Preparation and synbiotic interaction mechanism of microcapsules of Bifidobacterium animalis F1-7 and human milk oligosaccharides (HMO).

Probiotics such as Bifidobacterium spp. generally possess important physiological functions. However, maintaining probiotic viability is a challenge during processing, storage, and digestive transit period. Microencapsulation is widely considered to be an attractive approach. In this study, B. animalis F1-7 microcapsules and B. animalis F1-7-HMO microcapsules were successfully prepared by emulsification/internal gelation with high encapsulation efficiency (90.67 % and 92.16 %, respectively). The current study revealed that HMO-supplemented microcapsules exhibited more stable lyophilized forms and thermal stability. Additionally, a significant improvement in probiotic cell viability was observed in such microcapsules during simulated gastrointestinal (GI) fluids or storage. We also showed that the individual HMO mixtures 6'-SL remarkably promoted the growth and acetate yield of B. animalis F1-7 for 48 h (p < 0.05). The synbiotic combination of 6'-SL with B. animalis F1-7 enhanced SCFAs production in vitro fecal fermentation, decreasing several harmful intestinal bacteria such as Dorea, Escherichia-Shigella, and Streptococcus while enriching the probiotic A. muciniphila. This study provides strong support for HMO or 6'-SL combined with B. animalis F1-7 as an innovative dietary ingredient to bring health benefits. The potential of the synbiotic microcapsules with this combination merits further exploration for future use in the food industry.

Optimization and release characteristics of catechin-loaded calcium pectinate beads by internal gelation.

The aim of this study was to optimize the composition of catechin-loaded calcium pectinate gel (CPG) beads formed using internal gelation and to evaluate the sustained-release behavior of catechin. The pectin concentration, catechin-to-pectin ratio, and calcium carbonate-to-pectin ratio were optimized for the sustained catechin release (2.89, 28.92, and 32.79%, respectively). The catechin release profiles were analyzed using the simple enzyme kinetic-like semi empirical model newly proposed in this study. The actual release rate was found to be the fastest in the simulated intestinal fluid (SIF), followed by the simulated gastric fluid (SGF) and the pH 4.5 buffer, whereas the thermodynamic equilibrium was achieved fastest in the pH 4.5 buffer, followed by SGF and SIF. Glutaraldehyde treatment suppressed catechin release in all tested media. These results suggest that internally gelled CPG beads are suitable for catechin delivery, and crosslinkers, such as glutaraldehyde, can effectively sustain their release.

Biomineralization-Inspired Intermediate Precursor for the Controllable Gelation of Polyphenol-Macromolecule Hydrogels.

Hydrogels composed of polyphenols and various macromolecules have been widely reported to have the advantage of facile preparation, mainly through the formation of hydrogen bonds. However, the traditional preparation method involves the direct mixing of polyphenols and macromolecules, which generally occurs too quickly and uncontrollably, and results in poor homogeneity, injectability, and shape designability. Here, inspired by the intermediate precursor during biomineralization, to facilitate transformation in a controllable way, we propose a novel and universal internal gelation method that creates an intermediate precursor by controlling the pH value to manipulate the elimination and generation of hydrogen bonds between a polyphenol and macromolecules. The precursor strategy greatly improves the homogeneity, injectability, and shape designability of the hydrogel while also achieving a controllable gelation process, and the gelation time can be accurately adjusted. The hydrogels prepared with this method exhibited superior capability to seal leaks, provided complete wound coverage, and showed the potential to be a shape-designable wearable strain sensor. Our study opens up a new way to construct and apply polyphenol-macromolecule hydrogels in a more controllable manner.

Encapsulation of Human-Bone-Marrow-Derived Mesenchymal Stem Cells in Small Alginate Beads Using One-Step Emulsification by Internal Gelation: In Vitro, and In Vivo Evaluation in Degenerate Intervertebral Disc Model.

Cell microencapsulation in gel beads contributes to many biomedical processes and pharmaceutical applications. Small beads (<300 µm) offer distinct advantages, mainly due to improved mass transfer and mechanical strength. Here, we describe, for the first time, the encapsulation of human-bone-marrow-derived mesenchymal stem cells (hBM-MSCs) in small-sized microspheres, using one-step emulsification by internal gelation. Small (127−257 µm) high-mannuronic-alginate microspheres were prepared at high agitation rates (800−1000 rpm), enabling control over the bead size and shape. The average viability of encapsulated hBM-MSCs after 2 weeks was 81 ± 4.3% for the higher agitation rates. hBM-MSC-loaded microspheres seeded within a glycosaminoglycan (GAG) analogue, which was previously proposed as a mechanically equivalent implant for degenerate discs, kept their viability, sphericity, and integrity for at least 6 weeks. A preliminary in vivo study of hBM-MSC-loaded microspheres implanted (via a GAG-analogue hydrogel) in a rat injured intervertebral disc model demonstrated long-lasting viability and biocompatibility for at least 8 weeks post-implantation. The proposed method offers an effective and reproducible way to maintain long-lasting viability in vitro and in vivo. This approach not only utilizes the benefits of a simple, mild, and scalable method, but also allows for the easy control of the bead size and shape by the agitation rate, which, overall, makes it a very attractive platform for regenerative-medicine applications.

Alginate Self-Crosslinking Ink for 3D Extrusion-Based Cryoprinting and Application for Epirubicin-HCl Delivery on MCF-7 Cells.

3D-printed hydrogels are particularly advantageous as drug-delivery platforms but their loading with water-soluble active compounds remains a challenge requiring the development of innovative inks. Here, we propose a new 3D extrusion-based approach that, by exploiting the internal gelation of the alginate, avoids the post-printing crosslinking process and allows the loading of epirubicin-HCl (EPI). The critical combinations of alginate, calcium carbonate and d-glucono-δ-lactone (GDL) combined with the scaffold production parameters (extrusion time, temperature, and curing time) were evaluated and discussed. The internal gelation in tandem with 3D extrusion allowed the preparation of alginate hydrogels with a complex shape and good handling properties. The dispersion of epirubicin-HCl in the hydrogel matrix confirmed the potential of this self-crosslinking alginate-based ink for the preparation of 3D-printed drug-delivery platforms. Drug release from 3D-printed hydrogels was monitored, and the cytotoxic activity was tested against MCF-7 cells. Finally, the change in the expression pattern of anti-apoptotic, pro-apoptotic, and autophagy protein markers was monitored by liquid-chromatography tandem-mass-spectrometry after exposure of MCF-7 to the EPI-loaded hydrogels.

Pectin-based bioinks for 3D models of neural tissue produced by a pH-controlled kinetics.

Introduction: In the view of 3D-bioprinting with cell models representative of neural cells, we produced inks to mimic the basic viscoelastic properties of brain tissue. Moving from the concept that rheology provides useful information to predict ink printability, this study improves and expands the potential of the previously published 3D-reactive printing approach by introducing pH as a key parameter to be controlled, together with printing time. Methods: The viscoelastic properties, printability, and microstructure of pectin gels crosslinked with CaCO3 were investigated and their composition was optimized (i.e., by including cell culture medium, HEPES buffer, and collagen). Different cell models representative of the major brain cell populations (i.e., neurons, astrocytes, microglial cells, and oligodendrocytes) were considered. Results and Discussion: The outcomes of this study propose a highly controllable method to optimize the printability of internally crosslinked polysaccharides, without the need for additives or post-printing treatments. By introducing pH as a further parameter to be controlled, it is possible to have multiple (pH-dependent) crosslinking kinetics, without varying hydrogel composition. In addition, the results indicate that not only cells survive and proliferate following 3D-bioprinting, but they can also interact and reorganize hydrogel microstructure. Taken together, the results suggest that pectin-based hydrogels could be successfully applied for neural cell culture.

Fabrication and Evaluation of Alginate/Bacterial Cellulose Nanocrystals-Chitosan-Gelatin Composite Scaffolds.

It is common knowledge that pure alginate hydrogel is more likely to have weak mechanical strength, a lack of cell recognition sites, extensive swelling and uncontrolled degradation, and thus be unable to satisfy the demands of the ideal scaffold. To address these problems, we attempted to fabricate alginate/bacterial cellulose nanocrystals-chitosan-gelatin (Alg/BCNs-CS-GT) composite scaffolds using the combined method involving the incorporation of BCNs in the alginate matrix, internal gelation through the hydroxyapatite-d-glucono-δ-lactone (HAP-GDL) complex, and layer-by-layer (LBL) electrostatic assembly of polyelectrolytes. Meanwhile, the effect of various contents of BCNs on the scaffold morphology, porosity, mechanical properties, and swelling and degradation behavior was investigated. The experimental results showed that the fabricated Alg/BCNs-CS-GT composite scaffolds exhibited regular 3D morphologies and well-developed pore structures. With the increase in BCNs content, the pore size of Alg/BCNs-CS-GT composite scaffolds was gradually reduced from 200 µm to 70 µm. Furthermore, BCNs were fully embedded in the alginate matrix through the intermolecular hydrogen bond with alginate. Moreover, the addition of BCNs could effectively control the swelling and biodegradation of the Alg/BCNs-CS-GT composite scaffolds. Furthermore, the in vitro cytotoxicity studies indicated that the porous fiber network of BCNs could fully mimic the extracellular matrix structure, which promoted the adhesion and spreading of MG63 cells and MC3T3-E1 cells on the Alg/BCNs-CS-GT composite scaffolds. In addition, these cells could grow in the 3D-porous structure of composite scaffolds, which exhibited good proliferative viability. Based on the effect of BCNs on the cytocompatibility of composite scaffolds, the optimum BCNs content for the Alg/BCNs-CS-GT composite scaffolds was 0.2% (w/v). On the basis of good merits, such as regular 3D morphology, well-developed pore structure, controlled swelling and biodegradation behavior, and good cytocompatibility, the Alg/BCNs-CS-GT composite scaffolds may exhibit great potential as the ideal scaffold in the bone tissue engineering field.

Study on the Technology of Monodisperse Droplets by a High-Throughput and Instant-Mixing Droplet Microfluidic System.

In this study, we report a novel high-throughput and instant-mixing droplet microfluidic system that can prepare uniformly mixed monodisperse droplets at a flow rate of mL/min designed for rapid mixing between multiple solutions and the preparation of micro-/nanoparticles. The system is composed of a magneton micromixer and a T-junction microfluidic device. The magneton micromixer rapidly mixes multiple solutions uniformly through the rotation of the magneton, and the mixed solution is sheared into monodisperse droplets by the silicone oil in the T-junction microfluidic device. The optimal conditions of the preparation of monodisperse droplets for the system have been found and factors affecting droplet size are analyzed for correlation; for example, the structure of the T-junction microfluidic device, the rotation speed of the magneton, etc. At the same time, through the uniformity of the color of the mixed solution, the mixing performance of the system is quantitatively evaluated. Compared with mainstream micromixers on the market, the system has the best mixing performance. Finally, we used the system to simulate the internal gelation broth preparation of zirconium broth and uranium broth. The results show that the system is expected to realize the preparation of ceramic microspheres at room temperature without cooling by the internal gelation process.

Preparation of internally-crosslinked alginate microspheres: Optimization of process parameters and study of pH-responsive behaviors.

In this study, the effects of various parameters of the water-in-oil emulsification/internal gelation method on the properties of calcium-alginate microparticles were evaluated and optimized. Results showed that the spherical-shaped microparticles with the highest circularity and high production yield can be produced by alginate solution with a concentration of 2 wt.%, calcium carbonate/alginate ratio of 10/1 (w/w), water/oil volume ratio of 1/20, emulsifier concentration of 5 % (v/v), and emulsification speed of 1000 rpm. Two model drugs including simvastatin lactone and simvastatin ß-hydroxyacid were loaded into the microspheres with promising encapsulation efficiencies of 73 % and 69 %, respectively. The microspheres showed a pH-responsive swelling behavior with a percentage of 10.60 %, 352.65 %, 690.03 %, and 1211.46 % at the pH values of 2.0, 4.5, 7.4, and 8.5, respectively. The microspheres showed an increasing trend of release rate in direct proportion to pH. These findings would be useful for therapeutic applications which need pH-responsive drug carriers.

Mild formation of core-shell hydrogel microcapsules for cell encapsulation.

Internal gelation has been an important sol-gel route for the preparation of spherical microgel for drug delivery, cell therapy, or tissue regeneration. Despite high homogeneity and permeability, the internal gelated microgels often result in weak mechanical stability, unregular interface morphology and low cell survival rate. In this work, we have extensively improved the existing internal gelation approach and core-shell hydrogel microcapsules (200-600µm) with a smooth surface, high mechanical stability and cell survival rate, are successfully prepared by using internal gelation. A coaxial flow-focusing capillary-assembled microfluidic device was developed for the gelation. Rapid gelling behavior of alginate in the internal gelation makes it suitable for producing well-defined and homogenous alginate hydrogel microstructures that serve as the shell of the microcapsules. 2-[4-(2-Hydroxyethyl)piperazin-1-yl]ethanesulfonic acid (HEPES) was used in the shell stream during the internal gelation. Thus, a high concentration of acid in the oil solution can be used for better crosslinking the alginate while maintaining high cell viability. We further demonstrated that the gelation conditions in our approach were mild enough for encapsulating HepG2 cells and 3T3 fibroblasts without losing their viability and functionality in a co-culture environment.

Shear-resistant hydrogels to control permeability of porous tubular scaffolds in vascular tissue engineering.

Aiming to perfuse porous tubular scaffolds for vascular tissue engineering (VTE) with controlled flow rate, prevention of leakage through the scaffold lumen is required. A gel coating made of 8% w/v alginate and 6% w/v gelatin functionalized with fibronectin was produced using a custom-made bioreactor-based method. Different volumetric proportions of alginate and gelatin were tested (50/50, 70/30, and 90/10). Gel swelling and stability, and rheological, and uniaxial tensile tests reveal superior resistance to the aggressive biochemical microenvironment, and their ability to withstand physiological deformations (~10%) and wall shear stresses (5-20 dyne/cm2). These are prerequisites to maintain the physiologic phenotypes of vascular smooth muscle cells and endothelial cells (ECs), mimicking blood vessels microenvironment. Gels can induce ECs proliferation and colonization, especially in the presence of fibronectin and higher percentages of gelatin. The custom-designed bioreactor enables the development of reproducible and homogeneous tubular gel coating. The permeability tests show the effectiveness of tubular scaffolds coated with 70/30 alginate/gelatin gel to occlude wadding pores, and therefore prevent leakages. The synthesized double-layered tubular scaffolds coated with alginate/gelatin gel and fibronectin represent both promising substrate for ECs and effective leakproof scaffolds, when subjected to pulsatile perfusion, for VTE applications.

Extending Viability of Bifidobacterium longum in Chitosan-Coated Alginate Microcapsules Using Emulsification and Internal Gelation Encapsulation Technology.

Bifidobacteria are considered one of the most important intestinal probiotics because of their significant health impact. However, this ability is usually limited by gastrointestinal fluid and temperature sensitivity. Emulsification and internal gelation is an encapsulation technique with great potential for probiotic protection during storage and the gastrointestinal transit process. This study prepared microcapsules using an emulsification and internal gelation encapsulation method with sodium alginate, chitosan, and Bifidobacterium longum as wall material, coating material, and experimental strain, respectively. Optical, scanning electron, and focal microscopes were used to observe the microcapsule surface morphology and internal viable cell distribution, and a laser particle size analyzer and zeta potentiometer were used to evaluate the chitosan-coating characteristics. In addition, microcapsule probiotic viability after storage, heat treatment, and simulated gastrointestinal fluid treatment were examined. Alginate microcapsules and chitosan-coated alginate microcapsules both had balling properties and uniform bacterial distribution. The latter kept its balling properties after freeze-drying, verified by scanning electronic microscopy (SEM), and had a clear external coating, observed by an optical microscope. The particle size of chitosan-coated alginate microcapsules was slightly larger than the uncoated microcapsules. The zeta potential of alginate and chitosan-coated alginate microcapsules was negative and positive, respectively. Heat, acid and bile salt tolerance, and stability tests revealed that the decrease of viable cells in the chitosan-coated alginate microcapsule group was significantly lower than that in uncoated microcapsules. These experimental results indicate that the chitosan-coated alginate microcapsules protect B. longum from gastrointestinal fluid and high-temperature conditions.

Growth and survival of microencapsulated probiotics prepared by emulsion and internal gelation.

Efficient microencapsulation of probiotics by most existing methods is limited by low throughput. In this work, Saccharomyces boulardii and Enterococcus faecium were microencapsulated by a method based on emulsion and internal gelation. The growth and survival of microencapsulated microbes under different stressors were investigated using free non-encapsulated ones as a control. The results showed that the prepared micro-beads by emulsion and internal gelation exhibited a spherical and smooth shape, with sizes between 300 and 500 µm. Both S. boulardii and E. faecium grew well and survived better when encapsulated in micro-beads. The survival rates were increased 25% and 40% for microencapsulated S. boulardii and E. faecium respectively when compared with non-encapsulated controls under high temperature and high humidity. The increases of survival rates were 60% for microencapsulated S. boulardii and 25% for E. faecium in simulated gastric juice. And the increases were 15% and 20% respectively when the survival rates of the microencapsulated S. boulardii and E. faecium were determined in simulated intestinal juice. The microencapsulation by emulsion and internal gelation offers an effective way to protect microbes in adverse in vitro and in vivo conditions and is promising for the large-scale production of probiotics microencapsulation.

Synthesis of alginate-silica hybrid hydrogel for biocatalytic conversion by ß-glucosidase in microreactor.

The organic-inorganic hybrid materials have been used in different fields to immobilize biomolecules since they offer many advantages. The aim of this study was to optimize and characterize the alginate-silica hybrid hydrogel as a stable and injectable form for microfluidic systems using internal gelation method and increase the stability and activity of immobilized enzyme for biocatalytic conversions as well. Characterization was carried out by scanning electron microscopy, energy dispersive spectroscopy/mapping, Brunauer-Emmett-Teller, Barrett-Joyner-Halenda, and Fourier-transform infrared spectroscopy analyses, and the shrinkages of monoliths were evaluated. Subsequent to optimizing the enzyme concentration (40 µg), hydrolytic conversion of 4-nitrophenyl ß-d-glucopyranoside (pNPG) was performed to understand the behavior of the bioconversion in the microfluidic system. The yield was 94% which reached the equilibrium at 24 h indicating that the alginate-silica gel derived microsystem overcome some drawbacks of monolithic systems. Additionally, bioconversion of Ruscus aculeatus saponins was carried out at the same setup in order to obtain aglycon part, which has pharmaceutical significance. Although pure aglycon could not be achieved, an intermediate compound was obtained based on the HPLC analysis. The developed formulation can be utilized for various life science applications.

Macroporous alginate foams crosslinked with strontium for bone tissue engineering.

Nowadays, the need of novel strategies to repair and regenerate bone defects in the field of biomedical applications has increased. Novel approaches include the design of natural bioactive scaffolds mimicking bone tissue. These bioactive scaffolds have to possess biophysical properties suitable to address biological response towards newly bone tissue formation. In particular, scaffold porosity and pore size play a pivotal role in cell migration, adhesion and proliferation, thus increasing cell-material surface interaction and osteogenic signals transmission. Here we propose the development of macroporous alginate foams (MAFs) with porous and well interconnected structure, useful to enhance growth and osteogenic differentiation of human Mesenchymal Stem Cells (hMSCs). Moreover, in this study we report a new method for MAFs fabrication based on the combination of internal gelation technique with gas foaming. Strontium was employed in combination with calcium as cross-linking agent for the alginate chains and as enhancer of the osteogenic differentiation. The influence of strontium ions on the gelation kinetics, physical properties and degradation in physiological medium of MAFs was investigated. Our results suggest that the combination of internal gelation technique with gas foaming followed by freeze-drying is an easy and straightforward procedure to prepare alginate foams with high porosity and interconnectivity, able to support cell infiltration. Finally, biological assays showed how scaffolds with high strontium content are able to support cell growth and differentiation in long times by promoting osteogenic marker expression.

Preparation, Characterization and Properties of Alginate/Poly(γ-glutamic acid) Composite Microparticles.

Alginate (Alg) is a renewable polymer with excellent hemostatic properties and biocapability and is widely used for hemostatic wound dressing. However, the swelling properties of alginate-based wound dressings need to be promoted to meet the requirements of wider application. Poly(γ-glutamic acid) (PGA) is a natural polymer with high hydrophility. In the current study, novel Alg/PGA composite microparticles with double network structure were prepared by the emulsification/internal gelation method. It was found from the structure characterization that a double network structure was formed in the composite microparticles due to the ion chelation interaction between Ca2+ and the carboxylate groups of Alg and PGA and the electrostatic interaction between the secondary amine group of PGA and the carboxylate groups of Alg and PGA. The swelling behavior of the composite microparticles was significantly improved due to the high hydrophility of PGA. Influences of the preparing conditions on the swelling behavior of the composites were investigated. The porous microparticles could be formed while compositing of PGA. Thermal stability was studied by thermogravimetric analysis method. Moreover, in vitro cytocompatibility test of microparticles exhibited good biocompatibility with L929 cells. All results indicated that such Alg/PGA composite microparticles are a promising candidate in the field of wound dressing for hemostasis or rapid removal of exudates.

Effect of acidification on the protection of alginate-encapsulated probiotic based on emulsification/internal gelation.

BACKGROUND: The method of emulsification/internal gelation is commonly used to prepare alginate microspheres for lactic acid bacteria (LAB). This paper focused on the influence of acidification parameters, i.e. acid/Ca molar ratio and acidification time, on the physical properties and cell protection efficiency of microspheres and their correlations. RESULTS: With increasing acid/Ca molar ratio and acidification time, the average diameter of microspheres decreased and their mechanical strength increased. Interestingly, wet alginate microspheres shrank in simulated gastric juice (SGJ) while they swelled in bile salts solution (BS). The shrinkage or swelling ratio decreased with increasing mechanical strength. Correlation analysis showed that the encapsulated cell survivals in both SGJ and BS were positively correlated with the mechanical strength of microspheres but negatively with the shrinkage or swelling ratio. BacLight LIVE/DEAD assay suggested that the viability of encapsulated cells in fresh, SGJ-treated and BS-treated microspheres was closely related to cell membrane integrity. CONCLUSION: Acidification is a key step during microsphere preparation, which strongly affected the physical properties of alginate microspheres, resulting in different cell protection efficiency. The resulting well-protected LAB can be applied in probiotics foods. © 2016 Society of Chemical Industry.

Alginate-hyaluronan composite hydrogels accelerate wound healing process.

In this paper we propose polysaccharide hydrogels combining alginate (ALG) and hyaluronan (HA) as biofunctional platform for dermal wound repair. Hydrogels produced by internal gelation were homogeneous and easy to handle. Rheological evaluation of gelation kinetics of ALG/HA mixtures at different ratios allowed understanding the HA effect on ALG cross-linking process. Disk-shaped hydrogels, at different ALG/HA ratio, were characterized for morphology, homogeneity and mechanical properties. Results suggest that, although the presence of HA does significantly slow down gelation kinetics, the concentration of cross-links reached at the end of gelation is scarcely affected. The in vitro activity of ALG/HA dressings was tested on adipose derived multipotent adult stem cells (Ad-MSC) and an immortalized keratinocyte cell line (HaCaT). Hydrogels did not interfere with cell viability in both cells lines, but significantly promoted gap closure in a scratch assay at early (1 day) and late (5 days) stages as compared to hydrogels made of ALG alone (p<0.01 and 0.001 for Ad-MSC and HaCaT, respectively). In vivo wound healing studies, conducted on a rat model of excised wound indicated that after 5 days ALG/HA hydrogels significantly promoted wound closure as compared to ALG ones (p<0.001). Overall results demonstrate that the integration of HA in a physically cross-linked ALG hydrogel can be a versatile strategy to promote wound healing that can be easily translated in a clinical setting.

Preparation and characterization of alginate-gelatin microencapsulated Bacillus subtilis SL-13 by emulsification/internal gelation.

Gelatin was blended with sodium alginate (NaALG) to obtain a novel microbial fungicide, and dispersed micron Bacillus subtilis SL-13 microspheres prepared by emulsification/internal gelation method. Microscopic examination revealed that microcapsules were nearly spherical in shape. Fourier transform infrared spectroscopy, differential scanning calorimetry, and X-ray diffraction confirmed that the electrostatic interaction was occurred when gelatin added into NaALG. The maximum encapsulation efficiency was 93.44% at a gelatin concentration of 1.5%. Particle size, swelling, and biodegradation of beads increased with gelatin content increase. Furthermore, the viability of encapsulated SL-13 could be preserved at more than 10(8) CFU/mL after 120 d storage at 25 °C. The number of viable cells released from microcapsules presented an initial rapid increase followed by a gradual increase, and reached the maximum as 10(10) CFU/mL on day 35. Thus, it is feasible to prepare uniform, rounded shape, and well-dispersed micron microcapsules of SL-13 via emulsification/internal gelation using NaALG and gelatin composites. This encapsulation strategy could be considered as a potential alternative to future applications in the agricultural industry.

Novel zinc alginate hydrogels prepared by internal setting method with intrinsic antibacterial activity.

In this paper, a controlled gelation of alginate was performed for the first time using ZnCO3 and GDL. Uniform and transparent gels were obtained and investigated as potential wound dressings. Homogeneity, water content, swelling capability, water evaporation rate, stability in normal saline solution, mechanical properties and antibacterial activity were assessed as a function of zinc concentration. Gelation rate increased at increasing zinc content, while a decrease in water uptake and an improvement of stability were found. Release of zinc in physiological environments showed that concentration of zinc released in solution lies below the cytotoxicity level. Hydrogels showed antimicrobial activity against Escherichia coli. The hydrogel with highest zinc content was stabilized with calcium by immersion in a calcium chloride solution. The resulting hydrogel preserved homogeneity and antibacterial activity. Furthermore, it showed even an improvement of stability and mechanical properties, which makes it suitable as long-lasting wound dressing.