Comparative in vivo mucoadhesion studies of thiomer formulations using magnetic resonance imaging and fluorescence detection

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.

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.

Ocular drug delivery to the anterior segment using nanocarriers: A mucoadhesive/mucopenetrative perspective

There is a growing demand for effective treatments for ocular conditions that improve patient compliance and reduce side-effects. While methods such as implants and injections have proven effective, topical administration remains the method of choice for the delivery of therapeutics to the anterior segment of the eye. However, topical administration suffers from multiple drawbacks including low bioavailability of the target therapeutic, systemic toxicity, and the requirement for high therapeutic doses due to the effective clearance mechanisms that exist in the eye. Nanoparticles that have tunable mucoadhesion and/or mucopenetration offer outstanding potential to overcome the anatomical and physiological barriers present to improve ocular bioavailability, reduce toxicity, and increase ocular retention, among other benefits. The current review highlights recent advances in the field of developing nanocarriers with tunable mucoadhesion and mucopenetration for drug delivery to the eye.

Significant biopolymers and their applications in buccal mediated drug delivery

Considerable research exercises have been directed towards the development of efficient and safe drug delivery systems. Various materials are used in different pharmaceutical formulations for the development of efficient drug delivery systems in the treatment of disease. Biopolymers are a choice of research as an excipient delivery system due to their biodegradability, low toxicity, safe, stable, and renewable nature. Biopolymers are naturally occurring polymers or polymer matrix composites, that are extracted from animals, bacteria, fungi, and plants. Cellulose, starches are carbohydrate-based polymers, and wool, silk, gelatin, and collagen are protein-based biopolymers. Biopolymers are obtained from various sources but biopolymers, that belong to the carbohydrate origin, have been found very promising in drug delivery through various routes. The review mainly focuses on the biopolymers currently in use for buccal-mediated pharmaceutical drug delivery systems because the buccal route is an efficient drug delivery system that allows direct systemic circulation of drugs. It also prevents the hydrolysis of the drug molecule in the gastrointestinal tract and thus increases the bioavailability of the drug. The present review discusses the overview of other drug delivery routes, challenges with conventional drug delivery systems, pharmaceutical applications of some biopolymers used in buccal drug delivery systems, that are published recently, currently in use, or used over the past decade.

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.

A transferrin receptor-binding mucoadhesive elastin-like recombinamer: In vitro and in vivo characterization

The development of mucoadhesive materials is of great interest and is also a major challenge. Being adsorption sites, mucosae are suitable targets for drug delivery, but as defensive barriers they are complex biological surfaces to interact with, mainly due to their protective mucus layer. As such, first- and second-generation mucoadhesives focused on material-mucus interactions, whereas the third generation of mucoadhesives introduced structural motifs that are able to interact with the cells beneath the mucus layer. The combination of different prerequisites (water solubility, soft gel formation at body temperature and able to interact with the mucus) in a single molecule is easily achieved using elastin-like recombinamers (ELRs) given their multiple block design. Moreover, we have been able to introduce a short amino-acid sequence known as T7 that is able to bind to transferrin receptors in the epithelial cell layer. The T7 sequence enhances the cell-binding properties of the mucoadhesive ELR (MELR), as demonstrated using a Caco-2 epithelial cell model. In vivo experiments confirmed the mucoadhesive properties found in vitro. STATEMENT OF SIGNIFICANCE: The development of a mucoadhesive material is a major challenge. Mucosae are suitable targets for drug delivery, but as defense barriers, they are complex surfaces to interact with. In this work we report the first ELR that combines different functional blocks, in a single molecule, which provide it with the properties of soft-gel forming at body temperature and being able of efficiently adhering to the mucus layer of mucosas, as well as to the underlying epithelial cell layer, as demonstrated in vitro and in vivo. The rationally designed materials presented in this work sets the basis for developing ELR-based, mucosa-directed drug delivery systems, which could improve patient's compliance, enhancing drug retention at the mucosal site.

Comparative Analysis of Microbicidal and Anti-inflammatory Properties of Novel Taurine Bromamine Derivatives and Bromamine T

Taurine, the most abundant free amino acid in leukocyte cytosol traps hypohalous acids (HOCl and HOBr) to produce N-chlorotaurine (taurine chloramine, NCT and N-bromotaurine (taurine bromamine, Tau-NHBr,) respectively. Both haloamines show anti-inflammatory and antimicrobial properties. However, the therapeutic applicability of Tau-NHBr is limited due to its relatively poor stability. To overcome this disadvantage, we have synthesized the stable N-bromotaurine compounds N-monobromo-2,2-dimethyltaurine (Br-612) and N-dibromo-2,2-dimethyltaurine (Br-422). The aim of this study was to compare anti-inflammatory and microbicidal properties of Br-612 and Br-422 with that of Tau-NHBr and bromamine T (BAT). We have shown that all the tested compounds show similar anti-inflammatory properties. Importantly, the stable N-bromotaurine compounds exerted even stronger microbicidal activity than Tau-NHBr. Finally, for the purpose of topical application of these compounds we have developed a carbomer-based bioadhesive solid dosage form of BAT and Br-612, featuring sustained release of the active substance.

Application of a Compact Magnetic Resonance Imaging System with 1.5 T Permanent Magnets to Visualize Release from and the Disintegration of Capsule Formulations in Vitro and in Vivo

Although magnetic resonance imaging (MRI) has potential in assessments of formulations, few studies have been conducted because of the size and expense of the instrument. In the present study, the processes of in vitro and in vivo release in a gelatin capsule formulation model were visualized using a compact MRI system with 1.5 T permanent magnets, which is more convenient than the superconducting MRI systems typically used for clinical and experimental purposes. A Gd-chelate of diethylenetriamine-N,N,N',N″,N″-pentaacetic acid, a contrast agent that markedly enhances proton signals via close contact with water, was incorporated into capsule formulations as a marker compound. In vitro experiments could clearly demonstrate the preparation-dependent differences in the release/disintegration of the formulations. In some preparations, the penetration of water into the formulation and generation of bubbles in the capsule were also observed prior to the disintegration of the formulation. When capsule formulations were orally administered to rats, the release of the marker into the stomach and its transit to the duodenum were visualized. These results strongly indicate that the compact MRI system is a powerful tool for pharmaceutical studies.

Spray-dried mucoadhesives for intravesical drug delivery using N-acetylcysteine- and glutathione-glycol chitosan conjugates

This work describes N-acetylcysteine (NAC)- and glutathione (GSH)-glycol chitosan (GC) polymer conjugates engineered as potential platform useful to formulate micro-(MP) and nano-(NP) particles via spray-drying techniques. These conjugates are mucoadhesive over the range of urine pH, 5.0-7.0, which makes them advantageous for intravesical drug delivery and treatment of local bladder diseases. NAC- and GSH-GC conjugates were generated with a synthetic approach optimizing reaction times and purification in order to minimize the oxidation of thiol groups. In this way, the resulting amount of free thiol groups immobilized per gram of NAC- and GSH-GC conjugates was 6.3 and 3.6mmol, respectively. These polymers were completely characterized by molecular weight, surface sulfur content, solubility at different pH values, substitution and swelling degree. Mucoadhesion properties were evaluated in artificial urine by turbidimetric and zeta (ζ)-potential measurements demonstrating good mucoadhesion properties, in particular for NAC-GC at pH 5.0. Starting from the thiolated polymers, MP and NP were prepared using both the Büchi B-191 and Nano Büchi B-90 spray dryers, respectively. The resulting two formulations were evaluated for yield, size, oxidation of thiol groups and ex-vivo mucoadhesion. The new spray drying technique provided NP of suitable size (<1μm) for catheter administration, low degree of oxidation, and sufficient mucoadhesion property with 9% and 18% of GSH- and NAC-GC based NP retained on pig mucosa bladder after 3h of exposure, respectively.

STATEMENT OF SIGNIFICANCE

The aim of the present study was first to optimize the synthesis of NAC-GC and GSH-GC, and preserve the oxidation state of the thiol moieties by introducing several optimizations of the already reported synthetic procedures that increase the mucoadhesive properties and avoid pH-dependent aggregation. Second, starting from these optimized thiomers, we studied the feasibility of manufacturing MP and NP by spray-drying techniques. The aim of this second step was to produce mucoadhesive drug delivery systems of adequate size for vesical administration by catheter, and comparable mucoadhesive properties with respect to the processed polymers, avoiding thiolic oxidation during the formulation. MP with acceptable size produced by spray-dryer Büchi B-191 were compared with NP made with the apparatus Nano Büchi B-90.

Coated minispheres of salmon calcitonin target rat intestinal regions to achieve systemic bioavailability: Comparison between intestinal instillation and oral gavage

Achieving oral peptide delivery is an elusive challenge. Emulsion-based minispheres of salmon calcitonin (sCT) were synthesized using single multiple pill (SmPill®) technology incorporating the permeation enhancers (PEs): sodium taurodeoxycholate (NaTDC), sodium caprate (C10), or coco-glucoside (CG), or the pH acidifier, citric acid (CA). Minispheres were coated with an outer layer of Eudragit® L30 D-55 (designed for jejunal release) or Surelease®/Pectin (designed for colonic release). The process was mild and in vitro biological activity of sCT was retained upon release from minispheres stored up to 4months. In vitro release profiles suggested that sCT was released from minispheres by diffusion through coatings due to swelling of gelatin and the polymeric matrix upon contact with PBS at pH6.8. X-ray analysis confirmed that coated minispheres dissolved at the intended intestinal region of rats following oral gavage. Uncoated minispheres at a dose of ~2000I.U.sCT/kg were administered to rats by intra-jejunal (i.j.) or intra-colonic (i.c.) instillation and caused hypocalcaemia. Notable sCT absolute bioavailability (F) values were: 5.5% from minispheres containing NaTDC (i.j), 17.3% with CG (i.c.) and 18.2% with C10 (i.c.). Coated minispheres administered by oral gavage at threefold higher doses also induced hypocalcaemia. A highly competitive F value of 2.7% was obtained for orally-administered sCT-minispheres containing CG (45μmol/kg) and coated with Eudragit®. In conclusion, the SmPill® technology is a potential dosage form for several peptides when formulated with PEs and coated for regional delivery. PK data from instillations over-estimates oral bioavailability and poorly predicts rank ordering of formulations.

Spray Dried Chitosan Microparticles for Intravesical Delivery of Celecoxib: Preparation and Characterization

PURPOSE

Chitosan microparticles containing celecoxib (CB), were developed as chemoprevention of bladder cancer. Furthermore two inclusion complexes of CB with methyl-β-cyclodextrin (C1 and C2) were prepared to improve the solubility of the drug.

METHODS

C1 and C2 were obtained by freeze-drying and characterized in the solid state and in solution. Microparticles loaded with CB or C1 or C2 were prepared by spray drying and fully characterized.

RESULTS

The yield and encapsulation efficiencies of microparticles depended by both the viscosity and the presence of the inclusion complex in the feed medium nebulised. Generally, the microparticles exhibited a spherical shape with mean diameter of approximately 2 μm which was compatible with local intravesical administration using a catheter. The CB release studies from the microparticles allowed us to identify both immediate release systems (microparticles including the complexes) and prolonged release systems (microparticles including CB alone). The latter exhibited good adhesion to the bladder mucosa, as highlighted by a mucoadhesion study. Histological studies revealed a desquamation of the superficial cells when the bladder mucosa was treated with microparticles loaded with CB, while the morphology of the urothelium did not change when it was treated with microparticles loaded with the inclusion complex.

CONCLUSION

A new CB intravesical formulation than can easily be administered with a catheter and is able to release the drug at the target site for several hours was realized. This new delivery system could be a good alternative to classic oral CB administration.

Oral transmucosal drug delivery for pediatric use

The formulation of medicines for children remains a challenge. An ideal pediatric formulation must allow accurate dose administration and be in a dosage form that can be handled by the target age group. It is also important to consider the choices and the amount of excipients used in the formulation for this vulnerable age group. Although oral formulations are generally acceptable to most pediatric patients, they are not suitable for drugs with poor oral bioavailability or when a rapid clinical effect is required. In recent years, oral transmucosal delivery has emerged as an attractive route of administration for pediatric patients. With this route of administration, a drug is absorbed through the oral mucosa, therefore bypassing hepatic first pass metabolism and thus avoiding drug degradation or metabolism in the gastrointestinal tract. The high blood flow and relatively high permeability of the oral mucosa allow a quick onset of action to be achieved. It is a simple and non-invasive route of drug administration. However, there are several barriers that need to be overcome in the development of oral transmucosal products. This article aims to provide a comprehensive review of the current development of oral transmucosal delivery specifically for the pediatric population in order to achieve systemic drug delivery. The anatomical and physiological properties of the oral mucosa of infants and young children are carefully examined. The different dosage forms and formulation strategies that are suitable for young patients are discussed.

Mucoadhesive intestinal devices for oral delivery of salmon calcitonin

One of the major challenges faced by therapeutic polypeptides remains their invasive route of delivery. Oral administration offers a potential alternative to injections; however, this route cannot be currently used for peptides due to their limited stability in the stomach and poor permeation across the intestine. Here, we report mucoadhesive devices for oral delivery that are inspired by the design of transdermal patches and demonstrate their capabilities in vivo for salmon calcitonin (sCT). The mucoadhesive devices were prepared by compressing a polymeric matrix containing carbopol, pectin and sodium carboxymethylcellulose (1:1:2), and were coated on all sides but one with an impermeable and flexible ethyl cellulose (EC) backing layer. Devices were tested for in vitro dissolution, mucoadhesion to intestinal mucosa, enhancement of drug absorption in vitro (Caco-2 monolayer transport) and in vivo in rats. Devices showed steady drug release with ≈75% cumulative drug released in 5h. Devices also demonstrated strong mucoadhesion to porcine small intestine to withstand forces up to 100 times their own weight. sCT-loaded mucoadhesive devices exhibited delivery of sCT across Caco-2 monolayers and across the intestinal epithelium in vivo in rats. A ≈52-fold (pharmacokinetic) and ≈44-fold (pharmacological) enhancement of oral bioavailability was observed with mucoadhesive devices when compared to direct intestinal injections. Oral delivery of devices in enteric coated capsules resulted in significant bioavailability enhancement.

Toward mucoadhesive hydrogel formulations for the management of xerostomia: the physicochemical, biological, and pharmacological considerations

Although hydrogel formulations that may be applied to many mucosal surfaces are now readily accessible, little research effort has been concentrated on the development of systems that may be usefully employed for the prolonged hydration of the oral cavity. To this end, and set within the context of oral care in general, this review considers the requirements for the design of hydrogel formulations with an affinity for buccal cells and details methods for evaluating the performance of these formulations as treatments for the management of xerostomia.

Mucosa-plate for direct evaluation of mucoadhesion of drug carriers

The method to prepare mucosa-plates, glass slides covalently coated with mucin, is demonstrated. The use of the plate to evaluate mucoadhesion of nanocarriers made from different four polymeric materials, N-succinylchitosan (NS-chitosan), alginate (ALG), ethylcellulose (EC), and a blend of EC and methylcellulose (EC/MC), was demonstrated. While different mucoadhesion of the four carriers could be detected using mucosa-plate, the conventional viscosity measurement could not differentiate their mucin-binding ability. ALG and NS-chitosan nanospheres showed the best attachment to the mucosa-plate compared to the EC/MC and EC spheres. Capsaicin, a model hydrophobic drug, was loaded into the carriers and the ability of the different polymeric carriers to retain capsaicin at the stomach tissue was compared using an ex vivo fresh porcine stomach assay. Ability to retain capsaicin at the stomach tissue correlated well with binding affinity toward the mucosa-plate and the loading capacity of the carriers.

Hydrogels in mucosal delivery

The concept of mucoadhesion and the molecular design requirements for the synthesis of mucoadhesive agents are both well understood and, as a result, hydrogel formulations that may be applied to mucosal surfaces are readily accessible. Nanosized hydrogel systems that make use of biological recognition or targeting motifs, by reacting to disease-specific environmental triggers and/or chemical signals to affect drug release, are now emerging as components of a new generation of therapeutics that promise improved residence time, faster response to stimuli and triggered release.

Engineered nanoparticles for biomolecular imaging

In recent years, the production of nanoparticles (NPs) and exploration of their unusual properties have attracted the attention of physicists, chemists, biologists and engineers. Interest in NPs arises from the fact that the mechanical, chemical, electrical, optical, magnetic, electro-optical and magneto-optical properties of these particles are different from their bulk properties and depend on the particle size. There are numerous areas where nanoparticulate systems are of scientific and technological interest, particularly in biomedicine where the emergence of NPs with specific properties (e.g. magnetic and fluorescence) for contrast agents can lead to advancing the understanding of biological processes at the biomolecular level. This review will cover a full description of the physics of various imaging methods, including MRI, optical techniques, X-rays and CT. In addition, the effect of NPs on the improvement of the mentioned non-invasive imaging methods will be discussed together with their advantages and disadvantages. A detailed discussion will also be provided on the recent advances in imaging agents, such as fluorescent dye-doped silica NPs, quantum dots, gold- and engineered polymeric-NPs, superparamagnetic iron oxide NPs (SPIONs), and multimodal NPs (i.e. nanomaterials that are active in both MRI and optical methods), which are employed to overcome many of the limitations of conventional contrast agents (e.g. gadolinium).

Development of a mucoadhesive nanoparticulate drug delivery system for a targeted drug release in the bladder

PURPOSE

Purpose of the present study was the development of a mucoadhesive nanoparticulate drug delivery system for local use in intravesical therapy of interstitial cystitis, since only a small fraction of drug actually reaches the affected site by conventional treatment of bladder diseases via systemic administration.

METHODS

Chitosan-thioglycolic acid (chitosan-TGA) nanoparticles (NP) and unmodified chitosan NP were formed via ionic gelation with tripolyphosphate (TPP). Trimethoprim (TMP) was incorporated during the preparation process of NP. Thereafter, the mucoadhesive properties of NP were determined in porcine urinary bladders and the release of TMP among simulated conditions with artificial urine was evaluated.

RESULTS

The particles size ranged from 183nm to 266nm with a positive zeta potential of +7 to +13mV. Under optimized conditions the encapsulation efficiency of TMP was 37%. The adhesion of prehydrated chitosan-TGA NP on the urinary bladder mucosa under continuous urine voiding was 14-fold higher in comparison to unmodified chitosan NP. Release studies indicated a more sustained TMP release from covalently cross linked particles in comparison to unmodified chitosan-TPP NP over a period of 3h in artificial urine at 37°C.

CONCLUSION

Utilizing the method described here, chitosan-TGA NP might be a useful tool for local intravesical drug delivery in the urinary bladder.

Bioadhesive microspheres for bioavailability enhancement of raloxifene hydrochloride: formulation and pharmacokinetic evaluation

Raloxifene hydrochloride (R-HCl), a BCS class II drug, remains a mainstay in the prevention and pharmacologic therapy of osteoporosis. Its absolute bioavailability, however, is 2% due to poor solubility and extensive first pass metabolism. The present study describes two simultaneous approaches to improve its bioavailability, complexation of R-HCl with cyclodextrin(s), and formulation of mucoadhesive microspheres of the complex using different proportions of carbopol and HPMC. Microspheres were pale yellow in color, free-flowing, spherical, and porous in outline. The particle size ranged between 3 and 15 μm, and entrapment efficiency was found to be within 81.63% to 87.73%. A significant improvement in the solubility of R-HCl was observed, and it differed with the combination of excipients used. X-ray diffraction and differential scanning calorimetry studies revealed that enhancement in drug solubility was resulted due to a change in its crystallinity within the formulation. Microspheres possessed remarkable mucoadhesion and offered controlled drug release, lasting up to 24 h. They produced a sharp plasma concentration-time profile of R-HCl within 30 min post-administration to Wistar rats. [AUC](0-24 h) was found to be 1,722.34 ng h/ml, and it differed significantly to that of pure drug powder (318.28 ng h/ml). More than fivefold increase in AUC and more than twofold increase in MRT were observed. FT-IR studies evidenced no interaction among drug and excipients. The results of this study showed that mucoadhesive microspheres could be a viable approach to improve the pharmacokinetic profile of R-HCl.

The impact of vehicles on the mucoadhesive properties of orally administrated nanoparticles: a case study with chitosan-4-thiobutylamidine conjugate

The aim of this study was to evaluate the impact of various vehicles on mucoadhesive properties of thiolated chitosan nanoparticles both in vitro and in vivo. Nanoparticles (NPs) were prepared by in situ gelation technique followed by labeling with fluorescein diacetate. Comparative studies on mucoadhesion were done with these thiolated chitosan NPs and unmodified chitosan NPs (control). The obtained nanoparticles displayed a mean diameter of 164.2 ± 6.9 nm and a zeta potential of 21.5 ± 5 mV. In an in vitro adhesion study, unhydrated thiolated NPs adhered strongly to freshly excised porcine small intestine, which was more than threefold increase compared to the control. In contrast, in the presence of various vehicles (PEG 300, miglyol 840, PEG 6000, cremophor EL, and caprylic triglyceride), the mucoadhesive properties of thiolated NPs were comparatively weak. Thiolated NPs suspended in caprylic triglyceride, for example, had a percent mucoadhesion of 22.50 ± 5.35% on the mucosa. Furthermore, results from in vivo mucoadhesion studies revealed that the dry form of nanoparticles exhibits the strongest mucoadhesion, followed by nanoparticles suspended in PEG 300, miglyol, and 100 mM phosphate buffer, in that order. Three hours after administration, the gastrointestinal residence time of the dry form of thiolated NPs was up to 3.6-fold prolonged. These findings should contribute to the design of highly effective oral mucoadhesive nanoparticulate drug delivery systems.

Gastro intestinal tracking and gastric emptying of solid dosage forms in rats using X-ray imaging

The aim of this research was to study the gastrointestinal transit and gastric emptying of non-disintegrating solid dosage forms in rats using X-ray imaging. Commercial gelatin minicapsules were filled with barium sulfate and enterically coated using Eudragit S100. The capsules were administered orally to rats followed by a solution of iodine based contrast agent iopromide. Images were obtained using a standard X-ray camera and digital film processing. Capsules were followed through the GI tract from the stomach to the small intestine, cecum and large intestine and the capsule location could be easily identified. Gastric emptying of different sized capsules was studied. The effect of fasting and time of administration on gastric retention was also studied. It was found that shortened capsules of 3.5 and 4.8mm length were emptied from the stomach whereas the commercial length 7.18mm capsules were retained. Surprisingly, 2.5h post administration more rats retained the capsules in the stomach in the fasted state than in the fed state. We found that X-ray imaging can be used for simple visualization and localization of solid dosage forms in rats in the fed state using shortened commercial minicapsules on rats.

In vivo determination of the time and location of mucoadhesive drug delivery systems disintegration in the gastrointestinal tract

OBJECTIVE

The objective of this study was to use magnetic resonance imaging (MRI) to detect the time when and the location at which orally delivered mucoadhesive drugs are released.

MATERIALS AND METHODS

Drug delivery systems comprising tablets or capsules containing a mucoadhesive polymer were designed to deliver the polymer to the intestine in dry powder form. Dry Gd-DTPA [diethylenetriaminepentaacetic acid gadolinium(III) dihydrogen salt hydrate] powder was added to the mucoadhesive polymer, resulting in a susceptibility artifact that allows tracking of the application forms before their disintegration and that gives a strong positive signal on disintegration. Experiments were performed with rats using T(1)-weighted spin-echo imaging on a standard 1.5-T MRI system.

RESULTS

The susceptibility artifact produced by the dry Gd-DTPA powder in tablets or capsules was clearly visible within the stomach of the rats and could be followed during movement towards the intestine. Upon disintegration, a strong positive signal was unambiguously observed. The time between ingestion and observation of a positive signal was significantly different for different application forms. Quantification of the remaining mucoadhesive polymer in the intestine 3 h after observed release showed significant differences in mucoadhesive effectiveness.

CONCLUSION

MRI allows detection of the exact time of release of the mucoadhesive polymer in vivo, which is a prerequisite for a reliable quantitative comparison between different application forms.

Thiomers: forms, functions and applications to nanomedicine

Thiolated polymers or designated thiomers are gained by immobilization of sulhydryl-bearing ligands on the polymeric backbone of well established polymers, such as chitosan and poly(acrylates). This functionalization leads to significantly improved properties compared with the corresponding unmodified polymers. Mucoadhesive properties are strongly improved by the formation of disulfide bonds between thiol groups of the thiomer and cysteine-rich glycoproteins of the mucus gel layer. Moreover, enzyme- and efflux-pump inhibiting, as well as significantly improved permeation-enhancing properties, are advantages of polymer thiolization. Thiomer micro- and nano-particlulate delivery systems can be generated via different techniques, such as in situ gelation and subsequent covalent crosslinking, radical emulsion polymerization, emulsification/solvent evaporation or air jet milling. As thiomer micro- and nano-particles were shown to exhibit the same features as thiolated polymers per se, they might be useful tools for the delivery of various types of challenging drugs.