Alginate Hydrogel Beads Research Articles

Recovery of gold using graphene oxide/calcium alginate hydrogel beads from a scrap solid state detector

Hydrogel beads was developed for the selective removal of gold from a scrap solid state detector. Beads were synthesized by graphene oxide impregnation in calcium alginate matrix (Gra-Alg) using sol gel method. Scrap solid state detector was dissolved in aqua regia. Copper (Cu) from the solution was recovered using conventional chemical separation where as gold(Au) from the supernatant solution was selectively isolated using Gra-Alg hydrogel beads. The characteristic XRD peak of graphene oxide was observed at 2θ = 11°. The maximum uptake capacity of the hydrogel beads is observed as 81.87 mg g−1. The sorption capacity of the hydrogel beads is highly dependent on the pH of the solution and more than 95% uptake of Au was observed at pH range 2–4. The equilibrium contact time of the sorption of gold on the hydrogel beads was 22 h. Isotherm study suggests that the system is following the Langmuir isotherm model and the maximum sorption capacity (Q0) was observed as 81.87 mg g-1. The experimental data fitted well with the second order pseudo kinetic equation with linear correlation coefficient value as 0.94 and the rate constant is 0.001 g mg-1 min-1.

Nanostructured lipid carriers incorporated in alginate hydrogel: Enhanced stability and modified behavior in gastrointestinal tract

The application of nanostructured lipid carriers (NLC) are influenced by their relatively poor stability, including storage stability and gastrointestinal stability. The aim of the present study was to develop NLC-hydrogel to improve the physical stability and modify the behavior of NLC in gastrointestinal tract. The quercetin-loaded NLC were successfully incorporated in alginate hydrogel beads using the extrusion dripping technique. Dynamic light scattering (DLS), transmission electron microscopy (TEM), X-ray diffraction (XRD), and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) were used to assess the influence of this incorporation on the feature of NLC, and results indicated that it had no obvious effect on the particle size, morphology, and inner structure of NLC. The incorporation of NLC in alginate hydrogel beads could effectively improve the physical stability of NLC compared with NLC dispersion and NLC-alginate sol. In vitro release study suggested that the quercetin release from NLC-alginate hydrogel beads was slower than that of NLC dispersion and NLC-alginate sol. In vitro digestion study revealed that only a small amount of incorporated NLC with a small size could diffuse into gastric fluid. Furthermore, because NLC diffused gradually from alginate hydrogel to intestinal fluid, the aggregation of NLC in intestinal fluid was prevented, and lipid matrix was gently hydrolyzed. These studies demonstrated that the incorporation of NLC in alginate hydrogel might be a promising method to improve the stability of NLC, modify the behavior of NLC in gastrointestinal tract, and control the release during digestion.

Preparation of mesoporous Ce-Ti oxide millispheres for efficient catalytic ozonation: Performance and mechanism

To achieve highly efficient ozonation during water treatment, it is crucial to develop catalysts combining high activity and excellent hydrodynamic as well as mass transfer properties. In this study, a series of catalysts of Ce-Ti bimetal oxide mesoporous millispheres were prepared through a green and economical route of precursor sol premixing - alginate hydrogel bead template method employing the low cost inorganic salts as the raw materials. The resulting catalysts were comprehensively characterized by N2 adsorption-desorption, XRD, XPS, SEM-EDS, TEM-SAED, Raman spectroscopy, and NH3-TPD. The effects of Ce/Ti ratio and calcination temperature on the structure and activity of the catalyst were investigated, and the performance and mechanism of the corresponding catalytic ozonation were explored. The results showed that the activities of amorphous catalysts were higher than those of the crystalline ones, and the catalytic activity was positively correlated with the density of surface acidic sites. It was revealed that hydroxyl radicals were the predominant reactive species during the catalytic oxidation by the prepared catalyst. The optimized Ce0.5Ti0.5O2 mesoporous millisphere of high specific surface area (199 m2 g–1) and suitable mesoporous structure (average pore diameter of 3.59 nm), was rich in Ce-O-Ti active sites and exhibited high catalytic activity. Almost complete (99%) mineralization of 100 mg L–1 oxalic acid could be achieved during the catalytic ozonation in 90 min. Moreover, negligible loss of catalytic activity was observed in five consecutive experiments. In addition, as compared with catalyst free, the Ce0.5Ti0.5O2 millisphere catalyst could increase the TOC removal by 18.7%–54.0% during ozonation of four toxic organic pollutants such as diclofenac, thus exhibiting promising potential in authentic water treatment.

Anthocyanins from jussara (Euterpe edulis Martius) extract carried by calcium alginate beads pre-prepared using ionic gelation

In order to take advantage of the functional properties of the jussara (Euterpe edulis Martius) extract, this study aimed at producing alginate hydrogel beads by ionic gelation process to carry jussara extract, increase its stability and to protect the anthocyanins from environmental conditions that interfere in stability and color of these compounds, such as the pH of the medium. Anthocyanins encapsulation from extract occurred by adsorption technique using blank alginate beads. Ionic gelation method was combined with complexation process using chitosan, whey protein concentrate or gelatin. Complexation technique using cationic polymers was effective in protecting these pigments during refrigerated storage. Gel strength of the hydrogel beads and anthocyanins retention was influenced by zeta potential and apparent viscosity of the materials used in the coating process. Chitosan presented higher zeta potential (+57.1 ± 2.0 mV) and apparent viscosity (0.013 ± 0.000 Pa.s) values and the beads coated with this material showed higher monomeric anthocyanins retention (8.4 ± 0.2 mg of cyanidin 3-glucoside equivalent/g of dry bead) than those coated with whey protein concentrate and gelatin (6.6 ± 0.3 and 5.2 ± 0.4 mg of cyanidin 3-glucoside equivalent/g of dry bead, respectively). Ionic gelation encapsulation process led to the formation of hydrogel beads containing anthocyanins, thus enabling the release profile of the compounds at specific pH conditions, such as the intestinal fluid.

Fabrication of detonation nanodiamond@sodium alginate hydrogel beads and their performance in sunlight-triggered water release.

Agricultural water use accounts for around 70% of total water use in the world. Enhancing agricultural water use efficiency is a key way to cope with water shortage. Here, sunlight-responsive hydrogel beads consisting of sodium alginate (SA) matrix and detonation nanodiamond (DND) were fabricated by an ion gelation technique, which has potential applications in controlled water release. The interaction between the DND and SA matrix was investigated by Fourier transform infrared (FTIR) spectra and X-ray diffraction (XRD). UV-vis diffuse reflectance spectra verified DND can absorb solar energy in the UV, visible and even near-infrared regions. DND dispersed in the hydrogel matrix can absorb sunlight and generate heat, increasing the temperature of the matrix and resulting in slow release of water from the elastic beads. In addition, the effects of DND content and pH were systematically studied to evaluate their water adsorption properties. The swelling kinetics of DND@SA hydrogel beads in distilled water could be fitted well with a pseudo-second-order kinetic model. Six consecutive cycles of water release–reswelling indicated that their easy regeneration and reusability. The novel and eco-friendly hydrogel beads should be applicable to on-demand, sequential, and long-term release of water via light exposure.

The Influence of Silver Nanoparticle Sizes on Antibacterial Activity, Cytotoxicity and Genotoxicity of Alginate Hydrogel Beads Containing Silver Nanoparticles

Sizes of silver nanoparticles (AgNPs) have been shown to affect the biological activity of AgNPs. Hydrogel beads loaded with AgNPs have been extensively employed for biomedical applications. However, the influence of AgNPs sizes on biological activity of AgNP-loaded hydrogel beads has not much studied. Our objectives were to investigate the effect of AgNP sizes on the antibacterial activity, the cyto- and genotoxicity of AgNPs/alginate hydrogel beads. AgNPs of different sizes (⁓10 nm for S-AgNPs, and ⁓50 nm for L-AgNPs) were incorporated into alginate hydrogel beads during the preparation. The results showed that, S-AgNPs/alginate hydrogel beads (⁓89% inhibition) at AgNP concentration of 10 µg/ml tended to inhibit the growth of E. coli greater than L-AgNPs/alginate hydrogel beads (⁓49% inhibition) at the same dose. Moreover, at this effective antibacterial concentration (10 µg/ml), S-AgNPs/alginate hydrogel beads exhibited weak cytotoxic effect to HaCaT cells whereas L-AgNPs/alginate hydrogel beads showed non-cytotoxicity to this cell line. Furthermore, treatment of HaCaT cells with 10 µg/ml of S-AgNPs/ or L-AgNPs/alginate hydrogel beads did not result in a significant change in %DNA in tail when compared to untreated cells. Therefore, these AgNPs/alginate hydrogel beads, especially with smaller sized AgNPs, can be used as an antibacterial biomaterial with low cytotoxicity and genotoxicity to human cells.

Optimization of phenol biodegradation by immobilized Bacillus subtilis isolated from hydrocarbons-contaminated water using the factorial design methodology

The ability of newly isolated bacteria, identified as Bacillus subtilis immobilized on alginate hydrogel beads, to degrade phenol was investigated under different parameters, such as phenol concentration, bead diameter and inoculums size, and was optimized using full factorial design methodology. A mathematical model that governs the degradation of phenol by the immobilized system was obtained and it fitted the experimental data very well. The model indicated that within the range of variables employed, all the parameters and their interactions influenced the biodegradation process, whereby the phenol concentration was the most significant factor. B. subtilis revealed a very high degradation activity and could be grown using phenol as the sole source of carbon. Phenol was degraded by the new bacteria in 8 h under the optimum conditions obtained by the desirability function: 100 mg L-1 phenol concentration, 3 mm beads diameter and 244.5 mg of cell dry per liter biomass size, with a desirability value of 91.25 %.

Carboxylated alginate hydrogel beads for methylene blue removal: formulation, kinetic and isothermal studies

Carboxylated alginate hydrogel beads for methylene blue removal: formulation, kinetic and isothermal studies

Alginate-Based Hydrogel Beads as a Biocompatible and Efficient Adsorbent for Dye Removal from Aqueous Solutions.

In this study, sodium alginate was employed as a starting material for preparing two kinds of biocompatible adsorbents, including calcium alginate hydrogel beads and magnetic hydrogel beads. Fourier transform infrared spectroscopy, X-ray diffraction pattern, and scanning electron microscopy/energy-dispersive X-ray techniques were used to characterize the prepared adsorbents. The performance of the prepared adsorbents for the removal of methyl violet from aqueous solution was studied in detail. Both kinetics and equilibrium aspects of methyl violet adsorption were investigated, and the obtained equilibrium and kinetics data were described with various adsorption models. The effects of initial dye concentration, adsorbent dosage, and temperature on adsorption performance were investigated. Thermodynamic parameters of adsorption were obtained as well.

Preparation of Calcium Phosphate Coated Simvastatin-Loaded PLGA Microspheres Dispersed Alginate Hydrogel Beads as a Controlled Drug Delivery Carrier

Simvastatin (SIM) is widely used as a cholesterol-lowering drug known to affect bone formation in vivo and its sustainable administration into localized area is of particular interest. We reported previously that sustained SIM release from poly (lactic-co-glycolide) (PLGA) microspheres could maintain relatively low concentration in the bone defect area, resulting in the improved bone regeneration effect. The aim of this study was to determine the release characteristics of SIM from calcium phosphate coated SIM-loaded PLGA Microspheres (CSPMs) dispersed into an alginate hydrogel bead (with different drug release profiles), since we speculated that further sustainable SIM release would be more effective related to stimulate the formulation of BMP-2, resulting in the promoted bone regeneration.

Performance of Phosphorus Sorption on Thermosensitive Zirconium Alginate Hydrogel Beads with Full-interpenetrating Network†

Performance of Phosphorus Sorption on Thermosensitive Zirconium Alginate Hydrogel Beads with Full-interpenetrating Network†

Immobilization of Calcined Layered Double Hydroxide into Alginate Hydrogel Beads for PNP and PAP Removal: Kinetics, Isotherms, Thermodynamics, and Mechanism

The calcined layered double hydroxide (CLDH)-alginate hydrogel beads were synthesized by embedding CLDH into alginate hydrogel beads. The beads were used to remove p-nitrophenol (PNP) and p-aminophenol (PAP) from aqueous solution. The structure and composition of CLDH-alginate hydrogel beads were characterized by scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), elemental mapping, transmission electron microscope (TEM), X-ray powder diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, BET, and X-ray photoelectron spectroscopy (XPS). The adsorption kinetic, isothermal, thermodynamic properties and adsorption mechanism of PNP and PAP on CLDH-alginate hydrogel beads were studied. The results demonstrated that the adsorption kinetic data fitted the pseudo-second-order model well with the correlation coefficients (R2) of 0.9975 and 0.9995 for PNP and PAP, respectively. The isothermal data followed the Freundlich equation, and the values of R2 for PNP and PAP were 0.9728 and 0.9946, respectively. The adsorption processes were feasible, spontaneous, and endothermic. The adsorption mechanism was predominated by anionic exchange and hydrogen bonding for PNP and hydrogen bonding for PAP, which was evidenced by the results of adsorption experiments, characterization of FTIR and XPS, and theoretical calculation. Furthermore, the CLDH-alginate hydrogel beads can be separated easily due to their larger particle size. This will provide convenience in practice application.

Alginate hydrogel beads as a carrier of low density lipoprotein/pectin nanogels for potential oral delivery applications

Alginate hydrogel beads have been extensively investigated as drug delivery systems due to promising gastric environment stability. In the present study, alginate hydrogel beads were prepared with Ca2+ or Fe3+ to serve as the loading vehicles for egg yolk low density lipoprotein (LDL)/pectin nanogels. Scanning electron microscope was carried out to confirm the successful incorporation of nanogels into the beads. The FT-IR spectra and swelling ratio analyses proved that incorporation of nanogels did not affect the physicochemical properties of the hydrogel beads. The developed hydrogel beads exhibited pH dependent release of curcumin pre-encapsulated in nanogels, with significant retention of curcumin in gastric condition compared to curcumin encapsulated in nanogels or alginate beads alone. Hydrogel beads prepared with low viscous alginate and Ca2+ showed limited swelling property and more sustained release of curcumin in simulated gastrointestinal conditions, compared to the beads prepared with high viscous alginate and Fe3+. Gradual dissociation of nanogels from the beads during incubation in simulated intestinal fluid was studied with transmission electron microscope. Our study demonstrated the promising potential of alginate beads as a carrier to protect LDL-based nanogels from destabilization in gastric condition, thus expanding their applications as oral delivery system.

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.

Magnetic nanocellulose alginate hydrogel beads as potential drug delivery system

Magnetic nanocellulose alginate hydrogel beads are produced from the assembly of alginate and magnetic nanocellulose (m-CNCs) as a potential drug delivery system. The m-CNCs were synthesized from cellulose nanocrystals (CNCs) that were isolated from rice husks (RH) by co-precipitation method and were incorporated into alginate-based hydrogel beads with the aim of enhancing mechanical strength and regulating drug release behavior. Ibuprofen was chosen as a model drug. The prepared CNCs, m-CNCs and the alginate hydrogel beads were characterized by various physicochemical techniques such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM) and vibrating sample magnetometer studies (VSM). Besides the magnetic property, the presence of m-CNCs increased the integrity of the alginate hydrogel beads and the swelling percentage. The drug release study exhibited a controlled release profiles and based on the drug release data, the drug release mechanism was analyzed and discussed based on mathematical models such as Korsmeyer-Peppas and Peppas-Sahlin.

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.

Achieving high antimicrobial activity: Composite alginate hydrogel beads releasing activated charcoal with an immobilized active agent

New composites based on Ca-alginate hydrogels were produced that release activated charcoal (AC) particles with adsorbed povidone iodine (PVP-I) as a model antimicrobial substance in a physiological-like environment. Composite beads with different alginate (0.5–1.5%w/w) and AC (1–20%w/w) concentrations were analyzed by FE-SEM and characterized regarding textural parameters, swelling, and AC release kinetics. PVP-I was easily adsorbed onto AC particles within the optimized beads (0.5%w/w alginate, 20%w/w AC) as indicated by UV–vis spectroscopy, EDX and FT-IR analyses. The obtained beads have shown strong bactericidal effects against two standard bacterial strains (Staphylococcus aureus and Pseudomonas aeruginosa) and clinical multi-resistant wound isolates (MRSA, Escherichia coli, Pseudomonas aeruginosa, Еnterococcus faecalis and Proteus mirabilis) and, at the same time, exhibited negligible PVP-I desorption in physiological saline solution. Thus, the obtained composites could provide utilization of potent antiseptics such as iodine, in wound dressings, without the concern of systemic absorption.

Graphene oxide incorporated alginate hydrogel beads for the removal of various organic dyes and bisphenol A in water

In the present study, we described a facile preparation of graphene oxide incorporated alginate hydrogel beads (SA/GO) and applied them in adsorbing organic pollutants in aqueous media. The results show that the incorporation of graphene oxide obviously decreased the pore size and swelling ratio of the hydrogel beads. The existence of the GO also significantly enhanced the adsorption capability of the SA/GO beads to various organic dyes, including heterocyclic dye, indigo dye, anthraquinone, and azo dye. Besides, the SA/GO beads show promising adsorption capability to the bisphenol A (BPA), a toxic chemical which could cause endocrine disruption. The adsorption isotherm and kinetic of the SA/GO beads were also studied in detail. The present study indicates that the SA/GO beads are a type of effective absorbent for various organic pollutants which have the potential to be applied in water purification fields.

Biomass-based carbon beads with a tailored hierarchical structure and surface chemistry for efficient batch and column uptake of methylene blue

There is interest in cultivating an economic and controllable method for preparing biomass-based adsorptive materials for efficient removal of dyes from water. Herein a new bead-like material, i.e. alginate-derived carbon beads with a tailored hierarchical structure and surface chemistry, was prepared by using CaCO3-encapsulated calcium alginate (CA) hydrogel beads as the starting material and subsequent controllable carbonization and oxidation treatment. The resultant samples were characterized by SEM, TEM, FTIR, N2 sorption and XRD, etc. Analyses showed that hierarchical carbon beads with a tailored density of oxygen-containing functional groups have been successfully prepared. Adsorption of methylene blue (MB) was studied systematically through batch and column adsorption analyses, and noting the effect of pH, contact time, initial dye concentrations and flow rates. The adsorption kinetics and isotherms fitted well with the pseudo-second-order kinetic model and Langmuir isotherm model, respectively; and the maximum adsorption capacity for MB was 397.9 mg/g. The results indicated that CaCO3/CA-ox could not only significantly improve the adsorption capacity but also exhibited a higher adsorption rate for MB compared with CA. Furthermore, compared to traditional powdery materials, this bead-like porous adsorbent is convenient for column adsorption and scale-up for practical applications, due to the easy regeneration and reusability.

Fabrication of carboxylated cellulose nanocrystal/sodium alginate hydrogel beads for adsorption of Pb(II) from aqueous solution

Carboxylated cellulose nanocrystal-sodium alginate (CCN-Alg) hydrogel beads were easily prepared through a cross-linking method. The structure and properties of the composite beads were characterized by TEM, FTIR, SEM, XPS, thermogravimetric analysis (TGA), and zeta potential measurement. A high ratio of 76% of the Pb(II) ion was adsorbed within the first 2h, and the adsorption equilibrium was nearly reached after 3h. The experimental isotherm could be fitted by the Langmuir model, yielding an extreme adsorption capacity of 338.98mgg−1. The adsorption process followed a pseudo-second-order kinetic model, and thermodynamic analyses confirmed that the adsorption is a spontaneous and endothermic process. Regeneration tests with acid treatment indicated that the CCN-Alg beads performed well in repeated Pb(II) adsorptions, as they could maintain an adsorption capacity of 223.2mgg−1 after five repeated cycles. These results indicate that these CCN-Alg beads are a potentially effective and sustainable adsorbent for application in wastewater treatment.