Sodium lauryl sulfate impedes drug release from zinc-crosslinked alginate beads: Switching from enteric coating release into biphasic profiles

An ionically cross-linked composite hydrogel electrolyte based on natural biomacromolecules for sustainable zinc-ion batteries

Zinc-ion batteries (ZIBs) are regarded as promising power sources for flexible and biocompatible devices due to their good sustainability and high intrinsic safety. However, their applications have been hindered by the issues of uncontrolled Zn dendrite growth and severe water-induced side reactions in conventional liquid electrolytes. Herein, an ionically cross-linked composite hydrogel electrolyte based on natural biomacromolecules, including iota-carrageenan and sodium alginate, is designed to promote highly efficient and reversible Zn plating/stripping. The abundant functional groups of macromolecules effectively suppress the reactivity of water molecules and facilitate uniform Zn deposition. Moreover, the composite hydrogel electrolyte exhibits a high ionic conductivity of 5.89 × 10-2 S cm-1 and a Zn2+ transference number of 0.58. Consequently, the Zn‖Zn symmetric cell with the composite hydrogel electrolyte shows a stable cycle life of more than 500 h. Meanwhile, the Zn‖NH4V4O10 coin cell with the composite hydrogel electrolyte retains a high specific capacity of approximately 200 mA h g-1 after 600 cycles at 2 A g-1. The Zn‖NVO pouch cell based on the composite hydrogel electrolyte also shows a high specific capacity of 246.1 mA h g-1 at 0.5 A g-1 and retains 70.7% of its initial capacity after 150 cycles. The pouch cell performs well at different bending angles and exhibits a capacity retention rate of 98% after returning to its initial state from 180° folding. This work aims to construct high-performance hydrogel electrolytes using low-cost natural materials, which may provide a solution for the application of ZIBs in flexible biocompatible devices.

Novel Zinc/Silver Ions-Loaded Alginate/Chitosan Microparticles Antifungal Activity against Botrytis cinerea

Addressing the growing need for environmentally friendly fungicides in agriculture, this study explored the potential of biopolymer microparticles loaded with metal ions as a novel approach to combat fungal pathogens. Novel alginate microspheres and chitosan/alginate microcapsules loaded with zinc or with zinc and silver ions were prepared and characterized (microparticle size, morphology, topography, encapsulation efficiency, loading capacity, and swelling behavior). Investigation of molecular interactions in microparticles using FTIR-ATR spectroscopy exhibited complex interactions between all constituents. Fitting to the simple Korsmeyer-Peppas empirical model revealed the rate-controlling mechanism of metal ions release from microparticles is Fickian diffusion. Lower values of the release constant k imply a slower release rate of Zn2+ or Ag+ ions from microcapsules compared to that of microspheres. The antimicrobial potential of the new formulations against the fungus Botrytis cinerea was evaluated. When subjected to tests against the fungus, microspheres exhibited superior antifungal activity especially those loaded with both zinc and silver ions, reducing fungal growth up to 98.9% and altering the hyphal structures. Due to the slower release of metal ions, the microcapsule formulations seem suitable for plant protection throughout the growing season. The results showed the potential of these novel microparticles as powerful fungicides in agriculture.

Recent insights into polysaccharide-based hydrogels and their potential applications in food sector: A review

Hydrogels are ideal for various food applications because of their softness, elasticity, absorbent nature, flexibility, and hygroscopic nature. Polysaccharide hydrogels are particularly suitable because of the hydrophilic nature, their food compatibility, and their non-immunogenic character. Such hydrogels offer a wide range of successful applications such as food preservation, pharmaceuticals, agriculture, and food packaging. Additionally, polysaccharide hydrogels have proven to play a significant role in the formulation of food flavor carrier systems, thus diversifying the horizons of newer developments in food processing sector. Polysaccharide hydrogels are comprised of natural polymers such as alginate, chitosan, starch, pectin and hyaluronic acid when crosslinked physically or chemically. Hydrogels with interchangeable, antimicrobial and barrier properties are referred to as smart hydrogels. This review brings together the recent and relevant polysaccharide research in these polysaccharide hydrogel applications areas and seeks to point the way forward for future research and interventions. Applications in carrying out the process of flavor carrier system directly through their incorporation in food matrices, broadening the domain for food application innovations. The classification and important features of polysaccharide-based hydrogels in food processing are the topics of the current review study.

IgG functionalized polymeric nanoparticles for oral insulin administration

The oral route is the best way to administer a drug; however, fitting peptide drugs in this route is a major challenge. In insulin cases, less than 0.5% of the administered dose achieves systemic circulation. Oral delivery by nanoparticles can increase insulin permeability across the intestinal epithelium while maintaining its structure and activity until release in the gut. This system can be improved to increase permeability across intestinal cells through active delivery. This study aimed to improve a nanoparticle formulation by promoting functionalization of its surface with immunoglobulin G to increase its absorption by intestinal epithelium. The characterization of formulations showed an adequate size and a good entrapment efficiency. Functionalized nanoparticles led to a desirable increase in insulin release time. Differential scanning calorimetry, infrared spectroscopy and paper chromatography proved the interactions of nanoparticle components. With immunoglobulin G, the nanoparticle size was slightly increased, which did not show aggregate formation. The developed functionalized nanoparticle formulation proved to be adequate to carry insulin and potentially increase its internalization by epithelial gut cells, being a promising alternative to the existing formulations for orally administered low-absorption peptides.

Bio-Nanocomposite Hydrogel Based on Zinc Alginate/Graphene Oxide: Morphology, Structural Conformation, Thermal Behavior/Degradation, and Dielectric Properties

Bio-nanocomposite hydrogels based on sodium alginate (SA) as polymer matrix and graphene oxide (GO) nanosheets with zinc as crosslinking agent were synthesized with the aim of incorporating the intrinsic properties of their constituents (bioactivity and antimicrobial activity). Thus, stable and highly interconnected networks were obtained from GO nanosheets dispersed in SA matrices through interactions with low amounts of zinc. The GO nanosheets were successfully incorporated into the alginate matrix in the form of a complex nano-network involving different interactions: Bonds between alginate chains induced by Zn ions (egg box structure), interactions between GO nanosheets through Zn ions and hydrogen bonds between alginate chains, and GO nanosheets. The molecular interactions and morphology were confirmed by Fourier-transform infrared spectroscopy and transmission electron microscopy. The composite’s structural organization showed enhanced thermal stability. The glass transition temperature shifted to a higher temperature due to the reduced mobility induced by additional crosslinking bonds after incorporating the GO nanosheets and Zn into the polymer matrix. Finally, the dielectric behavior revealed that charge carrier mobility was hampered by the compact structure of the nanonetwork, which reduced conductivity. The combined properties of these nanocomposite hydrogels make them attractive biomaterials in the field of regenerative medicine and wound care since both surface bioactivity and antibacterial behavior are two critical factors involved in the success of a biomaterial.

Surfactant modified alginate composite gels for controlled release of protein drug

This study aims to modify alginate with sodium dodecyl sulfate (SDS) to reduce the release of oral protein in the acidic stomach environment and transport it to the colon medium. Bovine serum albumin (BSA), which was chosen as a model protein, was loaded into surfactant modified calcium alginate beads (SDS/Ca-Alg). The encapsulation efficiency of BSA in SDS/Ca-Alg beads was found significantly higher (96.3%) compared to that of beads without SDS. The most remarkable result is that protein release from the modified gel in the stomach environment was significantly reduced compared to protein release from the plain alginate gel. At the same time, the release time of the whole drug in the intestinal environment was significantly prolonged. The SDS-modified alginate beads are proposed as suitable carriers for the passage of orally taken protein-type drugs into the colon medium by preventing their degradation in acidic gastric fluid.

Hydrogels: soft matters in photomedicine

Photodynamic therapy (PDT), a shining beacon in the realm of photomedicine, is a non-invasive technique that utilizes dye-based photosensitizers (PSs) in conjunction with light and oxygen to produce reactive oxygen species to combat malignant tissues and infectious microorganisms. Yet, for PDT to become a common, routine therapy, it is still necessary to overcome limitations such as photosensitizer solubility, long-term side effects (e.g., photosensitivity) and to develop safe, biocompatible and target-specific formulations. Polymer based drug delivery platforms are an effective strategy for the delivery of PSs for PDT applications. Among them, hydrogels and 3D polymer scaffolds with the ability to swell in aqueous media have been deeply investigated. Particularly, hydrogel-based formulations present real potential to fulfill all requirements of an ideal PDT platform by overcoming the solubility issues, while improving the selectivity and targeting drawbacks of the PSs alone. In this perspective, we summarize the use of hydrogels as carrier systems of PSs to enhance the effectiveness of PDT against infections and cancer. Their potential in environmental and biomedical applications, such as tissue engineering photoremediation and photochemistry, is also discussed.

Textural, mechanical, and microstructural properties of restructured pimiento alginate-guar gels

Textural, mechanical, microstructural, and thermal properties of reconstituted pimiento alginate-guar gels subjected to thermal and mechanical stresses during pasteurization process were investigated. Alginate-guar gelling system at ratio 2:1 at different calcium chloride concentrations (2-8%) and varying acid conditions including citric and lactic acid 1% were evaluated. Textural profile analysis parameters viz. hardness, springiness, gumminess, cohesiveness, adhesiveness as well as mechanical properties, structural, thermal, and morphological characteristics of pimiento strips were examined. Gel strength and elasticity of pimiento strips were increased at higher calcium levels. Fracturability was decreased clearly revealed the gel system, regain its strength in spite of high pulp content (25%) and can maintain its own structure. Increase in hardness and reduction in springiness showed loss of elasticity, which may be attributed to the gel shrinkage during thermal processing, making it more compact and dense. Therefore, the restructured pimiento strips were completely thermo stable at pasteurization temperature. By increasing alginate and calcium level in the pimiento strip, glass transition temperature was reduced from 112 to 98°C. Fourier transform infrared spectroscopy studies confirmed that the gel network structure at acidic conditions was stable and acid type did not has significant effect on the chemical interactions. The microstructural results showed ellipsoidal and compact structure in which can be an evidence of high elasticity and rigidity of pimiento gels. These results completely approved the high elasticity and rigidity of the pimiento strips and their ability to sustain successfully thermal and mechanical stresses with appreciable textural integrity during processing such as pasteurization. PRACTICAL APPLICATIONS: Restructured pimiento strip for stuffing into cocktail olives is a challenging problem in binary composite hydrogels of alginate and guar gum. The strips should be designed to be strong enough to handle mechanically and cut easily without tearing. Furthermore, it had to withstand to pasteurization process and be flexible to bend like a hairpin into the pit hole of olive. In addition, it also had low syneresis and shrinkage that the strips not fall out of the olive hole during storage. In the view point of marketing and nutritional aspects, it is more advantageous to develop a restructured fruit gel systems several times higher than the limiting 10% pulp because of its weak structure. Therefore, alginate-gel systems containing 25% pimiento pulp were evaluated at different levels of calcium chloride and thermal processing.

Synergistic effect of divalent cations in improving technological properties of cross-linked alginate beads

Gelling solution parameters are some of the most important variables in ionotropic gelation and consequently influence the technological characteristics of the product. To date, only a few studies have focused on the simultaneous use of multiple cations as gelling agents. With the aim to deeply explore this possibility, in this research we investigated the effect of two divalent cations (Ca²⁺ and Zn²⁺) on alginate beads formation and properties. Alginate beads containing prednisolone (P) as model drug were prepared by prilling technique. The main critical variables of the ionotropic gelation process i.e. composition of the aqueous feed solutions (sodium alginate and prednisolone concentration) and cross-linking conditions (Ca²⁺, Zn²⁺ or Ca²⁺+Zn²⁺), were studied. The obtained beads were characterized and their in vitro release performances were assessed in conditions simulating the gastrointestinal environment. Results evidenced a synergistic effect of the two cations, affecting positively both the encapsulation efficiency and the ability of the alginate polymeric matrix to control the drug release. A Ca²⁺/Zn²⁺ ratio of 4:1, in fact, exploited the Ca²⁺ ability of establish quicker electrostatic interactions with guluronic groups of alginate and the Zn²⁺ ability to establish covalent-like bonds with carboxylate groups of both guluronic and mannuronic moieties of alginate.

Synthesis and Characterization of PLGA Shell Microcapsules Containing Aqueous Cores Prepared by Internal Phase Separation

The preparation of microcapsules consisting of poly(D,L-lactide-co-glycolide) (PLGA) polymer shell and aqueous core is a clear challenge and hence has been rarely addressed in literature. Herein, aqueous core-PLGA shell microcapsules have been prepared by internal phase separation from acetone-water in oil emulsion. The resulting microcapsules exhibited mean particle size of 1.1 ± 0.39 μm (PDI = 0.35) with spherical surface morphology and internal poly-nuclear core morphology as indicated by scanning electron microscopy (SEM). The incorporation of water molecules into PLGA microcapsules was confirmed by differential scanning calorimetry (DSC). Aqueous core-PLGA shell microcapsules and the corresponding conventional PLGA microspheres were prepared and loaded with risedronate sodium as a model drug. Interestingly, aqueous core-PLGA shell microcapsules illustrated 2.5-fold increase in drug encapsulation in comparison to the classical PLGA microspheres (i.e., 31.6 vs. 12.7%), while exhibiting sustained release behavior following diffusion-controlled Higuchi model. The reported method could be extrapolated to encapsulate other water soluble drugs and hydrophilic macromolecules into PLGA microcapsules, which should overcome various drawbacks correlated with conventional PLGA microspheres in terms of drug loading and release.

Natural alginate biopolymer montmorillonite clay composites for vitamin B2 delivery

This work describes the in vitro release of a small drug, riboflavin, from novel calcium and barium crosslinked alginate–montmorillonite composite beads via oral route. Effect of crosslinking cation, concentration of montmorillonite and media on encapsulation efficiencies, and release profiles of riboflavin were studied. Beads were characterized using gravimetric swelling ability study, Fourier transform infrared spectroscopy, and scanning electron microscopy. Results indicate that addition of montmorillonite increases the encapsulation efficiencies and slows down the release rates significantly.

Enhanced drug encapsulation and extended release profiles of calcium-alginate nanoparticles by using tannic acid as a bridging cross-linking agent

Calcium alginate nanoparticles (NPs) suffer from sub-optimal stability in bio-relevant media leading to low drug encapsulation efficiency and uncontrolled release profiles. To sort out these drawbacks, a novel approach is proposed herein based on introducing tannic acid into these NPs to act as a bridging cross-linking aid agent. Calcium-alginate NPs were prepared by the ionotropic gelation method and loaded with diltiazem hydrochloride as a model drug. These NPs were characterized in terms of particle size, zeta potential, and morphology, and results were explained in accordance with Fourier-transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC). The incorporation of tannic acid led to more than four folds increase in drug encapsulation efficiency (i.e. from 15.3% to 69.5%) and reduced burst drug release from 44% to around 10% within the first 30 min. These findings suggest the possibility of improving the properties of Ca-alginate NPs by incorporating cross-linking aid agents under mild conditions.

In vitro liberation of indomethacin from chitosan gels containing microemulsion in different dissolution mediums

The objective of this research is to outline the liberation of indomethacin from different chitosan gels containing O/W microemulsion. The influence of surfactant, sodium lauryl sulfate, in two concentrations (0.5% and 0.75%, w/w) was determined in dissolution medium on the release of indomethacin, which was used as poor water-soluble model drug. Chitosan gels were prepared in four different concentrations of chitosan-1%, 1.5%, 2%, and 3% (w/w). Microemulsion enhanced the liberation of the indomethacin from chitosan gels into all dissolution mediums. Adding the surfactant into phosphate-buffered saline decreased the amount of liberated indomethacin from microemulsion, gel mixture, but increased the drug liberation from pure chitosan gels. It was detected that with the increased concentration of chitosan in the samples, the amount of indomethacin liberated (p < 0.05) also increased. A conclusion was drawn that the liberation of indomethacin from chitosan gels was influenced by increased pH of the samples. The high viscosity induced a higher release of indomethacin from 3% (w/w) chitosan hydrogel at pH 5.8 as compared with 3% (w/w) chitosan hydrogel at pH 3.8. The highest percentage of released indomethacin was determined when a mixture of microemulsion gel with higher chitosan content was used.

Zinc cross-linked hydroxamated alginates for pulsed drug release

INTRODUCTION

Alginates can be tailored chemically to improve solubility, physicochemical, and biological properties and its complexation with metal ion is useful for controlling the drug release.

MATERIALS AND METHODS

Synthesized N,O-dimethyl, N-methyl, or N-Benzyl hydroxylamine derivatives of sodium alginate were subsequently complexed with zinc to form beads. Hydroxamation of sodium alginate was confirmed by Fourier transform infra-red spectroscopy (FTIR) and differential scanning calorimetry (DSC).

RESULTS

The synthesized polymeric material exhibited reduced aqueous, HCl and NaOH solubility. The hydroxamated derivatives demonstrated pulsed release where change in pH of the dissolution medium stimulated the atenolol release.

CONCLUSION

Atenolol loaded Zn cross-linked polymeric beads demonstrated the sustained the plasma drug levels with increased half-life. Although the synthesized derivatives greatly altered the aqueous solubility of sodium alginate, no significant differences in in vitro and in vivo atenolol release behavior amongst the N,O-dimethyl, N-methyl, or N-Benzyl hydroxylamine derivatives of sodium alginate were observed.

Bile salt-reinforced alginate-chitosan beads

A polymeric delayed release protein delivery system was investigated with albumin as the model drug. The polysaccharide chitosan was reacted with sodium alginate in the presence of calcium chloride to form beads with a polyelectrolyte. In this study, attempts were made to extend albumin release in the phosphate buffer at pH 6.8 from the alginate-chitosan beads by reinforcing the matrix with bile salts. Sodium taurocholate was able to prevent albumin release at pH 1.2, protecting the protein from the acidic environment and extending the total albumin release at pH 6.8. This effect was explained by an interaction between the permanent negatively charged sulfonic acid of sodium taurocholate with the amino groups of chitosan. Mild formulation conditions, high bovine serum albumin (BSA) entrapment efficiency, and resistance to gastrointestinal release seem to be synergic and promising factors toward the development of an oral protein delivery form.

Mechanical Stability of Ionotropic Alginate Beads

In a series of experiments we measured the mechanical properties of single alginate beads by means of squeezing experiments between two parallel plates. We used multivalent counter-ions as cross-linking molecules for the formation of three dimensional alginate gels. In this article we examined pure Fe(II) (ferric), Fe(III) (ferrous) and Ca(II) (calcium) ions as cross-linking agents and different mixtures between these charged compounds. The results of squeezing experiments showed that capsules formed with pure ferrous ions were less stable than particles which were cross-linked with calcium or ferric ions. It turned out that at equal molar concentrations calcium and ferrous ions formed stronger gels than ferric ions. In addition to squeezing capsule experiments we also investigated different particles by optical microscopy and scanning electron microscopy. Experiments of Energy-dispersive X-ray spectroscopy (EDAX) show different compositions of these beads.