Spherical Gel Beads Research Articles

Dry alginate beads for fecal microbiota transplantation: From model strains to fecal samples

Clostridioides difficile infection (CDI) is a critical nosocomial infection with more than 124,000 cases per year in Europe and a mortality rate of 15–17 %. The standard of care (SoC) is antibiotic treatment. Unfortunately, the relapse rate is high (∼35 %) and SoC is significantly less effective against recurrent infection (rCDI). Fecal microbiota transplantation (FMT) is a recommended treatment against rCDI from the second recurrence episode and has an efficacy of 90 %. The formulation of diluted donor stool deserves innovation because its actual administration routes deserve optimization (naso-duodenal/jejunal tubes, colonoscopy, enema or several voluminous oral capsules).Encapsulation of model bacteria strains in gel beads were first investigated. Then, the encapsulation method was applied to diluted stools.Robust spherical gel beads were obtained. The mean particle size was around 2 mm. A high loading of viable microorganisms was obtained for model strains and fecal samples. For plate-counting, values ranged from 1015 to 1017 CFU/g for single and mixed model strains, and 106 to 108 CFU/g for fecal samples. This corresponded to a viability of 30 % to 60 % as assessed by flow cytometry.This novel formulation is promising as the technology is applicable to both model strains and bacteria contained in the gut microbiota.

Time dependent gelling properties of cuboid alginate gels made by external gelation method: Effects of alginate-CaCl2 solution ratios and pH

This study investigated the gel strength and syneresis of cuboid alginate gels (2 × 2x1.4 cm) using 2% Na-alginate solutions as a function of gelling time, CaCl2 solution concentrations (0.05 M - 0.20 M) and pH (4−11) in an external gelation method. This study also investigated the effects of providing a limited or excess amount of calcium ions needed to completely cross-link the alginate chains by altering the ratio between alginate and CaCl2 solutions. For comparison purpose, the gelling time and syneresis of alginate beads (2.5–3.0 mm in diameter) were also studied. The results showed that an increase in the CaCl2 concentration resulted in a faster gelling time, increased gel strength and higher degree of syneresis. Meanwhile, an increase in pH of the alginate and CaCl2 solutions resulted in the decrease of gel strength and the degree of syneresis. In the presence of excess CaCl2, the gels would reach the same equilibrium degree of syneresis (∼39%) after a certain gelling time, regardless of CaCl2 concentration. It was also observed that the degree of syneresis gradually increased from the start of gelation until a stable point was reached which corresponds to the end of gelation. This trend of syneresis was observed in both cuboid gels and spherical gel beads although stabilisation of syneresis occurred sooner in the gel beads (<2 h) compared to cuboid gels (>5 h). Since the smaller gel beads exhibited syneresis phenomena similar to that of large cuboid gels, it can be inferred that micron size gels may exhibit similar behaviour.

Sustained delivery of propranolol by using multiparticulate gastroretentive drug delivery system

PURPOSE: Gastroretentive systems can significantly prolong the gastric residence time of drugs. If a drug is stable in gastric acid, prolonged gastric retention improves bioavailability. The objective of the present investigation was to develop an extended and controlled release composition and formulation of propranolol using expandable, gelling, swellable hydrocolloid polymer along with mineral oil. METHODS: A formulation was prepared without using mineral oil by conventional ionotropic gelation method. All other formulations of oil entrapped floating gel beads of propranolol hydrochloride were prepared by using emulsion gelation method in which sodium alginate was used as a gelling agent and mineral oil was used to impart buoyancy to the formulation Spherical gel beads were formed instantaneously. The prepared beads were evaluated for diameter, surface morphology, encapsulation efficiency and drug release. RESULTS: Low concentration of oil containing formulation exhibited greater release of drug. As the concentration of oil increases, drug release decreases to certain extent. Percentage buoyancy of floating propranolol hydrochloride gel beads was found satisfactory. The highest mean diameter was observed in the formulation with 30% of mineral oil. The formulation with 35% of mineral oil had the highest drug loading and scanning electron microscopy revealed that the beads were spherical in shape with rough surfaces. CONCLUSION: Oil entrapped gel beads can be used as floating drug delivery system for extended drug release for both local and systemic drug delivery. Keywords: Floating drug delivery system; Emulsion gelation; Sodium alginate; Mineral oil; Propranolol hydrochloride.

PVA-alginate immobilized cells for anaerobic ammonium oxidation (anammox) process

The feasibility of an anaerobic ammonium oxidation (anammox) process combined with a cell-immobilization technique for autotrophic nitrogen removal was investigated. Anammox biomass was cultivated from local activated sludge and achieved significant anammox activity in 6 months. The development of a mature anammox biomass was confirmed by fluorescence in situ hybridization (FISH) analysis and off-line activity measurements. The abundance fraction of the anammox bacteria determined by FISH analysis was estimated by software. The anaerobic ammonia oxidizers occupied almost half of the total cells. Additionally, the anammox biomass was granulated as spherical gel beads of 3-4 mm in diameter by using a cell-immobilization technique. The nitrogen removal activity was proved to be successfully retained in the beads, with about 80% of nitrogenous compounds (NH(4) (+), NO(2) (- )and total nitrogen) removed after 48 h. These results offer a promising technique for the preservation of anammox microorganisms, the protection of them against the unfavorable surroundings, and the prevention of biomass washout towards the implementation of sustainable nitrogen elimination biotechnology. This is the first report on the immobilization of anammox biomass as gel beads.

Synthesis and characterization of both ionically and enzymatically cross-linkable alginate

Alginate with phenol moieties in the polymer side chains was synthesized through the conjugation reaction of alginate and tyramine. Immersing an aqueous solution of the alginate containing horseradish peroxidase into a solution containing H 2O 2 caused the solution to gel via peroxidase-catalyzed oxidative coupling of the phenols. In addition, alginate prepared under appropriate reaction conditions retained the attractive properties associated with unmodified alginate; spherical gel beads were formed by dropping an aqueous alginate solution (1.0 wt.%) into a solution containing calcium ions. The oxidative coupling of the phenols was effective for suppressing the destabilization of the alginate gel resulting from a loss of bonding between the divalent cations and alginate. The mechanical properties of the resultant gels were influenced by the preparation conditions of the alginate and the type of cross-linking.

Preparation of uniform calcium alginate gel beads by membrane emulsification coupled with internal gelation

AbstractWith the objective of making calcium alginate gel beads with small and uniform size, membrane emulsification coupled with internal gelation was proposed. Spherical gel beads with mean size of about 50 μm, and even smaller ones in water, and with narrow size distribution were successfully obtained. Experimental studies focusing mainly on the effect of process parameters on bead properties were performed. The size of the beads was mainly dependent on the diameter of the membrane pores. High transmembrane pressure made for large gel beads with wide size distribution. Low sodium alginate concentration produced nonspherical beads, whereas a high concentration was unsuitable for the production of small beads with narrow distribution. Thus 1.5% w/v was enough. A high surfactant concentration favored the formation of small beads, but the adverse effect on mass transfer should be considered in this novel process. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 848–852, 2003

Nucleotide isolation by boronic acid functionalized hydrophilic supports

Abstract Aminophenyboronic acid (APBA) carrying-gel beads were proposed as alternative sorbents for nucleotide isolation. For the preparation of two different types of gel beads with different surface characteristics, two hydrophilic monomers, 2-hydroxypropylmethacrylate (HPMA) and polyethyleneglycol methacrylate (PEGMA) were selected as the base materials. The spherical gel beads were obtained by the suspension copolymerization of HPMA or PEGMA with epoxypropyl methacrylate (EPMA) by using ethyleneglycol dimethacrylate (EGDMA) as the crosslinker. A boronic acid carrying ligand, m -aminophenylboronic acid (APBA) was covalently attached onto the both types of gel beads via the direct chemical reaction between epoxypropyl and amino groups. The equilibrium APBA binding capacities of HPMA and PEGMA gel beads were 47 and 34 mg g −1 , respectively. The reversible adsorption-desorption behavior of β-nicotinamide adenine dinucleotide (β-NAD) was investigated comparatively by using APBA carrying-HPMA and PEGMA based gel beads as sorbents in batch-fashion. While no-significant non-specific β-NAD adsorption was observed onto the plain (i.e. non-derivatized) gel beads, the equilibrium β-NAD adsorption capacities of APBA carrying-HPMA and PEGMA based gels were determined as 11 and 4 mg g −1 , respectively. The desorption yields higher than 90% could be achieved with both types of gels. The results indicated that the proposed materials could be efficiently used as pseudospecific-sorbent for nucleotide isolation.

Removal of Acetaldehyde and Propionaldehyde from Waste Gas in Packed Column with Immobilized Activated Sludge Gel Beads.

A new type of waste gas treatment was previously proposed in the packed column containing the immobilized activated sludge gel beads of 5 mm in diameter together with the hollow plastic balls of 10 mm in the optimal diameter with their optimal volume ratio of 1 to 2 to avoid compaction of the gel beads. The same type of biofilter is employed and analyzed for removal of acetaldehyde or propionaldehyde as a model of toxic and malodorant pollutants under a wide range of the inlet aldehyde concentrations. The same spherical gel beads as prepared previously by the PVA-boric acid method are stable and durable during storage as well as use in the removal operation. The biofilter gives a very low pressure drop to the waste gas stream through the packed bed. The acetaldehyde or propionaldehyde removal in the column decreases with an increase in the inlet aldehyde concentration. The kinetics data on the gel beads suspended in an air-tight batch reactor reveal that the Michaelis-Menten type rate equation is applicable to both respiration and pollutant biodegradation by the gel beads with negligible mass transfer effect. A model for removal of a single pollutant is developed assuming that the Henry's law constant determines the dissolved pollutant concentration in the gel bead, the pollutant is biodegraded according to the above rate equation and the contact efficiency of gel beads with waste gas has the same value of 0.24 as determined previously. The observed removals agree well with those calculated from the design equation developed. As a result the observed decrease in removal of aldehyde with its inlet concentration is due to the fact that the biodegradation rate itself approaches asymptotically the maximum one with the aldehyde concentration.

Suspension polymerization of poly(ethylene glycol) methacrylate: a route for swellable spherical gel beads with controlled hydrophilicity and functionality

Spherical and swellable gel beads were obtained by the suspension polymerization of poly(ethylene glycol) methacrylate macromonomer (PEG-MA). The average size and size distribution properties, the equilibrium swelling behaviour and the protein adsorption characteristics of PEG-MA-based gel beads were determined. In the suspension polymerization system, the organic phase including monomer, cross-linker and diluent solution was dispersed in an aqueous medium by using poly(vinylpyrrolidone) as the stabilizer. The diluent solution was prepared by mixing cyclohexanol and octanol at different volume ratios. The suspension polymerization experiments were designed in two separate parts. In the first part, ethylene glycol dimethacrylate was selected as the cross-linker and swellable PEG-MA-based gel beads were obtained by changing the cross-linker concentration, the monomer/diluent ratio and the stirring rate. In the second part, a more hydrophobic structure, divinylbenzene (DVB) was tried as a cross-linker. In this part, PEG-MA-DVB copolymer beads were obtained by changing the DVB/PEG-MA feed ratio. Then, the hydrophicility of the resulting gel beads could be controlled by changing the feed ratio of hydrophilic macromonomer to hydrophobic cross-linker. This property was also used to control the extent of nonspecific protein adsorption onto the surface of the gel beads. The non specific albumin adsorption onto the gel beads decreased with increasing PEG-MA content. No significant nonspecific adsorption at the isoelectric point of albumin was detected onto the gel beads produced with the higher PEG-MA/DVB feed ratios. For specific albumin adsorption, a triazinyl dye (i.e., cibacron blue, CB F3G-A) was covalently attached onto the surface of the copolymer beads via terminal hydroxyl groups of PEG-MA. The results of albumin adsorption experiments with the CB F3G-A carrying beads indicated that an appreciable specific albumin adsorption capacity could be obtained with the gel beads produced with a PEG-MA/DVB feed ratio of 1.5/4.0.

The collagen-containing alginate/poly(L-lysine)/alginate microcapsules.

A method of preparing microcapsules containing collagen fibrous network is reported in this study. This method takes advantage of miscibility of collagen and alginate and the ability of this mixture to form spherical gel beads in the presence of CaCl2. Collagen was then reconstituted within the microcapsules at 37 after alginate was liquefied with citrate. GH3 rat pituitary tumor cell, which can be cultured in both suspended and attached forms, were entrapped within the microcapsules. The cell proliferated faster in the collagen-containing capsule as compared to those in the conventional microcapsules.

Preparation of poly(N-normalpropyl- acrylamide) gel beads

The gel beads of N-normal-propylacrylamide are prepared by the radical copolymerization of N-normalpropylacrylamide and N,N′-methylene-bis-acrylamide in water. The optimum reaction conditions to obtain the gel beads are revealed from the phase diagram of the reaction system together with the scanning electron microscopy of the reaction products. The scanning electron microscopy of the reaction products also indicates the formation of the spherical gel beads of sub-micron size ranging from 250 to 500 nm in diameter. The viscosity measurements of the suspension of the gel beads indicate that the concentration dependence of the viscosity of the suspension is well described by Einstein’s theory of the viscosity of colloidal particles. The intrinsic viscosity of the suspension of gel beads is then determined. The density of the gel beads, which was obtained from the intrinsic viscosity of the suspension, indicates that the gel beads are in the swollen state at a temperature of 20 °C.

Force relaxation of single spherical gel beads under compression

Abstract A spherical bead, when submitted to an uniaxial compression between two parallel pistons, exhibits solvent migration effects both inside and outside the gel. We describe here some experiments of force relaxation on a strained bead, at different swelling ratio. We present a theoretical description that allows to determine the shear and the compression modulus, and the critical force one has to apply in order to deswell a bead which is swollen below its equilibrium ratio. We also show that mechanical tests do not allow for a direct observation of the deswelling force.

A new combined differential‐discrete cellular automaton approach for biofilm modeling: Application for growth in gel beads

The theoretical basis and quantitative evaluation of a new approach for modeling biofilm growth are presented here. Soluble components (e.g., substrates) are represented in a continuous field, whereas discrete mapping is used for solid components (e.g., biomass). The spatial distribution of substrate is calculated by applying relaxation methods to the reaction–diffusion mass balance. A biomass density map is determined from direct integration in each grid cell of a substrate-limited growth equation. Spreading and distribution of biomass is modeled by a discrete cellular automaton algorithm. The ability of this model to represent diffusion–reaction–microbial growth systems was tested for a well-characterized system: immobilized cells growing in spherical gel beads. Good quantitative agreement with data for global oxygen consumption rate was found. The calculated concentration profiles of substrate and biomass in gel beads corresponded to those measured. Moreover, it was possible, using the discrete spreading algorithm, to predict the spatial two- and three-dimensional distribution of microorganisms in relation to, for example, substrate flux and inoculation density. The new technique looks promising for modeling diffusion–reaction–microbial growth processes in heterogeneous systems as they occur in biofilms. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 718–731, 1998

A new combined differential-discrete cellular automaton approach for biofilm modeling: Application for growth in gel beads

The theoretical basis and quantitative evaluation of a new approach for modeling biofilm growth are presented here. Soluble components (e.g., substrates) are represented in a continuous field, whereas discrete mapping is used for solid components (e.g., biomass). The spatial distribution of substrate is calculated by applying relaxation methods to the reaction-diffusion mass balance. A biomass density map is determined from direct integration in each grid cell of a substrate-limited growth equation. Spreading and distribution of biomass is modeled by a discrete cellular automaton algorithm. The ability of this model to represent diffusion-reaction-microbial growth systems was tested for a well-characterized system: immobilized cells growing in spherical gel beads. Good quantitative agreement with data for global oxygen consumption rate was found. The calculated concentration profiles of substrate and biomass in gel beads corresponded to those measured. Moreover, it was possible, using the discrete spreading algorithm, to predict the spatial two- and three-dimensional distribution of microorganisms in relation to, for example, substrate flux and inoculation density. The new technique looks promising for modeling diffusion-reaction-microbial growth processes in heterogeneous systems as they occur in biofilms.

Arsenate sorption by Fe(III)-doped alginate gels

Although cationic metal contaminants can be effectively removed from wastewaters by treatment with biopolymers, application of biopolymers for the removal of anionic contaminants (such as As, Cr(VI), and Se) has been limited. The objective of this study was to examine the fundamental aspects of a possible remediation strategy for removal of anionic metal species employing the biopolymer alginic acid pretreated with Ca and Fe(III). Spherical gel beads (2 mm in diameter) were formed by dispensing the biopolymer solution dropwise into 0.1 M CaCl 2; Ca beads were then washed and equilibrated with 0.1 M FeCl 3 to achieve partial substitution of Fe(III) for Ca. The resulting Ca–Fe beads were found to be effective at removing As(V) from solution on a time scale of approximately 100 h. As(V) sorption was pH dependent; optimal removal and stability of the Ca–Fe beads was achieved at pH 4. At a given initial As(V) concentration, As(V) removal efficiency increased with increasing Fe content (number of beads); at an initial As(V) concentration of 400 μg/l, up to 94% removal was achieved at pH 4 after 120 h. For a given Fe content, uptake of As(V) increased with increasing initial As(V) concentration until saturation was reached. Sorption data was modeled using a single type of As(V) binding site. Data on As(V) sorption as a function of dissolved As(V) concentration and Fe content were used to obtain and validate the site density and conditional affinity constant for As(V) sorption.

Gel beads composed of collagen reconstituted in alginate

Spherical gel beads of collagen/alginate were prepared by discharging droplets of a mixture containing collagen (1.07-1.9 mg/ml) and alginate (1.2-1.5% w/v) into 1.5% w/v CaCl2 solution at 4°C. Collagen in the gel beads was reconstituted by raising the temperature to 37°C after alginate was liquefied by citrate. Scanning electron microscopy of the beads revealed the characteristic fibrous structure of collagen. To demonstrate the application of this new technique in cell culture, GH3 rat pituitary tumor cells were entrapped and grown in the gel beads. The immobilized cells proliferated to a density of 1.95 x 106 cell/ml which is about an order of magnitude higher than that grown in the alginate beads.

Heterogeneous Cross-Linking of Chitosan Gel Beads: Kinetics, Modeling, and Influence on Cadmium Ion Adsorption Capacity

Chitosan, a linear biopolymer of glucosamine residues, selectively adsorbs transition-metal ions such as cadmium from dilute solution. In order to process chitosan into a more durable form, a 5 wt % chitosan solution was cast into spherical gel beads of 3 mm diameter and then reacted with glutaraldehyde at free amine sites to form imine cross-links between linear chitosan chains. The rate processes of the heterogeneous cross-linking reaction and the effect of cross-linking on the cadmium ion adsorption capacity were determined. The cross-linking reaction was complete within 48 h at 27 °C, and the final extent of cross-linking ranged from 0.07 to 2.40 mol of glutaraldehyde consumed/mol of amine. Heterogeneous cross-linking was modeled as a shrinking core process where the molecular diffusion of glutaraldehyde through the cross-linked shell of the gel bead limited the overall rate of glutaraldehyde consumption. The effective diffusion coefficient of glutaraldehyde through the cross-linked layer was 4.7 × 10-8 cm2/s. The saturation adsorption capacity of cadmium ions on the cross-linked gel beads exponentially decreased from 250 to 100 mg of Cd/g of chitosan as the extent of cross-linking increased from 0 to 1.3 mol of glutaraldehyde consumed/mol of amine. At higher extents of cross-linking, the saturation adsorption capacity remained at 100 mg of Cd/g of chitosan. Highly porous chitosan beads formed by freeze-drying of cross-linked gel beads had the same cadmium ion adsorption capacity as the cross-linked gel beads over the same extents of cross-linking.

Stability of calcium-alginate during citric acid production of immobilized Aspergillus niger

This article introduces an easy to handle immobilization apparatus for the entrapment of microbial cells, organelles and enzymes in spherical gel beads. Ca-alginate beads with entrapped cells of Aspergillus niger showed typical shrinking behaviour (from 3.00 mm to 2.25 mm particle diameter). A loss of stability down to 20% of the initial strength during precultivation of the fungus and within the following citric acid production occurred. The observed particle shrinkage was due to the increasing acidification of the medium, whereas the decreased mechanical strength was caused by the entrapped growing microorganism. This was confirmed by electron scanning micrographs, indicating a sponge-like gel structure within the region of enhanced mycelium growth which reduced diffusional resistance of the matrix. Therefore no differences were found between citric acid production of Ca-alginate entrapped Aspergillus niger at 3 mm and 1.5 mm initial particle size.

Modelling the effects of mass transfer on kinetics of propene epoxidation of immobilized Mycobacterium cells: 2. Product inhibition

An existing model for the external and internal mass transfer effects on the kinetics of propene epoxidation of calcium alginate-entrapped cells was extended to account for inhibition of the produced propene oxide. The intrinsic kinetics of the product-inhibited epoxidation reaction were derived and its applicability was demonstrated using independent time course experiments in a circulation batch-reactor system. The problem of coupled product-inhibited epoxidation and oxygen diffusion to and in the spherical gel beads was solved applying the collocation method. The predicted and experimental propene and oxygen-consumption rates were found to be in agreement for various degrees of oxygen-diffusion limitation and propene oxide inhibition.

PH effect on the separation of α-chymotrypsin by affinity chromatography

For the separation of enzyme (α-chymotripsin) the characteristics of affinity chromatography were studied. The system employed Sepharose CL-4B as a gel matrix (a packing meterial), 4-phenylbutylamine as a ligand and a-chymotrypsin as a solute. Moment analysis was used to determine the retention time in a column, in which the longitudinal dispersion in the mobile phase, the radial diffusion inside the porous spherical gel beads and the Sorption on the ligands attached to the gel bead were simultaneously taking place. To analyze the effect of pH on the retention time an ionization model was incorporated into the chromatrgraphic model. Dependence of adsorption equilibrium constant and the retention time on pH were investigated. From the experimental data the approximate pK values could be obtained.