Current pharmaceutical strategies for efficient site specific delivery in inflamed distal intestinal mucosa

Citrulline and kynurenine to tryptophan ratio: potential EED (environmental enteric dysfunction) biomarkers in acute watery diarrhea among children in Bangladesh

Two emerging biomarkers of environmental enteric dysfunction (EED) include plasma citrulline (CIT), and the kynurenine (KYN): tryptophan (TRP)/ (KT) ratio. We sought to investigate the plasma concentration of CIT and KT ratio among the children having dehydrating diarrhea and examine associations between concentrations of CIT and KT ratio with concurrent factors. For this analysis, we used cross-sectional data from a total of 102, 6-36 months old male children who suffered from non-cholera acute watery diarrhea and had some dehydration admitted to an urban diarrheal hospital, in Bangladesh. CIT, TRP, and KYN concentrations were determined at enrollment from plasma samples using ELIZA. At enrollment, the mean plasma CIT concentration was 864.48 ± 388.55 µmol/L. The mean plasma kynurenine, tryptophan concentrations, and the KT ratio (× 1000) were 6.93 ± 3.08 µmol/L, 33.44 ± 16.39 µmol/L, and 12.12 ± 18.10, respectively. With increasing child age, KYN concentration decreased (coefficient: - 0.26; 95%CI: - 0.49, - 0.04; p = 0.021); with increasing lymphocyte count, CIT concentration decreased (coef.: - 0.01; 95% CI: - 0.02,0.001, p = 0.004); the wasted child had decreased KT ratio (coef.: - 0.6; 95% CI: - 1.18, - 0.02; p = 0.042) after adjusting for potential covariates. The CIT concentration was associated with blood neutrophils (coef.: 0.02; 95% CI: 0.01, 0.03; p < 0.001), lymphocytes (coef.: - 0.02; 95% CI: - 0.03, - 0.02; p < 0.001) and monocyte (coef.: 0.06; 95% CI: 0.01, 0.11; p = 0.021); KYN concentration was negatively associated with basophil (coef.: - 0.62; 95% CI: - 1.23, - 0.01; p = 0.048) after adjusting for age. In addition, total stool output (gm) increased (coef.: 793.84; 95% CI: 187.16, 1400.52; p = 0.011) and also increased duration of hospital stay (hour) (coef.: 22.89; 95% CI: 10.24, 35.54; p = 0.001) with increasing CIT concentration. The morphological changes associated with EED may increase the risk of enteric infection and diarrheal disease among children. Further research is critically needed to better understand the complex mechanisms by which EED biomarkers may impact susceptibility to dehydrating diarrhea in children.

Oral delivery of curcumin via multi-bioresponsive polyvinyl alcohol and guar gum based double-membrane microgels for ulcerative colitis therapy

Anti-inflammatory drugs for ulcerative colitis (UC) treatment should specifically penetrate and accumulate in the colon tissue. Herein, a multi-bioresponsive anti-inflammatory drug (curcumin, CUR)-loaded heterogeneous double-membrane microgels (CUR@microgels) for oral administration was fabricated in this study, in which the inner core was derived from polyvinyl alcohol (PVA) and guar gum (GG) and the outer gel was decoration with alginate and chitosan by polyelectrolyte interactions. The structure and morphology of microgels were characterized. In vitro, the formulation exhibited good bio-responses at different pH conditions and sustained-release properties in simulated colon fluid with a drug-release rate of 84.6 % over 34 h. With the assistance of the outlayer gels, the microgels effectively delayed the premature drug release of CUR in the upper gastrointestinal tract. In vivo studies revealed that CUR@microgels specifically accumulated in the colon tissue for 24 h, which suggest that the interlayer gels were apt to reach colon lesion. As expected, the oral administration of microgels remarkably alleviated the symptoms of UC and protected the colon tissue in DSS-induced UC mice. The above results indicated that these facilely fabricated microgels which exhibited excellent biocompatibility and multi-bioresponsive drug release, had an apparent effect on the treatment of UC, which represents a promising drug delivery strategy for CUR in a clinical application.

Oil-Based Delivery Control Release System Targeted to the Later Part of the Gastrointestinal Tract-A Mechanistic Study

Oil-based drug delivery systems have been studied in different aspects. The present study proposes a new application for an oil-based delivery system, focusing on controlled release until the drug reaches the later part of the small intestine. Bulk surfactants and interfacial surfactants were added into the oil formulation to provide a better mechanistic understating of the lipolysis. Validation of the modified in vitro method shows the overall conversion from medium-chain triglyceride oil (MCT oil) to free fatty acids (FFA) of 100 ± 4% in five replicates. This fully converted level and high reproducibility are fundamental for the following investigations where any retarding effect can be distinguished from the experimental errors. The results show that viscosity and thermodynamic activity have limited retardation. Furthermore, the former may change the kinetics of lipolysis, while the latter changes the equilibrium level. The gel-forming retarder (ethylcellulose) displayed a strong effect. Whereas the lipolysis was significantly retarded (>50%) when the retarders altered the interfacial composition (poloxamer 407), degradable interfacial surfactants did not have the same effect. However, surface-active, lipolysis-resistant retarders with a high CMC did not show a retarding effect.

Synthesis, Characteristics, and Pharmaceutical Properties of Ibuprofen-Cyclodextrin-PEG Conjugate

The NSAIDs ibuprofen was chemically conjugated to the PEG-graft-β-CyD with an ester bond and its aqueous solubility was clearly improved. The preliminary release profile of ibuprofen in rat gastrointestinal tract contents was performed at 37°C within 12 hours. The polymeric conjugate almost did not release ibuprofen in the contents of stomach, released ibuprofen only 7.4% in the contents of small intestine, and evidently released ibuprofen up to 58.7% in the contents of colon, respectively. These results demonstrated that the polymeric conjugate was site-specifically biodegraded in the rat colonic contents. On the other hand, the xylene-induced ear swelling technique, the hot plate test, and the brewer's yeast-induced hyperthermia model in mice were performed for evaluating the anti-inflammatory, analgesic, and antipyretic activities of the polymeric conjugate, respectively. The results revealed that the polymeric conjugate maintained a long and stable pharmacodynamic efficiency over a period of 24 hours. Hence, the present polymeric ibuprofen-cyclodextrin-PEG conjugate may be of value as an orally administered long-acting prodrug of ibuprofen through colon-targeting delivery.

Insights into Anti-Inflammatory Activity and Internalization Pathway of Onion Peel-Derived Gold Nano Bioconjugates in RAW 264.7 Macrophages

Green synthesis of nanoparticles plays an important role in their efficient therapeutic effects in various biomedical applications. Here, we prepared gold nano bioconjugates (GNBCs) from the ethyl acetate fraction of onion peels and investigated their anti-inflammatory activity in lipopolysaccharide-stimulated RAW 264.7 macrophages. The GNBCs were characterized by UV-visible spectroscopy, dynamic light scattering, and transmission electron microscopy. Comparative studies have been conducted among GNBCs, fractionate alone [onion peel drug (OPD)], and the standard drug dexamethasone in various anti-inflammatory assays. It was observed that GNBCs showed comparatively good therapeutic efficacy than the fractionate alone. At the lowest 10 μg/mL concentration, the GNBC and OPD exhibited 70.86 and 91.98% of reactive oxygen species production, 10.88 and 20.97 ng/μL of nitrite production, 337 and 378 pg/mL of TNF-α production, 27.1 and 30.64 pg/mL of IL-6 production, respectively, by maintaining a satisfactory cell viability. Moreover, to understand the mechanistic pathway of GNBCs in their entry into the macrophages, their localization, and duration, uptake studies have been performed where a caveolar-mediated endocytosis pathway is found to be prominent. Hence, this study will lead to the development of cheap, green synthesis of nano bioconjugates and their role in inflammation.

Polymeric long-acting drug delivery systems (LADDS) for treatment of chronic diseases: Inserts, patches, wafers, and implants

Non-oral long-acting drug delivery systems (LADDS) encompass a range of technologies for precisely delivering drug molecules into target tissues either through the systemic circulation or via localized injections for treating chronic diseases like diabetes, cancer, and brain disorders as well as for age-related eye diseases. LADDS have been shown to prolong drug release from 24 h up to 3 years depending on characteristics of the drug and delivery system. LADDS can offer potentially safer, more effective, and patient friendly treatment options compared to more invasive modes of drug administration such as repeated injections or minor surgical intervention. Whilst there is no single technology or definition that can comprehensively embrace LADDS; for the purposes of this review, these systems include solid implants, inserts, transdermal patches, wafers and in situ forming delivery systems. This review covers common chronic illnesses, where candidate drugs have been incorporated into LADDS, examples of marketed long-acting pharmaceuticals, as well as newly emerging technologies, used in the fabrication of LADDS.

Anti-diarrheal therapeutic potential of diminazene aceturate stimulation of the ACE II/Ang-(1-7)/Mas receptor axis in mice: A trial study

The angiotensin (Ang) II converting enzyme (ACE II) pathway has recently been shown to be associated with several beneficial effects on the body, especially on the cardiac system and gastrointestinal tract. ACE II is responsible for converting Ang II into the active peptide Ang-(1-7), which in turn binds to a metabotropic receptor, the Mas receptor (MasR). Recent studies have demonstrated that Diminazene Aceturate (DIZE), a trypanosomicide used in animals, activates the ACE II pathway. In this study, we aimed to evaluate the antidiarrheal effects promoted by the administration of DIZE to activate the ACE II/Ang-(1-7)/MasR axis in induced diarrhea mice models. The results show that activation of the ACE II pathway exerts antidiarrheal effects that reduce total diarrheal stools and enteropooling. In addition, it increases Na⁺/K⁺-ATPase activity and reduces gastrointestinal transit and thus inhibits contractions of intestinal smooth muscle; decreases transepithelial electrical resistance, epithelial permeability, PGE2-induced diarrhea, and proinflammatory cytokines; and increases anti-inflammatory cytokines. Enzyme-linked immunosorbent assay (ELISA) demonstrated that DIZE, when activating the ACE II/Ang-(1-7)/MasR axis, can still interact with GM1 receptors, which reduces cholera toxin-induced diarrhea. Therefore, activation of the ACE II/Ang-(1-7)/MasR axis can be an important pharmacological target for the treatment of diarrheal diseases.

Macrophages-targeting mannosylated nanoparticles based on inulin for the treatment of inflammatory bowel disease (IBD)

In the present experimental series, we have developed a novel nanocomposite to target activated macrophages in the colon with real time imaging and therapeutic capabilities. This binary nanocomposite was formed by the covalent conjugation of mannosylated NPs (Man-NPs) with carbon dots (CDs). Man-NPs were prepared using a self-assembly method based on mannosylated decamethylenediamine-grafted carboxymethyl inulin amphiphilic acid. While, the CDs were synthesized using a simple bottom-up process using citric acid monohydrate and diethylenetriamine, which were tightly bonded to the Man-NPs surface by carbodimide coupling. The resulting nanocomposite had a uniform size of 241.3 nm with a negative charge and a high drug casing density of 25.54 wt% and blue self-fluorescence were emitted. Whereas, in vitro observation of cellular uptake indicated the greater nanocomposite uptake in inflamed macrophage as compared to the untreated macrophage and mannose receptor-negative cell lines, 4T1 respectively. However, in vivo bio distribution exhibited a large number (60%) of CDs/Man-NPs nanocomposite accumulated in the inflamed colon of colitis mice. It should be noted that the novel nanocomposite, as macrophage-targeted drug delivery, could have promise for the treatment of inflammatory bowel disease (IBD).

Carboxymethyl chitosan microspheres loaded hyaluronic acid/gelatin hydrogels for controlled drug delivery and the treatment of inflammatory bowel disease

A major drawback of oral treatment of inflammatory bowel disease (IBD) is the non-specific distribution of drugs during long-term treatment. Despite its effectiveness as an anti-inflammatory drug, curcumin (CUR) is limited by its low bioavailability in IBD treatment. Herein, a pH-sensitive composite hyaluronic acid/gelatin (HA/GE) hydrogel drug delivery system containing carboxymethyl chitosan (CC) microspheres loaded with CUR was fabricated for IBD treatment. The composition and structure of the composite system were optimized and the physicochemical properties were characterized using infrared spectroscopy, X-ray diffraction, swelling, and release behavior studies. In vitro, the formulation exhibited good sustained release property and the drug release rate was 65% for 50 h. In vivo pharmacokinetic experiments indicated that high level of CUR was maintained in the colon tissue for more than 24 h; it also played an anti-inflammatory role by evaluating the histopathological changes through hematoxylin and eosin (H&E), myeloperoxidase (MPO), and immunofluorescent staining. Additionally, the formulation substantially inhibited the level of the main pro-inflammatory cytokines of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) secreted by macrophages, compared to the control group. The pharmacodynamic experiment showed that the formulation group of CUR@gels had the best therapeutic effect on colitis in mice. The composite gel delivery system has potential for the effective delivery of CUR in the treatment of colitis. This study also provides a reference for the design and preparation of a new oral drug delivery system with controlled release behavior.

In vitro and in vivo amelioration of colitis using targeted delivery system of cyclosporine a in New Zealand rabbits

Necessity to develop the efficient targeted delivery of highly potent immunosuppressant for IBD in order to avoid surgical procedure, led to fabrication and evaluation of its anti-inflammatory potential. Previously formulated cyclosporine A (Cyp A) into enteric coated capsules was further evaluated for its site-specificity in the treatment of TNBS induced colitis. Contact angle measurement studies showed excellent spreadability of the developed formulation over the hydrophilic biological tissue substrate. HET-CAM study demonstrates that the formulation prepared is nonirritant to the highly vascular tissues and hence can be used for the immunological sensitive tissues like inflamed intestine in IBD. Further the developed formulation has been characterized for site specificity to distal parts of intestine by pharmacokinetic studies. The appearance of drug in systemic circulation at approximately 5 hours in New Zealand strain of rabbits confirms drug delivery at distal parts of intestine. Significant reduced levels of TNF-α, IL-6 and IL-10 in drug treated animals signifies inhibition of inflammatory reactions at the TNBS treated site. Simultaneously, the change in body weight of same group of animals was observed for 15 days. Results showed a marginal recovery of body weight in Cyp A treated TNBS induced colitis animals. In conclusion, all in vitro and in vivo results confirm the successful site specific delivery and anti-inflammatory efficacy of developed formulation of Cyp A in TNBS induced colitis in New Zealand rabbits.

A Colon-Targeted Prodrug, 4-Phenylbutyric Acid-Glutamic Acid Conjugate, Ameliorates 2,4-Dinitrobenzenesulfonic Acid-Induced Colitis in Rats

An elevated level of endoplasmic reticulum (ER) stress is considered an aggravating factor for inflammatory bowel disease (IBD). To develop an ER-stress attenuator that is effective against colitis, 4-phenylbutyric acid (4-PBA), a chemical chaperone that alleviates ER stress, was conjugated with acidic amino acids to yield 4-PBA-glutamic acid (PBA-GA) and 4-PBA-aspartic acid (PBA-AA) conjugates. The PBA derivatives were converted to 4-PBA in the cecal contents, and the conversion was greater with PBA-GA than that with PBA-AA. After oral administration of PBA-GA (oral PBA-GA), up to 2.7 mM PBA was detected in the cecum, whereas 4-PBA was not detected in the blood, indicating that PBA-GA predominantly targeted the large intestine. In 2,4-dinitrobenzenesulfonic acid-induced colitis in rats, oral PBA-GA alleviated the damage and inflammation in the colon and substantially reduced the elevated levels of ER stress marker proteins in the inflamed colon. Moreover, PBA-GA was found to be as effective as the currently used anti-IBD drug, sulfasalazine. In conclusion, PBA-GA is a colon-targeted prodrug of 4-PBA and is effective against rat colitis probably via the attenuation of ER stress in the inflamed colon.

Site-specific targeted drug delivery systems for the treatment of inflammatory bowel disease

Inflammatory bowel disease (IBD) includes Crohn's disease and ulcerative colitis and manifests as a complex and dysregulated immune response. To date, there is no cure for IBD; thus, lifelong administration of maintenance drugs is often necessary. Since conventional IBD treatment strategies do not target the sites of inflammation, only limited efficacy is observed with their use. Moreover, the possibility of severe side effects resulting from systemic drug redistribution is high when conventional drug treatments are used. Therefore, a straightforward disease-targeted drug delivery system is desirable. Based on the pathophysiological changes associated with IBD, novel site-specific targeted drug delivery strategies that deliver drugs directly to the inflammation sites can enhance drug accumulation and decrease side effects. This review summarizes novel inflammation targeted delivery systems in the management of IBD. It also discusses the challenges and new perspectives in this field.

pH-dependent ileocolonic drug delivery, part I: in vitro and clinical evaluation of novel systems

After the pH dependency of novel pH-dependent ileocolonic drug delivery systems is confirmed in vitro, their performance should be evaluated in human volunteers.

Colon targeted bioadhesive pellets of curcumin and cyclosporine for improved management of inflammatory bowel disease

The objective of the present work was to develop and optimize multiparticulate pH-dependent bioadhesive pellets of curcumin and cyclosporine for the management of intestinal bowel disease (IBD). The bioadhesive sustained release pellets were intended for targeting the affected site for an improved therapeutic effect. Bioadhesive pellet cores of curcumin and cyclosporine were formulated using Carbopol 940 (CP940) and hydroxypropyl cellulose (HPC-H) by the extrusion/spheronization method, and drug delivery to the colon was controlled by the pH-sensitive polymer Eudragit® S100. Microcrystalline cellulose (Avicel PH101) was found to be the best forming agent for pellet core. The ratio of CP940 to HPC-H was kept at 1:1 to achieve 100% bioadhesion. The in vitro dissolution profiles of coated pellets depicted that 12.327 ± 0.342% of curcumin and 14.751 ± 0.112% of cyclosporine were released at the end of 6 h (at pH 6.8), whereas 71.278 ± 0.100% of curcumin and 76.76 ± 0.195% of cyclosporine were released at the end of 24 h (at pH 7.4). The drug release profile was found to follow zero-order kinetics for both drugs. The selected formulation was evaluated on an acetic acid-induced ulcerative colitis in the rat model to evaluate the efficiency of drug-loaded pellets coated with Eudragit®S100. The pharmacodynamic study revealed the therapeutic efficacy of Eudragit®S100-coated pellets of curcumin and cyclosporine in alleviating the conditions of the acetic acid-induced colitis model as reflected by weight gain as well as improvement of clinical, macroscopic and microscopic parameters of induced colitis, as compared with free curcumin and cyclosporine. The combination of curcumin and cyclosporine has been proven to have a synergistic effect for the successful management of IBD when used in a low dose as compared with individual drugs with high doses. Hence, curcumin- and cyclosporine-loaded bioadhesive pellets may act as a promising targeted drug delivery system in the management of IBD. Graphical abstract.

An In Situ Gelling System for the Local Treatment of Inflammatory Bowel Disease (IBD). The Loading of Maqui (Aristotelia Chilensis) Berry Extract as an Antioxidant and Anti-Inflammatory Agent

The aim of the present work was the development of an innovative in situ gelling system, to be applied on the mucosa of the distal colon via rectal route. The system consisted of three polymers having different functions: gellan (GG), able to jellify in presence of ions; methylcellulose (MC), a thermosensitive polymer with a gelation temperature close to 50 °C; and hydroxypropylcellulose (HPC), a mucoadhesive polymer. The three polymers were able to act synergistically, increasing the permanence of the vehicle on the mucosa and forming a protective gel layer. A DoE approach, "simplex centroid mixture design," was used to identify the optimal quantitative composition of the vehicle. The response variables considered were: vehicle viscosity at room temperature; increase in vehicle viscosity on increasing temperature (from room to physiological value) and upon dilution with simulated colonic fluid (SCF); and viscoelastic behavior, thixotropic area, and mucoadhesion properties of the gel formed at 37 °C upon dilution in SCF. The optimized vehicle was loaded with maqui berry extract (MBE), known for its antioxidant and anti-inflammatory properties. MBE loading (0.5% w/w) into the vehicle improved rheological and mucoadhesive properties of the formulation. Both MBE and the optimized vehicle were not cytotoxic towards human fibroblasts and Caco-2 cells. Moreover, the optimized vehicle did not affect MBE antioxidant properties.

Reactive oxygen species responsive nanoplatforms as smart drug delivery systems for gastrointestinal tract targeting

The pharmacological therapy for gastrointestinal (GI) diseases, such as inflammatory bowel diseases, continues to present challenges in targeting efficacy. The need for maximal local drug exposure at the inflamed regions of the GI tract has led research to focus on a disease-targeted drug delivery approach. Smart nanomaterials responsive to the reactive oxygen species (ROS) concentrated in the inflamed areas, can be formulated into nanoplatforms to selectively release the active compounds, avoiding unspecific drug delivery to healthy tissues and limiting systemic absorption. Recent developments of ROS-responsive nanoplatforms include combination with other materials to obtain multi-responsive systems and modifications/derivatization to increase the interactions with biological tissues, cell uptake and targeting. This review describes the applications of ROS-responsive nanosystems for on-demand drug delivery to the GI tract.

Conjugation of Amisulpride, an Anti-Psychotic Agent, with 5-Aminosalicylic Acid via an Azo Bond Yields an Orally Active Mutual Prodrug against Rat Colitis

Amisulpride (ASP), an anti-psychotic agent, is a pharmacologically equivalent to sulpiride (SP). Because SP demonstrates anti-ulcer and anti-colitic activities, ASP with an aniline moiety was azo-coupled to salicylic acid to generate 5-(aminoethanoylsulfamoyl)-N-[(1-ethylpyrrolidin-2-yl)methyl]-2-methoxybenzamide (ASP-azo-ASA), with the expectation that it would act as a colon-specific mutual prodrug against colitis. Following a 24 h incubation, approximately 80% of ASP-azo-ASA was cleaved to form ASP and 5-aminosalicylic acid (5-ASA) in the cecal contents, whereas it remained stable in the small intestinal contents. Oral gavage of ASP-azo-ASA (oral ASP-azo-ASA) delivered 5-ASA to the cecum to levels comparable with those observed for sulfasalazine (SSZ; clinical colon-specific prodrug of 5-ASA) and without detectable concentrations of ASP in the blood, indicating efficient colonic delivery. Oral ASP-azo-ASA ameliorated 2, 4-dinitrobenzenesulfonic acid hydrate (DNBS)-induced colitis in rats more effectively than oral SSZ. Additionally, oral ASP-azo-ASA lowered the levels of inflammatory mediators in the inflamed distal colon more effectively than oral SSZ. Combined treatment with 5-ASA and ASP via the rectal route more effectively reversed colonic damage and inflammation than treatment with 5-ASA or ASP alone, confirming the mutual anti-colitic actions of 5-ASA and ASP. In conclusion, ASP-azo-ASA is an orally active mutual prodrug against rat colitis with limited systemic absorption of ASP.

A Probiotic Spore-Based Oral Autonomous Nanoparticles Generator for Cancer Therapy

Spores, the dormant life forms of probiotics, can germinate to metabolically active vegetative cells with the disintegration of their hydrophobic protein coat in the intestinal microenvironment, which provides the possibility for the formation of nanoparticles (NPs) in vivo. Inspired by the natural physiological process of spores, herein, an oral autonomous NPs generator is developed to overcome the spatially variable gastrointestinal tract environment and multibiological barriers. Spores modified with deoxycholic acid (DA) and loaded with chemotherapeutic drugs (doxorubicin and sorafenib, DOX/SOR) serve as an autonomous production line of NPs, which can efficaciously protect the drugs passing through the rugged environment of the stomach and furthermore can be transported to the intestinal environment and colonized rapidly. Subsequently, the DOX/SOR/Spore-DA NPs are produced by the autonomous NPs generator in the intestinal regions based on the disintegrated hydrophobic protein and the hydrophilic DA, and they can efficiently penetrate the epithelial cells via the bile acid pathway, increasing basolateral drug release. In vitro and in vivo studies confirm that this biological nanogenerator can autonomously produce substantial NPs in the intestine, providing a promising strategy for cancer therapy.

Targeted delivery of phycocyanin for the prevention of colon cancer using electrospun fibers

Phycocyanin (PC), a water-soluble biliprotein, exhibits potent anti-colon cancer properties. However, its application in functional foods is limited by the poor stability and low bioavailability of PC. In this study, we successfully encapsulated PC by coaxial electrospinning. The colon targeted release of PC was achieved with retention of the antioxidant activity of PC. The PC-loaded electrospun fiber mat (EFM) obtained inhibited HCT116 cell growth in a dose-dependent and time-dependent manner. In particular, the PC-loaded EFM exerted its anti-cancer activity by blocking the cell cycle at the G0/G1 phase and inducing cell apoptosis involving the decrease of Bcl-2/Bax, activation of caspase 3 and release of cytochrome c. This study suggests that co-axial electrospinning is an efficient and effective way to deliver PC and improve its bioavailability; thus, it represents a promising approach for encapsulating functional ingredients for colon cancer prevention.

In Vitro Methods to Study Colon Release: State of the Art and An Outlook on New Strategies for Better In-Vitro Biorelevant Release Media

The primary focus of this review is a discussion regarding in vitro media for colon release, but we also give a brief overview of colon delivery and the colon microbiota as a baseline for this discussion. The large intestine is colonized by a vast number of bacteria, approximately 1012 per gram of intestinal content. The microbial community in the colon is complex and there is still much that is unknown about its composition and the activity of the microbiome. However, it is evident that this complex microbiota will affect the release from oral formulations targeting the colon. This includes the release of active drug substances, food supplements, and live microorganisms, such as probiotic bacteria and bacteria used for microbiota transplantations. Currently, there are no standardized colon release media, but researchers employ in vitro models representing the colon ranging from reasonable simple systems with adjusted pH with or without key enzymes to the use of fecal samples. In this review, we present the pros and cons for different existing in vitro models. Furthermore, we summarize the current knowledge of the colonic microbiota composition which is of importance to the fermentation capacity of carbohydrates and suggest a strategy to choose bacteria for a new more standardized in vitro dissolution medium for the colon.

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.