Designing of pH-Sensitive Hydrogels for Colon Targeted Drug Delivery; Characterization and In Vitro Evaluation

Thermosensitive and pH-responsive quercus infectoria gall-containing gel with long-lasting anti-inflammatory activity for ulcerative colitis

In the study, quercus infectoria gall (QIG) was used to develop a pH/thermosensitive gel in situ delivery system for enema administration of to treat acute ulcerative colitis (UC). The QIG ethanol extract pH/temperature-sensitive gel (QIG-pH-TSG) was characterized by using DSC, SEM, rheological and drug release analyses. The therapeutic effect in UC mice of the obtained gel were studied. The gel was maintained in a flowing liquid state under nonphysiological conditions (25 °C) to facilitate drug administration, and was transformed into a pseudoplastic liquid state under physiological conditions (37 °C), which prolonged its retention time in the colon. The gel drug was completely released within 24 h, and the temperature and viscosity of the gel were within the required range. In the in vitro anti-inflammatory test, QIG-pH-TSG decreased the level of TNF-α and IL-6, and increased IL-10 in RAW 264.7 actived by LPS. Moreover, the administration of QIG-pH-TSG resulted in a decrease in the colon histopathological score and an increase in colonic length, and also could reduce the IL-6, TNF-α, and C-reactive protein (CRP) levels in UC mice along with significant increases in IL-10 level in the colon. The QIG-pH-TSG could increase the concentration of QIG at the local inflammatory site and lead to an effective repair of the colonic mucosa. Therefore, the pH/thermosensitive in situ gel may serve as a drug delivery system for QIG to treat UC and overcome the limitations of some existing formulations. These results indicated that this composite gel was effectively in UC mice and the study provided a practical reference for the application of QIG-pH-TSG in the treatment of UC.

pH-Sensitive Hydrogels Fabricated with Hyaluronic Acid as a Polymer for Site-Specific Delivery of Mesalamine

Hydrogels with the main objective of releasing mesalamine (5-aminosalicylic acid) in the colon in a modified manner were formulated in the present work using a free-radical polymerization approach. Different ratios of hyaluronic acid were cross-linked with methacrylic and acrylic acids using methylenebis(acrylamide). The development of a new polymeric network and the successful loading of drug were revealed by Fourier transform infrared spectroscopy. Thermogravimetric analysis demonstrated that the hydrogel was more thermally stable than the pure polymer and drug. Scanning electron microscopy (SEM) revealed a rough and hard surface which was relatively suitable for efficient loading of drug and significant penetration of dissolution medium inside the polymeric system. Studies on swelling and drug release were conducted at 37 °C in acidic and basic conditions (pH 1.2, 4.5, 6.8, and 7.4, respectively). Significant swelling and drug release occurred at pH 7.4. Swelling, drug loading, drug release, and gel fraction of the hydrogels increased with increasing hyaluronic acid, methacrylic acid, and acrylic acid concentrations, while the sol fraction decreased. Results obtained from the toxicity study proved the formulated system to be safe for biological systems. The pH-sensitive hydrogels have the potential to be beneficial for colon targeting due to their pH sensitivity and biodegradability. Inflammatory bowel disease may respond better to hydrogel treatment as compared to conventional dosage forms. Specific amount of drug is released from hydrogels at specific intervals to maintain its therapeutic concentration at the required level.

Functional Hydrogels for Delivery of the Proteolytic Enzyme Serratiopeptidase

Hydrogels are superior wound dressings because they can provide protection and hydration of the wound, as well as the controlled release of therapeutic substances to aid tissue regeneration and the healing process. Hydrogels obtained from natural precursors are preferred because of their low cost, biocompatibility, and biodegradability. We describe the synthesis of novel functional hydrogels based on two natural products-citric acid (CA) and pentane-1,2,5-triol (PT, a product from lignocellulose processing) and poly(ethylene glycol) (PEG-600)-via an environment friendly approach. The hydrogels were prepared via monomer crosslinking through a polycondensation reaction at an elevated temperature in the absence of any solvent. The reagents were blended at three different compositions with molar ratios of hydroxyl (from PT and PEG) to carboxyl (from CA) groups of 1:1, 1:1.4, and 1.4:1, respectively. The effect of the composition on the physicomechanical properties of materials was investigated. All hydrogels exhibited pH-sensitive behavior, while the swelling degree and elastic modulus were dependent on the composition of the polymer network. The proteolytic enzyme serratiopeptidase (SER) was loaded into a hydrogel via physical absorption as a model drug. The release profile of SER and the effects of the enzyme on healthy skin cells were assessed. The results showed that the hydrogel carrier could provide the complete release of the loaded enzyme.

Research progress of colon-targeted oral hydrogel system based on natural polysaccharides

The quality of life is significantly impacted by colon-related diseases. There have been a lot of interest in the oral colon-specific drug delivery system (OCDDS) as a potential carrier to decrease systemic side effects and protect drugs from degradation in the upper gastrointestinal tract (GIT). Hydrogels are effective oral colon-targeted drug delivery carriers due to their high biodegradability, substantial drug loading, and great biocompatibility. Natural polysaccharides give the hydrogel system unique structure and function to effectively respond to the complex environment of the GIT and deliver drugs to the colon. In this paper, the physiological factors of colonic drug delivery and the pathological characteristics of common colonic diseases are summarized, and the latest advances in the design, preparation and characterization of natural polysaccharide hydrogels are reviewed, which are expected to provide new references for colon-targeted oral hydrogel systems using natural polysaccharides as raw materials.

Biodegradable Gg-cl-poly(NIPAm-co-AA)/-o-MWCNT based hydrogel for combined drug delivery system of metformin and sodium diclofenac: in vitro studies

In the present study Gg-cl-poly(NIPA-co-AA) and Gg-cl-poly(NIPA-co-AA)/-o-MWCNT hydrogels were synthesized using free radical polymerization. We looked into whether combining metformin with diclofenac, a nonsteroidal anti-inflammatory drug (NSAID), would be effective in examining complex formation and analysing the types and intensities of complexes that could result from metformin-diclofenac interactions. The interaction of metformin and diclofenac was studied in vitro at various pH levels and body temperatures. The structure and morphology of the produced hydrogel were characterised using FTIR spectra, SEM analysis, and drug loading tests. As a model drug, the hydrogel was loaded with metformin hydrochloride and sodium diclofenac (DS), and the medicines were released pH-dependently. To explore the drug release kinetics and mechanism, the zero order and first order kinetic models, the Korsemeyar-Peppas model, the Higuchi model, and the Hixson-Crowell model have all been employed. Drug release studies revealed notable characteristics in connection to physiologically predicted pH values, with a high release rate at pH = 9.2. At pH = 9.2, however, both metformin and sodium diclofenac exhibited a Fickian mechanism. Combination treatment may reduce the effective dose of a single drug and hinder metabolic rescue mechanisms. More study is needed to detect any negative effects on individuals.

Release Rate Studies of 5-Aminosalacylic Acid Coated with Atomic Layer-Deposited Al2O3 and ZnO in an Acidic Environment

5-Aminosalicylic acid (5-ASA) is a first-line defense drug used to treat mild cases of inflammatory bowel disease. When administered orally, the active pharmaceutical ingredient is released throughout the gastrointestinal tract relieving chronic inflammation. However, delayed and targeted released systems for 5-ASA to achieve optimal dose volumes in acidic environments remain a challenge. Here, we demonstrate the application of atomic layer deposition (ALD) as a technique to synthesize nanoscale coatings on 5-ASA to control its release in acidic media. ALD Al₂O₃ (38.0 nm) and ZnO (24.7 nm) films were deposited on 1 g batch powders of 5-ASA in a rotatory thermal ALD system. Fourier transform infrared spectroscopy, scanning electron microscopy, and scanning/transmission electron microscopy establish the interfacial chemistry and conformal nature of ALD coating over the 5-ASA particles. While Al₂O₃ forms a sharp interface with 5-ASA, ZnO appears to diffuse inside 5-ASA. The release of 5-ASA is studied in a pH 4 solution via UV-vis spectroscopy. Dynamic stirring, mimicking gut peristalsis, causes mechanical attrition of the Al₂O₃-coated particles, thereby releasing 5-ASA. However, under static conditions lasting 5000 s, the Al₂O₃-coated particles release only 17.5% 5-ASA compared to 100% release with the ZnO coating. Quartz crystal microbalance-based etch studies confirm the stability of Al₂O₃ in pH 4 media, where the ZnO films etch 41× faster than Al₂O₃. Such results are significant in achieving a nanoscale coating-based drug delivery system for 5-ASA with controlled release in acidic environments.

A Review on Biomedical Application of Polysaccharide-Based Hydrogels with a Focus on Drug Delivery Systems

Over the last years of research on drug delivery systems (DDSs), natural polymer-based hydrogels have shown many scientific advances due to their intrinsic properties and a wide variety of potential applications. While drug efficacy and cytotoxicity play a key role, adopting a proper DDS is crucial to preserve the drug along the route of administration and possess desired therapeutic effect at the targeted site. Thus, drug delivery technology can be used to overcome the difficulties of maintaining drugs at a physiologically related serum concentration for prolonged periods. Due to their outstanding biocompatibility, polysaccharides have been thoroughly researched as a biological material for DDS advancement. To formulate a modified DDS, polysaccharides can cross-link with different molecules, resulting in hydrogels. According to our recent findings, targeted drug delivery at a certain spot occurs due to external stimulation such as temperature, pH, glucose, or light. As an adjustable biomedical device, the hydrogel has tremendous potential for nanotech applications in involved health areas such as pharmaceutical and biomedical engineering. An overview of hydrogel characteristics and functionalities is provided in this review. We focus on discussing the various kinds of hydrogel-based systems on their potential for effectively delivering drugs that are made of polysaccharides.

In Vitro and In Vivo Evaluation of Hydroxypropyl-β-cyclodextrin-grafted-poly(acrylic acid)/poly(vinyl pyrrolidone) Semi-Interpenetrating Matrices of Dexamethasone Sodium Phosphate

In this paper, we fabricated semi-interpenetrating polymeric network (semi-IPN) of hydroxypropyl-β-cyclodextrin-grafted-poly(acrylic acid)/poly(vinyl pyrrolidone) (HP-β-CD-g-poly(AA)/PVP) by the free radical polymerization technique, intended for colon specific release of dexamethasone sodium phosphate (DSP). Different proportions of polyvinyl pyrrolidone (PVP), acrylic acid (AA), and hydroxypropyl-beta-cyclodextrin (HP-β-CD) were reacted along with ammonium persulphate (APS) as initiator and methylene-bis-acrylamide (MBA) as crosslinker to develop a hydrogel system with optimum swelling at distal intestinal pH. Initially, all formulations were screened for swelling behavior and AP-8 was chosen as optimum formulation. This formulation was capable of releasing a small amount of drug at acidic pH (1.2), while a maximum amount of drug was released at colonic pH (7.4) by the non-Fickian diffusion mechanism. Fourier transformed infrared spectroscopy (FTIR) revealed successful grafting of components and development of semi-IPN structure without any interaction with DSP. Thermogravimetric analysis (TGA) confirmed the thermal stability of developed semi-IPN. X-ray diffraction (XRD) revealed reduction in crystallinity of DSP upon loading in the hydrogel. The scanning electron microscopic (SEM) images revealed a rough and porous hydrogel surface. The toxicological evaluation of semi-IPN hydrogels confirmed their bio-safety and hemocompatibility. Therefore, the prepared hydrogels were pH sensitive, biocompatible, showed good swelling, mechanical properties, and were efficient in releasing the drug in the colonic environment. Therefore, AP-8 can be deemed as a potential carrier for targeted delivery of DSP to treat inflammatory bowel diseases.