Alginate Hydrogel Beads Research Articles

Preparation of colorimetric hydrogel beads for hydrofluoric acid detection

Colorimetric HF-sensitive hydrogel beads were prepared using alginate hydrogel as a host matrix and a pyrocatechol violet (PV)–titanium(IV) bis(ammonium lactato)dihydroxide (TALH) complex as a HF-sensing dye. The PV–TALH complex dye was released into a HF solution from the host matrices and turned the transparent HF solution yellow. From the results of control experiments, this yellow color was exclusively observed when the beads were exposed to HF. The color change allowed the detection of HF with the naked eye. Optimal conditions for the preparation of the HF-sensitive hydrogel were determined with consideration of the swelling behavior of the alginate hydrogel beads.

Protein encapsulation in alginate hydrogel beads: Effect of pH on microgel stability, protein retention and protein release

Hydrogel beads (microgels) are promising delivery systems for encapsulation and release of proteins because they can be fabricated from food-grade biopolymers using mild processes. In this study, a model globular protein (whey protein) was encapsulated in calcium-alginate beads (D43 = 290–520 μm) fabricated using an extrusion device with a vibrating nozzle. Protein-loaded beads were fabricated at three different pH values (pH 3, 5 and 7) to study the influence of protein-alginate electrostatic interactions on protein encapsulation, retention, and release. Protein encapsulation and retention was highest at low pH, while protein release was highest at high pH. Confocal microscopy and spectrophotometry measurements indicated that increasing the pH could trigger protein release from alginate beads formed at pH 3. These results suggest that hydrogel beads are suitable for encapsulation and pH-triggered release of proteins, which may be advantageous for certain food applications.

Induction of hepatic tissues in multicellular spheroids composed ofmurine fetal hepatic cells and embedded hydrogel beads.

IntroductionThree-dimensional (3D) multicellular spheroids are useful tools for simulation of cellular functions in vitro. However, it is difficult to culture certain epithelial cell types under 3D spheroid conditions because these cells cannot resist autonomous cell death, triggered by disordered cell polarity. The objective of this study was to find a method that enables spheroid culture of such epithelial cells utilizing hydrogel beads without cell death.MethodsWe used murine E14.5 fetal hepatic cells for the spheroid composition because they are sensitive to disorganized structures. Spheroids were formed by injecting 1-μl fresh medium containing 1000 fetal hepatic cells and the same number of alginate hydrogel beads (20 μm in diameter) into a 3% methylcellulose medium in the presence of dexamethasone and oncostatin M to induce hepatic differentiation. After 7 days of culture, microstructures were observed using hematoxylin and eosin staining and immunostaining using anti-CK8/18 antibody. Albumin secretion rate was determined by the enzyme-linked immunosorbent assay method. In addition, polarity-related proteins, E-cadherin, ezrin, and MRP2 were observed with immunostaining.ResultsControl spheroids without the use of alginate hydrogel beads showed extensive internal lack of epithelial hepatic cells. The spheroids containing alginate hydrogel beads exhibited sheet- or cord-like structures of epithelial hepatic cells, and it was clear that cell death of epithelial cells had been prevented. Albumin secretion data also supported the improvement of epithelial hepatic cell viability when alginate hydrogel beads were used. Localization of polarity-related proteins indicated the partial reconstitution of cell polarity in the spheroids using alginate hydrogel beads.ConclusionBased on these data, we concluded that the application of alginate hydrogel beads was effective in improving the epithelial hepatic cell culture of multicellular spheroids.

Calcium alginate hydrogel beads with high stiffness and extended dissolution behaviour

Alginate hydrogel bead has been widely explored as a vehicle for controlled delivery application due to its non-toxicity, renewability, and ease of formation. However, alginate hydrogel beads are known to have a low stiffness, i.e., Young modulus <1MPa, and a short dissolution time of between 1h and 2h in gastrointestinal fluid. This study aimed to fabricate calcium alginate hydrogel beads with desired properties like high stiffness and extended dissolution behaviour. A temperature-controlled extrusion–dripping method incorporating an immiscible interphase column was used to produce the ultra-high concentration (UHC) calcium hydrogel beads directly from unmodified alginate solution. The UHC beads have an extraordinary internal structure with thick calcium-alginate matrices and large pores in between the matrices. The Young’s modulus value of UHC calcium alginate beads was 3.6MPa, which was approximately 8times higher than the normal calcium alginate beads. The release profile for the model drug (i.e., methylene blue) encapsulated in UHC beads was found to be extended to 4h at 80% of drug release (t80). The kinetics of drug release fitted well with the Korsmeyer–Peppas model (r2⩾0.99) and followed the non-Fickian mechanism. These findings show that the preparation of calcium alginate beads featuring high stiffness and extended dissolution profile can be achieved without any chemical modification or additives. The UHC calcium alginate bead holds excellent promise as an encapsulation carrier of drugs or food used in controlled delivery applications.

In situ pore-forming alginate hydrogel beads loaded with in situ formed nano-silver and their catalytic activity.

An aqueous mixture of sodium carbonate (Na2CO3) and sodium alginate (Na-ALG) was added dropwise into an aqueous solution of Ca(NO3)2, leading to the formation of calcium alginate (Ca-ALG) hydrogel beads. Meanwhile Na2CO3 as a pore-forming precursor was transformed in situ into CaCO3 nanoparticles (CaCO3 NPs). SEM images show that CaCO3 NPs aggregates with a size of ∼10 μm were uniformly distributed in the Ca-ALG hydrogel beads. After subsequent erosion using acetic acid, Ca-ALG hydrogel beads with a uniform microporous structure were obtained. The porosity and specific surface area of such in situ pore-formed hydrogel beads are 16 and 14 times higher than those of the beads prepared in the absence of Na2CO3. Additionally, their porous structure can be modulated by varying the amount of Na2CO3. The obtained porous Ca-ALG hydrogel beads were further immersed into an aqueous solution of AgNO3. Under UV irradiation, the Ag(+) ions adsorbed in the Ca-ALG were in situ reduced to Ag nanoparticles (Ag NPs). SEM and TEM images show that Ag NPs with a size of ∼10 nm were uniformly distributed in the matrix of the hydrogel beads. The loading amount of Ag in the beads can also be modulated by varying the amount of Na2CO3. Furthermore, the resultant Ca-ALG beads loaded with Ag NPs (Ag/Ca-ALG) were used as catalysts. Their catalytic activity was evaluated by using the reduction reaction of 4-nitrophenol as a model reaction. The rate constant of the reaction in the presence of dry porous Ag/Ca-ALG beads was found to be 36 times higher than that in the presence of beads prepared in the absence of Na2CO3. Such a high catalytic efficiency can be attributed to their porous structure and consequent high Ag-loading capacity.

Comparative investigation of the binding characteristics of poly-l-lysine and chitosan on alginate hydrogel

The binding properties of poly-l-lysine and chitosan to alginate have been evaluated quantitatively and compared. Poly-l-lysine bound to alginate hydrogel more rapidly than chitosan as poly-l-lysine has a smaller molar hydrodynamic volume. In addition, poly-l-lysine showed a much higher binding capacity (6.14:1) for alginate hydrogel beads than chitosan (2.71:1), and a little higher binding stoichiometry (0.58) to sodium alginate molecules in solution than chitosan (0.49). An exothermic heat of alginate-poly-l-lysine complexes formation of 2.02kJ/mol was detected. For alginate–chitosan complexes, the binding enthalpy has been seen to be −3.49kJ/mol. The stability of the polyelectrolyte complexes was related to their binding enthalpy. The alginate-poly-l-lysine complexes could be disintegrated and rebuilt. By contrast, chitosan was bound with alginate in a steady state. These results provide fundamental insights regarding the structure and property relationships of macromolecules, and will be helpful in designing and selecting appropriate polymers.

Effect of Dynamic Culture and Periodic Compression on Human Mesenchymal Stem Cell Proliferation and Chondrogenesis.

We have recently developed a bioreactor that can apply both shear and compressive forces to engineered tissues in dynamic culture. In our system, alginate hydrogel beads with encapsulated human mesenchymal stem cells (hMSCs) were cultured under different dynamic conditions while subjected to periodic, compressive force. A customized pressure sensor was developed to track the pressure fluctuations when shear forces and compressive forces were applied. Compared to static culture, dynamic culture can maintain a higher cell population throughout the study. With the application of only shear stress, qRT-PCR and immunohistochemistry revealed that hMSCs experienced less chondrogenic differentiation than the static group. The second study showed that chondrogenic differentiation was enhanced by additional mechanical compression. After 14days, alcian blue staining showed more extracellular matrix formed in the compression group. The upregulation of the positive chondrogenic markers such as Sox 9, aggrecan, and type II collagen were demonstrated by qPCR. Our bioreactor provides a novel approach to apply mechanical forces to engineered cartilage. Results suggest that a combination of dynamic culture with proper mechanical stimulation may promote efficient progenitor cell expansion in vitro, thereby allowing the culture of clinically relevant articular chondrocytes for the treatment of articular cartilage defects.

Isolation and culture of chicken primordial follicles

The establishment of a primordial follicle culture system is important for the study of follicular development. Hence, the objective of this study was to isolate chicken primordial follicles and establish culture methods. Ovaries from 2-wk-old chickens were treated with trypsin-EDTA, collagenase II, or collagenase type IA, along with a mechanical isolation technique. Isolated follicles were cultured under different conditions. Results showed a significant difference in the follicular recovery and survival rates among different enzymes and methods used. The maximal follicular yield was obtained by trypsin+EDTA and collagenase II digestion, followed by collagenase type IA digestion. However, the highest follicular viability rate was observed in groups of collagenase type IA digestion and the mechanical isolation method. Enzymatic treatment resulted in higher misshapen oocytes or follicles, though the diameters of the follicles were not significantly changed. In addition, our follicle culture results for different conditions showed maximal survival rates of primordial follicles in alginate hydrogel beads after 12 d of culture. Thus, we successfully established methods for isolating and culturing chicken primordial follicles. The present method will greatly facilitate investigation of the regulation of follicular development.

Cellulose nanocrystal–alginate hydrogel beads as novel adsorbents for organic dyes in aqueous solutions

A new generation of recyclable adsorbents comprising of cellulose nanocrystals and alginate (CNC–ALG) with superior adsorption capacity was developed. Sustainable nanomaterials like cellulose nanocrystals derived from pulp fibres and cellulosic biomass are ideal systems to remove contaminants in our water systems. Their use will reduce our dependence on adsorbents, such as activated carbon that contribute to greenhouse gases production. Adsorption characteristics of CNC–ALG hydrogel beads were evaluated using batch adsorption studies of methylene blue (MB) in aqueous solution. The influence of various parameters, such as contact time, adsorbent dosage, initial dye concentration, pH, temperature, ionic strength, crosslinking time and bead size on the MB adsorption were investigated. Thermodynamic analyses confirmed that the adsorption process is spontaneous and exothermic. The kinetics and mechanism of adsorption were best described by a pseudo-second order kinetic model and intra-particle diffusion model. Equilibrium adsorption data fitted well to the Langmuir adsorption isotherm yielding a maximum adsorption capacity of 256.41 mg/g, which is comparable to activated carbon. We demonstrated that after five adsorption–desorption cycles, the removal efficiency of MB remained at ~97 %, and the CNC–ALG hydrogel beads are effective adsorbents for the removal of organic dyes from wastewaters.

Hydrogel beads from sugar cane bagasse and palm kernel cake, and the viability of encapsulated Lactobacillus acidophilus

AbstractCarboxymethyl cellulose and hydrogel beads produced from sugar cane bagasse (SCB) and palm kernel cake (PKC) were characterised, and the ability of the hydrogel beads to encapsulate and protect the probiotic bacteria of Lactobacillus acidophilus (LA-5) under simulated gastrointestinal conditions was investigated. Encapsulation with SCB and PKC hydrogel beads was performed with 87.4% and 80.9% efficiency, respectively, compared with that with alginate hydrogel beads, which had 75.0% efficiency. LA-5 free cells and those encapsulated in alginate hydrogel beads showed no survival. LA-5 cells encapsulated in SCB and PKC hydrogel beads retained high survival under stomach conditions of pH 2 after 1.5 h (&gt;6 log CFU/ml) and 3 h (&gt;4 log CFU/ml). However, no survival of cells was observed under colon conditions of pH 7.5 after 24 h. SCB and PKC hydrogel beads were able to protect the cells against the pH conditions of the stomach but not of the colon.

Interactions between Chitosan and Alginate Dialdehyde Biopolymers and Their Layer-by-Layer Assemblies.

Biopolymers are researched extensively for their applications in biomaterials science and drug delivery including structures and complexes of more than one polymer. Chemical characterization of complexes formed between chitosan (CHI) and alginate dialdehyde (ADA) biopolymers established that while electrostatic interactions dominate (as determined from X-ray photoelectron spectroscopy (XPS)) covalent cross-linking between these biopolymers also contribute to their stability (evidenced from immersion in salt solution). It was furthermore found that imine bond formation could not be directly detected by any of the techniques XPS, FTIR, (1)H NMR, or fluorescence. The layer-by-layer assemblies of the biopolymers formed on silica colloids, glass slides, and alginate hydrogel beads were evaluated using XPS, as well as zeta potential measurements for the silica colloids and changes to hydration properties for the hydrogels. It was found that the degree of oxidation of ADA affected the LbL assemblies in terms of a greater degree of CHI penetration observed when using the more conformationally flexible biopolymer ADA (higher degree of oxidation).

Determining the selectivity of divalent metal cations for the carboxyl group of alginate hydrogel beads during competitive sorption

To investigate the competitive sorption of divalent metal ions such as Ca2+, Cu2+, Ni2+, and Pb2+ on alginate hydrogel beads, batch and column tests were conducted. The concentration of carboxyl group was found to be limited in the preparation of spherical hydrogel beads. From kinetic test results, 80% of sorption was observed within 4h, and equilibrium was attained in 48h. According to the comparison of the total uptake and release, divalent metal ions were found to stoichiometrically interact with the carboxyl group in the alginate polymer chain. From the Langmuir equation, the maximum capacities of Pb2+, Cu2+, and Ni2+ were calculated to be 1.1, 0.48, and 0.13mmol/g, respectively. The separation factor (α) values for αPb/Cu, αPb/Ni, and αCu/Ni were 14.0, 98.9, and 7.1, respectively. The sorption capacity of Pb2+ was not affected by the solution pH; however, the sorption capacities of Cu2+ and Ni2+ decreased with increasing solution pH, caused by competition with hydrogen. According to the result from the fixed column test, Pb2+ exhibited the highest affinity, followed by Cu2+ and Ni2+, which is in exact agreement with those of kinetic and isotherm tests. The sorbent could be regenerated using 4% HCl, and the regenerated sorbent exhibited 90% capacity upto 9 cycles.

Effect of the weight ratio of alginate-modified tapioca starch on the physicochemical properties and release kinetics of chlorogenic acid containing beads

Sodium alginate (SA)-modified tapioca starch (TS) solutions (RSA/TS) in different weight ratios (1/0, 0.75/0.25, 0.5/0.5 and 0.25/0.75), added with chlorogenic acid (CGA), were dripped into CaCl2 solution for obtaining calcium alginate (CA) hydrogel beads filled with TS containing chlorogenic acid (HBCA/TS). The beads size, morphology, encapsulation efficiency, textural and viscoelastic properties, CGA release in simulated gastrointestinal conditions, and the molecular interactions between beads components using DSC and FTIR were evaluated. The sphericity of the HBCA/TS filled with TS was lower than that made with only calcium alginate, but the diameter was larger. CGA release from the beads was due to a complex interplay between matrix porosity and tortuosity. Highest release % of CGA occurred for HB0.75/0.25 which showed the lowest Tan δ-strain %, hardness and cohesiveness values. The diffusion-relaxation model involving two mechanisms described better the CGA release experimental data.

PH-sensitive starch-g-poly(acrylic acid)/sodium alginate hydrogels for controlled release of diclofenac sodium

The pH-sensitive starch-g-poly(acrylic acid)/sodium alginate (St-g-PAA/SA) hydrogel beads for the controlled release of diclofenac sodium(DS) were prepared simply by crosslinking SA using calcium ions under the existence of the St-g-PAA superabsorbent. The St-g-PAA/SA-DS hydrogel beads were characterized by IR and scanning electron microscopy. The effects of weight ratio of St-g-PAA to SA and pH on the swelling behaviors of the hydrogel beads in pH 7.4 phosphate buffer solution were investigated. In addition, the effects of weight ratio of St-g-PAA to SA and the concentration of SA solution on the entrapment efficiency (EE) for DS and the cumulative release of DS were studied in detail. The St-g-PAA/SA-DS hydrogel beads are pH-sensitive with an interpenetrated polymer network. The introduced St-g-PAA superabsorbent has great influence on the swelling behavior and the cumulative release of DS. The pristine SA-DS hydrogel beads disintegrated in pH 7.4 phosphate buffer solution in 3 h, whereas the disintegration of SA-DS beads was delayed or avoided by introducing a proper amount of the St-g-PAA superabsorbent. Also, the burst release of DS was successfully overcome by the introduced St-g-PAA superabsorbent. A weight ratio of St-g-PAA to SA of 1:9 and an SA concentration of 4 wt % are very helpful for the sustained release of DS.

Insights into the Eco-Friendly Adsorption of Caffeine from Contaminated Solutions by Using Hydrogel Beads

The presence of drugstore products in water streams has become a major concern in environmental remediation. Preliminary studies have reported that caffeine has negative impacts in animals and ecology in general. Bioremediation emphasizes on the elimination of heavy metals and toxic organic pollutants, but little attention has been paid to the so-called pollutants of emerging concern (i.e. caffeine). This research evaluates the role of pH, adsorbent dose, salinity and time on the elimination of caffeine from aqueous solutions by using chitosan and alginate hydrogel beads. Experimental data indicates a strong pH effect on the adsorption, showing its highest values around neutral conditions. On the other hand, salinity has a negative effect on the adsorption, due to competition for the adsorption sites of both hydrogels. Finally, time dependence experiments demonstrate that less than 20 minutes are needed to reach adsorption equilibrium. These results suggest that biodegradable and cost-effective materials are good candidates for the removal of pollutants of emerging concern from contaminated waters.

Polydiacetylene liposome-encapsulated alginate hydrogel beads for Pb2+detection with enhanced sensitivity

A new polydiacetylene liposome-based sensor was successfully constructed for the colorimetric and fluorometric detection of Pb2+.

Evaluation of the nitroaldol reaction in the presence of metal ion-crosslinked alginates

Calcium alginate hydrogel beads have been found to promote the Henry reaction under mild conditions.

Fabrication of highly-stable Ag/CA@GTA hydrogel beads and their catalytic application

To enhance the stability of a catalyst that uses alginate as a carrier, Ag nanoparticle-loaded glutaraldehyde-crosslinked calcium alginate (Ag/CA@GTA) hydrogel beads were prepared. The Ag/CA@GTA hydrogel beads were characterized by UV-visible spectroscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, transmission electron microscopy and X-ray photoelectron spectroscopy analyses. Given that the mechanical strength of the support was remarkably enhanced by crosslinking alginate with GTA, the resulting Ag/CA@GTA beads exhibited high stability and durable activity, with more than 97% conversion within 10 successive cycles, for the catalytic reduction of 4-nitrophenol to 4-aminophenol by NaBH4 in aqueous solution. These Ag/CA@GTA hydrogel beads were expected to have potential as a highly efficient, cost-effective and eco-friendly heterogeneous catalyst for industrial applications.

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.

Study of the physical properties of calcium alginate hydrogel beads containing vineyard pruning waste for dye removal

In this work the morphological and surface properties of a biocomposite formulated with vineyard pruning waste entrapped in calcium alginate hydrogel beads were studied. The formulation of the calcium alginate hydrogel beads, containing vineyard pruning waste, was based on the capacity of this green adsorbent to remove dye compounds from wastewater, observing that in the optimum condition (1.25% of cellulosic residue, 2.2% of sodium alginate and 0.475molL−1 CaCl2) the percentage of dyes was reduced up to 74.6%. At lower concentration of CaCl2, high-resolution optical images show that the elongation of the vineyard-alginate biocomposite decreased, whereas the compactness increased. Moreover, higher concentrations of cellulosic residue increased the biocomposite roundness in comparison with biocomposite without the cellulosic residue. Interferometric perfilometry analysis (Ra, Rq, Rz and Rt) revealed that high concentrations of CaCl2 increased the roughness of the of the calcium alginate hydrogel beads observing vesicles in the external surface.