Oral Colon-specific Drug Delivery System Research Articles

Colon-specific controlled release of oral liposomes for enhanced chemo-immunotherapy against colorectal cancer

A colon-specific drug delivery system has great potential for the oral administration of colorectal cancer. However, the uncontrollable in vivo fate of liposomes makes their effectiveness for colonic location, and intratumoral accumulation remains unsatisfactory. Here, an oral colon-specific drug delivery system (CBS-CS@Lipo/Oxp/MTZ) was constructed by covalently conjugating Clostridium butyricum spores (CBS) with drugs loaded chitosan (CS)-coated liposomes, where the model chemotherapy drug oxaliplatin (Oxp) and anti-anaerobic bacteria agent metronidazole (MTZ) were loaded. Following oral administration, CBS germinated into Clostridium butyricum (CB) and colonized in the colon. Combined with colonic specifically β-glucosidase responsive degrading of CS, dual colon-specific release of liposomes was achieved. And the accumulation of liposomes at the CRC site furtherly increased by 2.68-fold. Simultaneously, the released liposomes penetrated deep tumor tissue via the permeation enhancement effect of CS to kill localized intratumoral bacteria. Collaborating with blocking the translocation of intestinal pathogenic bacteria from lumen to tumor with the gut microbiota modulation of CB, the intratumoral pathogenic bacteria were eliminated fundamentally, blocking their recruitment to immunosuppressive cells. Furtherly, synchronized with lipopolysaccharide (LPS) released from MTZ-induced dead Fusobacterium nucleatum and the tumor-associated antigens produced by Oxp-caused immunogenic dead cells, they jointly enhanced tumor infiltration of CD8+ T cells and reactivated robust antitumor immunity.

A novel and simple oral colon-specific drug delivery system based on the pectin/modified nano-carbon sphere nanocomposite gel films

The 3-aminopropyltriethoxysilane modified nano-carbon sphere (MNCS) was added into pectin-Ca2+ film to improve the controlled release properties of the pectin-based oral colon-specific drug delivery system (OCDDS). The FT-IR measurements indicated the successful modification of nano-carbon sphere via silylation reaction and the electrostatic interaction between the pectin molecules and MNCS in the composite film. The FE-SEM showed the pore structure when the MNCS was mingled with the pectin. The 5-fluorouracil (5-FU) was employed as the drug model and the controlled release properties of the corresponding OCDDSs were determined. The values of the encapsulation efficiency ranged from 30.1% to 52.6%. All composite film based OCDDSs presented higher encapsulation efficiency than single pectin-Ca2+ based OCDDS. The drug release studies emerged that almost all the OCDDSs from composite films presented better release properties than single pectin-Ca2+ based OCDDS. The sample C revealed best release performance with the cumulative release rate of 32.17%, 22.77% and 63.89% in the simulated gastric fluid, small intestinal fluid and colon fluid, respectively. In addition, the kinetics studies were performed to analyze the release data. The cytotoxicity assay indicated good biocompatibility of the composite carriers.

Chemical cross-linking approach for prolonging diclofenac sodium release from pectin-based delivery system

To overcome the instability of pectin-Ca2+ gels based oral colon-specific drug delivery system (OCDDS) in the upper gastrointestinal tract, the chemical cross-linked pectin carriers were prepared by adding succinic anhydride and glutaric dialdehyde as the cross-linking reagents. The diclofenac sodium was employed as the water-soluble drug model to calculate the controlled release properties. The encapsulation efficiency and loading efficiency were measured and the sample PG1 shows the best efficiency of 78.81% and 7.78%, respectively. The simulative release rate was estimated and the cumulative release rate of sample PG1 reached to a maximum of 3.04, 3.66 and 79.43% in SGF, SSIF and SCF. The release data was employed to fit the First order, Higuchi, Bhaskar, and Ritger-peppas model and the goodness of the fit was calculated by the regression coefficient. The succinic anhydride and glutaric dialdehyde cross-linked pectin were characterized by FTIR to prove the cross-linking reaction. In addition, FE-SEM characterization of sample PG1 indicated the rally microsphere with smooth surface. The sample PG1 after the digestion was also characterized by the FE-SEM, and irregularly structure was obtained.

Enzyme-responsive mechanism based on multi-walled carbon nanotubes and pectin complex tablets for oral colon-specific drug delivery system

The purpose of this work was to explore the potential application of MCNT as a colon-specific delivery system based on the enzyme responsive mechanism. A novel type of enzyme-sensitive colon-specific tablet (PM-tablet) based on pectin and multi-walled carbon nanotube (MCNT) was prepared by wet granulation tabletting method. The PM-tablet in the presence of pectinase exhibited enzyme degradation release and achieve a precise release in the colon. Our study had proposed a novel idea for the application of MCNT on the oral colon-specific drug delivery system.

Oral colon-specific drug delivery system reduces the nephrotoxicity of rhubarb anthraquinones when they produce purgative efficacy.

Rhubarb is commonly used to treat constipation in China and anthraquinones (AQs) are the active components present in rhubarb. However, an increasing number of studies have reported that AQs induce nephrotoxicity. In the present study, rhubarb total free anthraquinones (RTFA) oral colon-specific drug delivery granules (RTFA-OCDD-GN) were prepared to determine whether RTFA-OCDD-GN could reduce the nephrotoxicity that occurs when AQs produce purgative efficacy. RTFA-OCDD-GN were prepared using pH-enzyme double-layer coating technology and the cumulative release rate of RTFA in RTFA-OCDD-GN was assessed. The first black stool time, the number and state of feces over 8 h were observed to measure the purgative efficacy. In the nephrotoxicity test, biochemical and histopathological examinations were performed following 20 and 40 days administration, and 20 days convalescence. The cumulative release rate of RTFA in RTFA-OCDD-GN was >80% in simulated colonic fluid. RTFA-OCDD-GN produced considerable purgative efficacy compared with rhubarb medical material samples (RMMS). Following 40 days RMMS administration, blood urea nitrogen, creatinine and urine β2-microglobulin levels in the high-dosage group were significantly increased compared with the control and RTFA-OCDD-GN groups (P<0.05). All specimens from the high-dosage RMMS group exhibited swelling/degeneration of renal proximal convoluted tubule epithelial cells. No difference in pathological conditions and biochemical indicators was detected between the RTFA-OCDD-GN groups and the control group. The nephrotoxicity of AQs was significantly reduced following RTFA-OCDD-GN administration, which produced considerable purgative efficacy compared with RMMS.

Role of Polysaccharides in Colon-Specific Drug Delivery

Copyright © 2015, School of Pharmacy, Ahvaz Jundishapur University of Medical Sciences. This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International License (http://creativecommons.org/licenses/by-nc/4.0/) which permits copy and redistribute the material just in noncommercial usages, provided the original work is properly cited. Oral colon delivery has gained wide interest not just for the treatment of local diseases of the colon, such as inflammatory bowel disease (IBD) or Crohn’s disease, but also as a reliable approach for peptide and protein drug delivery (1). Owing to the distal location of the colon in the gastrointestinal (GI) tract, an oral colon-specific drug delivery system must withstand the conditions in the upper GI tract and should rapidly release the drug upon entry into the colon. The slow movement of material through the colon allows the presence of a large microbial population, much greater than that in the stomach or small intestine. These bacteria produce a wide range of reductive and hydrolytic enzymes, many of which are not present in the upper GI tract (2). Therefore, taking susceptibility to degradation by colonic enzymes into consideration, different natural or synthetic polymers have been employed in approaches such as prodrugs, hydrogels, matrices, and biodegradable coating materials. These polymers protect the drug from the conditions in the upper GI tract and undergo degradation via cleavage by colonic microbial enzymes, thus enabling drug release in the colon environment. A large number of polysaccharides are resistant to degradation by gastric and intestinal bacteria and are specifically hydrolyzed by colonic microbial flora; thus, they show potential for use as colon-specific drug delivery systems (3). Naturally occurring polysaccharides originate from plants (pectin, inulin and guar gum), animals (chitosan and chondroitin sulfate), algae (alginates), or bacteria (dextran). They are inexpensive, non-toxic, and have varied structures and properties. Furthermore, because of their safety and biocompatibility characteristics, these polysaccharides have also been widely used as excipients in the pharmaceutical industry. The problems typically encountered with polysaccharides are their high water solubility and poor filmforming property, which can lead to premature drug release from polysaccharide-based systems at off-target sites. Several methods have been used to overcome these obstacles. One way of decreasing the solubility of polysaccharides is to make them more water-resistant and yet enzymatically degradable by using derivatives such as calcium-bound pectin (4). The other approaches are based on combining polysaccharides with other insoluble film-forming polymers that limit the hydration of polysaccharides and thus inhibit premature drug release. In this respect, various polymers such as ethyl cellulose and polymethacrylates (5) have been used. The formation of polyelectrolyte complexes with an anionic (pectin) and a cationic polysaccharide (chitosan) was successfully assessed (6). Most recently, a combination of a polysaccharide-based system and the other colonic delivery systems such as pHand time-dependent polymers have been the broad direction of interest because of the significant advantages of site-specificity of drug release in the colon. and owing to the various benefits of naturally occurring polysaccharides.

The pharmacokinetic study on the mechanism of toxicity attenuation of rhubarb total free anthraquinone oral colon-specific drug delivery system

Rhubarb is commonly used as laxatives in Asian countries, of which anthraquinones are the major active ingredients, but there are an increased number of concerns regarding the nephrotoxicity of anthraquinones. In this study, we compared the pharmacokinetic characteristics of rhubarb anthraquinones in rats after orally administered with rhubarb and rhubarb total free anthraquinone oral colon-specific drug delivery granules (RTFA-OCDD-GN), and then explained why these granules could reduce the nephrotoxicity of anthraquinones when they produced purgative efficacy. A sensitive and reliable high performance liquid chromatography (HPLC) method has been fully validated for simultaneous determination of the five active components of rhubarb, and successfully applied to investigate and compare the remarkable differences in pharmacokinetic study of rhubarb anthraquinones after orally administered with rhubarb and RTFA-OCDD-GN. The results showed that, compared with rhubarb group, the AUC, Cmax, t1/2z and Vz/F of aloe-emodin, rhein, emodin and chrysophanol in rats receiving the RTFA-OCDD-GN were significantly decreased, and the Tmax of the four analytes was prolonged. Moreover, the Tmax of rhein, the Cmax of chrysophanol and emodin all have significant differences (P<0.05). Simultaneously, anthraquinone prototype excretion rates in urine and feces of aloe-emodin, rhein, emodin, chrysophanol and physcion were all increased. These findings suggested that oral colon-specific drug delivery technology made anthraquinone aglycone to colon-specific release after oral administration. This allowed anthraquinones to not only play the corresponding purgative effect but also avoid intestinal absorption and promote excretion. And thereby greatly reduced the nephrotoxicity of rhubarb. The result is a new breakthrough in rhubarb toxicity attenuated research.

The New Progress and Outlook of Oral Colon-specific Drug Delivery System for Treating Cancer

The morbidity of colon cancer is increasingly frequent in past years. Although quite a few researches about colon targeted drugs have achieved certain results and there are quite a few drugs for treatment at present, insufficient of dosage form and function still exists. The paper will give an outlook about a kind of multi-functional colon targeted delivery system.

Modified Approaches for Colon Specific Drug Delivery System: A Review

The colon is a site where both local and systemic delivery of drugs can take place. Local delivery allows topical treatment of inflammatory bowel disease. However, treatment can be made effective if the drugs can be targeted directly into the colon, thereby reducing the systemic side effects. This review mainly describes the primary approaches for CDDS (Colon Specific Drug Delivery) namely prodrugs, pH and time dependent systems, and microbially triggered systems, which achieved limited success and had limitations as compared with newer CDDS namely pressure controlled colonic delivery capsules. Oral administration of different dosage forms is the most commonly used method due to flexibility in design of dosage form and high patient acceptance, but the gastrointestinal tract presents several formidable barriers to drug delivery. In oral colon-specific drug delivery system, colon has a large amount of lymphoma tissue (facilitates direct absorption in to the blood), negligible brush boarder membrane activity, and much less pancreatic enzymatic activity as compared with the small intestine. Colon-specific drug delivery has gained increased importance not just for the delivery of the drugs for treatment of local diseases associated with the colon but also for its potential for the delivery of proteins and therapeutic peptides. Different approaches are designed based on prodrug formulation, pH-sensitivity, time-dependency (lag time), microbial degradation and osmotic pressure etc to formulate the different dosage forms like tablets, capsules, multiparticulates, microspheres, liposomes for colon targeting. The delivery of drugs to the colon has a number of therapeutic implications in the field of drug delivery. In the recent times, the colon specific delivery systems are also gaining importance not only for local drug delivery of drugs but also for the systemic delivery of protein and peptide drugs. This review updated the research on different approaches formulation and evaluation of colon-specific drug delivery.

Preparation, &lt;I&gt;In Vitro&lt;/I&gt; and &lt;I&gt;In Vivo&lt;/I&gt; Evaluation of Budesonide Loaded Core/Shell Nanofibers as Oral Colonic Drug Delivery System

Budesonide (BUD) loaded ethylcellulose (EC)-core/Eudragit S100-shell nanofibers (BUD-core/shell-NFs) have been successfully prepared using a coaxial electrospinning technique. The drug encapsulation efficiency was 90.48%. SEM and TEM analysis showed that fine core-shell structured nanofibers with an average diameter 190 nm and uniform core diameters 74 nm were prepared. The BUD-loaded Eudragit S100/EC composite nanofibers (BUD-NFs) were prepared using a blend electrospinning method and used as a control. In vitro release tests in HCl 0.1 N, phosphate buffer solutions pH 6.8 and 7.4 were studied. Moreover, the colon-specific characteristics were directly proven in vivo by the content of BUD in different segments of the gastrointestinal (GI) tract in rats after oral administration. Taken together, the results confirmed that BUD-core/shell-NFs had desired pH-dependent drug release profile, displayed a sustained and complete drug release in the colon, as well as protected BUD from being released completely in the upper portion of the GI tract. Compared with BUD-NFs, the BUD-core/shell-NFs have much better potential to be developed as oral colon-specific drug delivery system (OCDDS) to overcome the disadvantages of current oral formulations of BUD.

PH-controllable release using functionalized mesoporous silica nanoparticles as an oral drug delivery system

We designed a novel oral colon-specific drug delivery system (OCDDS) using a modification of mesoporous silica nanoparticle (MSN) surfaces with pH-sensitive trimethylammonium (TA) groups through a pH-sensitive hydrazone bond. The pH-sensitive TA groups can efficiently increase the loading amounts of anionic drugs by a strong electrostatic attraction. After oral administration, the acidic pH of gastric juice can fully hydrolyze the TA–hydrazone bonds and further eliminate the positive charges of TA groups from MSN surfaces. When the hydrolyzed complexes were further delivered to the colon's pH of 7–8, a rapid and complete release of adsorbed drugs was observed. From the studies of spectroscopic characterizations, we demonstrated that the combination of pH-sensitive hydrazone–TA groups and nano-sized particles of the MSN carriers took the advantages of increasing the accessible surface areas of drug molecules and varying the charges of MSN surfaces, which can increase dissolution and release rate of hydrophobic drug molecules. In addition, a cell viability assay also indicated that no cytotoxicity of MSN–hydrazone–TA complexes was observed even with treatment in an extremely high nanoparticle concentration. Consequently, our new formulation is highly biocompatible for the OCDDS, and we can completely solve the low stability, low solubility, and low drug bioavailability in the free form of drug molecules for the design of OCDDS.

Chitosan-g-PAA hydrogels for colon-specific drug delivery: Preparation, swelling behavior and in vitro degradability

A series of cross-linked hydrogels for colon-specific drug delivery were synthesized by graft copolymerization of Chitosan and acrylic acid using N, N′-methylene-bis-(acrylamide) as a cross-linker. Their swelling behavior in different pH buffer solutions and colonic enzymatic degradability were studied. The obtained results show that these hydrogels have good pH sensitivity which can avoid drug release in stomach, and their swelling kinetics in stimulant intestinal environment follow second-order swelling kinetics equation. The factors influencing the swelling kinetics include the degree of cross-linking and the composition, which may control no release or a little amount release of drug inside the hydrogels in the small intestine by tailoring these factors. The gels are degradable by colonic enzymes and there is a correlativity between the degradation of networks and the swelling degree of the gels, which may trigger the release of drug in the colon. The hydrogels show a great potential for their application in oral colon-specific drug delivery system.