Preparation of alginate coated chitosan hydrogel beads by thermosensitive internal gelation technique

Chitosan hydrogel beads were successfully prepared by the method of thermosensitive internal gelation technique. The prepared beads were spherical, smooth-surfaced and non-aggregated with a diameter of 1.7–2.1 mm. The diameters of beads can be controlled and have a correlation with the initial drop size, the concentration of CaCl₂, alginate and the time of solidification. The bead is comprised of three parts, which are chitosan/glycerophosphate (CS/GP) hydrogel core, chitosan-alginate (CS/SA) gel layer in the middle and calcium-alginate gelatin capsules in outer layer. Swelling studies indicate that the beads can be stable in simulated gastric fluid. But the beads shrink sharply when removed to simulated intestinal fluid. Drug release behavior showed that release of ornidazole in the beads is much slower than in the CS/GP hydrogel.     

麦饭石含量对载药复合凝胶小球释药性能的影响

以瓜尔胶-g-聚丙烯酸/麦饭石复合水凝胶(GG-g-PAA/MS)和海藻酸钠(SA)为原料,双氯芬酸钠(DS)为模拟药物,采用离子凝胶法制备了载药复合凝胶小球,考察了pH敏感性以及MS含量对复合凝胶小球的包封率、载药率、溶胀性和药物释放行为的影响.结果表明:凝胶小球具有明显的pH敏感性,在不同pH介质中溶胀率和释放速率...     

Preparation and evaluation of berberine alginate beads for stomach-specific delivery

The purpose of this research was to prepare floating calcium alginate beads of berberine for targeting the gastric mucosa and prolonging their gastric residence time. The floating beads were prepared by suspending octodecanol and berberine in sodium alginate (SA) solution. The suspension was then dripped into a solution of calcium chloride. The hydrophobic and low-density octodecanol enhanced the sustained-release properties and floating ability of the beads. The bead formulation was optimized for different weight ratios of octodecanol and SA and evaluated in terms of diameter, floating ability and drug loading, entrapment and release. In vitro release studies showed that the floating and sustained release time were effectively increased in gastric media by addition of octodecanol. In vivo studies with rats showed that a significant increase in gastric residence time of beads had been achieved.     

Monoolein cubic phase including in situ ionically gelled alginate and its salt-responsive release property

Salt-responsive monoolein (MO) cubic phase was prepared by in situ ionically gelling alginate contained in its water channels. On the TEM micrographs, bilayers, and water channels, characteristic of MO cubic phase were observed, and alginate and CaCl₂ had little effect on the structure. According to the differential scanning calorimetric thermogram, the cubic-to-hexagonal phase transition temperature of the cubic phase containing CaCl₂ solution was 46.8°C and it was much lower than that of the cubic phase containing distilled water, 60.5°C. The transition temperature was not significantly affected by alginate. The phase transition temperatures measured by the calorimetric analysis were in accordance with those determined by polarized optical microscopy. An initial burst release of dye (i.e., amaranth) was observed when the gelled alginate was not contained in the water channel of the cubic phase. A sustained release was obtained with the cubic phase containing the gelled alginate. The release of dye loaded in the cubic phase containing the gelled alginate was significantly promoted when the cubic phase came into contact with PBS (10?mM, pH 7.4), possibly because the multivalent cation (Ca²⁺) bound to alginate chains could be replaced by the monovalent cation (Na⁺).     

Preparation and characterization of crosslinked alginate–CMC beads for controlled release of nitrate salt

Carboxymethyl cellulose (CMC)/sodium alginate (SA) hydrogel beads were successfully prepared by Ca²⁺ ions crosslinking followed by gamma irradiation. The factors affecting beads formation are the composition of SA in the blend and concentration of calcium chloride as a crosslinking agent. The results indicated that the addition of CMC to SA increases the swelling (%) upto (1:3) (CMC:SA) ratio. The effect of different irradiation doses (2.5, 5, and 10 kGy) on swelling (%) was studied. At low doses, swelling (%) decreases upto 5 kGy then starts to increase at 10 kGy. The degree of the swelling (%) and release (%) of ammonium nitrate salt from beads were investigated under different pH (1.2, 5 and 7). The beads were characterized by FTIR, SEM and TGA to investigate molecular structure, morphology and thermal stability of beads.     

In vitro and in vivo degradation of an injectable bone repair composite

In vitro and in vivo degradation behaviors of an injectable bone regeneration composite (IBRC) which comprised of nano-hydroxyapatite/collagen (nHAC) particles in alginate hydrogel carrier were investigated. In vitro degradation quantitative testing indicated that the alginate had a faster degradation rate in simulated body fluid (SBF) than in deionized water at 37 °C. Similarly, IBRC also had a higher degradation rate in SBF than in deionized water at 37 °C, which was evaluated by alginate molecular weight measurement, mechanical properties test and degradation kinetics evaluation. But molecular weight of alginate degraded slower in IBRC than that in aqueous solution. In vitro results showed that degradation medium SBF had influence on degradation of alginate molecules. In the in vivo degradation study, surprisingly, there was no obvious decreasing of molecular weight of alginate from 0 to 8 weeks. IBRC degraded mostly after 24 weeks implantation and was replaced by connective tissue. No fibrous capsule and acute inflammatory reaction were found during the observed 24 weeks after IBRC implantation. There is only a mild short-term inflammatory response in rat dorsum muscle. These results indicated that IBRC had a controllable degradability and biocompatibility. Therefore, IBRC may be a promising degradable material for bone repair and bone tissue engineering.     

Adsorption kinetics,isotherms and mechanisms of three-component covalent organic polymer/sodium alginate beads for ciprofloxacin removal from aqueous solution

Ciprofloxacin (CIP), an important representative fluoroquinolone antibiotic, has been frequently detected in water sources, thus threatening aquatic organisms and human health. In this work, a porous three-component covalent organic polymer (SLEL-6) was synthesized through multi-component (MC) reaction systems for adsorptive removal of CIP from aqueous solution, followed by an encapsulation process to achieve SLEL-6/sodium alginate (SA) beads with boosted adsorption ability, reusability and recyclability. By virtue of the hierarchical porous natures, functional groups as well as π-rich skeletons, SLEL-6 and SLEL-6/SA beads could deal with CIP contamination effectively. Moreover, the adsorption isotherms of CIP by SLEL-6 and SLEL-6/SA beads follow the Langmuir model showing high theoretical maximum adsorption capacities of 57.47 and 163.93 mg g⁻¹, respectively. Furthermore, the plausible mechanisms are proposed according to experimental studies of influencing factors, coupled with characterizations before and after adsorption. This work therefore highlighting the immense potential of COP-based SA composite beads as new-type globular adsorbents for eliminating fluoroquinolones from aqueous solution.     

Polyaniline-coated magnetite nanoparticles incorporated in alginate beads for the extraction and enrichment of polycyclic aromatic hydrocarbons in water samples

A magnetic solid-phase extraction sorbent consisting of polyaniline-coated magnetite nanoparticles entrapped in alginate beads (PANI/alginate/Fe₃O₄) was successfully synthesised and applied for the extraction and preconcentration of polycyclic aromatic hydrocarbons (PAHs) in water samples. The magnetite nanoparticles helped to provide an easy and rapid isolation of the sorbent from the sample solution using an external magnet. The alginate beads helped to increase the surface area for polyaniline coating. The polyaniline-coated alginate/magnetite composite helped to increase the extraction efficiency due to the π–π interactions between the polyaniline and the PAHs. Various parameters that affected the extraction efficiencies were optimised including the polymerisation time, the amount of sorbent, sample pH, extraction time, ionic strength, and desorption conditions. Under the optimal conditions, a linear response was achieved in the concentration range of 0.040–50.0 µg L^?1, and the limit of detection was 0.010 µg L^?1. This simple, convenient, cost-effective, and environmentally friendly method was successfully applied for the extraction and enrichment of PAHs in water samples. The recoveries ranged from 86.0% to 97.8% with a relative standard deviation <10 %.     

Reduction of uranium concentration in well water by Chlorella (Chlorella pyrendoidosa) a fresh water algae immobilized in calcium alginate

A great deal of research has been directed towards the problem of reduction of uranium concentration from few hundreds of ppb to less than 20 ppb, a limit of uranium in drinking water from ground water resources fixed in Dec, 2001 by US, Environmental Protection Agency. Laboratory simulated experiments were carried out for the reduction of U(VI) concentration in well water from few thousands of ppb to less than 20 ppb. Well water samples were spiked with U(IV) ranging from 1000 to 2000 ppb. The contaminated solutions were passed through a glass column containing of chlorella impregnated beads of calcium alginate. Chlorella(Chlorella pyrendoidosa), a fresh water algae, was immobilized in sodium alginate in the form of beads by using 0.2M calcium chloride solution. The solution was passed again through a charcoal solution to remove any trace of impurities. The concentration of uranium after treatment ranged from 10 to 20 ppb. The concentration of other major cations and anions in the solution were also monitored. This low cost kit was proposed for on-line removal of uranium from ground water used for drinking purposes. For taking care of waste disposal, 99-100% of the adsorbed uranium on beads was recovered by 0.1M HNO₃. The desorption results suggest that the uptake of uranium by Chlorella is a physico-chemical adsorption on the cell surface, not a biological activity. The uranium in the algal cells is coupled to the ligand, which can be easily substituted with NO₃ ^-. This revised version was published online in July 2006 with corrections to the Cover Date.     

Using Zeolite/Polyvinyl alcohol/sodium alginate nanocomposite beads for removal of some heavy metals from wastewater

Functionalized Polyvinyl alcohol/sodium alginate (PVA/SA) beads were synthesized via blending Polyvinyl alcohol (PVA) with sodium alginate (SA) and the glutaraldehyde was used as a cross-linking agent. The zeolite nanoparticles (Zeo NPs) incorporated PVA/SA resulting Zeo/PVA/SA nanocomposite (NC) beads were synthesized for removal of some heavy metal from wastewater. The synthesizes beads were characterized via Fourier transforms infrared spectroscopy (FTIR), X-ray diffraction (XRD), particle size analyzer (PSA), and scanning electron microscope (SEM). The adsorption kinetics of the selected metal ions onto Zeo/PVA/SA NC beads followed the pseudo-first-order model (PFO) and the adsorption isotherm model was well fitted by the Langmuir model. Moreover, the thermodynamic studies were also examined; the outcomes showed that the adsorption mechanisms of the selective metal ions were endothermic, the chemical in nature, spontaneous adsorption on the surface of the Zeo/PVA/SA NC beads. The removal efficiency using Zeo/PVA/SA NC modified beads reached maximum at the pH value of 6.0 for Pb²⁺, Cd²⁺, Sr²⁺, Cu²⁺, Zn²⁺, Ni²⁺, Mn²⁺ and Li²⁺ with 99.5, 99.2, 98.8, 97.2, 95.6, 93.1, 92.4 and 74.5%, respectively, while the highest removal are achieved at pH = 5 for Fe³⁺ and Al³⁺ with 96.5 and 94.9%, respectively and decreased at lower or higher pH values. The survival count (%) of the E. coli cells were 34% on the SA beads, 11% on the PVA/SA, and 1% on the Zeo/PVA/SA NC modified beads, after 120 min exposure at 25 °C. Reusability experimental displays that the synthesized beads preserved a significant decrease in the sorption capacity after 10 repeating cycles. The Zeo/PVA/SA NC beads were able to eliminate 60–99.8% of Al³⁺, Fe³⁺, Cr³⁺, Co²⁺, Cd²⁺, Zn²⁺, Mn²⁺, Ni²⁺, Cu²⁺, Li²⁺, Sr²⁺, Si²⁺, V²⁺, and Pb²⁺ ions from the natural wastewater samples collected from 10th Ramadan City, Cairo, Egypt.     

Physical property testing of a novel hybrid natural rubber-graft-cassava starch/sodium alginate bead for encapsulating herbicide

A novel bead of modified starch for encapsulating 2,4-dichlorophenoxy acetate (2,4 DA) was made from natural rubber-graft-cassava starch (NS) and sodium alginate (SA) in a water-based system. The particle size and zeta potential of pristine NS, the NS/SA blend and the NS/SA blend containing 2,4 DA were evaluated. The swelling ratio in water of the beads was investigated and found to be enhanced as a function of the SA portion in the hydrogel due to an increase in the hydrophilic groups in the beads. In addition, the chemical interaction between 2,4 DA and the polymer matrix was investigated by FTIR and XRD. The results suggest that an NS/SA matrix is a good polymer membrane for encapsulating 2,4 DA in a water medium and the beads are also easily decomposed in the natural environment after use.     

Fabrication of zirconium(IV) cross-linked alginate/kaolin hybrid beads for nitrate and phosphate retention

The extreme nitrate (NO₃⁻) species in drinking water leads to methemoglobinemia (blue baby syndrome) disease in new born toddlers whereas the excess phosphate (PO₄³⁻) and NO₃⁻ contents lead to the eutrophication (algae growth) problem of water sources. Upto date, the environmental researchers have developing the suitable adsorbent materials for providing NO₃⁻ and PO₄³⁻ free water system. In present study, a low-cost alginate (Alg) assisted kaolin (KN) (AlgKN) composite beads were prepared and utilized for the removal of NO₃⁻ and PO₄³⁻. To improve the sorption capacity (SC) and stability, Zr⁴⁺ ions were coated onto AlgKN to get Zr@AlgKN composite beads which were prepared via., hydrothermal (Hydro) and in situ precipitation (In situ) methods. The hydro assisted Zr@AlgKN composite beads possess an enhanced SC than the in situ assisted adsorbents. In batch scale, the parameters responsible for the adsorption process such as contact time, co-ions, adsorbent dosage, pH, initial ions concentration and temperature were optimized. The adsorbents were characterized by XRD, FTIR, BET, EDAX and SEM analysis. The adsorption experimental data was fitted with isotherms, kinetics and thermodynamic parameters. The regeneration and field applicability study of the Zr@AlgKN composite beads were also investigated.     

Sodium alginate/HPMC/liquid paraffin emulsified (o/w) gel beads,by factorial design approach; and in vitro analysis

The present study involved development of a novel sodium alginate (SA)/HPMC/light liquid paraffin emulsified (o/w) gel beads containing Diclofenac sodium (DS) as an active pharmaceutical ingredient and its site specific delivery by using hard gelatin capsule fabricated by enteric coated Eudragit L-100 polymer. Emulsified gel beads were formulated by 3-level factorial design, ionic gelatin method. The obtained beads were characterized by Fourier transform infrared, X-ray diffraction and Field emission scanning electron microscope analysis. The variables such as SA (X₁), HPMC (X₂), were optimized for drug loading and in vitro drug release with the help of response surface methodology (RSM). The RSM analysis predicted that SA was significant for both drug loading (p = 0.0005) and drug release (p = 0.0041). HPMC was only significant for drug release (p = 0.0154). The cross-product contribution (2FI) and quadratic model were found to be adequate and statistically accurate with correlation value (R²) of 0.9054 and 0.9450 to predict the drug loading and drug release respectively. An increase in concentration of HPMC and SA decreases the drug loading as well as the drug release. The obtained optimum values of drug loading and DS released were 7.43 % and 85.54 % respectively, which were well in agreement with the predicted value by RSM.     

Effect of gamma radiation on the physico-chemical properties of alginate-based films and beads

Alginate solution (3%, w/v) was prepared using deionized water from its powder. Then the solution was exposed to gamma radiation (0.1?25 kGy). The alginate films were prepared by solution casting. It was found that gamma radiation has strong effect on alginate solution. At low doses, mechanical strength of the alginate films improved but after 5 kGy dose, the strength started to decrease. The mechanism of alginate radiolysis in aqueous solution is discussed. Film formation was not possible from alginate solution at doses >5 kGy. The mechanical properties such as puncture strength (PS), puncture deformation (PD), viscoelasticity (Y) coefficient of the un-irradiated films were investigated. The values of PS, PD and Y coefficient of the films were 333 N/mm, 3.20 mm and 27%, respectively. Alginate beads were prepared from 3% alginate solution (w/v) by ionotropic gelation method in 5% CaCl₂ solution. The rate of gel swelling improved in irradiated alginate-based beads at low doses (up to 0.5 kGy).     

Designing Swellable Beads of Alginate and Gelatin for Controlled Release of Pesticide (Cypermethrin)

In the present study biopolymeric beads of sodium alginate and gelatin were prepared by employing CaCl₂ as a crosslinking agent. A series of such microspheres of different compositions were prepared by varying the amounts of sodium alginate, gelatin and CaCl₂ in the feed mixture. The beads were loaded with an insecticide like cypermethrin. The prepared loaded and unloaded beads were characterized by FTIR spectral and Environmental scanning electron microscopy (ESEM) techniques, to gain insight into the molecular structure and morphology of beads, respectively. The swelling experiments were performed for different composition of beads and at varying pH and temperature of the swelling media. The swelling controlled release of insecticide was also investigated for 8 days in bi-distilled water as a release medium. The release experiments were performed under the static and varying experimental conditions and the data obtained were fitted to Fick's equation to evaluate diffusion coefficients of insecticide. The results were further analyzed by Fick's power law equation, and the possible mechanisms of the insecticide release were explored at different experimental conditions. Soil–pot experiments were also performed to demonstrate the applicability of the present controlled release technique to agricultural fields.     

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.     

Ionically crosslinked alginate/carboxymethyl chitin beads for oral delivery of protein drugs

Complex beads composed of alginate and carboxymethyl chitin (CMCT) were prepared by dropping aqueous alginate-CMCT into an iron(III) solution. The structure and morphology of the beads were characterized by IR spectroscopy and scanning electron microscopy (SEM). IR confirmed electrostatic interactions between iron(III) and the carboxyl groups of alginate as well as CMCT, and the binding model was suggested as a three-dimensional structure. SEM revealed that CMCT had a porous morphology while alginate and their complex beads had a core-layer structure. The swelling behavior, encapsulation efficiency, and release behavior of bovine serum albumin (BSA) from the beads at different pHs were investigated. The BSA encapsulation efficiency was fairly high (>90%). It was found that CMCT disintegrated at pH 1.2 and alginate eroded at pH 7.4 while the complex beads could effectively retain BSA in acid (>85%) and reduce the BSA release at pH 7.4. The results suggested that the iron(III)-alginate-CMCT bead could be a suitable polymeric carrier for site-specific protein drug delivery in the intestine.     

A Novel Approach for Testing the Hixon‐Crowel Model For In Vitro Release of Vitamin B2 From Chitosan Coated Calcium Alginate Beads

The dynamic release of a model drug (vitamin B₂) from chitosan coated calcium alginate beads has been studied in the media of varying pH and the Hixon‐Crowel model has been applied to the experimental data, using a novel ‘curve area measurement’ (CAM) approach. The two release profiles, namely experimental and ideal, were found to be in close agreement except for the initial phase of the release process.     

Preparation and characterization of PVA/SA/HA composite hydrogels for wound dressing

A composite hydrogel based on, by introducing, polyvinyl alcohol, sodium alginate, and hyaluronic acid was fabricated using CaCl₂ as a cross-linker. The physical properties including morphology, water vapor transmission rate, and hydrophilicity were investigated. All PVA/SA/HA composite hydrogels with different compositions had highly homogeneous and interconnected pores, and the morphologies of the PVA/SA/HA hydrogels ranged from fibrous structure to irregular structure with increasing content of SA. The introduction of sodium alginate enhanced the hydrophilicity and water vapor transmission capacity of the hydrogel; however, the hydrophilicity of the composite hydrogels decreased with the increasing cross-linker content.     

Examination of the Higuchi Model for the Release of Vitamin B2 from Multilayered Calcium Alginate/Chitosan Beads in Varying pH Medium

The release of model drug vitamin B₂ from calcium alginate/chitosan multi‐layered beads has been studied in the media of varying pH (3 h in the medium of pH 1.0 and for the remaining time in pH 7.4) at 37°C. The quantitative deviation of experimental data from the Higuchi model has been interpretated by using a newly developed ‘curve area measurement’ (CAM) approach. The higher deviation in the initial phase has been explained on the basis of porous structure of beads due to the use of low molecular weight polymers in the preparation of beads.