Chemically modified polyacrylamide-g-guar gum-based crosslinked anionic microgels as pH-sensitive drug delivery systems: preparation and characterization

Recent updates on guar gum derivatives in colon specific drug delivery

Colon specific delivery of therapeutics have gained much attention of pharmaceutical researchers in the recent past. Colonic specific targeting of drugs is used not only for facilitating absorption of protein or peptide drugs, but also localization of therapeutic agents in colon to treat several colonic disorders. Among various biopolymers, guar gum (GG) exhibits pH dependent swelling, which allows colon specific release of drug. GG also shows microbial degradation in the colonic environment which makes it a suitable excipient for developing colon specific drug delivery systems. The uncontrolled swelling and hydration of GG can be controlled by structural modification or by grafting with another polymeric moiety. Several graft copolymerized guar gum derivatives are investigated for colon targeting of drugs. The efficacy of various guar gum derivatives are evaluated for colon specific delivery of drugs. The reviewed literature evidenced the potentiality of guar gum in localizing drugs in the colonic environment. This review focuses on the synthesis of several guar gum derivatives and their application in developing various colon specific drug delivery systems including matrix tablets, coated formulations, nano or microparticulate delivery systems and hydrogels.

Applications of guar gum polysaccharide for pharmaceutical drug delivery: A review

Bio-based materials are rapidly replacing synthetic materials owing to their significant biomedical applications, easy availability, nontoxicity, biodegradability and biocompatibility. Guar gum (GG) is a plant-derived biocompatible and biodegradable polymeric compound found abundantly in nature. It is a non-ionic, hydrophilic carbohydrate and is a cost-effective hydrocolloid polysaccharide considered as a wonderful representative of the new generation of plant gums. Various composites of guar gum with other polymers have been reported in last few decades and they are extensively used in different industries like food, textile, mining, petrochemical, paper and explosives etc. Easy availability, non-toxicity, eco-friendly and biodegradable nature of GG has made it ideal candidate for for drug delivery (DD) applications. GG based hydrogels, films, scaffolds and nanoparticles have been explored widely for their DD applications. These non-toxic DD carriers can be used for targeted drug delivery. This review article directs the current efforts and improvements on GG and GG-based materials to be used in DD.

pH Effect on Particle Aggregation of Vanillin End-Capped Polylactides Bearing a Hydrophilic Group Connected by a Cyclic Acetal Moiety

To enhance the pH-responsiveness of poly(lactic acid) (PLA) particles, desired vanillin acetal-based initiators were synthesized and functional PLA was initiated at the chain end. PLLA-V6-OEG₃ particles were prepared using polymers with various M_n values of 2400-4800 g/mol. PLLA-V6-OEG₃ was appropriated to achieve a pH-responsive behavior under physiological conditions within 3 min via the six-membered ring diol-ketone acetal. Moreover, it was found that the polymer chain length (M_n) influenced the aggregation rate. TiO₂ was selected as the blending agent to improve the aggregation rate. The PLLA-V6-OEG₃ blended with TiO₂ was found to accelerate the aggregation rate compared with that without TiO₂, and the best ratio of polymer/TiO₂ was 1:1. To study the effect of the chain end for stereocomplex polylactide (SC-PLA) particles, PLLA-V6-OEG₄ and PDLA-V6-OEG₄ were successfully synthesized. The obtained results of SC-PLA particle aggregation implied that the types of chain end and the molecular weight of polymer could influence the aggregation rate. The SC-V6-OEG₄ blended with TiO₂ could not make our target to aggregate under physiological conditions within 3 min. This study motivated us to control the particle aggregation rate under physiological conditions for applying as a target drug carrier which is significantly influenced by not only the molecular weight but also the hydrophilicity of the chain-end as well as the number of acetal bonds.

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.

pH-Sensitive Polyacrylic Acid-Gated Mesoporous Silica Nanocarrier Incorporated with Calcium Ions for Controlled Drug Release

In this work, polyacrylic acid-functionalized MCM-41 was synthesized, which was made to interact with calcium ions, in order to realize enhanced pH-responsive nanocarriers for sustained drug release. First, mesoporous silica nanoparticles (MSNs) were prepared by the sol-gel method. Afterward, a (3-trimethoxysilyl)propyl methacrylate (TMSPM) modified surface was prepared by using the post-grafting method, and then the polymerization of the acrylic acid was performed. After adding a calcium chloride solution, polyacrylic acid-functionalized MSNs with calcium-carboxyl ionic bonds in the polymeric layer, which can prevent the cargo from leaking out of the mesopore, were prepared. The structure and morphology of the modified nanoparticles (PAA-MSNs) were characterized by X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), and N₂ adsorption-desorption analysis, etc. The controlled release of guest molecules was studied by using 5-fluorouracil (5-FU). The drug molecule-incorporated nanoparticles showed different releasing rates under different pH conditions. It is considered that our current materials have the potential as pH-responsive nanocarriers in the field of medical treatment.

Facile synthesis of pH-responsive sodium alginate/carboxymethyl chitosan hydrogel beads promoted by hydrogen bond

In this work, a novel synthesis strategy of sodium alginate/carboxymethyl chitosan hydrogel beads promoted by hydrogen bond was described. The beads were prepared by dropping the blends of two polymers into the citric acid solution. Besides hydrogen bonding, electrostatic interactions were also involved in the formation of the hydrogel beads. The thermal stability experiments revealed that the more the content of carboxymethyl chitosan, the better the thermal stability of the beads. The beads exhibited excellent pH sensitivity, pH reversibility, and lactoferrin loading capacity. The swelling ratio of the bead and its protein releasing profile was pH-dependent, which could prevent premature protein release in the gastric environment. Also, the circular dichroism results demonstrated that lactoferrin could maintain its structure during the loading and releasing process. The obtained results revealed that the hydrogel beads prepared in this work could be used as a potential protein carrier for oral delivery.

From oil to microparticulate by prilling technique: Production of polynucleate alginate beads loading Serenoa Repens oil as intestinal delivery systems

Natural oils that are rich in biologically active polyunsaturated fatty acids have many health benefits but have insufficient bioavailability and may oxidize in the gastrointestinal tract. For these reasons and to improve the handling as well, the possibility of incorporating a natural oil, extracted from Serenoa Repens fruits (SR-oil), in alginate-based beads was investigated. SR-oil has been used from centuries in both traditional and modern medicine for various nutraceutical or therapeutic purposes such as, in both sexes, as a general tonic, for genitourinary problems, to increase sexual vigor, as a diuretic or to treat in male lower urinary tract symptoms and benign prostatic hyperplasia. In this study, alginate-based beads prepared by vibration technology, also known as prilling technique, were explored as SR-oil delivery systems. Twenty-seven different formulations (F1-F27) were produced starting from stable emulsions for the period of the production. The formulations having spheroid shape (sfericity factor <0.07), high formulation yield (>90%) and high encapsulation efficiency (EE% > 80) were selected for further characterizations. Gas chromatographic analysis revealed a high loading of lauric acid as principal component of SR-oil allowing to calculate the content of total fatty acids (>50%) into the beads. Swelling behavior and release features were also studied at different pH values. The swelling of the beads and their SR-oil release were negligible for the first 2 h in simulated gastric fluid (pH 1.2), and appreciable in simulated intestinal fluid (pH 6.8). The release data were fitted by various equations to define the release kinetic mechanism. In addition, the selected formulation (F16) was stable to the oxidation not only during the formulation process, but also after 3 months of storage at room temperature. In summary, these polynucleate alginate beads, produced by prilling technique, are promising systems for improving the intestinal specific delivery and bioavailability of health-promoting bioactive SR-oil.

Chemical Modifications of Guar Gum for Drug Delivery Applications: A Review

Guar gum is a natural excipient extracted from the plant seed of Cyamopsis tetragonolobus, belonging to the Leguminosae family. In the pharmaceutical industries, it contributes an important role due to its non-toxicity, ease of availability, biodegradability and eco-friendly nature. The major constituents of guar gum is galactomannan which is composed of D-galactose anhydride and mannose anhydride. Hydroxyl groups present in galactomannan can be modified by carboxymethylation, grafting or cross-linking with other excipients for developing modified polymers having desirable properties. Guar gum is commonly used as a suspending, emulsifying, stabilizing, gelling and thickening agent in various dosage forms. The guar gum derivatives are also useful in controlling the drug release from the pharmaceutical dosage forms. In this review, different aspects of synthesis of guar gum derivatives and its applications in various drug delivery systems is described.

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.

Carbohydrate-based nanocarriers and their application to target macrophages and deliver antimicrobial agents

Many deadly infections are produced by microorganisms capable of sustained survival in macrophages. This reduces exposure to chemadrotherapy, prevents immune detection, and is akin to criminals hiding in police stations. Therefore, the use of glyco-nanoparticles (GNPs) as carriers of therapeutic agents is a burgeoning field. Such an approach can enhance the penetration of drugs into macrophages with specific carbohydrate targeting molecules on the nanocarrier to interact with macrophage lectins. Carbohydrates are natural biological molecules and the key constituents in a large variety of biological events such as cellular communication, infection, inflammation, enzyme trafficking, cellular migration, cancer metastasis and immune functions. The prominent characteristics of carbohydrates including biodegradability, biocompatibility, hydrophilicity and the highly specific interaction of targeting cell-surface receptors support their potential application to drug delivery systems (DDS). This review presents the 21^st century development of carbohydrate-based nanocarriers for drug targeting of therapeutic agents for diseases localized in macrophages. The significance of natural carbohydrate-derived nanoparticles (GNPs) as anti-microbial drug carriers is highlighted in several areas of treatment including tuberculosis, salmonellosis, leishmaniasis, candidiasis, and HIV/AIDS.

A glimpse of biodegradable polymers and their biomedical applications

Over the past two decades, biodegradable polymers (BPs) have been widely used in biomedical applications such as drug carrier, gene delivery, tissue engineering, diagnosis, medical devices, and antibacterial/antifouling biomaterials. This can be attributed to numerous factors such as chemical, mechanical and physiochemical properties of BPs, their improved processibility, functionality and sensitivity towards stimuli. The present review intended to highlight main results of research on advances and improvements in terms of synthesis, physical properties, stimuli response, and/or applicability of biodegradable plastics (BPs) during last two decades, and its biomedical applications. Recent literature relevant to this study has been cited and their developing trends and challenges of BPs have also been discussed.

Electrically Triggered Transdermal Drug Delivery Utilizing Poly(Acrylamide)-graft-Guar Gum: Synthesis, Characterization and Formulation Development

Objective:

The study aimed to prepare electrically-triggered transdermal drug delivery systems (ETDS) using electrically responsive polyacrylamide-graft-gaur gum (PAAm-g-GaG) copolymer.

Methods:

The PAAm-g-GaG copolymer was synthesized by adopting free radical polymerization grafting method. This PAAm-g-GaG copolymer hydrogel acts as a drug reservoir and blend films of Guar Gum (GaG) and Polyvinyl Alcohol (PVA) were included as Rate Controlling Membranes (RCM) in the system. The PAAm-g-GaG copolymer was characterized by FTIR, neutralization equivalent values, thermogravimetric analysis and elemental analysis.

Results:

On the basis of results obtained, it is implicit that the drug permeation decreased with an increase in the concentration of glutaraldehyde and RCM thickness; while drug permeation rate was increased with increasing applied electric current strength from 2 to 8 mA. A two fold increase in flux values was observed with the application of DC electric current. An increase in drug permeation was witnessed under on condition of electric stimulus and permeation was decreased when electric stimulus was "off". The skin histopathology study confirmed the changes in skin structure when electrical stimulus was applied.

Conclusion:

The electrically-sensitive PAAm-g-GaG copolymer is a useful biomaterial for transdermal drug delivery application.

Fabrication and characterization of hydroxypropyl guar-poly (vinyl alcohol)-nano hydroxyapatite composite hydrogels for bone tissue engineering

Biocompatible bone implants composed of natural materials are highly desirable in orthopedic reconstruction procedures. In this study, novel and ecofriendly bionanocomposite hydrogels were synthesized using a blend of hydroxypropyl guar (HPG), poly vinyl alcohol (PVA), and nano-hydroxyapatite (n-HA) under freeze-thaw and mild reaction conditions. The hydrogel materials were characterized using various techniques. TGA studies indicate that both composites, HPG/PVA and HPG/PVA/n-HA, have higher thermal stability compared to HPG alone whereas HPG/PVA/n-HA shows higher stability compared to PVA alone. The HPG/PVA hydrogel shows porous morphology as revealed by the SEM, which is suitable for bone tissue regeneration. Additionally, the hydrogels were found to be transparent and flexible in nature. In vitro biomineralization study performed in simulated body fluid shows HPG/PVA/n-HA has an apatite like structure. The hydrogel materials were employed as extracellular matrices for biocompatibility studies. In vitro cell viability studies using mouse osteoblast MC3T3 cells were performed by MTT, Trypan blue exclusion, and ethidium bromide/acridine orange staining methods. The cell viability studies reveal that composite materials support cell growth and do not show any signs of cytotoxicity compared to pristine PVA. Osteoblastic activity was confirmed by an increased alkaline phosphatase enzyme activity in MC3T3 bone cells grown on composite hydrogel matrices.

Guar gum and its composites as potential materials for diverse applications: A review

Naturally occurring polymers are currently of prime importance among which polysaccharides occupies superior position due to their easy availability, eco- friendly and non-toxic nature. Guar gum, one of the naturally occurring polymer, is a galactomannan acquired by ground endosperm of Cyamopsis tetragonolobus or Cyamopsis psoraloides. It belongs to the family leguminosae. Presence of large number of hydroxyl groups increases its H- bonding ability when dissolved in water that enhance the viscosity and gelling properties of the guar gum solution. Based upon these properties, guar gum is used in several industries such as textile, food, petrochemical, mining and paper for varied applications. It is used as suspending, emulsifying, gelling and stabilising agent in the conventional dosage forms. Last few decades have marked the increase in development of various composites of guar gum that have intrinsic utilization in various fields. Immobilization of guar gum with the others not only enhances its properties but also enriches its utilization in numerous fields for diverse applications such as water purification, drug delivery, pharmaceutical, cosmetic and food industries, etc. Guar gum derivatives are found to have therapeutic importance in certain physiological disorders also. In this review article, we have summarized various possible composites of guar gum and their most probable applications in different fields.

Guar gum-crosslinked-Soya lecithin nanohydrogel sheets as effective adsorbent for the removal of thiophanate methyl fungicide

Rapid increase in use of fungicides for the agricultural and industrial purposes has marked the deterioration of water resources which ultimately affects the human life. Accordingly, various attempts have been made in the removal of these noxious compounds. In the same context, we are presenting biopolymers based nanohydrogel sheets; guar gum-crosslinked-Soya lecithin nanohydrogel sheets (GG-crosslinked-SY NHS) used for the effective removal of a fungicide; thiophanate methyl from aqueous solution. Guar gum and soya lecithin were employed as the biopolymers in the fabrication of nanohydrogel sheets due to their non- toxic nature, easy availability, cheapness and significant properties. Due to the presence of highly reactive functional groups onto the surface of GG-crosslinked-SY NHS, good adsorption results have been obtained. Maximum adsorption capacity of 59.205mg/g was observed with 20mg GG-crosslinked-SY NHS and 25ppm thiophanate methyl solution concentration as calculated from the Langmuir isotherm. Results showed that neutral pH favoured the adsorption process. Kinetics results were indicative of the physical interactions between the thiophanate methyl and GG-crosslinked-SY NHS surface. Thermodynamic results have shown the spontaneous and endothermic adsorption process.

Taste masking of ofloxacin and formation of interpenetrating polymer network beads for sustained release

The objective of this study was to carry out taste masking of ofloxacin (Ofl) by ion exchange resins (IERs) followed by sustained release of Ofl by forming interpenetrating polymer network (IPN) beads. Drug-resin complexes (DRCs) with three different ratios of Ofl to IERs (1:1, 1:2, 1:4) were prepared by batch method and investigated for in vivo and in vitro taste masking. DRC of methacrylic acid-divinyl benzene (MD) resin and Ofl prepared at a ratio of 1:4 was used to form IPN beads. IPN beads of MD 1:4 were prepared by following the ionic cross-linking method using sodium carboxymethyl xanthan gum (SCMXG) and SCMXG-sodium carboxymethyl cellulose (SCMXG-SCMC). IPN beads were characterized with FT-IR and further studied on sustained release of Ofl at different pH. In vivo taste masking carried out by human volunteers showed that MD 1:4 significantly reduced the bitterness of Ofl. Characterization studies such as FT-IR, DSC, P-XRD and taste masking showed that complex formation took place between drug and resin. In vitro study at gastric pH showed complete release of drug from MD 1:4 within 30 min whereas IPN beads took 5 h at gastric pH and 10 h at salivary pH for the complete release of drug. As the crosslinking increased the release kinetics changed into non-Fickian diffusion to zero-order release mechanism. MD 1:4 showed better performance for the taste masking of Ofl and IPNs beads prepared from it were found useful for the sustained release of Ofl at both the pH, indicating a versatile drug delivery system.

Stimuli-Regulated Smart Polymeric Systems for Gene Therapy

The physiological condition of the human body is a composite of different environments, each with its own parameters that may differ under normal, as well as diseased conditions. These environmental conditions include factors, such as pH, temperature and enzymes that are specific to a type of cell, tissue or organ or a pathological state, such as inflammation, cancer or infection. These conditions can act as specific triggers or stimuli for the efficient release of therapeutics at their destination by overcoming many physiological and biological barriers. The efficacy of conventional treatment modalities can be enhanced, side effects decreased and patient compliance improved by using stimuli-responsive material that respond to these triggers at the target site. These stimuli or triggers can be physical, chemical or biological and can be internal or external in nature. Many smart/intelligent stimuli-responsive therapeutic gene carriers have been developed that can respond to either internal stimuli, which may be normally present, overexpressed or present in decreased levels, owing to a disease, or to stimuli that are applied externally, such as magnetic fields. This review focuses on the effects of various internal stimuli, such as temperature, pH, redox potential, enzymes, osmotic activity and other biomolecules that are present in the body, on modulating gene expression by using stimuli-regulated smart polymeric carriers.

pH-Responsive polymers

This review summarizes pH-responsive monomers, polymers and their derivative nano- and micro-structures including micelles, cross-linked micelles, microgels and hydrogels.

Hydrazone linkages in pH responsive drug delivery systems

Stimuli-responsive polymeric drug delivery systems using various triggers to release the drug at the sites have become a major focus area. Among various stimuli-responsive materials, pH-responsiveness has been studied extensively. The materials used for fabricating pH-responsive drug delivery systems include a specific chemical functionality in their structure that can respond to changes in the pH of the surrounding environment. Various chemical functionalities, for example, acetal, amine, ortho ester, amine and hydrazone, have been used to design materials that are capable of releasing their payload at the acidic pH conditions of the tumor or infection sites. Hydrazone linkages are significant synthons for numerous transformations and have gained importance in pharmaceutical sciences due to their various biological and clinical applications. These linkages have been employed in various drug delivery vehicles, such as linear polymers, star shaped polymers, dendrimers, micelles, liposomes and inorganic nanoparticles, for pH-responsive drug delivery. This review paper focuses on the synthesis and characterization methods of hydrazone bond containing materials and their applications in pH-responsive drug delivery systems. It provides detailed suggestions as guidelines to materials and formulation scientists for designing biocompatible pH-responsive materials with hydrazone linkages and identifying future studies.

Release Behavior of Ketoprofen from Chitosan/Alginate Microcapsules

Chitosan/alginate microcapsules were prepared continuously by an air extrusion method. The influences on loading efficiency and release, such as air flow-rate, chitosan molecular weight and concentration, alginate concentration, pH of chitosan solution, ethyl cellulose, and freezing drying the capsules were studied. Freezing drying chitosan/alginate microcapsules was important for controlled release of ketoprofen. High molecular weight and high concentration of chitosan did not increase loading of ketoprofen, but reduced the release of the ketoprofen. The addition of ethyl cellulose increased the loading of ketoprofen and the release time was prolonged. Increasing sodium alginate concentration reduced the loading efficiency with no clear distinction on the release of ketoprofen. The ketoprofen entrapped in the pH sensitive chitosan/alginate microcapsules gave controlled release in intestinal fluid.

Guar gum as a promising starting material for diverse applications: A review

Guar gum is the powdered endosperm of the seeds of the Cyamopsis tetragonolobus which is a leguminous crop. The endosperm contains a complex polysaccharide called galactomannan, which is a polymer of d-galactose and d-mannose. This hydroxyl group rich polymer when added to water forms hydrogen bonding imparting significant viscosity and thickening to the solution. Due to its thickening, emulsifying, binding and gelling properties, quick solubility in cold water, wide pH stability, film forming ability and biodegradability, it finds applications in large number of industries. In last few decades a lot of research has been done on guar gum to fit it into particular application, as such or by its structural modifications. This review gives an overview of the nature, chemistry and properties of guar gum and discusses recent developments in its modifications and applications in major industries like hydraulic fracturing, explosives, food, agriculture, textile, paper, cosmetics, bioremediation, drug delivery, medical and pharmaceuticals. This article would help researchers engaged in biopolymer area and other end-users who want to begin research in natural polysaccharides.