Recent advances in alginate-based composite gel spheres for removal of heavy metals

The discharge of heavy metal ions from industrial wastewater into natural water bodies is a consequence of global industrialisation. Due to their high toxicity and resistance to degradation, these heavy metal ions pose a substantial threat to human health as they accumulate and amplify. Alginate-based composite gels exhibit good adsorption and mechanical properties, excellent biodegradability, and non-toxicity, making them environmentally friendly heavy metal ion adsorbents for water with promising development prospects. This paper introduces the basic properties, cross-linking methods, synthetic approaches, modification methods, and manufacturing techniques of alginate-based composite gels. The adsorption properties and mechanical strength of these gels can be enhanced through surface modification, multi-component mixing, and embedding. The main production processes involved are sol-gel and cross-linking methods. Additionally, this paper reviews various applications of alginate composite gels for common heavy metals, rare earth elements, and radionuclides and elucidates the adsorption mechanism of alginate composite gels. This study aimed to provide a reference for synthesising new, efficient, and environmentally friendly alginate-based adsorbents and to contribute new ideas and directions for addressing the issue of heavy metal pollution.

Contemporary Aspects of Designing Marine Polysaccharide Microparticles as Drug Carriers for Biomedical Application

The main goal of modern pharmaceutical technology is to create new drug formulations that are safer and more effective. These formulations should allow targeted drug delivery, improved drug stability and bioavailability, fewer side effects, and reduced drug toxicity. One successful approach for achieving these objectives is using polymer microcarriers for drug delivery. They are effective for treating various diseases through different administration routes. When creating pharmaceutical systems, choosing the right drug carrier is crucial. Biomaterials have become increasingly popular over the past few decades due to their lack of toxicity, renewable sources, and affordability. Marine polysaccharides, in particular, have been widely used as substitutes for synthetic polymers in drug carrier applications. Their inherent properties, such as biodegradability and biocompatibility, make marine polysaccharide-based microcarriers a prospective platform for developing drug delivery systems. This review paper explores the principles of microparticle design using marine polysaccharides as drug carriers. By reviewing the current literature, the paper highlights the challenges of formulating polymer microparticles, and proposes various technological solutions. It also outlines future perspectives for developing marine polysaccharides as drug microcarriers.

Experimental Advances in the Real-Time Recording of Cross-Linking Alginate In Situ Gelation: A Review

Alginate-based hydrogels are promising smart materials widely employed in the food, bioengineering, and energy sectors. The development and optimization of their production require a thorough knowledge of gelation. In recent years, advanced experimental procedures have been developed for real-time cross-linking alginate reaction monitoring. Novel methods, such as customized rheometric setups, enable the recording of mechanical properties and morphological changes during hydrogel formation. These innovative techniques provide important insights into the gelation stages, the reaction rate, the diffusion of cross-linker to polymer chains, and the homogeneity of the gelling structures. Based on real-time experimental data, kinetic models are developed to enhance comprehension of the reaction mechanism and, eventually, to predict the gelation progress. The aim is to enable better control of the characterization of both the complex gelation and the propagated structures. This review aspires to present a comprehensive overview and evaluation of the breakthrough innovations of the real-time in situ recording of cross-linking alginate hydrogels and bead formation. A detailed analysis of the pioneering experimental developments provides a deep comprehension of the alginate gelation, including the parameters controlling the reaction.

Swelling of Homogeneous Alginate Gels with Multi-Stimuli Sensitivity

A new two-step method is suggested for the preparation of homogeneous alginate gels. In the first step, alginate chains are weakly bonded by Ca2+ ions in an aqueous solution with a low pH. In the next step, the gel is immersed into a strong solution of CaCl2 to finalize the cross-linking process. Homogeneous alginate gels preserve their integrity in aqueous solutions with a pH ranging from 2 to 7 and ionic strength in the interval from 0 to 0.2 M, at temperatures ranging from room temperature up to 50 °C, and can be used in biomedical applications. The immersion of these gels into aqueous solutions with low pH induces the partial breakage of ionic bonds between chains (treated as gel degradation). This degradation affects the equilibrium and transient swelling of homogeneous alginate gels and makes them sensitive to the history of loading and environmental conditions (pH, ionic strength and temperature of aqueous solutions). As sensitivity to the environmental stimuli is a characteristic feature of polymer networks connected by catch bonds, homogeneous alginate gels may serve as a simple model, mimicking the behavior of more sophisticated structures in living matter.

Hep3Gel: A Shape-Shifting Extracellular Matrix-Based, Three-Dimensional Liver Model Adaptable to Different Culture Systems

Drug-induced hepatotoxicity is a leading cause of clinical trial withdrawal. Therefore, in vitro modeling the hepatic behavior and functionalities is not only crucial to better understand physiological and pathological processes but also to support drug development with reliable high-throughput platforms. Different physiological and pathological models are currently under development and are commonly implemented both within platforms for standard 2D cultures and within tailor-made chambers. This paper introduces Hep3Gel: a hybrid alginate-extracellular matrix (ECM) hydrogel to produce 3D in vitro models of the liver, aiming to reproduce the hepatic chemomechanical niche, with the possibility of adapting its shape to different manufacturing techniques. The ECM, extracted and powdered from porcine livers by a specifically set-up procedure, preserved its crucial biological macromolecules and was embedded within alginate hydrogels prior to crosslinking. The viscoelastic behavior of Hep3Gel was tuned, reproducing the properties of a physiological organ, according to the available knowledge about hepatic biomechanics. By finely tuning the crosslinking kinetics of Hep3Gel, its dualistic nature can be exploited either by self-spreading or adapting its shape to different culture supports or retaining the imposed fiber shape during an extrusion-based 3D-bioprinting process, thus being a shape-shifter hydrogel. The self-spreading ability of Hep3Gel was characterized by combining empirical and numerical procedures, while its use as a bioink was experimentally characterized through rheological a priori printability evaluations and 3D printing tests. The effect of the addition of the ECM was evident after 4 days, doubling the survival rate of cells embedded within control hydrogels. This study represents a proof of concept of the applicability of Hep3Gel as a tool to develop 3D in vitro models of the liver.

Preparation and Characteristics of Alginate Microparticles for Food, Pharmaceutical and Cosmetic Applications

Alginates are the most widely used natural polymers in the pharmaceutical, food and cosmetic industries. Usually, they are applied as a thickening, gel-forming and stabilizing agent. Moreover, the alginate-based formulations such as matrices, membranes, nanospheres or microcapsules are often used as delivery systems. Alginate microparticles (AMP) are biocompatible, biodegradable and nontoxic carriers, applied to encapsulate hydrophilic active substances, including probiotics. Here, we report the methods most frequently used for AMP production and encapsulation of different actives. The technological parameters important in the process of AMP preparation, such as alginate concentration, the type and concentration of other reagents (cross-linking agents, oils, emulsifiers and pH regulators), agitation speed or cross-linking time, are reviewed. Furthermore, the advantages and disadvantages of alginate microparticles as delivery systems are discussed, and an overview of the active ingredients enclosed in the alginate carriers are presented.

Encapsulation of Mesona chinensis Benth Extract in Alginate Beads Enhances the Stability and Antioxidant Activity of Polyphenols under Simulated Gastrointestinal Digestion

The aim of this study was to investigate the stability and antioxidant activity of the polyphenols from Mesona chinensis Benth extract (MCE) and its alginate-based encapsulation by extrusion technique during simulated gastrointestinal digestion. The encapsulation efficacy ranged from 41.1 ± 4.7 to 56.7 ± 3.4% with different concentrations of MCE (50-75% v/v), sodium alginate (1.2-1.8% w/v), and CaCl₂ solution (3-5% w/v). The optimal condition for MCE-loaded alginate beads (MCB) was composed of 75% MCE, 1.5% alginate, and 3% CaCl₂ solution, which provided the highest encapsulation efficiency with a spherical structure and a mean particle diameter of 1516.67 ± 40.96 μm. Fourier transform infrared spectroscopy (FT-IR) reported no chemical interaction between alginate and MCE. The release of total phenolic content (TPC) was only 8.9% after placing MCB in water for 4 h. After simulated digestion, changes in TPC and ferric reducing antioxidant power (FRAP) of MCE significantly decreased by 25.0% and 29.7%, respectively. Interestingly, the incorporation of MCB significantly increased TPC and FRAP in the digesta compared to those of MCE during gastrointestinal tract conditions. The findings suggest that the encapsulation of MCE with alginate as a carrier helps to improve the bioaccessibility and biological activity of M. chinensis polyphenols.

Alginate-Based Smart Materials and Their Application: Recent Advances and Perspectives

Nature produces materials using available molecular building blocks following a bottom-up approach. These materials are formed with great precision and flexibility in a controlled manner. This approach offers the inspiration for manufacturing new artificial materials and devices. Synthetic artificial materials can find many important applications ranging from personalized therapeutics to solutions for environmental problems. Among these materials, responsive synthetic materials are capable of changing their structure and/or properties in response to external stimuli, and hence are termed "smart" materials. Herein, this review focuses on alginate-based smart materials and their stimuli-responsive preparation, fragmentation, and applications in diverse fields from drug delivery and tissue engineering to water purification and environmental remediation. In the first part of this report, we review stimuli-induced preparation of alginate-based materials. Stimuli-triggered decomposition of alginate materials in a controlled fashion is documented in the second part, followed by the application of smart alginate materials in diverse fields. Because of their biocompatibility, easy accessibility, and simple techniques of material formation, alginates can provide solutions for several present and future problems of humankind. However, new research is needed for novel alginate-based materials with new functionalities and well-defined properties for targeted applications.

Recent Development of Alginate-Based Materials and Their Versatile Functions in Biomedicine, Flexible Electronics, and Environmental Uses

Alginate is a natural polysaccharide that is easily chemically modified or compounded with other components for various types of functionalities. The alginate derivatives are appealing not only because they are biocompatible so that they can be used in biomedicine or tissue engineering but also because of the prospering bioelectronics that require various biomaterials to interface between human tissues and electronics or to serve as electronic components themselves. The study of alginate-based materials, especially hydrogels, have repeatedly found new frontiers over recent years. In this Review, we document the basic properties of alginate, their chemical modification strategies, and the recent development of alginate-based functional composite materials. The newly thrived functions such as ionically conductive hydrogel or 3D or 4D cell culturing matrix are emphasized among other appealing potential applications. We expect that the documentation of relevant information will stimulate scientific efforts to further develop biocompatible electronics or smart materials and to help the research domain better address the medicine, energy, and environmental challenges faced by human societies.

Improving alginate printability for biofabrication: establishment of a universal and homogeneous pre-crosslinking technique

Many different biofabrication approaches as well as a variety of bioinks have been developed by researchers working in the field of tissue engineering. A main challenge for bioinks often remains the difficulty to achieve shape fidelity after printing. In order to overcome this issue, a homogeneous pre-crosslinking technique, which is universally applicable to all alginate-based materials, was developed. In this study, the Young's Modulus after post-crosslinking of selected hydrogels, as well as the chemical characterization of alginate in terms of M/G ratio and molecular weight, were determined. With our technique it was possible to markedly enhance the printability of a 2% (w/v) alginate solution, without using a higher polymer content, fillers or support structures. 3D porous scaffolds with a height of around 5 mm were printed. Furthermore, the rheological behavior of different pre-crosslinking degrees was studied. Shear forces on cells as well as the flow profile of the bioink inside the printing nozzle during the process were estimated. A high cell viability of printed NIH/3T3 cells embedded in the novel bioink of more than 85% over a time period of two weeks could be observed.

Alginate Nanoparticles for Drug Delivery and Targeting

Nanotechnology refers to the control, manipulation, study and manufacture of structures and devices at the nanometer size range. The small size, customized surface, improved solubility and multi-functionality of nanoparticles will continue to create new biomedical applications, as nanoparticles allow to dominate stability, solubility and bioavailability, as well controlled release of drugs. The type of a nanoparticle, and its related chemical, physical and morphological properties influence its interaction with living cells, as well as determine the route of clearance and possible toxic effects. This field requires cross-disciplinary research and gives opportunities to design and develop multifunctional devices, which allow the diagnosis and treatment of devastating diseases. Over the past few decades, biodegradable polymers have been studied for the fabrication of drug delivery systems. There was extensive development of biodegradable polymeric nanoparticles for drug delivery and tissue engineering, in view of their applications in controlling the release of drugs, stabilizing labile molecules from degradation and site-specific drug targeting. The primary aim is to reduce dosing frequency and prolong the therapeutic outcomes. For this purpose, inert excipients should be selected, being biopolymers, e.g. sodium alginate, commonly used in controlled drug delivery. Nanoparticles composed of alginate (known as anionic polysaccharide widely distributed in the cell walls of brown algae which, when in contact with water, forms a viscous gum) have emerged as one of the most extensively characterized biomaterials used for drug delivery and targeting a set of administration routes. Their advantages include not only the versatile physicochemical properties, which allow chemical modifications for site-specific targeting but also their biocompatibility and biodegradation profiles, as well as mucoadhesiveness. Furthermore, mechanical strength, gelation, and cell affinity can be modulated by combining alginate nanoparticles with other polymers, surface tailoring using specific targeting moieties and by chemical or physical cross-linking. However, for every physicochemical modification in the macromolecule/ nanoparticles, a new toxicological profile may be obtained. In this paper, the different aspects related to the use of alginate nanoparticles for drug delivery and targeting have been revised, as well as how their toxicological profile will determine the therapeutic outcome of the drug delivery system.

Development and Evaluation of a Reconstitutable Dry Suspension to Improve the Dissolution and Oral Absorption of Poorly Water-Soluble Celecoxib

This study aims at developing and evaluating reconstitutable dry suspension (RDS) improved for dissolution rate, oral absorption, and convenience of use of poorly water-soluble celecoxib (CXB). Micro-sized CXB particle was used to manufacture nanosuspension by using bead milling and then RDS was made by spray-drying the nanosuspension with effective resuspension agent, dextrin. The redispersibility, morphology, particle size, crystallinity, stability, dissolution, and pharmacokinetic profile of the RDS were evaluated. RDS was effectively reconstituted into nanoparticles in 775.8 ± 11.6 nm. It was confirmed that CXB particles are reduced into needle-shape ones in size after the bead-milling process, and the description of CXB was the same in the reconstituted suspension. Through the CXB crystallinity study using differential scanning calorimetry (DSC) and XRD analysis, it was identified that CXB has the CXB active pharmaceutical ingredient (API)’s original crystallinity after the bead milling and spray-drying process. In vitro dissolution of RDS was higher than that of CXB powder (93% versus 28% dissolution at 30 min). Furthermore, RDS formulation resulted in 5.7 and 6.3-fold higher area under the curve (AUC_∞) and peak concentration (C_max) of CXB compared to after oral administration of CXB powder in rats. Collectively, our results suggest that the RDS may be a potential oral dosage formulation for CXB to improve its bioavailability and patient compliance.

Passive and active droplet generation with microfluidics: a review

Precise and effective control of droplet generation is critical for applications of droplet microfluidics ranging from materials synthesis to lab-on-a-chip systems. Methods for droplet generation can be either passive or active, where the former generates droplets without external actuation, and the latter makes use of additional energy input in promoting interfacial instabilities for droplet generation. A unified physical understanding of both passive and active droplet generation is beneficial for effectively developing new techniques meeting various demands arising from applications. Our review of passive approaches focuses on the characteristics and mechanisms of breakup modes of droplet generation occurring in microfluidic cross-flow, co-flow, flow-focusing, and step emulsification configurations. The review of active approaches covers the state-of-the-art techniques employing either external forces from electrical, magnetic and centrifugal fields or methods of modifying intrinsic properties of flows or fluids such as velocity, viscosity, interfacial tension, channel wettability, and fluid density, with a focus on their implementations and actuation mechanisms. Also included in this review is the contrast among different approaches of either passive or active nature.

Alginate Bead Based Hexagonal Close Packed 3D Implant for Bone Tissue Engineering

Success of bone tissue engineering (BTE) relies on the osteogenic microarchitecture of the biopolymeric scaffold and appropriate spatiotemporal distribution of therapeutic molecules (growth factors and drugs) inside it. However, the existing technologies have failed to address both the issues together. Keeping this perspective in mind, we have developed a novel three-dimensional (3D) implant prototype by stacking hexagonal close packed (HCP) layers of calcium alginate beads. The HCP arrangement of the beads lead to a patterned array of interconnected tetrahedral and octahedral pores of average diameter of 142.9 and 262.9 μm, respectively, inside the implant. The swelling pattern of the implants changed from isotropic to anisotropic in the z-direction in the absence of bivalent calcium ions (Ca²⁺) in the swelling buffer. Incubation of the implant in simulated body fluid (SBF) resulted in a 2.7-fold increase in the compressive modulus. The variation in the relaxation times as derived from the Weichert viscoelasticity model predicted a gradual increase in the interactions among the alginate molecules in the matrix. We demonstrated the tunability of the spatiotemporal drug release from the implant in a tissue mimicking porous semisolid matrix as well as in conventional drug release set up by changing the spatial coordinates of the "drug loaded depot layer" inside the implant. The therapeutic potential of the implant was confirmed against Escherichia coli using metronidazole as the model drug. Detailed analysis of cell viability, cell cycle progression, and cytoskeletal reorganization using osteoblast cells (MG-63) proved the osteoconductive nature of the implant. Expression of differentiation markers such as alkaline phosphatase, runx2, and collagen type 1 in human mesenchymal stem cell in vitro confirmed the osteogenic nature of the implant. When tested in vivo, VEGF loaded implant was found capable of inducing angiogenesis in a mice model. In conclusion, the bead based implant may find its utility in non-load-bearing BTE.

Nutrient removal and lipid production by Coelastrella sp. in anaerobically and aerobically treated swine wastewater

Coelastrella sp. QY01, a microalgae species isolated from a local pond, was identified and used for the treatment of anaerobically and aerobically treated swine wastewater (AnATSW). Microalgal growth characteristics, nutrient removal and lipid accumulation of QY01 cultivated in the initial concentration of AnATSW ranged from 63 to 319mg NH3-N/L were examined. The specific growth rate of QY01 cultivated in cultures ranged from 0.269 to 0.325day(-1) with a biomass productivity from 42.77 to 57.46mgL(-1)day(-1). Removal rates for NH3-N, TP and inorganic carbon in AnATSW at the various nutrient concentrations ranged from 90% to 100%, from 90% to 100% and from 74% to 78%, respectively. The lipid content of QY01 ranged from 22.4% to 24.8%. The lipid productivity was positive correlation with the biomass productivity. 40% AnATSW was optimal for QY01 cultivation, in which nutrient removal and productivity of biomass and lipid were maximized.

Electrically Controllable Microparticle Synthesis and Digital Microfluidic Manipulation by Electric-Field-Induced Droplet Dispensing into Immiscible Fluids

The dispensing of tiny droplets is a basic and crucial process in a myriad of applications, such as DNA/protein microarray, cell cultures, chemical synthesis of microparticles, and digital microfluidics. This work systematically demonstrates droplet dispensing into immiscible fluids through electric charge concentration (ECC) method. It exhibits three main modes (i.e., attaching, uniform, and bursting modes) as a function of flow rates, applied voltages, and gap distances between the nozzle and the oil surface. Through a conventional nozzle with diameter of a few millimeters, charged droplets with volumes ranging from a few μL to a few tens of nL can be uniformly dispensed into the oil chamber without reduction in nozzle size. Based on the features of the proposed method (e.g., formation of droplets with controllable polarity and amount of electric charge in water and oil system), a simple and straightforward method is developed for microparticle synthesis, including preparation of colloidosomes and fabrication of Janus microparticles with anisotropic internal structures. Finally, a combined system consisting of ECC-induced droplet dispensing and electrophoresis of charged droplet (ECD)-driven manipulation systems is constructed. This integrated platform will provide increased utility and flexibility in microfluidic applications because a charged droplet can be delivered toward the intended position by programmable electric control.

Structured microparticles with tailored properties produced by membrane emulsification

This paper provides an overview of membrane emulsification routes for fabrication of structured microparticles with tailored properties for specific applications. Direct (bottom-up) and premix (top-down) membrane emulsification processes are discussed including operational, formulation and membrane factors that control the droplet size and droplet generation regimes. A special emphasis was put on different methods of controlled shear generation on membrane surface, such as cross flow on the membrane surface, swirl flow, forward and backward flow pulsations in the continuous phase and membrane oscillations and rotations. Droplets produced by membrane emulsification can be used for synthesis of particles with versatile morphology (solid and hollow, matrix and core/shell, spherical and non-spherical, porous and coherent, composite and homogeneous), which can be surface functionalised and coated or loaded with macromolecules, nanoparticles, quantum dots, drugs, phase change materials and high molecular weight gases to achieve controlled/targeted drug release and impart special optical, chemical, electrical, acoustic, thermal and magnetic properties. The template emulsions including metal-in-oil, solid-in-oil-in-water, oil-in-oil, multilayer, and Pickering emulsions can be produced with high encapsulation efficiency of encapsulated materials and narrow size distribution and transformed into structured particles using a variety of solidification processes, such as polymerisation (suspension, mini-emulsion, interfacial and in-situ), ionic gelation, chemical crosslinking, melt solidification, internal phase separation, layer-by-layer electrostatic deposition, particle self-assembly, complex coacervation, spray drying, sol-gel processing, and molecular imprinting. Particles fabricated from droplets produced by membrane emulsification include nanoclusters, colloidosomes, carbon aerogel particles, nanoshells, polymeric (molecularly imprinted, hypercrosslinked, Janus and core/shell) particles, solder metal powders and inorganic particles. Membrane emulsification devices operate under constant temperature due to low shear rates on the membrane surface, which range from (1-10)×10(3) s(-1) in a direct process to (1-10)×10(4) s(-1) in a premix process.

Injectable PEGylated fibrinogen cell-laden microparticles made with a continuous solvent- and oil-free preparation method

A new methodology is reported for the continuous, solvent- and oil-free production of photopolymerizable microparticles containing encapsulated human dermal fibroblasts. A precursor solution of cells in photoreactive poly(ethylene glycol) (PEG)-fibrinogen (PF) polymer was transported through a transparent injector exposed to light irradiation before being atomized in a jet-in-air nozzle. Shear rheometry data revealed the crosslinking kinetics of the PF/cell solution, which was then used to determine the amount of irradiation required to partially polymerize the mixture just prior to atomization. The partially polymerized drops of PF/cells fell into a gelation bath for further crosslinking until fully polymerized hydrogel microparticles were formed. As the drops of solution exited the air-in-jet nozzle, their viscosity was designed to be sufficiently high so as to prevent rapid mixing and/or dilution in the gelation bath, but without undergoing complete gelation in the nozzle. Several parameters of this system were varied to control the size and polydispersity of the microparticles, including the cell density, the flow rate and the air pressure in the nozzle. The system was capable of producing cell-laden microparticles with an average diameter of between 88.1 to 347.1 μm, and a dispersity of between 1.1 and 2.4, depending on the parameters chosen. Varying the precursor flow rate and/or cell density was beneficial in controlling the size and polydispersity of the microparticles; all microparticles exhibited very high cell viability, which was not affected by these parameters. In conclusion, this dropwise photopolymerization methodology for preparing cell-laden microparticles is an attractive alternative to existing techniques that use harsh solvents/oils and offer limited control over particle size and polydispersity.

Preparation methods of alginate nanoparticles

This article reviews available methods for the formation of alginate nano-aggregates, nanocapsules and nanospheres. Primarily, alginate nanoparticles are being prepared by two methods. In the "complexation method", complex formation on the interface of an oil droplet is used to form alginate nanocapsules, and complex formation in an aqueous solution is used to form alginate nano-aggregates. In a second method w/o emulsification coupled with gelation of the alginate emulsion droplet can be used to form alginate nanospheres. We review advantages and disadvantages of these methods, and give an overview of the properties of the alginate particles produced with these methods.

Microfluidics assisted generation of innovative polysaccharide hydrogel microparticles

Capillary flow-based approach such as microfluidic devices offer a number of advantages over conventional flow control technology because they ensure highly versatile geometry and can be used to produce monodisperse spherical and non-spherical polymeric microparticles. Based on the principle of a flow-focusing device to emulsify the coflow of aqueous solutions in an organic phase, we were able to produce the following innovative polysaccharide hydrogel microparticles: - Janus hydrogel microparticles made of pectin–pectin (homo Janus) and pectin–alginate (hetero Janus) were produced. The efficiency of separation of the two hemispheres was investigated by confocal scanning laser microscopy (CSLM) of previously labelled biopolymers. The Janus structure was confirmed by subjecting each microparticle hemisphere to specific enzymatic degradation. As a proof of concept, free BSA or BSA grafted with dextran, were encapsulated in each hemisphere of the hetero Janus hydrogel microparticles. While BSA, free or grafted with dextran, was always confined in the alginate hemisphere, a fraction of BSA diffused from the pectin to the alginate hemisphere. Methoxy groups along the pectin chain will be responsible of the decrease of the number of attractive electrostatic interactions occurring between amino groups of BSA and carboxylic groups of pectin. - Pectin hydrogel microparticles of complex shapes were successfully produced by combining on-chip the phenomenon of gelation and water diffusion induced self-assembly, using dimethyl carbonate as continuous phase, or by deformation of the pre-gelled droplets off-chip at a fluid–fluid interface. Sphere, oblate ellipsoid, torus or mushroom-type morphologies were thus obtained. Moreover, it was established that after crossing the interface during their collect, mushroom-type microparticles did not migrate in the calcium or DMC phase but stayed at the liquid–liquid interface. These new and original hydrogel microparticles will open up opportunities for studying relationships between combined enzymatic hydrolysis and active release for Janus particles and relationships between shape and swelling behaviour for anisotropic pectin microparticles.

Preparation of monodisperse calcium alginate microcapsules via internal gelation in microfluidic-generated double emulsions

Monodisperse hollow and core-shell calcium alginate microcapsules are successfully prepared via internal gelation in microfluidic-generated double emulsions. Microfluidic emulsification is introduced to generate monodisperse oil-in-water-in-oil (O/W/O) double emulsion templates, which contain Na-alginate, CaCO3 nanoparticles, and photoacid generator in the middle aqueous phase, for synthesizing Ca-alginate microcapsules. The internal gelation of the aqueous middle layer of O/W/O double emulsions is induced by crosslinking alginate polymers with Ca(2+) ions that are released from CaCO3 nanoparticles upon UV exposure of the photoacid generator. The as-prepared hollow and core-shell calcium alginate microcapsules are highly monodisperse and spherical in water. Model proteins Bovine serum albumin (BSA) molecules can be encapsulated into the Ca-alginate microcapsules after the capsule preparation, which demonstrates an alternative route for loading active drugs or chemicals into carriers to avoid the inactivation during the carrier preparation. The proposed technique in this study provides an efficient approach for synthesis of monodisperse hollow or core-shell calcium alginate microcapsules with large cavity or encapsulated lipophilic drugs, chemicals, and nutrients.

Microfluidic generation and selective degradation of biopolymer-based Janus microbeads

We describe a microfluidic approach for generating Janus microbeads from biopolymer hydrogels. A flow-focusing device was used to emulsify the coflow of aqueous solutions of one or two different biopolymers in an organic phase to synthesize homo or hetero Janus microbeads. Biopolymer gelation was initiated, in the chip, by diffusion-controlled ionic cross-linking of the biopolymers. Pectin-pectin (homo Janus) and, for the first time, pectin-alginate (hetero Janus) microbeads were produced. The efficiency of separation of the two hemispheres, which reflected mixing and convection phenomena, was investigated by confocal scanning laser microscopy (CSLM) of previously labeled biopolymers. The interface of the hetero Janus structure was clearly defined, whereas that of the homo Janus microbeads was poorly defined. The Janus structure was confirmed by subjecting each microbead hemisphere to specific enzymatic degradation. These new and original microbeads from renewable resources will open up opportunities for studying relationships between combined enzymatic hydrolysis and active compound release.

Hydrocolloids as thickening and gelling agents in food: a critical review

Hydrocolloids are widely used in many food formulations to improve quality attributes and shelf-life. The two main uses are as thickening and gelling agents. As thickening agents, they find uses in soups, gravies, salad dressings, sauces and toppings while as gelling agents, they are extensively used in products like jam, jelly, marmalade, restructured foods and low sugar/calorie gels. The role of specific hydrocolloids for thickening and for gel formation is reviewed pinpointing specific applications in food formulations and for product development.