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As a kind of potential absorbent, polysaccharide materials are limited due to weak stability, low absorption and recovery rate. Herein, a novel composite adsorbent – the magnetic composite gel beads (CMC/SA/graphene oxide@Fe3O4) were prepared by combining carboxymethyl chitosan (CMC), sodium alginate (SA) with graphene oxide@Fe3O4, and then utilized for the adsorption of Cu2+, Cd2+ and Pb2+ from the wastewater. The physicochemical property of CMC/SA/graphene oxide@Fe3O4 beads were characterized in detail. The CMC/SA/graphene oxide@Fe3O4 magnetic gel beads could separate easily from the wastewater and showed a higher stability due to the addition of graphene oxide@Fe3O4. The adsorption experiments show that the adsorption of Cu2+, Cd2+ and Pb2+ on the magnetic gel bead was well fitted with pseudo-second-order model and Langmuir isotherm model, and the maximum adsorption capacity of Cu2+, Cd2+ and Pb2+ reached 55.96, 86.28 and 189.04 mg/g, respectively. Moreover, the magnetic gel beads had selective adsorption toward Pb2+. In addition, the magnetic gel beads still obtained 90% of the adsorption rates after five cycles, and showed good adsorption efficiency in the simulated real environment. This work proves that the CMC/SA/graphene oxide@Fe3O4 magnetic gel beads as the adsorbents have promising potential in wastewater treatment.

Alginate spherical hydrogel beads have several applications in biomedical and biological processes in which the bead size and sphericity are critical factors affecting mass transfer phenomena. Electrospraying technology facilitates generation of small and almost uniform beads with higher diffusion rate resulting in process performance improvement. There are several key factors affecting particle size and shape behavior of electrosprayed alginate beads meanwhile interactions between these factors introduce complexity in determining appropriate conditions to produce spherical beads with the size of interest. Thus, the need to achieve reliable products has put growing emphasis on the use of modeling methodology to establish correlations between particle size and affecting variables as well as sphericity coefficient and meaningful factors. Obviously, a more applicable model based on intentionally manipulatable factors would spark a great deal of interest for practical engineering applications. In this regard we employed a central composite design (CCD) and response surface methodology (RSM) to model the diameter and sphericity coefficient of electrosprayed alginate beads for the first time. Two quadratic models were obtained in which the effectiveness order of the variables were found. We could benefit from this RSM-based empirical model not only for better understanding the complex physics of the electrospraying process, but also for selection of factors and their levels to produce alginate micro-beads with appropriate size and sphericity. The results indicate that the alginate concentration, voltage and needle size have the strongest influence on both response variables. The quite spherical beads with a minimum size of 130 μm can be obtained at alginate concentration of 1.5%, voltage of 11 kV, and needle size of 26 G.

Although alginate-based hydrogels are widely used, determining their mechanical properties and explaining their ability to form a hydrogel in situ remains a challenge. A new method of external gelation using calcium chloride (CaCl2) is proposed to quantify the formation of alginate hydrogel and its mechanical properties as well as to observe its temporal behaviour. To this end, small inhomogeneous alginate beads were formed, which comprised a shell and a core. The bead’s shell consisted of calcium alginate hydrogel, while its core was sodium alginate sol. The beads were mechanically tested with a texture analyser to provide a detailed description of the structure. Different alginate samples could be clearly identified, and the M(mannuron)/G(guluron) acid ratios could be extrapolated quickly and easily from the test results if calibrated by NMR. This enables a fast and cost-effective characterisation of different alginates with regard to their composition and gel formation properties.

This study designed chitosan species-coated calcium alginate beads through concurrent core-coat formation. Chitosan oleate was synthesized by carbodiimide chemistry and characterized by 1H NMR and FTIR techniques. Chitosan or chitosan oleate was coated onto the forming alginate or alginate/tripolyphosphate core using vibratory nozzle extrusion-microencapsulation approach, followed by calcium crosslinking. Chlorpheniramine maleate served as a model water-soluble drug. The molecular characteristics, size, shape, morphology, swelling, erosion, water uptake, drug content and drug release profiles of beads were evaluated. Discrete spherical coated beads were obtained through minimizing successive bead adhesion through an interplay of nozzle vibrational frequency and polymeric solution flow rate. The tripolyphosphate ions in the core possessed higher diffusional kinetics than alginate and were better able to attract chitosan species onto bead surfaces to facilitate alginate-chitosan coacervation. Amphiphilic chitosan oleate formed smaller aggregates than chitosan. It interacted with greater ease with core alginate and tripolyphosphate. The gain in alginate/tripolyphosphate interaction with chitosan oleate at the core-coat interface enhanced bead robustness against swelling and water uptake with drug release consequently dependent on the loss of alginate-drug interaction.

In recent decades, magnetic bead material has attracted considerable attention in water and wastewater purification. In this study, the potential of magnetic kaolinite immobilized in chitosan beads (MKa@CB) to remove Pb(II) and Cd(II) ions from an aqueous environment has been successfully investigated. The addition of magnetic kaolinite generates more active sites, whereas that of chitosan enhances the stability of synthesized bead materials, which enable them to effectively interact with the targeted contaminants. Various factors including agitation time, solution pH, and competitive ions were examined to optimize the removal efficiency of the MKa@CB. The adsorption kinetics and isotherm studies indicated that the adsorption fitted well to the pseudo-second-order kinetic model as well as to the Langmuir isotherm. The prepared adsorbent could be reused up to four cycles without any significant adsorption capacity loss. Thus, the synthesized MKa@4%CB can be a promising adsorbent in effectively removing Pb(II) and Cd(II) from water.

A tetra-amine copper(II) chitosan bead system (TAC@CS composite beads) was developed by grafting tetra-amine copper(II) (TAC) with chitosan (CS) and utilized for phosphate removal. The prepared TAC@CS composite beads possess enhanced phosphate sorption capacity (SC) of 41.42 ± 0.071 mg/g than copper grafted chitosan (Cu@CS) composite, TAC and chitosan which were found to be 37.01 ± 0.803, 33.20 ± 0.650 and 7.24 ± 0.059 mg/g respectively. In batch mode, various adsorption influencing parameters like contact time, initial phosphate concentration, solution pH, co-anions and temperature were optimized for maximum phosphate sorption. The prepared adsorbents were characterized by FTIR, XRD, UV–Visible, SEM and EDAX analysis. The adsorption isotherms and thermodynamic parameters of the adsorbent were studied. The feasible phosphate uptake mechanism of TAC@CS biocomposite beads was reported. The reusability studies of TAC@CS composite beads were carried out using NaOH as elutant. The suitability of TAC@CS composite beads at field conditions was tested with phosphate contaminated field water samples collected from nearby areas of Dindigul district.

Alginate/bacterial cellulose nanocomposite beads, with well-controlled size and regular spherical shapes, were prepared in a simple manner by entrapping Gluconacetobacter xylinus in barium alginate hydrogel beads, followed by cultivation of the entrapped cells in culture media with a low sodium ion concentration. The entire surface of the alginate hydrogel beads containing the cells was covered with cellulose fibers (∼30nm) after 36h of cultivation. The cellulose crystallinity index of the alginate/bacterial cellulose beads was 0.7, which was slightly lower than that of bacterial cellulose prepared by cultivating dispersed cells. The water vapor sorption capacity of the alginate/bacterial cellulose beads increased significantly from 0.07 to 38.00 (g/g dry bead) as cultivation time increased. These results clearly indicate that alginate/bacterial cellulose beads have a much higher surface area, crystallinity, and water-holding capacity than alginate beads. The immobilization of lipase on the surface of the nanocomposite beads was also investigated as a potential application of this system. The activity and specific activity of lipase immobilized on alginate/bacterial cellulose beads were 2.6- and 3.8-fold higher, respectively, than that of lipase immobilized on cellulose beads. The alginate/bacterial cellulose nanocomposite beads prepared in this study have several potential applications in the biocatalytic, biomedical, and pharmaceutical fields because of their biocompatibility, biodegradability, high crystallinity, and large surface area.

Developing alginate-based beads with liquid-core-shell structure is highly appealing for industrial applications as a promising delivery matrix material. Herein, based on the reaction-diffusion mechanism, a facile method that includes dissolving natural polymer in calcium ion core solution followed by dripping it to alginate shell bath is proposed through interfacial gelation. By facilely tuning the viscosity and surface tension, the boundary condition for forming spherical beads with applicable mechanical properties was obtained. The universal viscosity-boundary relationship was independent of the type or charge condition of polymers in liquid-core. However, chitosan in the core solution significantly affected mechanical properties due to polyelectrolyte interaction with alginate, based on FTIR and SEM analyses. Moreover, a larger spherical zone was obtained by adding a surfactant into the shell bath. By varying calcium ion concentration and reaction time, beads of superior mechanical properties were obtained with an increase in shell membrane compactness.

This paper reports the synthesis of magnetic and pH-sensitive beads derived from κ-carrageenan and carboxymethyl chitosan for drug delivery. The magnetic Fe3O4 nanoparticles were synthesized inside a mixture of biopolymers by in situ method. The structural properties of hydrogel beads were characterized by TEM, SEM, XRD, and VSM techniques. The swelling ratio of beads indicated pH-dependent properties with maximum water absorbing at pH 7.4. Introducing magnetic nanoparticles caused a decrease in swelling capacity from 16.4 to 10 g/g. Drug loading and release efficiency were investigated using diclofenac sodium as a model system. The in vitro drug release studies exhibited significant behaviors on the subject of physiological simulated pHs and external alternative magnetic fields. The maximum cumulative release was around 82% at pH 7.4. The presence of magnetite nanoparticles certainly influenced the drug release patterns. The response of beads to external stimulus makes them as good candidates for novel drug delivery systems.

WOS: 000400213300023, PubMed: 28385225, Boron exists in various types of water environments, and it is difficult and costly to remove B with conventional treatment methods from drinking water. Clearly, alternative and cost effective treatment techniques are imperative. In the present study, an innovative and environment friendly method based on hybrid systems consisting of various chitosan composite beads and Lemna gibba were evaluated for removal of B from drinking water. Our results from batch adsorption experiment indicated that a plant based chitosan composite bead has a higher capacity of B removal than mineral-based chitosan composite beads. Almost 50% of total B removal was achieved using the hybrid system based on dried Lemna-chitosan composite beads and Lemna gibba combination in 4 days. Even at the high B concentration (8 mg B L-1), B in drinking water could be reduced to less than 2.4 mg L-1 when 0.05 g plant-based chitosan composite beads and 12 Lemna fronds were used for 50 mL test solution. (C) 2017 Elsevier Ltd. All rights reserved.

Amine-terminated poly(amido amine) (PAMAM) dendrimers have been attached to sodium hyaluronates (NaHAs) by a coupling reaction. The morphology of NaHAs was varied from the common network to the bead & string network, which gave rise to the decrease in viscosity of NaHAs. The bead & string network was more abundant for the covalent network complex than the noncovalent one. The beads, that is, the nano-knots of the network consist of the covalent-bonded NaHA/dendrimer composites, and the strings are NaHA chains. Beads became small and strings decreased in number with decreasing a molecular weight of NaHA. The complexation of sodium poly- l -glutamates (NaPGAs) with PAMAM dendrimers was different in the manner from that of NaHAs with dendrimers. Flexible NaPGAs produced globular composites with dendrimers.

Considering relatively fast drug release rate of Ca+2/gellan beads in phosphate buffer solution, a novel glipizide-loaded bead system was developed through ionotropic gelation of gellan with trivalent Al+3 ions and covalent cross-linking with glutaraldehyde (GA). Following GA-treatment, spherical Al+3/gellan beads contracted leaving wrinkles on bead surface. A maximum of 97.67% drug entrapment efficiency was achieved; however GA-treatment reduced the same by 11.89%. All the beads released only 10% drug in acidic medium in 2 h; however it was found 38–47% for Al+3/gellan beads and only 15% for GA-treated beads in weakly alkaline medium. The drug release did correlate well with their swelling behaviors. The anomalous drug transport mechanism shifted to super case II transport for GA-treated beads, where the polymer relaxation phenomenon was dominant. The drug was relatively stable, amorphous in the beads. Thus both GA-treated and -untreated Al+3/gellan beads could be useful carriers for the controlled oral delivery of glipizide.

The objective of this study was to prepare and cross-link carrageenan beads that may be used as a controlled release delivery system. The influence of the bulk carrageenan and cross-linker concentrations on the bead size was studied in order to assess the mechanism of cross-linking between epichlorohydrin and the polysaccharide. The conditions were optimised on macroparticles (3.1 mm in diameter) for a better understanding of the cross-link density and its effect on the morphology and surface topography of the bead. It was shown that low epichlorohydrin concentrations led to unstable and weak beads with uneven and cracked surfaces. The optimum cross-linker concentration, which resulted in smooth and stable gel beads, was applied to microparticles (76 μm in diameter). The swelling/shrinking behaviour of these cross-linked microgels in saline solutions showed great potential for the application of these micro-sponges as delivery systems in food or pharmaceutical products.

Stearic acid monoglyceride as suspension agent, divinylsulfone (DVS) as the crosslinker, cyclohexane as the continuous organic phase and nano-calcium carbonate as the porogen were used to produce hydroxypropyl methylcellulose (HPMC) porous gels in bead form by inversing phase suspension crosslinking. Effects of porogen dosage on the gel surface and inner morphology, density, porosity, swelling kinetics have been studied. Results show that the interpenetrate pores can be formed in gel beads when the porogen dosage reached 70 wt% of the dry HPMC. The equilibrium swelling ratios of the gel beads increased from 30.1 (g/g) to 37.4 (g/g) when the fraction of CaCO 3 dosage increased from 0 to 100 wt% of the dry HPMC and the equilibrium swelling time of the gels decreased from about 400 to 20 min. The results also show that the gel re-swelling capability is related to the porous structure.

The inhomogeneity of alginate gel beads prepared by an external diffusion method has been characterised using spatially resolved nuclear magnetic resonance or “magnetic resonance imaging” (MRI) and transmission electron microscopy (TEM). The beads exhibited various degrees of inhomogeneity although reducing the length of exposure to the gelling bath and the presence of non-gelling ions decreased gel inhomogeneity. In order to gain information regarding the gastro-intestinal functionality of these beads for in vivo applications, they were exposed to simulated gastro-intestinal conditions. The increased polymer concentration at the edge of the beads was shown to persist throughout our gastro-intestinal model despite the centre of the bead becoming progressively more porous in nature. The porosity of the alginate gels has been quantified by image analysis of transmission electron micrographs and shown to depend on both location within the bead and gastro-intestinal conditions. We suggest that such changes in porosity of these alginate beads during simulated gastro-intestinal conditions may make these an attractive option for controlled delivery applications in vivo.

Calcium alginate (CA), chitosan-coated calcium alginate (CCA-I), and chitosan–calcium alginate complex (CCA-II) gel beads, in which an oil-in-water emulsion containing allyl isothiocyanate (AITC) was entrapped, were prepared and characterized for efficient oral delivery of AITC. The AITC entrapment efficiency was 81% for CA gel beads, whereas about 30% lower values were determined for the chitosan-treated gel beads. Swelling studies showed that all the gel beads suddenly shrunk in simulated gastric fluid (pH 1.2). In simulated intestinal fluid (pH 7.4), CA and CCA-I gel beads rapidly disintegrated, whereas CCA-II gel beads highly swelled without degradation probably due to the strong chitosan–alginate complexation. Release studies revealed that most entrapped AITC was released during the shrinkage, degradation, or swelling of the gel beads, and the chitosan treatments, especially the chitosan–alginate complexation, were effective in suppressing the release. CCA-II gel beads showed the highest bead stability and AITC retention under simulated gastrointestinal pH conditions.

Here we report the synthesis and study of N-succinyl chitosan based hydrogel beads, stabilized with glycopolymeric network (NSC/Glc-gel) for application in anticancer drug delivery of doxorubicin (DOX). The bio-recognition of lectins by NSC/Glc-gel bead was also studied by UV–vis spectrophotometry. The beads were characterized using FT-IR, SEM and Thermogravimetric analysis. The extent of DOX loading was proportional to the degree of succinylation and the swelling kinetics of the beads showed pH dependency. The beads exhibited sustained release of DOX over a period of more than 15 days in an acidic pH, mimicking the microenvironment of tumor cells, and even lesser release at physiological pH. Release exponent ‘n’ derived from Korsmeyer–Peppas model implied that NSC88/Glc-gel (88% succinylation of chitosan) beads followed fickian diffusion controlled release mechanism whereas NSC75/Glc-gel (75% succinylation of chitosan) beads follow zero order release profile. The synthesized beads also displayed specificity to lectin Concanavalin A.

Pectinate beads containing trimethyl chitosan chloride (TMC) as an absorption enhancer were prepared using Coomassie Brilliant Blue G 250 (CB) as a relatively high molecular weight water-soluble model drug. Effects of different formulation variables, such as cross-linker type, cross-linking time, cross-linker concentration, TMC: pectin ratio, pectin concentration and voltage of the bead generator, were assessed on in vitro bead characteristics by release and swelling–erosion studies. The bead formulation was optimized by factorial design. Some measures were taken to improve the bead characteristics and prolong their integrity during the gastrointestinal transit, such as biomineralization of the beads or coating them with high-methoxy pectin (PHM) or Eudragit L30-D 55 (EU). Possible CB-TMC complexation was investigated by Job's Plot method. The suitable system was obtained by coating the optimized core formulation with PHM or EU. TMC was found to form a complex with CB as a model anionic drug. Therefore, TMC-drug interactions can be used to modify the release characteristics of dosage forms.

The carboxymethyl sago pulp (CMSP) with a degree of substitution of 0.4% was synthesized from sago waste. The CMSP beads with an average diameter of 3.1–4.8 mm were formed by aluminium chloride gelation as well as further cross-linked by irradiation. To evaluate colon targeted release, a model drug, 5-aminosalicylic acid (5-ASA) was encapsulated in CMSP beads. Fourier-transform infrared spectroscopy and X-ray diffraction studies indicated intact and amorphous nature of entrapped drug. A pH dependent drug release was observed, and about 90% of the drug was released only at pH 7.4 over 9 h. Irradiated beads were resisted the drug release in an acidic environment at a higher extent than non-irradiated beads. The drug release from 6% (w/w) of 5-ASA loaded bead followed zero order, whereas, 15 and 22% loaded beads followed first order. The release exponent n value suggests non-Fickian transport of 5-ASA from the beads.