Time-Based Formulation Strategies for Colon Drug Delivery

Unraveling the role of pectin biodegradability and blend composition on the permeability of ethylcellulose-based blend films designed for colon targeting

Polysaccharides have often been used as the biodegradable compound in coated colon specific drug delivery systems. The selection of a specific polysaccharide is critical, as they are degraded by gut bacteria, leading to the site specific release of drugs in the colon. However, it is still not completely understood how bacterial enzymes act on the polysaccharides when they are incorporated in a coating that is primarlily made up of a hydrophobic polymer. Here, we explored to what extent pectinase degrades pectin in isolated pectin-ethylcellulose blend films by studying the film permeability. Comparison of the permeability coefficient of caffeine and the amount of pectin leakage from the blend film in the presence and absence of pectinase revealed that pectinase can still degrade the pectin in the film, on the condition that the polysaccharide is not completely encapsulated by ethylcellulose. This is different from the degradation of inulin by inulinase in the blend film of inulin in Eudragit RS as shown in our previous study (Ouyang et al., 2023). Pectin can provide a transmembrane channel for drugs due to its dissolution in water and degradation by pectinase. Pectins from apples and citrus with similar esterification degrees applied in this work had basically the same effect on film permeability and can serve as interchangeable materials for colon targeting coatings. Compatibility studies revealed a phase-separated structure of pectin-ethylcellulose films. As the proportion of pectin in the film increased, the blend film changed from a discontinuous structure to a bicontinuous structure, and the film permeability increased. Combined with the film structural characterization, the results show that the proportion of the blended components and the degradation of pectin in the film by pectinase are the determining factors affecting the permeability and microstructure of pectin-ethylcellulose blend films.

Gellan gum-based microbeads for Colon-targeted drug delivery: A promising polysaccharide for controlled and site-specific release

Targeting drug delivery to the colon presents significant challenges due to unfavorable pH conditions and enzymatic activity in the upper gastrointestinal tract. This obstacle can be overcome with colon-targeted microbeads, which have led to significant advancements in treating colonic diseases such as inflammatory bowel disease and colorectal cancer, as well as in achieving sustained delivery of macromolecules like peptides and proteins. Polysaccharide-based microbeads (MBs) formulated with gellan gum (GLG) offer a robust platform for controlled and site-specific drug release. GLG, a natural anionic polysaccharide, is renowned for its gelation properties in the presence of divalent cations, biocompatibility, and enzymatic degradability, making it ideal for colon-specific applications. In this review, we explored the potential of GLG-MBs for colon-targeted drug delivery and their physicochemical properties, drug release mechanisms, formulation strategies, therapeutic applications, methods for analytical characterizations, highlighting their advantages over conventional drug delivery, and target specificity towards the colonic disease. Furthermore, we discussed the significant limitations of GLG-MBs, such as burst release, processing, scaling up production, regulatory challenges, and clinical uniformity towards colonic environments. We explored the strategies to overcome key limitations in clinical translation, such as uniformity and regulatory hurdles. The review concludes by outlining the direction of advancing GLG-MBs, emphasizing their potential in achieving efficient and targeted drug delivery towards the colon.

Recent insights and applications of nanocarriers-based drug delivery systems for colonic drug delivery and cancer therapy: An updated review

Colorectal cancer (CRC) is the third most prevalent malignant tumor globally and is associated with high morbidity and mortality rates. The advancement of novel nanocarrier-based drug delivery systems has revolutionized therapeutic strategies for colonic drug delivery and cancer treatment. This review provides updated insights into various nanocarrier technologies, including quantum dots (QDs), polymeric nanoparticles (PNPs), magnetic and metallic nanoparticles, solid lipid nanoparticles (SLNs), and self-microemulsifying and self-nanoemulsifying drug delivery systems (SMEDDS/SNEDDS). These nanocarriers offer enhanced drug stability, controlled release, and targeted delivery, particularly for CRC treatment, resulting in up to 70 % improved therapeutic efficacy and a significant reduction in systemic toxicity as reported in preclinical studies. The review comprehensively discusses the structural composition, mechanisms of action, therapeutic potential, and imaging capabilities of these systems, with a focus on their applications in theranostics and targeted CRC therapy. For instance, polymeric nanoparticles have demonstrated a 50 % increase in bioavailability compared to conventional formulations, while QDs have enabled real-time imaging with high precision for tumor localization. Additionally, the toxicity profiles and challenges associated with these nanocarriers are critically evaluated. Despite significant progress in preclinical and clinical studies, the review highlights the need for optimizing biocompatibility, scalability, and regulatory standards to facilitate the clinical translation of these promising technologies. Emerging formulations such as graphene quantum dots and PEGylated nanoparticles have shown potential for achieving dual therapeutic and diagnostic applications with fewer adverse effects. Overall, nanocarrier-based systems hold great potential for personalized and more effective treatments in colon-targeted therapies.

VCAM-1 as a common biomarker in inflammatory bowel disease and colorectal cancer: unveiling the dual anti-inflammatory and anti-cancer capacities of anti-VCAM-1 therapies

Vascular cell adhesion molecule (VCAM)-1 has garnered significant research attention due to its potential as a disease biomarker and drug target across several inflammatory pathologies-including atherosclerosis, asthma, rheumatoid arthritis, and inflammatory bowel disease (IBD). The VCAM-1 protein has also been noted for its functional involvement in cancer metastasis and drug resistance to conventional chemotherapeutics. Although the anti-inflammatory and anti-cancer facets of VCAM-1 antagonisation have been examined separately, there is yet to be a review that explicitly addresses the functional interrelationship between these mechanisms. Furthermore, the pleiotropic mechanisms of anti-VCAM-1 therapies may present a useful paradigm for designing drug candidates with synergistic anti-inflammatory and anti-tumorigenic effects. The pathological overlap between inflammatory bowel disease (IBD) and colitis-associated colorectal cancer (CRC) serves as the quintessential disease model to observe this therapeutic duality. This review thereby details the adhesive mechanisms of VCAM-1 in colorectal disease-specifically, driving immune cell infiltration during IBD and tumour cell metastasis in CRC-and posits the potential of this receptor as a common drug target for both diseases. To explore this hypothesis, the current progress of novel VCAM-1-directed drug candidates in experimental models of IBD and CRC is also discussed.

Oral dosage forms for drug delivery to the colon: an existing gap between research and commercial applications

Oral drug administration is the preferred route for pharmaceuticals, accounting for ~90% of the global pharmaceutical market due to its convenience and cost-effectiveness. This study provides a comprehensive scientific and technological analysis of the latest advances in oral dosage forms for colon-targeted drug delivery. Utilizing scientific and patent databases, along with a bibliometric analysis and bibliographical review, we compared the oral dosage forms (technology) with the specific application of the technology (colon delivery) using four search equations. Our findings reveal a gap in the publications and inventions associated with oral dosage forms for colon release compared to oral dosage forms for general applications. While tablets and capsules were found the most used dosage forms, other platforms such as nanoparticles, microparticles, and emulsions have been also explored. Enteric coatings are the most frequently applied excipient to prevent the early drug release in the stomach with pH-triggered systems being the predominant release mechanism. In summary, this review provides a comprehensive analysis of the last advancements and high-impact resources in the development of oral dosage forms for colon-targeted drug delivery, providing insights into the technological maturity of these approaches.

Advancing Inflammatory Bowel Disease Treatment by Targeting the Innate Immune System and Precision Drug Delivery

Inflammatory bowel disease (IBD), encompassing Crohn's disease and ulcerative colitis, involves chronic inflammation of the gastrointestinal tract. Current immune-modulating therapies are insufficient for 30-50% of patients or cause significant side effects, emphasizing the need for new treatments. Targeting the innate immune system and enhancing drug delivery to inflamed gut regions are promising strategies. Neutrophils play a central role in IBD by releasing reactive oxygen species (ROS) and neutrophil extracellular traps (NETs) -DNA-based structures with cytotoxic proteins-that contribute to mucosal damage and inflammation. Recent studies linking ROS production, DNA repair, and NET formation have identified NETs as potential therapeutic targets, with preclinical models showing positive outcomes from NET inhibition. Innovative oral drug delivery systems designed to target gut inflammation directly-without systemic absorption-could improve treatment precision and reduce side effects. Advanced formulations utilize properties such as particle size, surface modifications, and ROS-triggered release to selectively target the distal ileum and colon. A dual strategy that combines a deeper understanding of IBD pathophysiology to identify inflammation-related therapeutic targets with advanced drug delivery systems may offer significant promise. For instance, pairing NET inhibition with ROS-responsive nanocarriers could enhance treatment efficacy, though further research is needed. This synergistic approach has the potential to greatly improve outcomes for IBD patients.

Modeling of drug release, erosion and diffusion fronts movement in high viscosity HPMC matrices containing a cellulolytic enzyme

A formerly developed mathematical model describing drug release from hydrophilic matrices (HMs) took into account resistance to drug release given by its dissolution and by the presence of a growing gel layer. Such a model was applied to previously reported release data obtained from HMs made of hydroxypropyl methylcellulose (HPMC), where acetaminophen was used as model drug and a cellulolytic product was added as "active" excipient to attain zero-order release kinetics. The Levich theory applied to acetaminophen intrinsic dissolution rate (IDR) data highlighted the suitability of such a drug for modeling purposes, given its good surface wettability. First assessment of the model ability to describe drug release from the abovementioned systems was carried out on partially coated matrices, representing a simplified physical frame, but results were then confirmed on uncoated systems. Experimental and model release data showed good agreement; therefore, the release-describing equation was combined with that of the global mass balance to obtain two new equations related to erosion and diffusion fronts time evolution. Changes over time in the dissolution and gel contributions to total resistance, calculated using model output parameters, highlighted that the enzyme, through its hydrolytic activity on HPMC, was responsible for a time-dependent reduction of the resistance component related to gel layer.

Construction of biopolymer-based hydrogel beads for encapsulation, retention, and colonic delivery of tributyrin: Development of functional beverages (fortified bubble tea)

Tributyrin (TB) can be hydrolyzed into short chain fatty acids (butyric acid) in the gastrointestinal tract, which are claimed to exhibit beneficial health effects in the colon. However, digestion of tributyrin in the stomach and small intestine may promote its absorption in the upper gastrointestinal tract, thereby reducing its potential colonic health benefits. In this study, we therefore developed a novel method of encapsulating emulsified tributyrin within biopolymer-based hydrogel beads (≈ 800 μm) that were then encapsulated inside the boba beads (≈ 8-10 mm) found in bubble tea. The hydrogel beads were designed to retain and protect the tributyrin under upper gastrointestinal tract (GIT) conditions, but then release it within the colon. The concentration of tributyrin within the boba beads was 33.3 mg/g, which is above the value reported to exhibit health benefits. The morphology, encapsulation properties, water holding capacity, stability, and swelling properties of the tributyrin-loaded boba beads were characterized. Tapioca-based beads exhibited a larger degree of swelling when incubated in water for 12h (>95 %), whereas agar-based beads did not (< 20 %). In addition, the potential gastrointestinal fate of both free and encapsulated tributyrin oil droplets was assessed using an in vitro digestion model. The free tributyrin oil droplets were almost completely hydrolyzed (103.2 %) by the end of the small intestine phase, whereas the tributyrin oil droplets encapsulated within the agar-based (29.4 %) or tapioca-based (40.3 %) boba beads were much more resistant to digestion. The tapioca-based beads were partially broken down as they passed through the simulated GIT, while the agar-based beads maintained their structural integrity. The tapioca-based beads were gradually broken down as they passed through the simulated GIT, while the agar-based ones maintained their structural integrity. Agar beads were also harder, more resilient, and chewier than the tapioca ones. Both types of boba beads tended to swell and disintegrate when heated to high temperatures (90 °C), with the effect being more pronounced for the agar beads. Overall, our results suggest that the agar-based boba beads had greater potential for the delivery of tributyrin to the colon than the tapioca-based ones. The recent popularity of bubble tea means that it may be a suitable vehicle for delivering bioactive food components, like functional lipids, vitamins, nutraceuticals, or probiotics.

Film Coating of Phosphorylated Mandua Starch on Matrix Tablets for pH-Sensitive Release of Mesalamine

Chemically modified mandua starch was successfully synthesized and applied to coat mesalamine-loaded matrix tablets. The coating material was an aqueous dispersion of mandua starch modified by sodium trimetaphosphate and sodium tripolyphosphate. To investigate the colon-targeting release competence, chemically modified mandua starch film-coated mesalamine tablets were produced using the wet granulation method followed by dip coating. The effect of the coating on the colon-targeted release of the resultant delivery system was inspected in healthy human volunteers and rabbits using roentgenography. The results show that drug release was controlled when the coating level was 10% w/w. The release percentage in the upper gastric phase (pH 1.2, simulated gastric fluid) was less than 6% and reached up to 59.51% w/w after 14 h in simulated colonic fluid. In addition to in vivo roentgenographic studies in healthy rabbits, human volunteer studies proved the colon targeting efficiency of the formulation. These results clearly demonstrated that chemically modified mandua starch has high effectiveness as a novel aqueous coating material for controlled release or colon targeting.

Colon Drug Delivery Systems Based on Swellable and Microbially Degradable High-Methoxyl Pectin: Coating Process and In Vitro Performance

Oral colon delivery systems based on a dual targeting strategy, harnessing time- and microbiota-dependent release mechanisms, were designed in the form of a drug-containing core, a swellable/biodegradable polysaccharide inner layer and a gastroresistant outer film. High-methoxyl pectin was employed as the functional coating polymer and was applied by spray-coating or powder-layering. Stratification of pectin powder required the use of low-viscosity hydroxypropyl methylcellulose in water solution as the binder. These coatings exhibited rough surfaces and higher thicknesses than the spray-coated ones. Using a finer powder fraction improved the process outcome, coating quality and inherent barrier properties in aqueous fluids. Pulsatile release profiles and reproducible lag phases of the pursued duration were obtained from systems manufactured by both techniques. This performance was confirmed by double-coated systems, provided with a Kollicoat® MAE outer film that yielded resistance in the acidic stage of the test. Moreover, HM pectin-based coatings manufactured by powder-layering, tested in the presence of bacteria from a Crohn's disease patient, showed earlier release, supporting the role of microbial degradation as a triggering mechanism at the target site. The overall results highlighted viable coating options and in vitro release characteristics, sparking new interest in naturally occurring pectin as a coating agent for oral colon delivery.

Cushion-coated pellets for tableting without external excipients

Multiple-unit dosage forms prepared by compacting pellets offer important manufacturing and compliance advantages over pellet-filled capsules. However, compaction may negatively affect the release control mechanism of pellets, and subunits may not be readily available after intake. Application of a cushioning layer to the starting units is here proposed as a strategy to obtain tablets with satisfactory mechanical strength, rapid disintegration and maintenance of the expected release profile of individual subunits while avoiding the use of mixtures of pellets and excipients to promote compaction and limit the impact of the forces involved. Cushion-coating with PEG1500, a soft and soluble material, was proved feasible provided that the processing temperature was adequately controlled. Cushioned gastro-resistant pellets were shown to consolidate under relatively low compaction pressures, which preserved their inherent release performance after tablet disintegration. Adhesion problems associated with the use of PEG1500 were overcome by applying an outer Kollicoat® IR film. Through design of experiment (DoE), robustness of the proposed approach was demonstrated, and the formulation as well as tableting conditions were optimized. The tableted cushion-coated pellet systems manufactured would allow a relatively high load of modified-release units to be conveyed, thus setting out a versatile and scalable approach to oral administration of multiple-unit dosage forms.

Guar gum as a microbially degradable component for an oral colon delivery system based on a combination strategy: formulation and in vitro evaluation

Oral colon delivery has widely been pursued exploiting naturally occurring polysaccharides degraded by the resident microbiota. However, their hydrophilicity may hinder the targeting performance. The aim of the present study was to manufacture and evaluate a double-coated delivery system leveraging intestinal microbiota, pH, and transit time for reliable colonic release. This system comprised a tablet core, a hydroxypropyl methylcellulose (HPMC) inner layer and an outer coating based on Eudragit® S and guar gum. The tablets were loaded with paracetamol, selected as a tracer drug because of the well-known analytical profile and lack of major effects on bacterial viability. The HPMC and Eudragit® S layers were applied by film-coating. Tested for in vitro release, the double-coated systems showed gastroresistance in 0.1 N HCl followed by lag phases of consistent duration in phosphate buffer pH 7.4, imparted by the HPMC layer and synergistically extended by the Eudragit® S/guar gum one. In simulated colonic fluid with fecal bacteria from an inflammatory bowel disease patient, release was faster than in the presence of β-mannanase and in control culture medium. The bacteria-containing fluid was obtained by an experimental procedure making multiple tests possible from a single sampling and processing run. Thus, the study conducted proved the feasibility of the delivery system and ability of guar gum to trigger release in the presence of colon bacteria without impairing the barrier properties of the coating. Finally, it allowed an advantageous simulated colonic fluid preparation procedure to be set up, reducing the time, costs, and complexity of testing and enhancing replicability.

Colon-targeted delivery of polyphenols: construction principles, targeting mechanisms and evaluation methods

Polyphenols have received considerable attention for their promotive effects on colonic health. However, polyphenols are mostly sensitive to harsh gastrointestinal environments, thus, must be protected. It is necessary to design and develop a colon-targeted delivery system to improve the stability, colon-targeting and bioavailability of polyphenols. This paper mainly introduces research on colon-targeted controlled release of polyphenols. The physiological features affecting the dissolution, release and absorption of polyphenol-loaded delivery systems in the colon are first discussed. Simultaneously, the types of colon-targeted carriers with different release mechanisms are described, and colon-targeting assessment models that have been studied so far and their advantages and limitations are summarized. Based on the current research on polyphenols colon-targeting, outlook and reflections are proposed, with the goal of inspiring strategic development of new colon-targeted therapeutics to ensure that the polyphenols reach the colon with complete bioactivity.

Development of a time-dependent oral colon delivery system of anaerobic Odoribacter splanchnicus for bacteriotherapy

Odoribacter (O.) splanchnicus is an anaerobic member of the human intestinal microbiota. Its decrease in abundance has been associated with inflammatory bowel disease (IBD), non-alcoholic fatty liver, and cystic fibrosis. Considering the anti-inflammatory properties of O. splanchnicus and its possible use for IBD, intestinal isolate O. splanchnicus 57 was here formulated for oral colonic release based on a time-dependent strategy. Freeze-drying protocol was determined to ensure O. splanchnicus 57 viability during the process. Disintegrating tablets, containing the freeze-dried O. splanchnicus 57, were manufactured by direct compression and coated by powder-layering technique with hydroxypropyl methylcellulose (Methocel™ E50) in a tangential-spray fluid bed. Eudragit® L was then applied by spray-coating in a top-spray fluid bed. Double-coated tablets were tested for release, showing gastric resistance properties and, as desired, lag phases of reproducible duration prior to release in phosphate buffer pH 6.8. The cell viability and anti-inflammatory activity of the strain were assessed after the main manufacturing steps. While freeze-drying did not affect bacterial viability, the tableting and coating processes were more stressful. Nonetheless, O. splanchnicus 57 cells survived manufacturing and the final formulations had 106-107 CFU/g of viable cells. The strain kept its anti-inflammatory properties after tableting and coating, reducing Escherichia coli lipopolysaccharide-induced interleukin-8 cytokine release from HT-29 cells. Overall, O. splanchnicus 57 strain was formulated successfully for oral colon delivery, opening new ways to formulate pure cultures of single anaerobic strains or mixtures for oral delivery.

Self-Assembled Polymers for Gastrointestinal Tract Targeted Delivery through the Oral Route: An Update

Gastrointestinal tract (GIT) targeted drug delivery systems have gained growing attention as potential carriers for the treatment of different diseases, especially local colonic diseases. They have lower side effects as well as enhanced oral delivery efficiency because of various therapeutics that are vulnerable to acidic and enzymatic degradation in the upper GIT are protected. The novel and unique design of self-assembled nanostructures, such as micelles, hydrogels, and liposomes, which can both respond to external stimuli and be further modified, making them ideal for specific, targeted medical needs and localized drug delivery treatments through the oral route. Therefore, the aim of this review was to summarize and critically discuss the pharmaceutical significance and therapeutic feasibility of a wide range of natural and synthetic biomaterials for efficient drug targeting to GIT using the self-assembly method. Among various types of biomaterials, natural and synthetic polymer-based nanostructures have shown promising targeting potential due to their innate pH responsiveness, sustained and controlled release characteristics, and microbial degradation in the GIT that releases the encapsulated drug moieties.

Crosslinked and PEGylated Pectin Chitosan Nanoparticles for Delivery of Phytic Acid to Colon

Polysaccharide-based nanoparticles (NPs) such as pectin/ chitosan (PN/CN) had always been of greatest interest because of their excellent solubility, biocompatibility, and higher suitability for oral drug delivery. This study employed blending-crosslinking of polymers (PN&CN) followed by emulsification-solvent evaporation to prepare and compare two sets of PEGylated NPs to deliver phytic acid (IP6) to colon orally as it has potential to manage colon cancer but fails to reach colon when ingested in pure form. The first set was crosslinked with Glutaraldehyde (GE) (GE*PN-CN-NPs) while the second set was crosslinked with sodium tripolyphosphate (TPP) (TPP*PN-CN-NPs). IP6-loaded-GE/TPP*PN-CN-NPs were optimized using a central composite design. Developed TPP*PN-CN-NPs had a smaller size (210.6±7.93nm) than GE*PN-CN-NPs (557.2±5.027nm). Prepared NPs showed <12% IP6 release at pH 1.2 whereas >80% release was observed at pH 7.4. Further, NPs were explored for cytocompatibility in J774.2 cell lines, cytotoxicity, and cellular uptake in HT-29 and DLD-1 cell lines. While exhibiting substantial cytotoxicity and cellular uptake in HT-29 and DLD-1, the NPs were deemedsafe in J774.2. The PEGylated-TPP*PN-CN-NPs showed time-dependent uptake in J774.2 cell lines. Conclusively, the employed NP development method successfully delivered IP6 to colon and may also open avenues for the oral delivery of other drugs to colon.