Sodium Alginate Hydrogel Beads Research Articles

Development of a powdered activated charcoal sodium alginate hydrogel bead concentration method for detecting viruses in wastewater

Developing a simple and cost-effective wastewater concentration method using powdered activated charcoal sodium alginate (PAC-NaA) hydrogel beads, enhanced for capturing viruses.

Preparation and Characterization of Silica-Coated Sodium Alginate Hydrogel Beads and the Delivery of Curcumin

In this study, to address the defects of sodium alginate (SA), such as its susceptibility to disintegration, silica was coated on the outer layer of sodium alginate hydrogel beads in order to improve its swelling and slow-release properties. Tetraethyl orthosilicate (TEOS) was used as the hydrolyzed precursor, and the solution of silica precursor was prepared by sol-gel reaction under acidic conditions. Then SA–silica hydrogel beads prepared by ionic crosslinking method were immersed into the SiO2 precursor solution to prepare SA–silica hydrogel beads. The chemical structure and morphology of the hydrogel beads were characterized by XRD, FTIR, and SEM, and the results showed that the surface of SA–silica beads was successfully encapsulated with the outer layer of SiO2, and the surface was smooth and dense. The swelling experiments showed that the swelling performance effectively decreased with the increase of TEOS molar concentration, and the maximum swelling ratio of the hydrogel beads decreased from 41.07 to 14.3, and the time to reach the maximum swelling ratio was prolonged from 4 h to 8 h. The sustained-release experiments showed that the SA–silica hydrogel beads possessed a good pH sensitivity, and the time of sustained-release was significantly prolonged in vitro. Hemolysis and cytotoxicity experiments showed that the SA-silica hydrogel beads were biocompatible when the TEOS molar concentration was lower than 0.375 M. The SA–silica-2 hydrogel beads had good biocompatibility, swelling properties, and slow-release properties at the same time.

W/O/W emulsion-filled sodium alginate hydrogel beads for co-encapsulation of vitamins C and E: Insights into the fabrication, lipolysis, and digestion behavior

In this study, vitamins C and E were simultaneously encapsulated in water-in-oil-in-water (W/O/W) emulsion-filled sodium alginate (SA) hydrogel beads, as well as the effects of SA concentrations (0.5%, 1.0%, 1.5%, and 2.0%) on the structures and lipolysis the of hydrogel beads were investigated. With increasing SA concentration, the beads showed larger sizes, denser structures and better textures. The droplets tightly penetrated the gel network at high SA concentrations. Digestion behavior revealed the disintegrated intramolecular structure at low SA concentrations. The beads with 0.5% SA were fragmented, losing the initial shape during digestion in the intestinal fluid. Additionally, lipid phases were released as W/O/W and O/W emulsion droplets after digestion. However, the high SA concentration-containing beads exhibited a well-preserved morphological structure after digestion, and the release profiles of lipid phase were mainly O/W emulsion droplets. Furthermore, vitamins C and E encapsulated in the beads exhibited high bioaccessibility (vitamin C: 90.20% and vitamin E: 95.19%).

Intestinal-specific oral delivery of lactoferrin with alginate-based composite and hybrid CaCO3-hydrogel beads

Sodium alginate hydrogel beads and sodium alginate/gellan gum composite hydrogel beads crosslinked by calcium chloride were prepared with different alginate concentrations (3–20 mg·mL−1). Additionally, a simple method for growing CaCO3in situ on the hydrogel to create novel inorganic-organic hybrid hydrogel beads was presented. FT-IR analysis revealed the involvement of hydrogen bonding and electrostatic interactions in bead formation. Swelling behavior in acidic conditions showed a maximum of 13 g/g for composite hydrogels and CaCO3-incorporated hybrid hydrogels. Lactoferrin encapsulation efficiency within these hydrogels ranged from 44.9 to 56.6%. In vitro release experiments demonstrated that these hydrogel beads withstand harsh gastric environments with <16% cumulative release of lactoferrin, achieving controlled release in intestinal surroundings. While composite sodium alginate/gellan gum beads exhibited slower gastrointestinal lactoferrin digestion, facile synthesis and pH responsiveness of CaCO3-incorporated hybrid hydrogel also provide new possibilities for future studies to construct a novel inorganic-organic synergetic system for intestinal-specific oral delivery.

Kinetic and adsorption isotherm studies of Malachite Green dye onto surfactant-tailored alginate hydrogel beads: An influence of surfactant hydrophobicity

This study details the synthesis and characterization of surfactant-modified sodium alginate hydrogel beads crosslinked with Ba2+ ions through ionotropic gelation. Cationic surfactants such as, dodecyltrimethylammonium bromide (DTAB), didodecyldimethylammonium bromide (DDAB), and butanediyl-α,ω-bis-(dimethyldodecylammonium bromide) (GEM), were employed in the modification process. The surfactant-modified ALG-DTAB, ALG-DDAB, and ALG-GEM beads were investigated for the removal of cationic dye Malachite Green (MG) to elucidate the impact of hydrophobicity of amphiphiles on the adsorption process. The characterizations were carried out using Rheometry, Field Emission Scanning Electron Microscopy (FESEM), Infrared Spectroscopy (IR), and Energy Dispersive X-ray Spectroscopy (EDX). Under optimized conditions, ALG-GEM and ALG-DDAB demonstrated highest maximum adsorption capacity (Qmax > 700 mgg−1). The adsorption data fitted well to pseudo-second order kinetic and Langmuir adsorption models, suggesting the involvement of chemisorption phenomena with notable contributions from pore diffusion. The effects of pH, initial dye concentration, adsorbent dose, temperature, and competing ions on the removal of MG were investigated. Interestingly, ALG-GEM beads exhibited an increase in adsorption capacity with rising pH and a subsequent decrease with increasing temperature, showcasing optimal adsorption at pH 7.0 and 25 °C. The study proposes that ALG beads modified with cationic surfactants with higher hydrophobicity could offer a promising avenue in wastewater treatment processes.

Preparation of emulsions-filled sodium alginate hydrogel beads to enhance the anti-cancer activity of fangchinoline in vivo and in vitro

Fangchinoline (Fan) is a natural alkaloids compound with a series of remarkable bioactivity, but the poor aqueous solubility limits the clinical application. Emulsions (EM) systems are commonly used to encapsulate and deliver hydrophobic active compound to enhance the bioavailability. Hydrogel beads (HGB) are three-dimensional hydrophilic polymer networks, which are able to immobilize colloidal delivery systems, resulting to the enhanced stability and controlled release in the gastrointestinal tract. In order to give full play to the bilateral advantages of emulsion and hydrogel, Fan loaded EM-filled sodium alginate HGB (Fan@EM-HGB) were designed and prepared in this paper. The average size of Fan@EM was 121.6 ± 2.7 nm and the zeta potential was -17.7 ± 0.3 mV. Physicochemical characterization demonstrated that Fan was successfully encapsulated in HGB with entrapment efficiency of 93.98 % and drug loading of 5.18 mg/g. The released behavior of Fan@EM-HGB followed a pH-controlled mechanism that was consistent with the first-order model. In vitro activity research shown that Fan@EM-HGB could significantly promote the apoptosis of A549 cells, with IC50 value more than 2.37 times higher than that of Fan. The in vivo results indicated that Fan@EM-HGB had an obvious anti- cancer effect, and molecular mechanism shown that Fan@EM-HGB could promote tumor cell apoptosis by inhibiting the activation of the PI3K/Akt/mTOR signaling pathway. The above research results suggest that nanoemulsions-filled hydrogel beads have potential application in delivery system for hydrophobic composition.

Chitosan coated graphene oxide incorporated sodium alginate hydrogel beads for the controlled release of amoxicillin

Biopolymers are crucial in pharmaceuticals, particularly for controlled drug release. In this study, we loaded the broad-spectrum antibacterial drug amoxicillin into sodium alginate, a well-known biopolymer. Graphene oxide was incorporated into the composite, and the hydrogel beads were coated with chitosan for its mucoadhesive properties. Various composites were formulated by adjusting the weight percentage of graphene oxide (GO).The fabricated beads demonstrated controlled and sustained drug release, with 98 % of the loaded drug molecules released over 24 h at gastric pH. The antibacterial test using the disc diffusion technique confirmed the drug release, exhibiting greater effectiveness against the gram-positive bacterium S. aureus than the gram-negative bacterium E. coli. The drug release data were optimized using zero order, first order, Higuchi, and Korsmeyer-Peppas models. The experimental data were best fit to the Korsmeyer-Peppas model with a relatively higher correlation coefficient value. Biocompatibility was evaluated through a cell viability test using mouse fibroblast cell lines (L929). The MTT viability assay confirmed high levels of cytocompatibility, even at higher concentrations (100 μg/mL), with 98.15 % viable cells. These results highlight the potential of the fabricated beads as an effective amoxicillin drug delivery system with biomedical applications.

Fe-loaded alginate hydrogel beads activating peroxymonosulfate for enhancing anaerobic fermentation of waste activated sludge: Performance and potential mechanism

The recovery of volatile fatty acids (VFAs) through anaerobic fermentation (AF) is usually restricted by the poor biodegradability of waste activated sludge (WAS). This study proposed a novel strategy, i.e. peroxymonosulfate (PMS) activated by Fe-loaded sodium alginate hydrogel beads (Fe-SA), to enhance AF performance. Experimental results demonstrated that the as-synthesized Fe-SA and PMS co-pretreatment synergistically enhanced WAS solubilization and VFAs production. The maximal VFAs yield of 2013 mg COD/L was achieved at the Fe-SA dosage of 4.0 mM/g TSS, which was 93.7% higher than that with sole PMS addition and 8.82 times higher than that of the control. Mechanistic studies elucidated that the generation of reactive radicals such as SO4•− and •OH from PMS was greatly induced by Fe-SA, which contributed to WAS disintegration and degradation of refractory compounds. Additionally, analysis of the key enzyme activities indicated that the Fe-SA could strengthen biological hydrolysis and acidogenesis of sludge during AF. Microbial analysis illustrated that Fe-SA evidently improved the abundances of fermentative microorganisms as well as functional gene expression via creating a favorable environment for microbial growth. This study demonstrated the applicable potential of Fe-SA hydrogel beads activating PMS for VFAs production and provides an important reference for developing advanced oxidation processes-based application in AF.

Microstructural influence on physical properties and release profiles of sesame oil encapsulated into sodium alginate-tamarind mucilage hydrogel beads

Ionic gelation of alginate has become one of the most widely used encapsulation techniques, with the main drawback that alginate hydrogels exhibit highly porous structural networks, which promotes high rates of release of encapsulated core materials. To retard the diffusion and loss of oil, and in turn to develop new alternatives as wall materials, this work aims to analyze the effect of structural properties of hydrogel beads prepared with sodium alginate (SA) and two blends of SA - tamarind seed mucilage (SA-TSM) as wall materials, in the release profiles of sesame oil (SO) encapsulated by ionic gelation. Three emulsions were formed using SA, or SA-TSM blends in mass ratios 1:1 and 1:2, with an SO dispersed phase fraction of 0.02 and mass ratio of wall material:SO 1:1. The resulting emulsions were dropped into a 2.5 % wt. CaCl2 solution to produce three different systems of hydrogel beads. They were characterized by their morphology, size, physical properties, oil encapsulation, swelling, and release performance. According to the results obtained, the hydrogel beads showed an ellipsoidal-like geometry with a mean size of ∼2.46 mm. SA-TSM hydrogel beads showed higher encapsulation efficiency (> 73.45%) than SA beads (61.49%). The kinetic curves of SO release showed two regions: a “burst effect” at short times followed by a "lag time" release. The Korsmeyer-Peppas model performed the best fit (R2 > 0.90) for the release of SO, indicating a diffusion-controlled Fickian transport mechanism for all the beads, the effective diffusion coefficients ranged from 5.18 × 10−11 to 6.46 × 10−11 m2/s. Therefore, TSM directly influences the structural and physical properties of SA-TSM hydrogel beads, demonstrating efficient structural support and filler function in the formation of wall materials, improving the encapsulation and controlling the release rate of SO in comparison with SA hydrogel beads.

Ion Imprinted Sodium Alginate Hydrogel Beads Enhanced with Carboxymethyl Cellulose and β-Cyclodextrin to Improve Adsorption for Cu2+

To achieve efficient adsorption and recycling of Cu2+ in wastewater, using Cu2+ as template ion, glutaraldehyde as crosslinker, three sodium alginate hydrogel beads including SA, SAC, and SAB beads were prepared by imprinting sol–gel method using sodium alginate (SA) with carboxymethyl cellulose (CMC) and β-cyclodextrin (β-CD) as different precursors, respectively. Scanning electron microscopy and Fourier transform infrared spectroscopy were used to characterize and analyze morphology and composition change of the hydrogel beads, respectively. When the mass ratio of SA to CMC or SA to β-CD reach 1:1, the SAC beads or SAB beads are nearly homogeneous sphere. Then the effects of pH, adsorption time, initial concentration of Cu2+, adsorbent dosage, and coexisting ions on the adsorption efficiency of three hydrogel beads were investigated. The results indicated that adding carboxymethyl cellulose and β-cyclodextrin into skeleton of beads increased the toughness of the beads and improved the adsorption capacity of Cu2+. Compared to the saturated adsorption capacity 510 mg/g of Cu2+ on SA, the saturated adsorption capacity of Cu2+ on SAB and SAC reached 817 mg/g and 822 mg/g, respectively. And their adsorption efficiency for Cu2+ are over 95% at 25 °C with pH of 7, contact time within 350 min, adsorbent dosage of 4 mg/50 mL, and initial concentration of 5 mg/L. Thus, SAC and SAB beads could be used as adsorption material for detecting and removing Cu2+ from wastewater.

Efficient dye removal using fixed-bed process based on porous montmorillonite nanosheet/poly(acrylamide-co-acrylic acid)/sodium alginate hydrogel beads

In this study, Montmorillonite nanosheet/poly(acrylamide-co-acrylic acid)/sodium alginate hydrogel beads with high handle capacity towards dyes effluent was investigated. Montmorillonite nanosheet cooperated with acrylamide and acrylic acid via hydrogen bond, amidation and polymerization interaction first, then crosslinked with sodium alginate by intertwining interaction to form 3D network structure, achieving free entrance and rapid adsorption for dye molecules. Batch adsorption tests revealed a multilayer and heterogeneous adsorption of methylene blue (MB) onto hydrogel beads according to pseudo two-order kinetic model and Freundlich isotherm model. The adsorption capacity of MB was controlled by the amount of adsorption sites in hydrogel beads, which could reach maximum of 530.7 mg/g. The adsorption mechanism is attributed to Ca ion-exchange and chemical bonding of COOH and OH groups with MB. Column tests showed an excellent dynamic adsorption performance of hydrogel beads towards MB wastewater compared with the traditional commercial adsorbents of granular active carbon and cation exchange resin, which achieved 380 bed volume (BV) of treated sewage to meet the emission standards using the single column. Moreover, 1625 BV and more treated dye effluent was achieved to be safety discharged via double column series in 5 circulation-regeneration, indicating the great potential of hydrogel beads in practical application. Such hydrogel realized the performance promotion of macromolecule polymers and nanoclay in materials design, and green application in water treatment.

Facile Fabrication of N-Slow Release Fertilizer Hydrogel Beads by Alginate-Based Composites

A novel slow-release N-fertilizer hydrogel beads were developed using sodium alginate (SA) and alginate-talcum (ST) composite as N-absorbent. In this work, the hydrogel composite were fabricated by simple method and low cost. N-fertilizer hydrogel beads were prepared two types, for SA types, which were different sodium alginate (1(SA1), 3(SA3), 5(SA5), 7(SA7), and 10(SA10) wt%). And, for ST types, sodium alginate and talcum were vary ratios to 1:0.5(S1T0.5), 1:1(S1T1), and 1:2 (S1T2). The chemical structure of hydrogel composite beads were characterized via Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). The release behavior were investigate by Zero-order kinetic model, First-order kinetic model, Higuchi model and Korsmeyer-Peppas model. We have found that the N-fertilizer release constants in Korsmeyer-Peppas model were decrease with increase SA content for 1-5 wt% in SA hydrogel beads. However, SA contents were more than 5 wt% which rapidly enhanced fertilizer release. In addition, to add talcum in ST hydrogel beads significantly reduced fertilizer release rate. The N-fertilizer hydrogel beads exhibits significantly slow release behavior. These results indicates that the development of slow-release fertilizer hydrogel beads can be improve the effectiveness of N-fertilizer.

Adsorption of lead ions from aqueous solutions by porous cellulose nanofiber–sodium alginate hydrogel beads

Herein we report a new type of adsorbent for the efficient removal of Pb(II), which is prepared from cellulose nanofiber (CNF) and sodium alginate (SA) via a simple cross-linking method. During this process, the porous structure of the hydrogel beads was formed by the disintegration of calcium phosphate. The performance and structure of the prepared beads were systematically examined by X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, zeta potential measurements, and scanning electron microscopy. Investigations revealed that the adsorption equilibrium was attained after approximately 120 min. In addition, 82% of Pb(II) ions were absorbed in the initial 40 min at 297 K. The adsorption process was consistent with a pseudo-second order kinetic model and the Langmuir adsorption isotherm model, and the limit adsorption capacity reached 318.47 mg g−1. Acid treatment and regeneration experiments verified that the adsorption capacity of Pb(II) on the beads was satisfactory, and the adsorption rate remained at >80% after 5 cycles. These results indicate that the prepared beads are potential adsorbents for water treatment.

Fabrication of poly(vinyl alcohol)/sodium alginate hydrogel beads and its application in photo-Fenton degradation of tetracycline

Developing a reusable and durable catalyst for heterogeneous photo-Fenton process is of great importance for the practical application in the environment remediation. In this study, poly(vinyl alcohol) (PVA)/sodium alginate (SA) hydrogel beads were constructed using FeCl3 and boric acid as cross-linking agents. Characterizations and tests were employed to investigate the structure, optical property and durability of the obtained beads. The photo-Fenton performance of the PVA/SA-FeCl3 beads was evaluated by degradation of tetracycline (TC) under visible-light irradiation. The results show that the constructed beads exhibit porous structure, display a broad absorption band in the visible region and behave excellent stability against mechanic effects. The photocatalytic experiment result indicates that the removal rate of TC reaches 90.5% under optimized conditions, while the removal rate of total organic carbon reaches 28.6%. By analyzing the degradation of TC after adding active species scavengers, a photocatalytic mechanism was proposed. Moreover, PVA/SA-6% FeCl3 beads could be easily separated and recycled in water purification. This work provides a facile and robust method to construct reusable and durable Fe(III)-containing hydrogel beads with acceptable photo-Fenton catalytic performance under visible-light irradiation, paving the way for its practical application in wastewater treatment.

Facile Preparation of Tannic Acid–Poly(vinyl alcohol)/Sodium Alginate Hydrogel Beads for Methylene Blue Removal from Simulated Solution

A novel hydrogel bead [tannic acid (TA)–poly(vinyl alcohol) (PVA)/sodium alginate (SA)] with high strength prepared by biocompatible PVA, TA, and biocompatible SA via an instantaneous gelation method was applied to remove methylene blue (MB) from aqueous solution. The obtained TA–PVA/SA hydrogel beads were fully characterized by thermogravimetric analysis, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and so on. The adsorption performances of TA–PVA/SA hydrogel beads for MB were investigated by changing the factors of TA content, initial concentration, pH, adsorbent dosage, contact time, and temperature systematically. The maximum capacity of TA–PVA/SA hydrogel beads for MB removal was obtained to be 147.06 mg/g at 30 °C, whose capability was better than that without TA. After fitting the adsorbed data, it was basically consistent with the Langmuir isotherm and pseudo-second-order kinetic model. Thermodynamic studies indicated that MB removal was spontaneous and exothermic in nature. It is concluded that the low-cost TA–PVA/SA hydrogel beads as an easily recoverable adsorbent have a great potential on the removal of hazardous dyes from wastewater.

Phosphorus recovery from water by lanthanum hydroxide embedded interpenetrating network poly (vinyl alcohol)/sodium alginate hydrogel beads

Sorption is recognized as an effective method for phosphorus removal or recovery in the aqueous environment. In this study, novel poly(vinyl alcohol)/sodium alginate/lanthanum hydroxide (PVA-SA-LH) hydrogel beads with an interpenetrating network (IPN) structure were synthesized, characterized and tested for phosphorus removal/recovery in wastewater. The hydrogel beads were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy with energy dispersive spectrometry (SEM & EDS) and X-ray photoelectron spectroscopy (XPS) before and after sorption. Results indicated the hydrogel beads had an increased phosphorus removal efficiency with an increased hydrogel beads’ dosage, reached their maximum sorption capacity for phosphorus at pH = 4, and exhibited favorable selective sorption towards phosphorus in the present of other anions. The pseudo-second-order kinetic model and Freundlich model fit the sorption process well. After five sorption-desorption runs, the sorbents’ sorption capacity for phosphorus remained above 75% of the first run. The column test indicated a possibility for practical application. Hence, the developed PVA-SA-LH hydrogel beads may be a new kind of sorbent for phosphorus removal and recovery in the future.

Phyto-crystallization of silver and gold by Erigeron annuus (L.) Pers flower extract and catalytic potential of synthesized and commercial nano silver immobilized on sodium alginate hydrogel

A green, eco-friendly approach for the synthesis of silver and gold nanoparticles (AgNPs and AuNPs) using Erigeron annuus (L.) pers flower extract as both the reducing and capping agent is reported for the first time. Optimal nanoparticle production was achieved by adjusting various parameters including pH, extract concentration, metal ion concentration, and time. Initial verification of AgNP and AuNP production was done by visual observation and measuring surface plasmon spectra at 434 and 537nm, respectively. The synthesized AgNPs and AuNPs were characterized by high resolution-transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), energy dispersive spectrophotometry (EDS), Fourier transform infrared spectroscopy (FTIR) and zeta potential. The catalytic potential of E. annuus flower extract, silver ions, synthesized AgNPs, commercial grade AgNPs, and a mixture of flower extract and AgNPs immobilized on sodium alginate hydrogel beads (Na/Al HB) was analyzed. The ability of these immobilized materials to degrade methylene blue was investigated. Commercial grade AgNPs immobilized with Na/Al HB 1.5g/20mL were observed to have good catalytic activity followed by a mixture of synthesized AgNPs immobilized with Na/Al HB and E. annuus flower extract immobilized with Na/Al HB at 1.5g/20mL.

Extended Release of Theophylline Through Sodium Alginate Hydrogel Beads: Effect of Glycerol on Entrapment Efficiency, Drug Release

Theophylline is the most useful bronchodilators for the treatment of severe reversible bronchospasm. The fluctuations of serum theophylline level in clinical practice and associated central nervous system side effects necessitate the development of an extended release formulation. In the present study, theophylline-loaded beads were prepared by extruding the dispersion of theophylline, sodium alginate, and glycerol into the cationic crosslinking solution of calcium chloride. The effect of the addition of glycerol was determined by entrapment efficiency, drug release, and morphology of beads. Absence of chemical interaction between drug, polymer, and counterions after production of beads was confirmed by Fourier transform infrared spectroscopy. Theophylline entrapment of up to 72% was achieved in beads with almost spherical shape and size ranging from 0.67 to 1.12 mm. Percentage entrapment of theophylline found to be more and release was extended up to the eleventh hour from the glycerol containing sodium alginate beads. Hence, sodium alginate glycerol beads could represent a promising oral drug delivery system to extend the release of theophylline.

Thermoresponsive N-vinyl caprolactam grafted sodium alginate hydrogel beads for the controlled release of an anticancer drug

A series of thermoresponsive sodium alginate-g-poly(vinyl caprolactam) (NaAlg-g-PNVCL) beads were prepared as drug delivery matrices of 5-flurouracil (5-FU) crosslinked by glutaraldehyde (GA) in the hydrochloric acid catalyst. Graft copolymers of sodium alginate with vinyl caprolactam were synthesized using azobisisobutyronitrile as an initiator, and characterized by Fourier infrared spectroscopy, differential scanning calrimetry and X-ray diffraction for analysis of the amorphous nature drug in the beads, and by scanning electron microscopy for the spherical nature of the beads. Preparation condition of the beads was optimized by considering the percentage of encapsulation efficiency, swelling behavior of beads and their release data. Effects of variables such as GA concentration, drug/polymer ratio and catalyst concentration on the release of 5-FU were carried out at two different temperatures (25 and 37 °C) in simulated intestinal fluid for 12 h. It was observed that, drug release from the beads decreased with increasing drug/polymer (d/p) ratio, extent of crosslinking agent and catalyst concentration. The swelling degree of graft copolymer beads was found to be increased with decreasing of environmental temperature. In vitro release studies were performed at 25 and 37 °C for 12 h, and showed that thermoresponsive graft copolymer beads had higher drug release behavior at 25 °C than that at 37 °C, following Fickian diffusion transport mechanism with slight deviation.

Synthesis and characterization of poly(N‐vinyl‐2‐pyrrolidone) grafted sodium alginate hydrogel beads for the controlled release of indomethacin

AbstractGraft copolymers of sodium alginate (NaAlg) with N‐vinyl‐2‐pyrrolidone were prepared using azobisisobutyronitrile as initiator. The graft copolymers (NaAlg‐g‐PVP) were characterized with Fourier transform infrared spectroscopy, elemental analysis, and differential scanning calorimetry. Polymeric hydrogel beads of NaAlg and NaAlg‐g‐PVP were prepared by crosslinking method using glutaraldehyde (GA) as a crosslinker in the hydrochloric acid catalyst (HCl) and these beads were used to deliver anti‐inflammatory drug, indomethacin (IM). Chemical stability of the IM after encapsulation into beads was confirmed by FTIR. Preparation conditions of the NaAlg‐g‐PVP beads were optimized by considering the percentage entrapment efficiency, particle size, swelling capacity and their release data. In vitro release studies were performed in simulated gastric fluid (pH 1.2) for the initial 2 h, followed by simulated intestinal fluid (pH 7.4) for 4 h. Effects of GA concentration, exposure time to GA, drug/polymer (d/p) ratio, and concentration of HCl on the release of IM were discussed. It was observed that IM release from the beads decreased with increasing GA concentration and exposure time. IM release also decreases with increasing d/p ratio and HCl concentration. The highest IM release was obtained to be 77% for beads crosslinked with 0.027M GA. Swelling experiments were also performed to compute molecular mass between crosslinks of the beads. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008