Dextran-based polyelectrolyte multilayers: Effect of charge density on film build-up and morphology

Control of the self-assembly and properties of quaternized dextran/heparin polyelectrolyte multilayer films by the degree of dextran substitution

The layer-by-layer (LbL) assembly of polyelectrolyte multilayer films offers a versatile approach to construct ultrathin films with controlled nanostructures and functionalities. The properties of LbL assemblies are strongly influenced by the intrinsic properties of the polyelectrolytes and the assembly conditions. In this study, we investigated the effect of charge content, concentration, deposition time, and molecular weight of polyelectrolytes on the formation and stability of LbL films composed of quaternized dextran (QDex) with varying degrees of substitution (DS) (30%-90%) and heparin (Hep). Surface plasmon resonance analysis revealed that the introduction of a QDex/tannic acid anchoring bilayer effectively reduced the desorption occurring during the deposition of both strong polyelectrolytes, resulting in continuous, exponential growth of QDex/Hep LbL films. The mass deposition increased with increasing DS of QDex, particularly when the QDex concentration and deposition time were optimized. The quartz crystal microbalance with dissipation (QCM-D) monitoring revealed that increasing DS of QDex led to LbL films with progressively higher apparent elastic modulus and viscosity, indicating a transition from soft, water-rich networks to more rigid, cohesive, and less dissipative structures due to enhanced electrostatic interactions (proved by isothermal titration calorimetry) and reduced chain mobility. Furthermore, spectroscopic ellipsometry analysis of 20-bilayer QDex/Hep assemblies deposited on real silica substrates confirmed the increase in film thickness with increasing DS of QDex, especially after the formation of nine QDex/Hep bilayers, where the film structure became more stable. The obtained findings provide detailed insights into the precise control of film growth and stability, which are essential for potential applications in tissue engineering and biomaterial field.

Porous oxidized dextran sponges for surgical hemostasis and infection control

Surgical procedures frequently result in varying degrees of bleeding and infection, which can impede patient recovery, particularly in situations of limited blood supply. Minimizing surgical blood loss and preventing infections remain crucial clinical challenges. To address these tissues, we developed a porous hemostatic sponge by aldehyde-functionalizing dextran. The high porosity and blood absorption capacity of ODex sponges enables them to effectively concentrate red blood cells, platelets, and coagulation factors, forming a blood clot together with the sponge matrix. The aldehyde groups bind to the amines in the tissue, helping to seal the bleeding site. This innovation significantly reduced clotting times in both in vitro and in vivo experiments. Furthermore, the sponge demonstrated excellent biocompatibility and potent antimicrobial activity. These findings highlight oxidized dextran as a highly promising hemostatic biomaterial with strong antimicrobial capabilities, offering the potential for broad clinical applications.

Glucans and applications in drug delivery

Glucan is a natural polysaccharide widely distributed in cereals and microorganisms that has various biological activities, including immunomodulatory, anti-infective, anti-inflammatory, and antitumor activities. In addition to wide applications in the broad fields of food, healthcare, and biomedicines, glucans hold promising potential as drug delivery carrier materials or ligands. Specifically, glucan microparticles or yeast cell wall particles are naturally enclosed vehicles with an interior cavity that can be exploited to carry and deliver drug payloads. The biological activities and targeting capacities of glucans depend largely on the recognition of glucan moieties by receptors such as dectin-1 and complement receptor 3, which are widely expressed on the cell membranes of mononuclear phagocytes, dendritic cells, neutrophils, and some lymphocytes. This review summarizes the chemical structures, sources, fundamental properties, extraction methods, and applications of these materials, with an emphasis on drug delivery. Glucans are utilized mainly as vaccine adjuvants, targeting ligands and as carrier materials for various drug entities. It is believed that glucans and glucan microparticles may be useful for the delivery of both small-molecule and macromolecular drugs, especially for potential treatment of immune-related diseases.

Emerging Polymer-Based Nanosystem Strategies in the Delivery of Antifungal Drugs

Nanosystems-based antifungal agents have emerged as an effective strategy to address issues related to drug resistance, drug release, and toxicity. Among the diverse materials employed for antifungal drug delivery, polymers, including polysaccharides, proteins, and polyesters, have gained significant attention due to their versatility. Considering the complex nature of fungal infections and their varying sites, it is crucial for researchers to carefully select appropriate polymers based on specific scenarios when designing antifungal agent delivery nanosystems. This review provides an overview of the various types of nanoparticles used in antifungal drug delivery systems, with a particular emphasis on the types of polymers used. The review focuses on the application of drug delivery systems and the release behavior of these systems. Furthermore, the review summarizes the critical physical properties and relevant information utilized in antifungal polymer nanomedicine delivery systems and briefly discusses the application prospects of these systems.

Role of Driving Force on Engineering Layer-by-Layer Protein/Polyphenol Coating with Flexible Structures and Properties

Protein-based coatings are of immense interest due to their rich biological functions. Layer-by-layer (LbL) assembly, as a powerful means of transferring protein functions to the material surface, has received widespread attention. However, the assembly mechanism of protein-based LbL coatings is still far from being explained, not only because of protein structure and function diversity but also characterization limitations. Herein, we monitored in situ the LbL assembly process of tannic acid (TA) and lysozyme (Lyz), a classic pair of polyphenol and protein, by combining quartz crystal microbalance with dissipation monitoring (QCM-D) and spectroscopic ellipsometry (SE). The water content, morphology, mechanical properties, antioxidant activity, and the driving force of TA-Lyz coating engineered under different pH values were analyzed in detail by various techniques. The water content, a key factor in TA-Lyz coatings, increased with increasing assembled pH values, which resulted in a porous morphology, inhomogeneous mechanical distribution, faster assembly growth, and better antioxidant activity in both acellular and cellular levels. In addition, high water content is unfavorable to both entropy and enthalpy changes, and the thermodynamic driving force of TA and Lyz assembly mainly comes from the enthalpy change brought by the noncovalent interaction between TA and Lyz. These results provide new insights into engineering the structure, function, and assembly mechanisms of protein-based coatings.

Dextran Formulations as Effective Delivery Systems of Therapeutic Agents

Dextran is by far one of the most interesting non-toxic, bio-compatible macromolecules, an exopolysaccharide biosynthesized by lactic acid bacteria. It has been extensively used as a major component in many types of drug-delivery systems (DDS), which can be submitted to the next in-vivo testing stages, and may be proposed for clinical trials or pharmaceutical use approval. An important aspect to consider in order to maintain high DDS' biocompatibility is the use of dextran obtained by fermentation processes and with a minimum chemical modification degree. By performing chemical modifications, artefacts can appear in the dextran spatial structure that can lead to decreased biocompatibility or even cytotoxicity. The present review aims to systematize DDS depending on the dextran type used and the biologically active compounds transported, in order to obtain desired therapeutic effects. So far, pure dextran and modified dextran such as acetalated, oxidised, carboxymethyl, diethylaminoethyl-dextran and dextran sulphate sodium, were used to develop several DDSs: microspheres, microparticles, nanoparticles, nanodroplets, liposomes, micelles and nanomicelles, hydrogels, films, nanowires, bio-conjugates, medical adhesives and others. The DDS are critically presented by structures, biocompatibility, drugs loaded and therapeutic points of view in order to highlight future therapeutic perspectives.

Molecular Insights into the Reaction Process of Alkali-Activated Metakaolin by Sodium Hydroxide

When metakaolin (MK) is alkalized with an alkaline activator, it depolymerizes under the action of the alkali. However, the process of MK alkalinization is still unrevealed. Here, we supplied a molecular insight into the process of MK alkalinization through reaction molecular dynamics (MD) simulation. The structure, dynamics, and process of MK alkalinization are systematically investigated. The results showed that the layered structure of MK was destroyed and the silicates in MK were dissolved by sodium hydroxide solution during the alkalinization reaction of MK. The aluminates in MK are not dissolved, indicating that aluminates are more stable than silicates. Moreover, the equilibrium structures of MK with H₂O and MK with NaOH solution show that only when both sodium hydroxide and water are involved in the alkalinization reaction, the silicates in MK undergo depolymerization. Also, the observed final state of MK alkalinization can be recognized as the precursor of alkali-activated materials (AAMs).