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

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.

Smart pills and drug delivery devices enabling next generation oral dosage forms

Oral dosage forms are the preferred solution for systemic treatment and prevention of disease conditions. However, traditional dosage forms face challenges regarding treatment adherence and delivery of biologics. Oral therapies that require frequent administrations face difficulties with patient compliance. In addition, only a few peptide- and protein-based drugs have been commercialized for oral administration so far, presenting a bioavailability that is generally low. Therefore, research and development on novel formulation strategies for oral drug delivery has bloomed massively in the last decade to overcome these challenges. On the one hand, approaches based on lumen-release of drugs such as 3D-printed capsules and prolonged gastric residence dosage forms have been explored to offer personalized medicine to the patient and reduce frequent dosing of small drug compounds that are currently in the market as powdered tablet or capsules. On the other hand, strategies based on mucus interfacing such as gastrointestinal patches, or even epithelium injections have been investigated in order to enhance the permeability of biologic macromolecules, which are mostly commercialized in the form of subcutaneous injections. Despite the fact that these methods are at an early development stage, promising results have been revealed in terms of personalized medicine and improved bioavailability. In this review, we offer a critical overview of novel ingestible millimeter-sized devices and technologies for oral drug delivery that are currently used in the clinic as well as those that could emerge on the market in a not too distant future.

An insight into gastrointestinal macromolecule delivery using physical oral devices

Oral delivery is preferred over other routes of drug administration by both patients and physicians. The bioavailability of some therapeutics that are delivered via the oral route is restricted due to the protease- and bacteria-rich environment in the gastrointestinal tract, and by the pH variability along the delivery route. Given these harsh environments, the oral delivery of therapeutic macromolecules is complicated and remains challenging. Various formulation approaches, including the use of permeation enhancers and nanosized carriers, as well as chemical alteration of the drug structure, have been studied as ways to improve the oral absorption of macromolecular drugs. Nevertheless, the bioavailability of marketed oral peptide medicines is often relatively poor. This review highlights the most recent and promising physical methods for improving the oral bioavailability of macromolecules such as peptides. These methods include microneedle injections, high-speed stream injectors, magnetic drug targeting, expandable hydrogels, and iontophoresis. We highlight the potential and challenges of these new technologies, which may impact the future approaches used by pharmaceutical companies to create more efficient and safer orally administered macromolecules. Teaser: Despite substantial effort, the oral delivery of macromolecules remains challenging due to their low bioavailability. This review discusses the potential, challenges, and safety concerns associated with new technologies and devices for oral macromolecule delivery.

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.

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.

Development and Characterisation of Gastroretentive Solid Dosage Form Based on Melt Foaming

Dosage forms with increased gastric residence time are promising tools to increase bioavailability of drugs with narrow absorption window. Low-density floating formulations could avoid gastric emptying; therefore, sustained drug release can be achieved. Our aim was to develop a new technology to produce low-density floating formulations by melt foaming. Excipients were selected carefully, with the criteria of low gastric irritation, melting range below 70°C and well-known use in oral drug formulations. PEG 4000, Labrasol and stearic acid type 50 were used to create metronidazole dispersion which was foamed by air on atmospheric pressure using in-house developed apparatus at 53°C. Stearic acid was necessary to improve the foamability of the molten dispersion. Additionally, it reduced matrix erosion, thus prolonging drug dissolution and preserving hardness of the moulded foam. Labrasol as a liquid solubiliser can be used to increase drug release rate and drug solubility. Based on the SEM images, metronidazole in the molten foam remained in crystalline form. MicroCT scans with the electron microscopic images revealed that the foam has a closed-cell structure, where spherical voids have smooth inner wall, they are randomly dispersed, while adjacent voids often interconnected with each other. Drug release from all compositions followed Korsmeyer-Peppas kinetic model. Erosion of the matrix was the main mechanism of the release of metronidazole. Texture analysis confirmed that stearic acid plays a key role in preserving the integrity of the matrix during dissolution in acidic buffer. The technology creates low density and solid matrix system with micronsized air-filled voids.

Intestinal permeation enhancers for oral peptide delivery

Intestinal permeation enhancers (PEs) are one of the most widely tested strategies to improve oral delivery of therapeutic peptides. This article assesses the intestinal permeation enhancement action of over 250 PEs that have been tested in intestinal delivery models. In depth analysis of pre-clinical data is presented for PEs as components of proprietary delivery systems that have progressed to clinical trials. Given the importance of co-presentation of sufficiently high concentrations of PE and peptide at the small intestinal epithelium, there is an emphasis on studies where PEs have been formulated with poorly permeable molecules in solid dosage forms and lipoidal dispersions.

Dual-functionalisation of gelatine nanoparticles with an anticancer platinum(ii)–bisphosphonate complex and mineral-binding alendronate

Mineral-binding gelatine nanoparticles can be loaded with tailored amounts of anticancer molecules, which may benefit the development of bone-seeking carriers for targeted delivery of drugs to treat bone tumours.

Oral drug delivery systems using chemical conjugates or physical complexes

Oral delivery of therapeutics is extremely challenging. The digestive system is designed in a way that naturally allows the degradation of proteins or peptides into small molecules prior to absorption. For systemic absorption, the intact drug molecules must traverse the impending harsh gastrointestinal environment. Technologies, such as enteric coating, with oral dosage formulation strategies have successfully provided the protection of non-peptide based therapeutics against the harsh, acidic condition of the stomach. However, these technologies showed limited success on the protection of therapeutic proteins and peptides. Importantly, inherent permeability coefficient of the therapeutics is still a major problem that has remained unresolved for decades. Addressing this issue in the context, we summarize the strategies that are developed in enhancing the intestinal permeability of a drug molecule either by modifying the intestinal epithelium or by modifying the drug itself. These modifications have been pursued by using a group of molecules that can be conjugated to the drug molecule to alter the cell permeability of the drug or mixed with the drug molecule to alter the epithelial barrier function, in order to achieve the effective drug permeation. This article will address the current trends and future perspectives of the oral delivery strategies.

Preparation and characterization of superporous hydrogel based on different polymers

Introduction:

Superporous hydrogel (SPH) swells very rapidly in a shorter period of time to an equilibrium size and contains highly porous structure.

Aim:

The synthesis of SPH of poly (acrylamide-co-acrylic acid) and its composites viz. Ac-Di-Sol and polyvinylpyrollidone (PVP) was carried out by solution polymerization.

Materials and Methods:

The SPH and SPH composites (SPHCs) were characterized by measurement of apparent density, porosity, swelling, mechanical strength, and scanning electron microscopy (SEM) studies.

Results:

FTIR studies confirmed the existence of acrylamide and acrylic acid in SPH. In distilled water SPH showed tremendous increase in equilibrium swelling capacity with conventional SPH as compared to its SPHCs of Ac-Di-Sol and PVP due to the increased in physical cross-linking network, respectively. The presence of Ac-Di-Sol and PVP in SPHCs increased the mechanical strength as compared to conventional SPH which is suitable for gastric retention. SEM pictures clearly indicated the formation of interconnected pores and capillary channels.

Conclusion:

The amount and type of polymers used affect almost all the characterization parameters of SPHs, and hence, depending upon the applications perspective such polymers could be used in drug delivery systems, successfully.

Controlled synthesis of radiolabelled amine methacrylate water-soluble polymers with end-groups of varying hydrophobicity and studies of adsorption behaviour

Radioactive initiators of increasing hydrophobicity, including fluorescent initiators, have been used to conduct the ambient ATRP of poly(2-(diethylamino)ethyl methacrylate) and the behaviour of the resultant polymers has been monitored with respect to surface adsorption using radio-techniques; considerable effects of end group type were observed.

Drug delivery applications for superporous hydrogels

INTRODUCTION

Considerable advances have been made to hydrogels with the development of faster swelling superporous hydrogels (SPHs). These new-generation hydrogels have large numbers of interconnected pores, giving them the capacity to absorb large amounts of water at an accelerated rate. This gives SPHs the ability to be used in a variety of novel drug delivery applications, such as gastric retention and peroral intestinal delivery of proteins and peptides.

AREAS COVERED

This review focuses on the applications of SPHs for drug transport and targeted drug therapies, as well as the characteristics and historical advancements made to SPH synthesis as it pertains to drug delivery. Manufacturing considerations and challenges that must be overcome are also discussed, such as scale-up, biocompatibility and safety.

EXPERT OPINION

Modern SPHs have high swelling and high mechanical strength making them suitable for many diverse pharmaceutical and biomedical applications. However, demonstrative preclinical animal studies still need to be confirmed in human trials, to further address safety issues and confirm therapeutic success when using SPHs as platforms for drug delivery. The focus of forthcoming applications of SPHs is likely to be in the area of oral site-specific delivery and regenerative medicine.

Chitosan superporous hydrogel composite-based floating drug delivery system: A newer formulation approach

OBJECTIVE

In this study efforts have been made to design a drug delivery system based on a superporous hydrogel composite, for floating and sustained delivery of Ranitidine hydrochloride.

MATERIALS AND METHODS

The characterization studies were performed by the measurement of apparent density, porosity, swelling studies, mechanical strength studies, and scanning electron microscopy studies. The prepared formulation was evaluated for buoyant behavior, in vitro drug release, kinetics of drug release, and stability. The release profile of Ranitidine hydrochloride was investigated by changing the release retardant polymer in the formulation. To ascertain the kinetics of drug release, the drug release profiles were fitted to mathematical models that included zero-order, first-order, Higuchi, Hixson-Crowell, Korsmeyer-Peppas, Weibull, and Hopfenberg models.

RESULTS

Scanning electron microscopy images clearly indicated the formation of interconnected pores and capillary channels, and cross-linked Chitosan molecules were observed around the peripheries of the pores. The prepared drug delivery system floated and delivered the Ranitidine hydrochloride for about 17 hours. The in vitro drug release from the proposed system was best explained by the Korsmeyer-Peppas model. The values of the diffusion exponent in the Korsmeyer-Peppas model ranged between 0.47 ± 0.02 and 0.66 ± 0.02, which appeared to indicate a coupling of the diffusion and erosion mechanisms, anomalous non-Fickian transport.

CONCLUSION

It was concluded that the proposed floating drug delivery system, based on the superporous hydrogel composite containing Chitosan as a composite material, is promising for stomach-specific delivery of Ranitidine hydrochloride.

Current challenges in non-invasive insulin delivery systems: a comparative review

The quest to eliminate the needle from insulin delivery and to replace it with non- or less-invasive alternative routes has driven rigorous pharmaceutical research to replace the injectable forms of insulin. Recently, various approaches have been studied involving many strategies using various technologies that have shown success in delivering insulin, which are designed to overcome the inherent barriers for insulin uptake across the gastrointestinal tract, mucosal membranes and skin. This review examines some of the many attempts made to develop alternative, more convenient routes for insulin delivery to avoid existing long-term dependence on multiple subcutaneous injections and to improve the pharmacodynamic properties of insulin. In addition, this article concentrates on the successes in this new millennium in developing potential non-invasive technologies and devices, and on major new milestones in modern insulin delivery for the effective treatment of diabetes.

Recent developments in superporous hydrogels

Superporous hydrogels (SPHs) were originally developed as a novel drug delivery system to retain drugs in the gastric medium. These systems should instantly swell in the stomach and maintain their integrity in the harsh stomach environment, while releasing the pharmaceutical active ingredient. For years, the synthetic features and properties of these SPH materials have been modified and improved to meet the requirements for gastric retention applications. Furthermore, an instant swelling hydrogel has also shown potential application for peroral intestinal peptide and protein absorption. This review discusses the formulation, characterization, properties and applications of these polymers.

Bioavailability of riboflavin from a gastric retention formulation

A gastric retention formulation (GRF) made of naturally occurring carbohydrate polymers and containing riboflavin was tested in vitro for swelling and dissolution characteristics as well as in fasting dogs for gastric retention. The bioavailability of riboflavin, a drug with a limited absorption site in the upper small intestine, from the GRF was studied in fasted healthy humans and compared to an immediate release formulation. It was found that when the GRF is dried and immersed in gastric juice it swells rapidly and releases its drug content in a zero-order fashion for a period of 24 h. In vivo studies in dogs showed that a rectangular shaped GRF stayed in the stomach of fasted dogs for more than 9 h, then disintegrated and reached the colon in 24 h. Endoscopic studies in dogs showed that the GRF hydrates and swells back to about 75% of its original size in 30 min. These in vivo results correlated with in vitro results. Pharmacokinetic parameters determined from urinary excretion data from six human subjects under fasting conditions showed that bioavailability depended on the size of the GRF. The biostudy indicated that bioavailability of riboflavin from a large size GRF was more than triple that measured after administration of an immediate release formulation. Deconvolved input functions from biostudy data suggest that the large size GRF stayed in the stomach for about 15 h.

Gastrointestinal transit and mucoadhesive characteristics of complexation hydrogels in rats

The aim of this study was to investigate the gastrointestinal (GI) transit and mucoadhesive properties of complexation hydrogels, poly(methacrylic acid-grafted-ethylene glycol). The fluorescent labeled complexation hydrogels containing different molar ratios of methacrylic acid/ethylene glycol and different particle diameters were synthesized by free radical solution polymerization. The GI transit profiles of microparticles after oral administration to rats were evaluated by determining the polymer remaining in the stomach and the small intestine. Moreover, the mucoadhesion to the duodenal mucosa was evaluated by an in situ perfusion method. The ethylene glycol content and particle size of the hydrogels influenced significantly the GI transit and mucoadhesive capacities. The microparticles composed of polymers prepared from 1:1 ratio of methacrylic acid/ethylene glycol and having diameters of <53 microm showed the strongest mucoadhesive capacity. These findings indicated that the hydrogels may be a promising tool for improving oral bioavailability of various drugs, which are poorly absorbed from the GI tract.

Are chitosan formulations mucoadhesive in the human small intestine?

Rapid passage through the proximal intestine can result in the low bioavailability of a drug substance with site-specific absorption characteristics in the upper gastrointestinal tract. To overcome this, there is increasing interest in developing gastro-retentive formulations and/or formulations that linger in the proximal parts of the small intestine, e.g. by using mucoadhesive polymers as excipients in formulations. In our recent study, we used neutron activation-based gamma scintigraphy to evaluate the gastro-retentive properties of formulations containing chitosan (Mw 150 kDa) in man. At the same time, we had an opportunity to monitor the transit of the formulations (40 or 95% of chitosan) in the small intestine. Gamma scintigraphic investigations revealed that although the chitosan studied had exhibited marked mucoadhesive capacities in vitro, retention of the chitosan formulations in the upper gastrointestinal tract was not sufficiently reproducible and the duration of retention was relatively short. In 3 volunteers out of 10, the formulation adhered to the gastric mucosa (retention times varied from 1.25 to 2.5 h) and in two volunteers to the upper small intestine (approximate retention time 45 min). In one case, the formulation adhered to the oesophagus. The system failed to increase the bioavailability of furosemide, a drug site-specifically absorbed in the upper gastrointestinal tract. As far as the kind of formulation studied is concerned, preparation of a system that is site-specific to the stomach and/or the upper small intestine seems difficult if the proposed mechanism of action is mucoadhesion. The results suggest that other mechanisms of action should also be studied.

Gastrointestinal patch systems for oral drug delivery

Gastrointestinal patch systems with integrated multifunctions could surmount the challenges associated with conventional drug delivery. Several gastrointestinal patch systems provide bioadhesion, drug protection and unidirectional release. This combination of function could improve the overall oral bioavailability of large molecules that can currently be delivered only by injection, for example, epoetin-alpha and granulocyte-colony-stimulating factor, which are commonly used to treat chemotherapy-associated anemia and leukopenia, respectively. Furthermore, self-regulated release and cell-specific targeting provide additional 'smart' characteristics to this innovative therapeutic platform.