Opening the Egg Box: NMR spectroscopic analysis of the interactions between s-block cations and kelp monosaccharides

A Novel Alginate Film Based on Nanocoating Approach for Enteric-Release Tablets

The objective of this study was to propose a new coating film for biodegradable polymers and environmentally friendly processing. Here, a novel implementation of solid lipid nanoparticles (SLN) into a biodegradable alginate (ALG) film composition created a new gastric-resistant film for an enteric-release tablet. Experiments were performed on a water-soluble substance (thiamine nitrate) to characterize the effects of SLN upon the addition of the ALG coating formulation. The coated tablets or cast films were characterized based on delayed-release properties, surface morphology, moisture resistance, and chemical interactions. The SLN-ALG film displayed gastric-resistant properties (< 10% drug substance dissolved at pH 1.2) and rapid disintegration in the intestinal medium (pH 6.8). Morphological analysis using a microscope and scanning electron microscope confirmed the uniformity and smoothness of the SLN-ALG film, which improved the mechanical properties of the film. Fourier transform infrared spectroscopy and differential scanning calorimetry indicated that SLN contributed to the formation of the film, which maintained free carboxylic groups, making the SLN-ALG film a higher acid resistance, but soluble in pH 6.8 buffer. These promising results suggest a novel nanotechnology-based coating formulation for various enteric-release dosage forms. Because of their biodegradability, the proposed ingredients and processes are safe and environment-friendly.

Bilayer Hydrogels for Wound Dressing and Tissue Engineering

A large number of different skin diseases such as hits, acute, and chronic wounds dictate the search for alternative and effective treatment options. The wound healing process requires a complex approach, the key step of which is the choice of a dressing with controlled properties. Hydrogel-based scaffolds can serve as a unique class of wound dressings. Presented on the commercial market, hydrogel wound dressings are not found among proposals for specific cases and have a number of disadvantages—toxicity, allergenicity, and mechanical instability. Bilayer dressings are attracting great attention, which can be combined with multifunctional properties, high criteria for an ideal wound dressing (antimicrobial properties, adhesion and hemostasis, anti-inflammatory and antioxidant effects), drug delivery, self-healing, stimulus manifestation, and conductivity, depending on the preparation and purpose. In addition, advances in stem cell biology and biomaterials have enabled the design of hydrogel materials for skin tissue engineering. To improve the heterogeneity of the cell environment, it is possible to use two-layer functional gradient hydrogels. This review summarizes the methods and application advantages of bilayer dressings in wound treatment and skin tissue regeneration. Bilayered hydrogels based on natural as well as synthetic polymers are presented. The results of the in vitro and in vivo experiments and drug release are also discussed.

Competing Effects of Hydration and Cation Complexation in Single-Chain Alginate

Alginic acid, a naturally occurring anionic polyelectrolyte, forms strong physically cross-linked hydrogels in the presence of metal cations. The latter engage in electrostatic interactions that compete with intra- and intermolecular hydrogen bonds, determining the gel structure and properties of the system in aqueous media. In this study, we use all-atom molecular dynamics simulations to systematically analyze the interactions between alginic acid chains and Na⁺ and Ca²⁺ counterions. The formed alginates originate from the competition of intramolecular hydrogen bonding and water coordination around the polyelectrolyte. In contrast to the established interpretation, we show that calcium cations strongly bind to alginate by disrupting hydrogen bonds within (1 → 4)-linked β-d-mannuronate (M) residues. On the other hand, Na⁺ cations enhance intramolecular hydrogen bonds that stabilize a left-hand, fourfold helical chain structure in poly-M alginate, resulting in stiffer chains. Hence, the traditionally accepted flexible flat-chain model for poly-M sequence is not valid in the presence of Na⁺. The two cations have a distinct effect on water coordination around alginate and therefore on its solubility. While Ca⁺ disrupts water coordination directly around the alginate chains, mobile Na⁺ cations significantly disrupt the second hydration layer.