Controlled release of diclofenac sodium from pH-responsive carrageenan-g-poly(acrylic acid) superabsorbent hydrogel

Designing network structure hydrogels derived from carrageenan- phosphated polymers by covalent and supramolecular interactions for potential biomedical applications

Recently, various efforts have been made to explore the potential of natural polysaccharides derived from sea weeds to promote sustainable development. Herein, carrageenan (CG), a polysaccharide extracted from red sea algae, was utilized to design network structures as hydrogels, aimed at significant applications in drug delivery (DD) systems. Hydrogels were designed by graft copolymerization reaction of poly(bis [2-methacryloyloxy] ethyl phosphate [poly(BMEP)] and poly(acrylic acid) [poly(AAc)] onto CG in the presence of a crosslinking agent. Hydrogels were developed by covalent linkage by graft copolymerization and supramolecular interactions, existing in the copolymers. Copolymers were characterized by Atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), 13C-nuclear magnetic resonance (NMR), and X-ray diffraction (XRD) instrumentations. The drug diffusion exhibited a sustained pattern due to polymer-drug interactions. The drug release followed non-Fickian diffusion mechanism and the release profile was most accurately depicted by first order kinetic model. The biocompatible nature of the copolymer was demonstrated from the hemolytic index value signifying minimal adverse interactions with blood component upon exposure. A protein adsorption test was performed using bovine serum albumin (BSA), exhibiting 8.15 ± 0.26 % albumin adsorption. Polymers exhibited mucoadhesive character, evidenced by their requirement of a detachment force measuring 195 ± 4.72 mN for separation from the membrane during interactions with the mucosal surface. The hydrogels exhibited antioxidant properties, evidenced by 2, 2'-Diphenylpicrylhydrazyl (DPPH) assay, revealing copolymer capable of scavenging 58.21 ± 2.26 % of free radical. The hydrogel revealed antimicrobial activity against P. aeruginosa and S. aureus bacteria, a property further enhanced in hydrogels with the drug doxycycline. These findings suggest suitability of these hydrogels for biomedical applications, with a significant emphasis on drug delivery.

UV-Crosslinked Poly(N-isopropylacrylamide) Interpenetrated into Chitosan Structure with Enhancement of Mechanical Properties Implemented as Anti-Fouling Materials

High-performance properties of interpenetration polymer network (IPN) hydrogels, based on physically crosslinked chitosan (CS) and chemically crosslinked poly(N-isopropylacrylamide) (PNiPAM), were successfully developed. The IPN of CS/PNiPAM is proposed to overcome the limited mechanical properties of the single CS network. In this study, the viscoelastic behaviors of prepared materials in both solution and gel states were extensively examined, considering the UV exposure time and crosslinker concentration as key factors. The effect of these factors on gel formation, hydrogel structures, thermal stabilities of networks, and HeLa cell adhesion were studied sequentially. The sol-gel transition was effectively demonstrated through the scaling law, which agrees well with Winter and Chambon's theory. By subjecting the CS hydrogel to the process operation in an ethanol solution, its properties can be significantly enhanced with increased crosslinker concentration, including the shear modulus, crosslinking degree, gel strength, and thermal stability in its swollen state. The IPN samples exhibit a smooth and dense surface with irregular pores, allowing for much water absorption. The HeLa cells were adhered to and killed using the CS surface cationic charges and then released through hydrolysis by utilizing the hydrophilic/hydrophobic switchable property or thermo-reversible gelation of the PNiPAM network. The results demonstrated that IPN is a highly attractive candidate for anti-fouling materials.

A novel pH-responsive hydrogel system based on Prunus armeniaca gum and acrylic acid: Preparation and evaluation as a potential candidate for controlled drug delivery

pH-responsive hydrogels have become effective and attractive materials for the controlled release of drugs at pre-determined destinations. In the present study, a novel hydrogel system based on Prunus armeniaca gum (PAG) and acrylic acid (AA) was prepared by a free radical mechanism using N, N-methylene bisacrylamide (MBA) as cross-linker and potassium persulfate (KPS) as initiator. A series of hydrogels varying PAG, AA, and MBA concentration was developed to determine the impact of these components. Formulated hydrogels were characterized for pH-responsive swelling, drug release, gel content, and porosity. Structural analysis was performed by FTIR, XRD, and SEM analysis. TGA study was applied to assess thermal stability. Oral acute toxicity and in vivo drug release were performed in rabbits. Hydrogels exhibited pH-dependent swelling and drug release. Swelling, drug loading and release, and porosity increased by increasing PAG and AA concentration while decreased by increasing MBA. The gel content of formulations was increased by increasing all three components. FTIR studies confirmed the development of copolymeric networks and the loading of drug. XRD studies revealed that hydrogels were amorphous, and the crystalline drug was changed into an amorphous form during loading. TGA results indicated that hydrogels were stable up to 600 °C. Acute oral toxicity results confirm that hydrogels were nontoxic up to a dose of 2 g/kg body weight in rabbits. The pharmacokinetic evaluation revealed that hydrogels prolonged the availability of the drug and the peak plasma concentration of the drug was obtained in 6 h as compared to the oral solution of the drug. Tramadol hydrochloride (THC) was used as a model drug. Hence, pH-responsive swelling and release, nontoxic nature and improved pharmacokinetics support that PAG-based hydrogels may be considered as potential controlled-release polymeric carriers.

New formulations based on salicyl-imine-chitosan hydrogels for prolonged drug release

The objective of this paper was to investigate the new formulations based on salicyl-imine-chitosan hydrogels as potential controlled drug release systems. They were prepared by in situ hydrogelation of chitosan with salicylaldehyde in the presence of diclofenac sodium salt (DCF) as model drug. FTIR, X-ray Spectroscopy, POM and SEM techniques were used to confirm the structural, supramolecular and morphological particularities of the formulations. Swelling test, in vitro enzymatic biodegradation and release profile were investigated in similar conditions mimicking the in vivo environment, and the release mechanism was assessed by fitting into five mathematical models. It was established that the formulations have the capacity to release DCF in a sustained manner for 10 days rate, the drug release rate being correlated to the crosslinking density and hydrogelation speed. The biodegradation occurred in three main stages, reaching a mass loss of 48% after 21 days. In order to be used in the biomedical field, the in vivo biocompatibility of the formulations was investigated on experimental rats. After 7 days of subcutaneous implantation, no influence on the hematologic profile, liver, kidney or immune defence capacity were observed, suggesting these formulations as valuable materials for biomedical devices.

Carrageenan hydrogel as a scaffold for skin-derived multipotent stromal cells delivery

Carrageenan is a thermoreversible polymer of natural origin widely used in food and pharmaceutical industry that presents a glycosaminoglycan-like structure. Herein, we show that kappa-type carrageenan extracted by a semi-refined process from the red seaweed Kappaphycus alvarezii displayed both chemical and structural properties similar to a commercial carrageenan. Moreover, both extracted carrageenan hydrogel and commercial carrageenan hydrogel can serve as a scaffold for in vitro culture of human skin-derived multipotent stromal cells, demonstrating considerable potential as cell-carrier materials for cell delivery in tissue engineering. Skin-derived multipotent stromal cells cultured inside the carrageenan hydrogels showed a round shape morphology and maintained their growth and viability for at least one week in culture. Next, the effect of the extracted carrageenan hydrogel loaded with human skin-derived multipotent stromal cells was evaluated in a mouse model of full-thickness skin wound. Macroscopic and histological analyses revealed some pointed ameliorated features, such as reduced inflammatory process, faster initial recovery of wounded area, and improved extracellular matrix deposition. These results indicate that extracted carrageenan hydrogel can serve as a scaffold for in vitro growth and maintenance of human SD-MSCs, being also able to act as a delivery system of cells to wounded skin. Thus, evaluation of the properties discussed in this study contribute to a further understanding and specificities of the potential use of carrageenan hydrogel as a delivery system for several applications, further to skin wound healing.

Localized and targeted delivery of NSAIDs for treatment of inflammation: A review

IMPACT STATEMENT

This work provides an overview of research currently being done exploring potential drug delivery device strategies for NSAIDs as an alternative to systemic delivery. Commentary on this field is made in an attempt to aid future experimental design, enabling researchers to determine the drugs and delivery vehicles which are most advantageous for them to pursue, as well as suggestions to standardize the reporting of such future research.

Controlled release fertilizers using superabsorbent hydrogel prepared by gamma radiation

Superabsorbent hydrogels (PVP/CMC) based on polyvinylpyrrolidone (PVP)/carboxylmethyl cellulose (CMC) of different copolymer compositions were prepared by gamma radiation. Factors affecting the gel content (%) and the swelling ratio (g/g) of hydrogel such as irradiation dose as well as copolymer composition were investigated. With increasing the CMC content in PVP/CMC hydrogels, increases the swelling and improves the water retention capability. The high swelling ratio was observed at copolymer composition of PVP/CMC (60/40). Fast swelling of the hydrogels was obtained after 20 min. The effect of different fertilizers and buffers of different pH’s on equilibrium swelling of hydrogels was investigated. Fertilizers such as urea, monopotassium-phosphate (MPK), and nitrogen-phosphate-potassium (NPK) were loaded onto the hydrogel to supply nitrogen, potassium and phosphorous nutrients. PVP/CMC hydrogels retained 28–36% after 72 h and slow retention was noticed up to 9 days. The swelling of hydrogel in fertilizer solutions is lower than that in water. The hydrogels showed adsorption desorption of fertilizers which governs by slow release property. The release rate of urea is much higher 10 times than that of phosphate. After 3 days, urea released 60%, while phosphate released 10–12%. The applicability of PVP/CMC hydrogels in the agricultural fields shows greater growth effect on zea maize plants. The growth of zea maize plant in soil mixed with PVP/CMC hydrogels loaded fertilizers is greater than untreated soil. The slow release fertilize, the high swelling and the slow water retention behaviors of PVP/CMC hydrogels encourage their use as safer release systems for fertilizers and as soil conditioner in agricultural applications.

Cross-linked β-cyclodextrin and carboxymethyl cellulose hydrogels for controlled drug delivery of acyclovir

To explore the potential role of polymers in the development of drug-delivery systems, this study investigated the use of β-cyclodextrin (β-CD), carboxymethyl cellulose (CMC), acrylic acid (AA) and N’ N’-methylenebis-acrylamide (MBA) in the synthesis of hydrogels for controlled drug delivery of acyclovir (ACV). Different proportions of β-CD, CMC, AA and MBA were blended with each other to fabricate hydrogels via free radical polymerization technique. Fourier transform infrared spectroscopy (FTIR) revealed successful grafting of components into the polymeric network. Thermal and morphological characterization confirmed the formation of thermodynamically stable hydrogels having porous structure. The pH-responsive behaviour of hydrogels has been documented by swelling dynamics and drug release behaviour in simulated gastrointestinal fluids. Drug release kinetics revealed controlled release behaviour of the antiviral drug acyclovir in developed polymeric network. Cross-linked β-cyclodextrin and carboxymethyl cellulose hydrogels can be used as promising candidates for the design and development of controlled drug-delivery systems.

Intestinal Targeting of Ganciclovir Release Employing a Novel HEC-PAA Blended Lyomatrix

A hydroxyethylcellulose-poly(acrylic acid) (HEC-PAA) lyomatrix was developed for ganciclovir (GCV) intestine targeting to overcome its undesirable degradation in the stomach. GCV was encapsulated within the HEC-PAA lyomatrix prepared by lyophilization. Conventional tablets were also prepared with identical GCV concentrations in order to compare the GCV release behavior from the lyomatrix and tablets. GCV incorporation (75.12%) was confirmed using FTIR, DSC, and TGA. The effect of GCV loading on the microstructure properties of the lyomatrix was evaluated by SEM, AFM, and BET surface area measurements. The in vitro drug release study showed steady and rapid release profiles from the GCV-loaded lyomatrix compared with the tablet formulation at identical pH values. Minimum GCV release was observed at acidic pH (≤40%) and maximum release occurred at intestinal pH values (≥90%) proving the intestinal targeting ability of the lyomatrix. Kinetic modeling revealed that the GCV-loaded lyomatrix exhibited zero-order release kinetics (n = 1), while the tablets were best described via the Peppas model. Textural analysis highlighted enhanced matrix resilience and rigidity gradient (12.5%, 20 Pa) for the GCV-loaded lyomatrix compared to the pure (7%, 9.5 Pa) HEC-PAA lyomatrix. Bench-top MRI imaging was used to confirm the mechanism of GCV release behavior by monitoring the swelling and erosion rates. The swelling and erosion rate of the tablets was not sufficient to achieve rapid zero-order GCV release as with the lyomatrix. These combined results suggest that the HEC-PAA lyomatrix may be suitable for GCV intestinal targeting after oral administration.

Enhanced drug release by selective cleavage of cross-links in a double-cross-linked hydrogel

Poly(acrylic acid) hydrogels were synthesized using two different cross-linking agents namely, cystamine and Jeffamine. The redox sensitive di-sulfide linkages could be selectively cleaved to enhance the release of doxorubicin.

Meticulous Overview on the Controlled Release Fertilizers

Owing to the high demand for fertilizer formulations that will exhaust the possibilities of nutrient use efficiency (NUE), regulate fertilizer consumption, and lessen agrophysicochemical properties and environmental adverse effects instigated by conventional nutrient supply to crops, this review recapitulates controlled release fertilizers (CRFs) as a cutting-edge and safe way to supply crops’ nutrients over the conventional ways. Essentially, CRFs entail fertilizer particles intercalated within excipients aiming at reducing the frequency of fertilizer application thereby abating potential adverse effects linked with conventional fertilizer use. Application of nanotechnology and materials engineering in agriculture particularly in the design of CRFs, the distinctions and classification of CRFs, and the economical, agronomical, and environmental aspects of CRFs has been revised putting into account the development and synthesis of CRFs, laboratory CRFs syntheses and testing, and both linear and sigmoid release features of CRF formulations. Methodical account on the mechanism of nutrient release centring on the empirical and mechanistic approaches of predicting nutrient release is given in view of selected mathematical models. Compositions and laboratory preparations of CRFs basing on in situ and graft polymerization are provided alongside the physical methods used in CRFs encapsulation, with an emphasis on the natural polymers, modified clays, and superabsorbent nanocomposite excipients.

New Semi-IPN Hydrogels Based on Cellulose for Biomedical Application

Cellulose pulp, obtained from a paper industry, has been dissolved in PEG/NaOH system and the resulting solution has been polymerized in the presence of monomer acrylic acid (AA) and crosslinker N,N′ methylene bisacrylamide via free radical polymerization. The Cell/PEG/poly (SA) ternary semi-IPN hydrogel, so prepared, was characterized by FTIR and TG analysis. The dynamic water uptake of various hydrogels, having different compositions, was investigated in the physiological buffer of pH 7.4 at 37°C. The various hydrogels exhibited chain-relaxation controlled swelling behavior. The uptake data was best interpreted by Schott kinetic model. The various diffusion coefficients, that is, initial (Di), average (Dave), and late time (DL), were also calculated using the dynamic water uptake data. The hydrogels showed fair pH and salt-dependent swelling behavior.

Evaluation of the in vitro and in vivo biocompatibility of carrageenan-based hydrogels

Carrageenans are highly sulphated galactans, well-known for their thermogelation properties which have been extensively exploited in food and cosmetics industry but poorly explored in the biomedicine field. In this study, we have assessed the in vitro and in vivo biocompatibility of κ-carrageenan hydrogels that have been explored for regenerative medicine and tissue engineering applications. The in vitro cytotoxicity of the materials using a L929 mouse fibroblast cell line was evaluated, and the effect of κ-carrageenan hydrogels on the activation of human polymorphonuclear neutrophils cells (hPMNs) was also evaluated by the quantification of reactive oxygen species by chemiluminescence. Subsequently, the inflammatory/immune reaction to κ-carrageenan hydrogels on subcutaneous implantation was studied in rats. Explants were retrieved after 1 and 2 weeks of implantation for histological and RT-PCR analysis. The cytotoxicity screening revealed that κ-carrageenan hydrogels did not significantly affect L929 metabolic activity. Moreover, hPMNs contact with κ-carrageenan resulted in a reduced and a neglectable signal regarding the detection of superoxide and hydroxyl anions, respectively. The results from the in vivo experiments indicated that κ-carrageenan induce a low inflammatory response. Overall, the data obtained suggest that κ-carrageenan hydrogels are biocompatible and thus can be further studied for their use in target biomedical applications.

Crosslinked ionic polysaccharides for stimuli-sensitive drug delivery

Polysaccharides are gaining increasing attention as components of stimuli-responsive drug delivery systems, particularly since they can be obtained in a well characterized and reproducible way from the natural sources. Ionic polysaccharides can be readily crosslinked to render hydrogel networks sensitive to a variety of internal and external variables, and thus suitable for switching drug release on-off through diverse mechanisms. Hybrids, composites and grafted polymers can reinforce the responsiveness and widen the range of stimuli to which polysaccharide-based systems can respond. This review analyzes the state of the art of crosslinked ionic polysaccharides as components of delivery systems that can regulate drug release as a function of changes in pH, ion nature and concentration, electric and magnetic field intensity, light wavelength, temperature, redox potential, and certain molecules (enzymes, illness markers, and so on). Examples of specific applications are provided. The information compiled demonstrates that crosslinked networks of ionic polysaccharides are suitable building blocks for developing advanced externally activated and feed-back modulated drug delivery systems.

Preparation of Salt-Resistance Superabsobent Microspheres by Inverse Suspension Polymerization

Novel salt-resistance superabsobent microspheres based on acrylamide (AM), 2-acrylamido-2-methylpropane sulphonic acid (AMPS) by inverse suspension copolymerization using ammonium persulfate (APS) as the initiator and N,N-methylene bisacrylamide (MBA) as the crosslinking agent and surfactant PVA as disperse agent are prepared. The experimental results of salt-resistance superabsobent microspheres show the salt absorbency decreased with the increase of salt concentration; The maximum salt absorbency is 132g/g within 75min in 0.9% NaCl solution and the effect of calcium ion on salt absorbency is much greater than that of sodium ion. FTIR indicates the structure of the acrylamide and 2-acrylamido-2- methylpropane sulphonic acid copolymer. SEM indicates that the number of the micropores largely decreased with the water/oil ratio increasing from 4% to 10%. Elemental analysis indicate that the measured values of carbon, sulfur, nitrogen, hydrogen four elements is very close to theoretical value.