Colon-specific drug delivery systems based on cyclodextrin prodrugs: In vivo evaluation of 5-aminosalicylic acid from its cyclodextrin conjugates

Oral Formulation of 5-Aminosalicylic Acid-Hemoglobin Bio-Adhesive Nanoparticles Enhance Therapeutic Efficiency in Ulcerative Colitis Mice: A Preclinical Evaluation

The oral formulation design for colon-specific drug delivery brings some therapeutic benefits in the ulcerative colitis treatment. We recently reported the specific delivery of hemoglobin nanoparticles-conjugating 5-aminosalicylic acid (5-ASA-HbNPs) to the inflamed site. In the current study, the therapeutic effect of the 5-ASA-HbNPs formulation was confirmed in vivo. This evaluation of 5-ASA-HbNPs not only shows longer colonic retention time due to adhesive properties, also provides full support for it as compared with free 5-ASA. It was considered as a suitable bio-adhesive nanoparticle with mucoadhesive property to pass through the mucus layer and accumulate into the mucosa. In UC model mice, a two-fold decrease in the disease activity indexes and colon weight/length ratios was significantly observed in the group treated with 5-ASA-HbNPs. This group received one percent of the standard dosage of 5-ASA (50 μg/kg), while, a similar result was observed for a significant amount of free 5-ASA (5 mg/kg). Furthermore, microscopic images of histological sections of the extracted colons demonstrated that the 5-ASA-HbNPs and 5-ASA groups displayed instances of inflammatory damage within the colon. However, in comparison to the colitis group, the extent of this damage was relatively moderate, suggesting 5-ASA-HbNPs improved therapeutic efficacy with the lower dosage form.

Cyclodextrin Polymers Functionalized with Histidine and Carcinine as Chelating Therapeutics for Copper Dyshomeostasis

In recent years, cyclodextrin polymeric nanoparticles have been designed to introduce new properties and extend their medical applications. Based on the features of cyclodextrins, we derivatized cross-linked cyclodextrin polymers with histidine or carcinine moieties. We found that amylases do not hydrolyze cyclodextrin polymers. The new polymers can form copper(II) complexes and may act as nanochelators to counteract copper(II) dyshomeostasis-related diseases. Furthermore, the copper(II) complexes show superoxide dismutase activity, similar to free carcinine and histidine complexes. The antioxidant biological activity of the copper(II) complex formed in situ may protect cells from oxidative damage related to copper dyshomeostasis.

Exploiting the Metabolism of the Gut Microbiome as a Vehicle for Targeted Drug Delivery to the Colon

The prevalence of colon-associated diseases has increased significantly over the past several decades, as evidenced by accumulated literature on conditions such as Crohn’s disease, irritable bowel syndrome, colorectal cancer, and ulcerative colitis. Developing therapeutics for these diseases is challenging due to physiological barriers of the colon, systemic side effects, and the intestinal environment. Therefore, in a search for novel methods to overcome some of these problems, researchers discovered that microbial metabolism by gut microbiotia offers a potential method for targeted drug delivery This overview highlights several drug delivery systems used to modulate the microbiota and improve colon-targeted drug delivery. This technology will be important in developing a new generation of therapies which harness the metabolism of the human gut microflora.

Preparation of MSZ Hydrogel and Its Treatment of Colitis

In order to control the release of mesalazine (MSZ) in the gastrointestinal tract to achieve better pharmacological effects in the colon, in this study, MSZ was added to hydroxypropyl-β-cyclodextrin (HP-β-CD) to form a water-soluble HP-β-CD/MSZ inclusion complex. Then, the inclusion compound was loaded into the structure of the bilayer polyelectrolyte complex microsphere formed by alginate (Alg), chitosan (Cs), and kappa carrageenan (κ-Car) as the hydrogel carrier, and the hydrogel beads with colon-specific release MSZ after oral administration were formed. The formed hydrogel beads have different swelling capabilities in different pH media and have the greatest swelling degree under pH 7.4. The encapsulation efficiency and drug loading of hydrogel beads can reach up to 83.23 and 18.31%, respectively, and the size of hydrogel beads can be reduced to less than 1 mm after drying, so that the size of oral administration can be reached. In vivo experiments also showed that the formed hydrogel beads had a better therapeutic effect on colitis than free drugs, and the microspheres were biodegradable, so the double-layer pH-sensitive microspheres could be effectively used in colon-targeting drug delivery.

Design, Synthesis and Studies on Novel Polymeric Prodrugs of Erlotinib for Colon Drug Delivery

AIMS

In the present study, polymer-drug conjugates were synthesized based on azo-bond cleavage drug delivery approach for targeting erlotinib as an anticancer drug specifically to the colon for the proficient treatment of colon cancer.

BACKGROUND

Colon Cancer (CC) is the third commonly detected tumor worldwide and makes up about 10% of all cases of cancers. Most of the chemotherapeutic drugs available for treating colon cancer are not only toxic to cancerous cells but also to the normal healthy cells. Among the various approaches to get rid of the adverse effects of anticancer agents, prodrugs are one of the most imperative approaches.

OBJECTIVE

The objective of the study is to chemically modify the erlotinib drug through azo-bond linkage and suitable spacer which will be finally linked to the polymeric backbone to give the desired polymer linked prodrug. The azo reductase enzyme present in the colon is supposed to cleave the azo-bond specifically and augment the drug release at the colon.

METHODS

The synthesized conjugates were characterized by IR and 1H-NMR spectroscopy. The cleavage of aromatic azo-bond resulted in a potential colon-specific liberation of drug from conjugate studied in rat fecal contents. In vitro release profiles of polyphosphazene-linked conjugates of erlotinib have been studied at pH 1.2, pH 6.8 and pH 7.4. The stability study was designed to exhibit that free drug was released proficiently and unmodified from polyphosphazene-erlotinib conjugates having aromatic azo-bond in artificial colon conditions.

RESULTS

The synthesized conjugates were demonstrated to be stable in simulated upper gastrointestinal tract conditions. The drug release kinetics shows that all the polymer-drug conjugates of erlotinib follow zero-order release kinetics which indicates that the drug release from the polymeric backbone is independent of its concentration. Kinetic study of conjugates with slope (n) shows the anomalous type of release with an exponent (n) > 0.89 indicating a super case II type of release.

CONCLUSION

These studies indicate that polyphosphazene linked drug conjugates of erlotinib could be promising candidates for the site-specific treatment of colon cancer with the least detrimental side-effects.

A review on 5-aminosalicylic acid colon-targeted oral drug delivery systems

Site-specific colon drug delivery is a practical approach for the treatment of local diseases of the colon with several advantages such as rapid onset of action and reduction of the dosage of the drug as well as minimization of harmful side effects. 5-aminosalicylic acid (5-ASA) is a drug of choice in the treatment of inflammatory bowel disease and colitis. For the efficient delivery of this drug, it is vital to prevent 5-ASA release in the upper part of the gastrointestinal tract and to promote its release in the proximal colon. Different approaches including chemical manipulation of drug molecule for production of prodrugs or modification of drug delivery systems using pH-dependent, time-dependent and/or bacterially biodegradable materials have been tried to optimize 5-ASA delivery to the colon. In the current review, the different strategies utilized in the design and development of an oral colonic delivery dosage form of 5-ASA are presented and discussed.

Drug delivery strategies in the therapy of inflammatory bowel disease

Inflammatory bowel disease (IBD) is a frequently occurring disease in young people, which is characterized by a chronic inflammation of the gastrointestinal tract. The therapy of IBD is dominated by the administration of anti-inflammatory and immunosuppressive drugs, which suppress the intestinal inflammatory burden and improve the disease-related symptoms. Established treatment strategies are characterized by a limited therapeutical efficacy and the occurrence of adverse drug reactions. Thus, the development of novel disease-targeted drug delivery strategies is intended for a more effective therapy and demonstrates the potential to address unmet medical needs. This review gives an overview about the established as well as future-oriented drug targeting strategies, including intestine targeting by conventional drug delivery systems (DDS), disease targeted drug delivery by synthetic DDS and disease targeted drug delivery by biological DDS. Furthermore, this review analyses the targeting mechanisms of the respective DDS and discusses the possible field of utilization in IBD.

Design, synthesis and ex vivo evaluation of colon-specific azo based prodrugs of anticancer agents

Colon-specific azo based prodrugs of anticancer agents like methotrexate (6), gemcitabine (7) and analogue of oxaliplatin (RTB-4) (8) were synthesized and characterized by modern analytical techniques. The prepared prodrugs were stable in acidic (pH 1.2) and basic (pH 7.4) buffers which showed their stability in upper GIT environment. Further, an assay was performed which demonstrated the presence of azoreductase enzyme in the rat fecal material, rat cecum content and other parts of intestinal content which reduce specifically the azo bond and release the drug. The in vitro cytotoxicity assay was also performed which clearly indicated that these azo based prodrugs are active against human colorectal cancer cell lines (COLO 205, COLO 320 DM and HT-29). The release behavior of prodrugs (10, 11 and 15) was 60-70% after 24h incubation at 37°C. Therefore, the synthesized azo linked prodrugs of methotrexate, gemcitabine and RTB-4 are the potential candidates for colon targeted drug delivery system with minimal undesirable side effects.

Chemically cross-linked and grafted cyclodextrin hydrogels: from nanostructures to drug-eluting medical devices

The unique ability of cyclodextrins (CDs) to form inclusion complexes can be transmitted to polymeric networks in which CDs are chemically grafted or cross-linked. Combination of CDs and hydrogels in a single material leads to synergic properties: the hydrophilic network enhances biocompatibility and prevents dilution in the physiological medium increasing the stability of the inclusion complexes, while CDs finely tune the mechanical features and the stimuli-responsiveness and provide affinity-based regulation of drug loading and release. Therefore, CD-functionalized materials are opening new perspectives in pharmacotherapy, emerging as advanced delivery systems (DDS) for hydrophobic and hydrophilic drugs to be administered via almost any route. Medical devices (catheters, prosthesis, vascular grafts, bone implants) can also benefit from surface grafting or thermofixation of CDs. The present review focuses on the approaches tested to synthesize nano- to macro-size covalently cross-linked CD networks: i) direct cross-linking through condensation with di- or multifunctional reagents, ii) copolymerization of CD derivatives with acrylic/vinyl monomers, and iii) grafting of CDs to preformed medical devices. Examples of the advantages of having the CDs chemically bound among themselves and to substrates are provided and their applicability in therapeutics discussed.

Advanced technologies for oral controlled release: cyclodextrins for oral controlled release

Cyclodextrins (CDs) are used in oral pharmaceutical formulations, by means of inclusion complexes formation, with the following advantages for the drugs: (1) solubility, dissolution rate, stability, and bioavailability enhancement; (2) to modify the drug release site and/or time profile; and (3) to reduce or prevent gastrointestinal side effects and unpleasant smell or taste, to prevent drug-drug or drug-additive interactions, or even to convert oil and liquid drugs into microcrystalline or amorphous powders. A more recent trend focuses on the use of CDs as nanocarriers, a strategy that aims to design versatile delivery systems that can encapsulate drugs with better physicochemical properties for oral delivery. Thus, the aim of this work was to review the applications of the CDs and their hydrophilic derivatives on the solubility enhancement of poorly water-soluble drugs in order to increase their dissolution rate and get immediate release, as well as their ability to control (to prolong or to delay) the release of drugs from solid dosage forms, either as complexes with the hydrophilic (e.g., as osmotic pumps) and/or hydrophobic CDs. New controlled delivery systems based on nanotechnology carriers (nanoparticles and conjugates) have also been reviewed.

Selectively functionalized cyclodextrins and their metal complexes

Cyclodextrins (CDs) are cyclic oligomers of alpha-1,4-linked D-glucopyranose. Due to their unique structure, marked by a chiral and hydrophobic cavity, CDs have been extensively used as chiral selectors and drug delivery systems. The functionalization both improve the CD applications and widen their use in many other fields, such as molecular recognition and enzyme mimicking. Moreover, the functionalization highly increases the metal binding properties of the CDs. This critical review is a report of recent applications concerning the CD derivatives and their metal complexes. The metal ion assists the host-guest interaction often increasing the properties of CDs to act as chiral receptors. Furthermore, it can act as a catalytic center in the mimicking of metalloenzymes based on functionalized CDs (164 references).

IDENTIFICATION OF LIGANDS BINDING SPECIFICALLY TO INFLAMMATORY INTESTINAL MUCOSA USING PHAGE DISPLAY

1. Even though current treatments for inflammatory bowel disease are effective, adverse reactions remain a problem. With the intention of developing a new drug delivery system, we attempted to identify molecules that are selectively adsorbed to inflamed bowel. 2. The PhD-C7C phage display peptide library was used for biopanning against mouse isolated bowel, either untreated (control) or with inflammation caused by ischaemia-reperfusion injury. One hundred clones were selected from among those obtained by two biopanning procedures and the amino acid sequences of these clones were identified by determination of the base sequences. 3. Then, 20 clones were selected by an alignment process, after which the three clones with the highest affinity for inflammatory bowel were identified. One of these three clones had significantly higher affinity for inflammatory bowel than for normal bowel. 4. In conclusion, biopanning against isolated bowel samples identified an amino acid sequence (SQSHPRH) with a specific high affinity for inflammatory bowel.