Synthesis and applications of polyacrylamide grafted agar as a matrix for controlled drug release of 5-ASA

Agar Graft Modification with Acrylic and Methacrylic Acid for the Preparation of pH-Sensitive Nanogels for 5-Fluorouracil Delivery

Agar, a naturally occurring polysaccharide, has been modified by grafting it with acrylic (AcA) and methacrylic (McA) acid monomers, resulting in acrylic or methacrylic acid grafted polymer (AA-g-AcA or AA-g-McA) with pH-sensitive swelling behavior. Different ratios between agar, monomers, and initiator were applied. The synthesized grades of both new polymer series were characterized using FTIR spectroscopy, NMR, TGA, DSC, and XRD to ascertain the intended grafting. The percentage of grafting (% G), grafting efficiency (% GE), and % conversion (% C) were calculated, and models with optimal characteristics were further characterized. The swelling behavior of the newly synthesized polymers was studied over time and in solutions with different pH. These polymers were subsequently crosslinked with varying amounts of glutaraldehyde to obtain 5-fluorouracil-loaded nanogels. The optimal ratios of polymer, drug, and crosslinker resulted in nearly 80% loading efficiency. The performed physicochemical characterization (TEM and DLS) showed spherical nanogels with nanometer sizes (105.7-250 nm), negative zeta potentials, and narrow size distributions. According to FTIR analysis, 5-fluorouracil was physically incorporated. The swelling and release behavior of the prepared nanogels was pH-sensitive, favoring the delivery of the chemotherapeutic to tumor cells. The biocompatibility of the proposed nanocarrier was proven using an in vitro hemolysis assay.

Fabricating gum polysaccharides based nano-composites for drug delivery uses via sustainable green approach

Recent advancements in development of natural polymer nono-composites led to exploration of potential of gum acacia (GA) and tragacanth gum (TG) for design of silver nanoparticles (AgNPs) impregnated grafted copolymers via green approach for use in drug delivery (DD). The formation of copolymers was confirmed by UV-Vis spectroscopy, TEM, SEM, AFM, XPS, XRD, FTIR,TGA and DSC. UV-Vis spectra indicated the formation of AgNPs using GA as reducing agent. TEM, SEM, XPS and XRD revealed impregnation of AgNPs inside the copolymeric network hydrogels. TGA inferred thermal stability of polymer enhanced by grafting and incorporation of AgNPs. The non-Fickian diffusion of antibiotic drug meropenem was revealed from drug encapsulated GA-TG-(AgNPs)-cl-poly(AAm) network which were also pH responsive and release profile was fitted in Korsmeyer-Peppas kinetic model. Sustained release was due to polymer-drug interaction. The polymer-blood interaction demonstrated biocompatible characteristics of polymer. Mucoadhesive property exhibited by copolymers because of supra-molecular interactions. Antimicrobial characteristics were shown by copolymers against bacteria S. flexneri, P. auroginosa, and B. cereus.

Design of polyacrylamide grafted sesbania gum-mediated pH-responsive IPN-based microbeads for delivery of diclofenac sodium: In-vitro-in-vivo characterizations

Microwave-assisted grafting of polyacrylamide on sesbania gum (PAAM-g-SG) was implemented employing a 3² full factorial experimental design and was hydrolyzed using sodium hydroxide (NaOH) to form H-PAAM-g-SG. Further, the diclofenac sodium-loaded novel pH-sensitive interpenetrating polymeric network (IPN) microbeads were designed using an optimized H-PAAM-g-SG and sodium alginate (SA). Different spectroscopic analysis including FTIR spectroscopy, ¹H NMR spectroscopy, elemental analysis, thermal analysis, etc. was performed to confirm the synthesis of PAAM-g-SG and diclofenac-loaded pH-sensitive IPN H-PAAM-g-SG-SA microbeads. Here, Ca⁺² ions combine with two strands of SA and form a round-shape structure that encloses uncross-linked H-PAAM-g-SG polymer and diclofenac sodium. As well, glutaraldehyde (GL) addition improved the mechanical strength due to acetal structure between hydroxyl of H-PAAM-g-SG and aldehyde of GL. The drug entrapment was confirmed proportional relationship to the Ca⁺² ions concentration whereas an increase in GL concentration resulted in a reduced drug entrapment. The pH pulsatile study assured the reversible swelling-shrinkage behavior of IPN microbeads due to the carboxyl group of PAAM-g-SG. The drug release from H-PAAM-g-SG-SA microbeads (batch: S9) was found to be 84.21 % (12h) which was non-significant (p > 0.05; f2 = 79 ∼ 90) over marketed formulation (83.31 %). Moreover, it follows the Korsmeyer Peppas (R² = 0.996) as the best-fit release kinetic model. The pH-sensitive release of diclofenac sodium from IPN H-PAAM-g-SG-SA microbeads was assured based on in vivo anti-inflammatory activity (p < 0.05). Therefore, developed novel pH-sensitive IPN microbeads based on H-PAAM-g-SG are a promising polymeric carrier substitute for delivery of drugs actuated by a pH stimulus.

Chemical modifications in the structure of marine polysaccharide as serviceable food processing and preservation assistant: A review

Marine polysaccharides are a kind of natural polysaccharides which isolated and extracted from marine organisms. Now some marine polysaccharides, such as chitosan, sodium alginate and agar, have been proven to exhibit antibacterial, antioxidant functions and biocompatibility, which are often used to preserve food or improve the physicochemical properties of food. However, they still have the defects of unsatisfactory preservation effect and biological activity, which can be remedied by its modification. Chemical modification is the most effective of all modification methods. The advances in common chemical modification methods of chitosan, sodium alginate, agar and other marine polysaccharides and research progress of modified products in food processing and preservation were summarized, and the influence of additional reaction conditions on the existence of chemical modification sites of polysaccharides was discussed. The modification of functional groups in natural marine polysaccharides leads to the change of molecular structure, which can improve the physical, chemical and biological properties of marine polysaccharides. Chemically modified products have been used in various fields of food applications, such as food preservatives, food additives, food packaging, and food processing aids. In general, chemical modification has excellent potential for food processing and preservation, which can improve the function of marine polysaccharides.

Natural Polysaccharide Strengthened Hydrogel Electrolyte and Biopolymer Derived Carbon for Durable Aqueous Zinc Ion Storage

Aqueous zinc-ion hybrid supercapacitors (ZHSCs) represent one of the current research subjects because of their flame retardancy, ease of manufacturing, and exceptional roundtrip efficiency. With the evolution into real useful energy storage cells, the bottleneck factors of the corrosion and dendrite growth problems must be properly resolved for largely boosting their cycling life and energy efficiency. Herein, a natural polysaccharide strengthened hydrogel electrolyte (denoted as PAAm/agar/Zn(CF3SO3)2) was engineered by designing an asymmetric dual network of covalently cross-linked polyacrylamide (denoted as PAAm) and physically cross-linked loose polysaccharide (e.g., agar) followed by intense uptake of Zn(CF3SO3)2 aqueous electrolyte. In this polymeric matrix, the PAAm chains are responsible for constructing the soft domains to immobilize the water molecules, and the agar component boosts the mechanical performance (by using its inherent reversible sacrificial bonds) and favors the electrolyte ion transport. Due to these reasons, the as-designed hydrogel electrolyte effectively inhibits the zinc dendrite growth, realizes the uniform Zn deposition, and affords a satisfactory ionic conductivity of 1.55 S m-1, excellent tensile strength (78.9 kPa at 507.7% stretchable), and high compression strength (118.0 kPa at 60.0% strain). Additionally, a biopolymer-derived N-doped carbon microsphere cathode material with a highly interconnected porous carbonaceous network (denoted as NC) was also synthesized, which delivers a high capacity of 92.8 mAh g-1, along with superb rate capability and long duration cycling lifespan (95.4% retention for 10000 cycles) in the aqueous Zn//NC ZHSC. More notably, with integrated merits of the PAAm/agar/Zn(CF3SO3)2 hydrogel electrolyte and NC, the as-built quasi-solid-state ZHSC achieves a high specific capacity of 73.4 mAh g-1 and superior energy density of 61.3 Wh kg-1 together with excellent cycling stability for 10000 cycles. This work demonstrated favorable practicability in the structural design of the hydrogel electrolytes and electrode materials for advanced ZHSC applications.

Effect of pectin and attapulgite filler on swelling, network parameters and controlled release of diltiazem hydrochloride from polyacrylic copolymer gel

Pectin grafted polyacrylic copolymer hydrogels were made by free radical crosslink copolymerization of acrylic acid (AA) and acrylamide (AM) in an aqueous solution of pectin. N'N-methylene bis acrylamide (MBA) was used as a crosslinker. During the polymerization reaction the attapulgite (APG) filler was also incorporated in situ into the network of the copolymer gel. Several filled hydrogels were prepared by varying the amount of pectin and APG filler. These hydrogels were characterized by FTIR, ¹³C NMR, XRD, TGA, SEM, mechanical properties, DMA, swelling, diffusion characteristics and network parameters. The release kinetics of a model drug diltiazem hydrochloride (DT) was studied with these hydrogels. The wt% of pectin, APG and MBA was optimized with a central composite design (CCD) model of response surface methodology (RSM) with equilibrium swelling ratio (ESR), drug adsorption (mg/100 mg gel) and drug release% in 16 h as response. Accordingly, the hydrogel prepared with 5:1 AA:AM molar ratio, 25 wt% monomer concentration, 1% each of initiator and MBA concentration, 18 wt% pectin and 2 wt% APG showed an optimized ESR of 17.75, drug loading of 27.58 and a drug release % of 92.5 in 16 h at a solution pH of 7.4.

Thermo Compression of Thermoplastic Agar-Xanthan Gum-Carboxymethyl Cellulose Blend

There is a gap in the literature for the preparation of agar-xanthan gum-carboxymethyl cellulose-based films by thermo compression methods. The present work aims to fill this gap by blending the polysaccharides in a plastograph and preparation of films under high pressure and temperature for a short duration of time. The pivotal aim of this work is also to know the effect of different mixing conditions on the physical, chemical, mechanical and thermal properties of the films. The films are assessed based on results from microscopic, infrared spectroscopic, permeability (WVTR), transmittance, mechanical, rheological and thermogravimetric analysis. The results revealed that the mixing volume and mixing duration had negative effects on the films' transparency. WVTR was independent of the mixing conditions and ranged between 1078 and 1082 g/m2·d. The mixing RPM and mixing duration had a positive effect on the film tensile strength. The films from the blends mixed at higher RPM for a longer time gave elongation percentage up to 78%. Blending also altered the crystallinity and thermal behavior of the polysaccharides. The blend prepared at 80 RPM for 7 min and pressed at 140 °C showed better percent elongation and light barrier properties.

Plant-Based Gums and Mucilages Applications in Pharmacology and Nanomedicine: A Review

Gums are carbohydrate biomolecules that have the potential to bind water and form gels. Gums are regularly linked with proteins and minerals in their construction. Gums have several forms, such as mucilage gums, seed gums, exudate gums, etc. Plant gums are one of the most important gums because of their bioavailability. Plant-derived gums have been used by humans since ancient times for numerous applications. The main features that make them appropriate for use in different applications are high stabilization, viscosity, adhesive property, emulsification action, and surface-active activity. In many pharmaceutical formulations, plant-based gums and mucilages are the key ingredients due to their bioavailability, widespread accessibility, non-toxicity, and reasonable prices. These compete with many polymeric materials for use as different pharmaceuticals in today's time and have created a significant achievement from being an excipient to innovative drug carriers. In particular, scientists and pharmacy industries around the world have been drawn to uncover the secret potential of plant-based gums and mucilages through a deeper understanding of their physicochemical characteristics and the development of safety profile information. This innovative unique class of drug products, useful in advanced drug delivery applications, gene therapy, and biosynthesis, has been developed by modification of plant-based gums and mucilages. In this review, both fundamental and novel medicinal aspects of plant-based gums and mucilages, along with their capacity for pharmacology and nanomedicine, were demonstrated.

Guar gum based hydrogel as controlled micronutrient delivery system: Mechanism and kinetics of boron release for agricultural applications

A boron loaded super-absorbent hydrogel (BLSAH) was developed through in situ incorporation of boron (B) in a guar gum-based hydrogel and characterized with FTIR, thermo-gravimetric analysis (TGA), scanning electron microscopy (SEM), and swelling studies, showing maximum absorption up to 356 g/g. The release pattern of B from the BLSAH and its kinetics was studied in water as well as soil. The B release pattern of the BLSAH was also compared with the commercial B fertilizer, boronated single super phosphate (bSSP). The BLSAH, following the Fickian mechanism, released 38% B, as compared with 51% of the bSSP, during the incubation period of 30 days in soil. The half-life period for the BLSAH (96.25 days) in soil was almost triple that of the bSSP's half-life (33.32 days), which is indicative of the slow and controlled release of B from the BLSAH. Thus, owing to its sustained nutrient release ability, the synthesized BLSAH exhibited wide potential for applications in agriculture sector.

Microwave assisted synthesis of polyacrylamide grafted polymeric blend of fenugreek seed mucilage-Polyvinyl alcohol (FSM-PVA-g-PAM) and its characterizations as tissue engineered scaffold and as a drug delivery device

Microwave assisted synthesis of graft copolymer of polymeric blend of Fenugreek seed mucilage (FSM)-Polyvinyl alcohol (PVA) with acrylamide (AM) was done by free radical polymerization using ammonium per sulfate (APS) as initiator. Varying amount of AM and APS was used to optimize the best grade based on highest percentage grafting efficiency and investigated with intrinsic viscosity measurement, Fourier Transformation infrared spectroscopy (FTIR),13C NMR spectra, X-ray diffraction, elemental analysis, Thermogravimetric analysis, Scanning electron microscopy. The results of intrinsic viscosity indicate that the optimized sample GF4 has longer chain length than in comparison to the native mucilage and thus exhibits more swelling tendencies and thus can be used as very good controlled release matrix system. The thermal analysis and X-ray indicates that GF4 is more stable and possess more amorphous properties than the native FSM. The NMR and FT-IR studies reveal that in GF4 there is prominent presence of amide and the hydroxyl groups indicating that grafting mechanism has efficiently taken place. Histological studies & SEM image for optimized grade implanted on animals revealed sufficient tissue growth and exhibited biodegradability proving the material to be biocompatible and suitable to be used as tissue engineered scaffolds. The controlled release behavior of the optimized polymeric system GF4 was evidenced by 95% release of loaded drug Enalapril maleate for 16 h. Graphical abstract.

Synthesis and quantitative analyses of acrylamide-grafted poly(lactide-co-glycidyl methacrylate) amphiphilic copolymers for environmental and biomedical applications

Bio-degradable/bio-compatible poly(lactide-co-glycidyl methacrylate), P(LA-co-GMA), a copolymer has been synthesized. The material contains curable CC groups, which enable its self-curing and grafting reactions with other vinyl monomers. The copolymer was grafted with a pH-responsive polyacrylamide (PAAm), by UV-assisted reactions using acrylamide (AAm) and N,N'-methylene bisacrylamide monomers, and various photoinitiator systems. The original copolymer and its partially-cured counterpart were employed in the grafting reaction. Chemical structures and properties of the resulting materials were characterized. Standard quantitative analysis techniques for measurement of the grafted AAm content and the degree of CC conversion have been developed by ¹H NMR and FTIR spectroscopy. FTIR offers more advantages, in terms of non-destructive analysis, ease of operation, and lower cost of analysis. The results show that the grafted products from pre-cured P(LA-co-GMA) copolymers contain higher grafted AAm contents than their uncured counterparts. The highest grafted AAm content was obtained by using benzophenone (BP) as an initiator, while camphorquinone (CQ) led to the lowest content. In contrast, the degree of CC conversion of the copolymer from the two initiator systems shows a reverse trend. These amphiphilic and pH-responsive grafted copolymers with tunable AAm contents have a high potential for use in various applications, especially in biomedical and environmental fields.

Controlled release of organic-inorganic nanohybrid:cefadroxil intercalated Zn-Al-layered double hydroxide

BACKGROUND

The intercalation of an antibiotic drug, cefadroxil (CD), into the inter-gallery of Zn, Al nitrate-layered double hydroxide (LDH) was accomplished using a co-precipitation method. This formed a nanostructured organic-inorganic hybrid material that can be exploited for the preparation of a controlled release formulation.

MATERIALS AND METHODS

The drug-LDH nanohybrid was characterized by using field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR) thermogravimetric (TG) analysis, X-ray powder diffraction (XRD) and UV-visible (UV-vis) absorption spectroscopy, which confirmed the intercalation process. Release tests of nanohybrid in the presence or absence of NaCl or poly-acrylamide (PAM) were performed in vitro in gastric (pH 1.2), lysosomal (pH 4.0), intestinal (pH 6.8) and blood (pH 7.4) simulated fluid using UV-vis spectroscopy.

RESULTS

At pH 1.2, LDH was dissolved and intercalated antibiotic released from ZnAl-CD in a molecular form, which led to a significant increase in the antibiotic's solubility. Results showed that the release of drug from nanohybrid at pH 4.0, 6.8 and 7.4 was a sustained process.

CONCLUSION

This material might reduce side effects by the release of the drug in a controlled manner. However, it was found that the presence of Cl or PAM species in the release media has a negative impact on the release behavior. The weathering mechanism is responsible for the release of CD from the nanocomposite at pH 1.2, while the mechanism of anion exchange may be responsible for the release behavior at pH 4.0, 6.8 and 7.4. A number of kinetic models were chosen to gain more insights into the mechanisms of drug release. At pH 1.2, the zero-order model most satisfactorily explained the release kinetics of CD, while the release data of CD at pH 4.0, 6.8 and 7.4 were governed by Bhaskar kinetics.

5-Fluorouracil ethosomes - skin deposition and melanoma permeation synergism with microwave

This study focuses on the use of ethosome and microwave technologies to facilitate skin penetration and/or deposition of 5-fluorouracil in vitro and in vivo. Low ethanol ethosomes were designed and processed by mechanical dispersion technique and had their size, zeta potential, morphology, drug content and encapsulation efficiency characterized. The skin was pre-treated with microwave at 2450 MHz for 2.5 min with ethosomes applied topically and subjected to in vitro and in vivo skin drug permeation as well as retention evaluation. The drug and/or ethosomes cytotoxicity, uptake and intracellular trafficking by SKMEL-28 melanoma cell culture were evaluated. Pre-treatment of skin by microwave promoted significant drug deposition in skin from ethosomes in vitro while keeping the level of drug permeation unaffected. Similar observations were obtained in vivo with reduced drug permeation into blood. Combination ethosome and microwave technologies enhanced intracellular localization of ethosomes through fluidization of cell membrane lipidic components as well as facilitating endocytosis by means of clathrin, macropinocytosis and in particularly lipid rafts pathways. The synergistic use of microwave and ethosomes opens a new horizon for skin malignant melanoma treatment.

Synthesis, characterization, and anti-microbial activity of superabsorbents based on agar–poly(methacrylic acid-glycine)

In this study, poly(methacrylic acid-glycine)-grafted agar-based hydrogels with optimized process parameters were synthesized via a two-step green-radiation induced grafting process using microwave heating. Poly(methacrylic acid) chains were graft copolymerized onto an agar backbone using ammonium persulfate as a free radical initiator and N,N′-methylene-bis-acrylamide as a cross-linking means using microwave heating. The influence of different reaction parameters was investigated on the percentage swelling behavior of the cross-linked hydrogel networks. The prepared hydrogel networks with optimum percentage swelling were characterized by Fourier transform infrared spectroscopy, time-of-flight secondary ion mass spectrometry, scanning electron microscopy, X-ray diffraction, and thermogravimetric analysis, using agar as a reference. The anti-bacterial activities of the prepared hydrogels against Gram-positive Staphylococcus aureus bacteria and Gram-negative Escherichia coli bacteria were investigated. Staphylococcus aureus was found to be more susceptible to the compounds compared to Escherichia coli. These results indicate that the prepared hydrogels have the potential to be applied as anti-bacterial agents.

Modified biopolymer-dextrin based crosslinked hydrogels: application in controlled drug delivery

This review describes hydrogels and their classifications along with the synthesis and properties of biopolymer-dextrin based crosslinked hydrogels towards potential application in controlled drug delivery.

Effect of silica precursor transformation on diclofenac sodium release

The present paper describes the preparation of a new type of ternary composites where pure silica gel or polysilsesquioxane was deposited on a polymer carrier loaded with a high dose of diclofenac sodium.

Synthesis of aspirin-loaded polymer-silica composites and their release characteristics

This study describes a novel approach to the synthesis of polymer-drug-silica nanocomposites via encapsulation/isolation of drug molecules, introduced into the polymer matrix by the silica gel. For the first time, tetraethoxysilane (TEOS) gelation in the vapor phase of the acidic catalyst is presented as an efficient method to enter the silica gel nanoparticles into the polymer-aspirin conjugate. The conducted studies reveal that the internal structure of the polymer carrier is significantly reorganized after the embedding of aspirin molecules and the silica gel. The total porosity of the polymer-drug-silica nanocomposites and the molecular structure of the silica gel embedded in the system strongly depend on the conditions of the silica source transformation. Additionally, the release of the drug was fine-tuned by adapting the conditions of hydrolysis and condensation of the silica gel precursor. Finally, to prove the usefulness of the proposed synthesis, the controlled release of aspirin from the polymer-drug-silica nanocomposites is demonstrated.