Studies of chitosan/Kollicoat SR 30D film-coated tablets for colonic drug delivery

Microbiota-sensitive drug delivery systems based on natural polysaccharides for colon targeting

Colon targeting is an ongoing challenge, particularly for the oral administration of biological drugs or local treatment of inflammatory bowel disease (IBD). In both cases, drugs are known to be sensitive to the harsh conditions of the upper gastrointestinal tract (GIT) and, thus, must be protected. Here, we provide an overview of recently developed colonic site-specific drug delivery systems based on microbiota sensitivity of natural polysaccharides. Polysaccharides act as a substrate for enzymes secreted by the microbiota located in the distal part of GIT. The dosage form is adapted to the pathophysiology of the patient and, thus, a combination of bacteria-sensitive and time-controlled release or pH-dependent systems can be used for delivery.

In Vitro and In Vivo Evaluations of Berberine-Loaded Microparticles Filled In-House 3D Printed Hollow Capsular Device for Improved Oral Bioavailability

The low oral bioavailability, short biological half-life, high dose, and frequent dosing of berberine (BBR) contribute to its restricted clinical use despite its extensive pharmacological activity. Thus, the objective of this study was to formulate sustained-release microparticles (MPs) using a pH-independent release polymer and to evaluate their potential to improve the oral bioavailability of BBR. BBR loaded MPs were prepared using the emulsion crosslinking method and evaluated for particle size, circularity, morphology, entrapment efficiency, solid-state analysis, swelling index, and in vitro BBR release study fitted with different models of release kinetics. The MPs exhibited desired particle sizes ranges between 11.09-11.62 μm and were almost spherical in shape, as confirmed by the circularity value and micrographic images. A loss of BBR crystallinity was observed after encapsulation in MPs, as evident from various solid-state analyses. The final optimized batch (F3) showed highest % BBR entrapment efficiency value of 81.63% ± 4.9. The in vitro BBR release performance in both acidic and alkaline media showed the desired sustained release behavior from the crosslinked MPs, where the maximum BBR release was observed at alkaline pH, which is in accordance with the swelling study data. In the in vivo study, the oral absorption profiles of BBR from both pristine and MPs formats were investigated using in-house prototyped 3D printed hollow capsules as a unit dose carrier. In vivo data showed sustained and prolonged absorption behavior of BBR from MPs compared to their pristine counterparts, which resulted in a cumulative increment of relative oral bioavailability to mitigate the aforementioned issues related to BBR. Graphical Abstract.

Clinical translation of advanced colonic drug delivery technologies

Targeted drug delivery to the colon offers a myriad of benefits, including treatment of local diseases, direct access to unique therapeutic targets and the potential for increasing systemic drug bioavailability and efficacy. Although a range of traditional colonic delivery technologies are available, these systems exhibit inconsistent drug release due to physiological variability between and within individuals, which may be further exacerbated by underlying disease states. In recent years, significant translational and commercial advances have been made with the introduction of new technologies that incorporate independent multi-stimuli release mechanisms (pH and/or microbiota-dependent release). Harnessing these advanced technologies offers new possibilities for drug delivery via the colon, including the delivery of biopharmaceuticals, vaccines, nutrients, and microbiome therapeutics for the treatment of both local and systemic diseases. This review details the latest advances in colonic drug delivery, with an emphasis on emerging therapeutic opportunities and clinical technology translation.

The Use of Natural Materials in Film Coating for Controlled Oral Drug Release

BACKGROUND

Although synthetic materials have been used in film coating processes for drug delivery for many years, substantial studies on natural materials have also been conducted because of their biodegradable and unique properties.

METHODS

Because of the ability to form and modify films for controlled oral drug delivery, increasing attention has been shown to these materials in the design of film coating systems in recent research.

RESULTS

This review aims to provide an overview of natural materials focusing on film coating for oral delivery, specifically in terms of their classification and their combinations in film coating formulations for adjusting the desired properties for controlled drug delivery.

CONCLUSIONS

Discussing natural materials and their potential applications in film coating would benefit the optimization of processes and strategies for future utilization.

Microwave-assisted Preparation of Cross-linked Gelatin-Paracetamol Matrices: Optimization Using the D-optimal Design

Objectives

This study was conducted to assess the effect of microwave heating on the preparation of paracetamol cross-linked gelatin matrices by using the design of experiment (DoE) approach and explore the influence of the duration of microwave irradiation, the concentrations of crosslinker, and the amount of sodium bicarbonate (salt) on paracetamol release. These parameters were also compared with those of the matrices prepared via conventional heating.

Materials and Methods

Twenty gel matrices were prepared with different durations of microwave irradiation, amounts of maize, and concentrations of sodium bicarbonate as suggested by Design Expert (DX®). The percentage drug release, the coefficient of variance (CV) in release, and the mean dissolution time (MDT) were the properties explored in the designed experimentation.

Results

Target responses were dependent on microwave irradiation time, cross-linker amount, and salt concentration. Classical and microwave heating did not demonstrate statistically significant difference in modifying the percentage of drug released from the matrices. However, the CVs of microwave-assisted formulations were lower than those of the gel matrices prepared via classical heating. Thus, microwave heating produced lesser variations in drug release. The optimized gel matrices demonstrated that the observed percentage of drug release, CV, and MDT were within the prediction interval generated by DX®. The release mechanism of the matrix formulations followed the Peppas-Korsmeyer anomalous transport model.

Conclusion

The DoE-supported microwave-assisted approach could be applied to optimize the critical factors of drug release with less variation.

Local delivery of macromolecules to treat diseases associated with the colon

Current treatments for intestinal diseases including inflammatory bowel diseases, irritable bowel syndrome, and colonic bacterial infections are typically small molecule oral dosage forms designed for systemic delivery. The intestinal permeability hurdle to achieve systemic delivery from oral formulations of macromolecules is challenging, but this drawback can be advantageous if an intestinal region is associated with the disease. There are some promising formulation approaches to release peptides, proteins, antibodies, antisense oligonucleotides, RNA, and probiotics in the colon to enable local delivery and efficacy. We briefly review colonic physiology in relation to the main colon-associated diseases (inflammatory bowel disease, irritable bowel syndrome, infection, and colorectal cancer), along with the impact of colon physiology on dosage form design of macromolecules. We then assess formulation strategies designed to achieve colonic delivery of small molecules and concluded that they can also be applied some extent to macromolecules. We describe examples of formulation strategies in preclinical research aimed at colonic delivery of macromolecules to achieve high local concentration in the lumen, epithelial-, or sub-epithelial tissue, depending on the target, but with the benefit of reduced systemic exposure and toxicity. Finally, the industrial challenges in developing macromolecule formulations for colon-associated diseases are presented, along with a framework for selecting appropriate delivery technologies.

Design and preparation of a novel colon-targeted tablet of hydrocortisone

ABSTRACT The objective of this research was to design a new colon-targeted drug delivery system based on chitosan. The properties of the films were studied to obtain useful information about the possible applications of composite films. The composite films were used in a bilayer system to investigate their feasibility as coating materials. Tensile strength, swelling degree, solubility, biodegradation degree, Fourier transform infrared spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), Scanning electron microscope (SEM) investigations showed that the composite film was formed when chitosan and gelatin were jointly reacted jointly. The results showed that a 6:4 blend ratio was the optimal chitosan/gelatin blend ratio. In vitro drug release results indicated that the Eudragit- and chitosan/gelatin-bilayer coating system prevented drug release in simulated intestinal fluid (SIF) and simulated gastric fluid (SGF). However, the drug release from a bilayer-coated tablet in SCF increased over time, and the drug was almost completely released after 24 h. Overall, colon-targeted drug delivery was achieved by using a chitosan/gelatin complex film and a multilayer coating system.

Cyclodextrin complexes of reduced bromonoscapine in guar gum microspheres enhance colonic drug delivery

Here, we report improved solubility and enhanced colonic delivery of reduced bromonoscapine (Red-Br-Nos), a cyclic ether brominated analogue of noscapine, upon encapsulation of its cyclodextrin (CD) complexes in bioresponsive guar gum microspheres (GGM). Phase–solubility analysis suggested that Red-Br-Nos complexed with β-CD and methyl-β-CD in a 1:1 stoichiometry, with a stability constant (K_c) of 2.29 × 10³ M^–1 and 4.27 × 10³ M^–1. Fourier transforms infrared spectroscopy indicated entrance of an O–CH₂ or OCH₃–C₆H₄–OCH₃ moiety of Red-Br-Nos in the β-CD or methyl-β-CD cavity. Furthermore, the cage complex of Red-Br-Nos with β-CD and methyl-β-CD was validated by several spectral techniques. Rotating frame Overhauser enhancement spectroscopy revealed that the H_a proton of the OCH₃–C₆H₄–OCH₃ moiety was closer to the H₅ proton of β-CD and the H₃ proton of the methyl-β-CD cavity. The solubility of Red-Br-Nos in phosphate buffer saline (PBS, pH ∼ 7.4) was improved by ∼10.7-fold and ∼21.2-fold when mixed with β-CD and methyl-β-CD, respectively. This increase in solubility led to a favorable decline in the IC₅₀ by ∼2-fold and ∼3-fold for Red-Br-Nos−β-CD-GGM and Red-Br-Nos–methyl-β-CD-GGM formulations respectively, compared to free Red-Br-Nos−β-CD and Red-Br-Nos–methyl-β-CD in human colon HT-29 cells. GGM-bearing drug complex formulations were found to be highly cytotoxic to the HT-29 cell line and further effective with simultaneous continuous release of Red-Br-Nos from microspheres. This is the first study to showing the preparation of drug-complex loaded GGMS for colon delivery of Red-Br-Nos that warrants preclinical assessment for the effective management of colon cancer.

Design, Development, and Optimization of Sterculia Gum-Based Tablet Coated with Chitosan/Eudragit RLPO Mixed Blend Polymers for Possible Colonic Drug Delivery

The purpose of this study is to explore the possible applicability of Sterculia urens gum as a novel carrier for colonic delivery system of a sparingly soluble drug, azathioprine. The study involves designing a microflora triggered colon-targeted drug delivery system (MCDDS) which consists of a central polysaccharide core and is coated to different film thicknesses with blends of chitosan/Eudragit RLPO, and is overcoated with Eudragit L00 to provide acid and intestinal resistance. The microflora degradation property of gum was investigated in rat caecal medium. Drug release study in simulated colonic fluid revealed that swelling force of the gum could concurrently drive the drug out of the polysaccharide core due to the rupture of the chitosan/Eudargit coating in microflora-activated environment. Chitosan in the mixed film coat was found to be degraded by enzymatic action of the microflora in the colon. Release kinetic data revealed that the optimized MCDDS was fitted well into first-order model, and apparent lag time was found to be 6 hours, followed by Higuchi release kinetics. In vivo study in rabbits shows delayed T max, prolonged absorption time, decreased C max, and absorption rate constant (Ka), indicating a reduced systemic toxicity of the drug as compared to other dosage forms.

Design, development and optimization of oral colon targeted drug delivery system of azathioprine using biodegradable polymers

The present study was aimed at designing a microflora triggered colon targeted drug delivery system (MCDDS) based on swellable polysaccharide, Sterculia gum in combination with biodegradable polymers with a view to specifically deliver azathioprine in the colonic region for the treatment of IBD with reduced systemic toxicity. The microflora degradation properties of Sterculia gum was investigated in rat caecal phosphate buffer medium. The polysaccharide tablet cores were coated to different film thicknesses with blends of Eudragit RLPO and chitosan and overcoated with Eudragit L00 to provide acid and intestinal resistance. Swelling and drug release studies were carried out in simulated gastric fluid, SGF (pH 1.2), simulated intestinal fluid, SIF (pH 6.8) and simulated colonic fluid, SCF (pH 7.4 under anaerobic environment), respectively. Drug release study in SCF revealed that swelling force of the Sterculia gum could concurrently drive the drug out of the polysaccharide core due to the rupture of the chitosan/Eudargit coating in microflora activated environment. The degradation of chitosan was the rate-limiting factor for drug release in the colon. Drug release from the MCDDS was directly proportional to the concentration of the pore former (chitosan), but inversely related to the Eudragit RLPO coating thickness.

Encapsulation of Liposomes within pH Responsive Microspheres for Oral Colonic Drug Delivery

A novel liposome-in-microsphere (LIM) formulation has been created comprising drug-loaded liposomes within pH responsive Eudragit S100 microspheres. The liposomes contained the model drug 5-ASA and were coated with chitosan in order to protect them during encapsulation within the microspheres and to improve site-specific release characteristics. In vitro drug release studies showed that LIMs prevented drug release within simulated stomach and small intestine conditions with subsequent drug release occurring in large intestine conditions. The formulation therefore has potential for oral colonic drug delivery.

Chitosan films: crosslinking with EDTA modifies physicochemical and mechanical properties

The present study was aimed to develop chitosan-EDTA films and evaluate their physico-chemical and mechanical properties. The physical properties suggested lowest swelling, volume and volume index of films prepared by employing equal weight of chitosan (CH) and EDTA (1.5% w/v). The CH:EDTA film (1:l, on weight basis) showed minimum contact angle, work of adhesion and high negative spreading coefficient indicating lipophilic behavior of film. Further, the FTIR and DSC analysis suggested maximum crosslinking density in film prepared with equal proportion of CH and EDTA. The mechanical properties explored using texture analyzer revealed increasing the proportions of EDTA rendered the films more flexible and decreased their hardness. Furthermore, in vitro permeation of 5-FU and mesalamine with different solubilities showed minimum permeation across CH–EDTA (1:1) film, indicating high crosslinking density that decreased void space inside the film. Hence, the CH–EDTA conjugate could be considered to be possess great potential for various pharmaceutical applications such as film based delivery systems, controlled and sustained delivery systems etc.

Chitosan-carboxymethyl tamarind kernel powder interpolymer complexation: investigations for colon drug delivery

The present study was aimed at evaluating the possible use of inter polymer complexed (IPC) films of chitosan (CH) and carboxymethyl tamarind kernel powder (CMTKP) for colon release of budesonide. Viscosity analysis of the supernatant liquid obtained after reacting CH and CMTKP in different proportions revealed 40:60 to be the optimum stoichiometric ratio. The FTIR spectra of IPC films formed from 50:50 or 40:60 ratio of CH:CMTKP did not reveal any reduction in the peaks at 1560cm(â1) and 1407cm(â1) after exposure to pH 1.2, suggesting resistance of the interaction between âCOO(â) groups of CMTKP and âNH(3) (+) groups of CH to gastric pH. Tablets containing Avicel pH 102 as diluent and coated to a weight gain of 10%, w/w with aqueous solutions of 40:60 or 50:50 ratio of CH:CMTKP did not release budesonide in pH 1.2 buffer. Histopathology of the rat colon after oral administration of these IPC film coated tablets revealed significantly greater (p<0.05) reduction in TNBS-induced ulcerative colitis as compared to that after administration of uncoated tablets. The Cmax of budesonide achieved after oral administration of these IPC film coated tablets was comparable to that observed after administration of uncoated tablets. The results strongly indicate versatility of CH-CMTKP IPC films to deliver budesonide in the colon.