nanoscale fabrication technologies. Micro and nanoscale drug carriers fabricated using these technologies, including bioadhesives, microparticles, micropatches, and nanoparticles, are described. Other applications of micro and nanoscale technologies are discussed, including fabrication of devices and tissue engineering models to precisely control or assess oral drug delivery in vivo and in vitro, respectively. Strategies to advance translation of micro and nanotechnologies into clinical trials for oral drug delivery are mentioned. Finally, challenges and future prospects on further integration of micro and nanoscale technologies with oral drug delivery systems are highlighted.

Investigation of Mucoadhesion and Degradation of PCL and PLGA Microcontainers for Oral Drug Delivery

Microfabricated devices have been introduced as a promising approach to overcome some of the challenges related to oral administration of drugs and, thereby, improve their oral bioavailability. In this study, we fabricate biodegradable microcontainers with different polymers, namely poly-ɛ-caprolactone (PCL), poly(lactic-co-glycolic acid) (PLGA) 50:50 and PLGA 75:25 by hot punching. The mucoadhesion of the microcontainers is assessed with an ex vivo retention model on porcine intestinal tissue. Finally, in vitro degradation studies of the biodegradable microcontainers are completed for six weeks in simulated intestinal medium with the addition of pancreatic enzymes. Through SEM inspection, the PLGA 50:50 microcontainers show the first signs of degradation already after two weeks and complete degradation within four weeks, while the other polymers slowly degrade in the medium over several weeks.

Biodegradable microcontainers - towards real life applications of microfabricated systems for oral drug delivery

Microfabrication techniques have been applied to develop micron-scale devices for oral drug delivery with a high degree of control over size, shape and material composition. Recently, microcontainers have been introduced as a novel approach to obtain unidirectional release to avoid luminal drug loss, enhance drug permeation, protect drug payload from the harsh environment of the stomach, and explore the ability for targeted drug delivery. However, in order to eventually pave the way for real life applications of these microfabricated drug delivery systems, it is necessary to fabricate them in biodegradable materials approved for similar applications and with strategies that potentially allow for large scale production. In this study, we for the first time evaluate biodegradable microcontainers for oral drug delivery. Asymmetric poly-ε-caprolactone (PCL) microcontainers with a diameter of 300 μm and a volume of 2.7 nL are fabricated with a novel single-step fabrication process. The microcontainers are loaded with the model drug paracetamol and coated with an enteric pH-sensitive Eudragit® S100 coating to protect the drug until it reaches the desired location in the small intestine. In vitro dissolution studies are performed to assess the drug load and release profile of the PCL microcontainers. Finally, in vivo studies in rats showed a higher bioavailability compared to conventional dosage forms and confirm the potential of biodegradable microcontainers for oral drug delivery.

Ex vivo intestinal perfusion model for investigating mucoadhesion of microcontainers

Micro fabricated delivery systems have shown promise in increasing oral bioavailability of drugs. Micrometer-sized polymeric devices (microcontainers) have the potential to facilitate unidirectional drug release directly into the intestinal mucosa whereby, drug absorption can be enhanced. The aim of this study was to develop an ex vivo model to investigate mucosal adhesion and orientation of microcontainers. Furthermore, to investigate how microcontainers with varying height, shape and material behave in regards to mucoadhesion and orientation. Microcontainers were placed at the top of an inclined piece of porcine small intestine. The tissue was perfused with biorelevant medium followed by microscopic examination to observe the orientation and amount of microcontainers on the tissue. The mucoadhesion of the microcontainers were evaluated based on the observed position on the tissue after being exposed to flow. When comparing the varying types of microcontainers, good adhesion was in general observed since most of the microcontainers were located in the beginning of the intestine. Microcontainers fabricated from the epoxy-based photoresist SU-8 had a slightly better adherence than those fabricated from poly-ɛ-caprolactone (PCL). The orientation of the microcontainers appeare to be dictated mainly by the height. In general, the model showed promising results in evaluating mucoadhesion and orientation.

Modular, Lightweight, Wireless Potentiostat-on-a-Disc for Electrochemical Detection in Centrifugal Microfluidics

Interfacing electrochemical sensors in a lab-on-a-disc (LoD) system with a potentiostat is often tedious and challenging. We here present the first multichannel, modular, lightweight, and wirelessly powered, custom-built potentiostat-on-a-disc (PoD) for centrifugal microfluidic applications. The developed potentiostat is in the form factor of a typical digital video disc (DVD) and weighs only 127 g. The design of the potentiostat facilitates easy and robust interfacing with the electrodes in the LoD system, while enabling real-time electrochemical detection during rotation. The device can perform different electroanalytical techniques such as cyclic voltammetry, square wave voltammetry, and amperometry while being controlled by custom-made software. Measurements were conducted with and without rotation using both in-house fabricated and commercial electrodes. The performance of the PoD was in good agreement with the results obtained using a commercial potentiostat with a measured current resolution of 200 pA. As a proof of concept, we performed a real-time release study of an electrochemically active compound from microdevices used for drug delivery.

Micromotors for drug delivery in vivo: The road ahead

Autonomously propelled/externally guided micromotors overcome current drug delivery challenges by providing (a) higher drug loading capacity, (b) localized delivery (less toxicity), (c) enhanced tissue penetration and (d) active maneuvering in vivo. These microscale drug delivery systems can exploit biological fluids, as well as exogenous stimuli, like light-NIR, ultrasound and magnetic fields (or a combination of these), towards propulsion/drug release. Ability of these wireless drug carriers towards localized targeting and controlled drug release, makes them a lucrative candidate for drug administration in complex microenvironments (like solid tumors or gastrointestinal tract). In this report, we discuss these microscale drug delivery systems for their therapeutic benefits under in vivo setting and provide a design-application rationale towards greater clinical significance. Also, a proof-of-concept depicting 'microbots-in-a-capsule' towards oral drug delivery has been discussed.

Microfabricated devices for oral drug delivery

Oral administration of drugs is most convenient for patients and therefore the ultimate goal when developing new medication. The physical barriers in the body, low pH of the stomach and degradation by enzymes in the gastrointestinal tract are a few of the obstacles to succeeding with oral drug delivery. Microfabricated devices show promise to overcome some of these hindrances and thereby improve the bioavailability of drugs after oral administration. There is an increasing focus on microfabricated oral drug delivery systems, and so far there have been three main groups of designs: patch-like structures, microcontainers and microwells. Here, we review the newest development in top-down microfabricated devices for oral drug delivery with coverage of the aspects of design, choice of material and fabrication techniques. Furthermore, the drug loading techniques and methods for testing are discussed. In addition, we discuss the future perspectives for microfabricated devices.