Dialdehyde modification of laminarin for facile synthesis of ultrafine silver nanoparticles with excellent antibacterial and wound healing properties

Scutellaria baicalensis Polysaccharide-Mediated Green Synthesis of Smaller Silver Nanoparticles with Enhanced Antimicrobial and Antibiofilm Activity

Silver nanoparticles (AgNPs) have attracted widespread attention in multidrug-resistant bacterial infections. However, the application of AgNPs synthesized by conventional methods is restricted by its high costs, toxicity, and poor stability. Herein, a water-soluble polysaccharide (Scutellaria baicalensis polysaccharide, SBP) rich in reducing sugars was used as both the reductant and stabilizer to greenly synthesize spherical AgNPs@SBP with smaller particle sizes (11.18 ± 2.50 nm) and higher negative zeta potential (-23.05 ± 2.76 mV), which was favorable to enhance its antimicrobial activity and improve pH and thermal stability. Besides, SBP facilitated the adhesion and penetration of AgNPs@SBP to methicillin-resistant Staphylococcus aureus (MRSA) and carbapenem-resistant Escherichia coli (CREC), thus significantly enhancing its antibacterial activity (increased by 32-fold and 64-fold, respectively). Likewise, AgNPs@SBP at a low concentration (7.8 μg/mL) could effectively penetrate and inhibit nearly 90% of MRSA and CREC biofilm formation. Antimicrobial mechanism studies showed that AgNPs@SBP could lead to more severe cell membrane damage and genetic material leakage by upregulating reactive oxygen species and depolarizing mitochondrial membrane potential, ultimately resulting in the apoptosis of bacteria. Overall, the wrapping of SBP significantly enhanced the antibacterial and antibiofilm activity of AgNPs, which possessed great potential in the prevention and treatment of multidrug-resistant bacterial infections.

Accelerated full-thickness skin wound tissue regeneration by self-crosslinked chitosan hydrogel films reinforced by oxidized CNC-AgNPs stabilized Pickering emulsion for quercetin delivery

BACKGROUND

The non-toxic self-crosslinked hydrogel films designed from biocompatible materials allow for controlled drug release and have gathered remarkable attention from healthcare professionals as wound dressing materials. Thus, in the current study the chitosan (CS) film is infused with oil-in-water Pickering emulsion (PE) loaded with bioactive compound quercetin (Qu) and stabilized by dialdehyde cellulose nanocrystal-silver nanoparticles (DCNC-AgNPs). The DCNC-AgNPs play a dual role in stabilizing PE and are involved in the self-crosslinking with CS films. Also, this film could combine the advantage of the controlled release and synergistic wound-healing effect of Qu and AgNPs.

RESULTS

The DCNC-AgNPs were synthesized using sodium periodate oxidation of CNC. The DCNC-AgNPs were used to stabilize oil-in-water PE loaded with Qu in its oil phase by high speed homogenization. Stable PEs were prepared by 20% v/v oil: water ratio with maximum encapsulation of Qu in the oil phase. The Qu-loaded PE was then added to CS solution (50% v/v) to prepare self-crosslinked films (CS-PE-Qu). After grafting CS films with PE, the surface and cross-sectional SEM images show an inter-penetrated network within the matrix between DCNC and CS due to the formation of a Schiff base bond between the reactive aldehyde groups of DCNC-AgNPs and amino groups of CS. Further, the addition of glycerol influenced the extensibility, swelling ratio, and drug release of the films. The fabricated CS-PE-Qu films were analyzed for their wound healing and tissue regeneration potential using cell scratch assay and full-thickness excisional skin wound model in mice. The as-fabricated CS-PE-Qu films showed great biocompatibility, increased HaCat cell migration, and promoted collagen synthesis in HDFa cells. In addition, the CS-PE-Qu films exhibited non-hemolysis and improved wound closure rate in mice compared to CS, CS-Qu, and CS-blank PE. The H&E staining of the wounded skin tissue indicated the wounded tissue regeneration in CS-PE-Qu films treated mice.

CONCLUSION

Results obtained here confirm the wound healing benefits of CS-PE-Qu films and project them as promising biocompatible material and well suited for full-thickness wound healing in clinical applications.

Laminarin ameliorates iodoacetamide-induced functional dyspepsia via modulation of 5-HT3 receptors and the gut microbiota

Visceral and somatic hypersensitivity is a common cause of functional dyspepsia. Marine bioactive components have been revealed to possess numerous valuable abilities. However, as a kind of polysaccharide extracted from brown algae, the study focused on the biological properties of laminarin is still limited, especially in gastrointestinal disorders. In our study, indicators associated with visceral sensational function and gastrointestinal microecology were determined to investigate the modulatory effects of laminarin on functional dyspepsia induced by iodoacetamide. Mice with visceral hypersensitivity were orally administrated with laminarin (50 and 100 mg per kg bw) for fourteen days. The results indicated that laminarin partly alleviated the dysfunction by regulating corticosterone secretion, the expression of 5HT3 receptors at both protein and mRNA levels, and mechanical transduction through the PIEZO2-EPAC1 axis. Furthermore, laminarin administration moderated the imbalanced gut microbial profile, including modulating the abundance of Bacteroidetes and Firmicutes. Our findings revealed that laminarin may restore the overexpression of 5HT3 receptors, the abnormal mechanical transduction, and impaired gut microecology. In conclusion, we provide evidence to support the utilization of laminarin as the ingredient of complementary and alternative medicine of regulating visceral and somatic hypersensitivity.

Zinc caproate: Ecofriendly synthesis, structural characterization, and antibacterial action

Disease-causing microorganisms such as Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) are among the primary contributors to morbidity and mortality of diarrhea in humans. Considering the challenges associated with antibiotic use, including antimicrobial resistance, this study aimed to develop a novel zinc-based agent for bacterial inactivation. To this end, zinc caproate (ZnCA) was synthesized using caproic acid (CA) and zinc oxide (ZnO) in anhydrous ethanol via the solvothermal method. Structural characterization techniques, including Fourier-transform infrared spectroscopy, single crystal X-ray diffraction analysis, and nuclear magnetic resonance spectroscopy, revealed the bidentate bridging coordination of zinc atoms with CA. The resulting two-dimensional ZnCA network was found to be composed of a distinct lamellar pattern, without any evident inter-layer interactions. Powder X-ray diffraction analysis, elemental analysis, and melting point analysis confirmed that ZnCA had an average particle size of 1.320 µm, a melting point of 147.2 °C, and a purity exceeding 98 %. Remarkably, ZnCA demonstrated potent antibacterial activity against E. coli and S. aureus, which exceeded the antibacterial efficacy of ZnO. ZnCA exerted its antibacterial effects by inhibiting biofilm formation, disrupting cell membrane integrity, increasing cell membrane permeability, and altering intracellular Ca2+-Mg2+-ATPase activity. These findings highlight the potential of ZnCA as a promising antibiotic substitute for the treatment of diarrhea in humans.

Marine polysaccharides: Biological activities and applications in drug delivery systems

The ocean is the common home of a large number of marine organisms, including plants, animals, and microorganisms. Researchers can extract thousands of important bioactive components from the oceans and use them extensively to treat and prevent diseases. In contrast, marine polysaccharide macromolecules such as alginate, carrageenan, Laminarin, fucoidan, chitosan, and hyaluronic acid have excellent physicochemical properties, good biocompatibility, and high bioactivity, which ensures their wide applications and strong therapeutic potentials in drug delivery. Drug delivery systems (DDS) based on marine polysaccharides and modified marine polysaccharide molecules have emerged as an innovative technology for controlling drug distribution on temporal, spatial, and dosage scales. They can detect and respond to external stimuli such as pH, temperature, and electric fields. These properties have led to their wide application in the design of novel drug delivery systems such as hydrogels, polymeric micelles, liposomes, microneedles, microspheres, etc. In addition, marine polysaccharide-based DDS not only have smart response properties but also can combine with the unique biological properties of the marine polysaccharide base to exert synergistic therapeutic effects. The biological activities of marine polysaccharides and the design of marine polysaccharide-based DDS are reviewed. Marine polysaccharide-based responsive DDS are expected to provide new strategies and solutions for disease treatment.

Using halofuginone-silver thermosensitive nanohydrogels with antibacterial and anti-inflammatory properties for healing wounds infected with Staphylococcus aureus

Contamination by pathogens, such as bacteria, can irritate a wound and prevent its healing, which may affect the physical fitness of the infected person. As such, the development of more novel nano-biomaterials able to cope with the inflammatory reaction to bacterial infection during the wound healing process to accelerate wound healing is required. Herein, a halofuginone‑silver nano thermosensitive hydrogel (HTPM&AgNPs-gel) was prepared via a physical swelling method. HTPM&AgNPs-gel was characterized based on thermogravimetric analysis, differential scanning calorimetry, morphology, injectability, and rheological mechanics that reflected its exemplary nature. Moreover, HTPM&AgNPs-gel was further tested for its ability to facilitate healing of skin fibroblasts and exert antibacterial activity. Finally, HTPM&AgNPs-gel was tested for its capacity to accelerate general wound healing and treat bacterially induced wound damage. HTPM&AgNPs-gel appeared spherical under a transmission electron microscope and showed a grid structure under a scanning electron microscope. Additionally, HTPM&AgNPs-gel demonstrated excellent properties, including injectability, temperature-dependent swelling behavior, low loss at high temperatures, and appropriate rheological properties. Further, HTPM&AgNPs-gel was found to effectively promote healing of skin fibroblasts and inhibit the proliferation of Escherichia coli and Staphylococcus aureus. An evaluation of the wound healing efficacy demonstrated that HTPM&AgNPs-gel had a more pronounced ability to facilitate wound repair and antibacterial effects than HTPM-gel or AgNPs-gel alone, and exhibited ideal biocompatibility. Notably, HTPM&AgNPs-gel also inhibited inflammatory responses in the healing process. HTPM&AgNPs-gel exhibited antibacterial, anti-inflammatory, and scar repair features, which remarkably promoted wound healing. These findings indicated that HTPM&AgNPs-gel holds great clinical potential as a promising and valuable wound healing treatment.

Functional bacterial cellulose nanofibrils with silver nanoparticles and its antibacterial application

Bacterial cellulose (BC) with good biocompatibility and superior mechanical properties has broad applications. BC functionalized with silver nanoparticles (AgNPs) has been assessed as an antimicrobial membrane for wound-healing treatment. During the AgNPs synthesis, avoiding the use of toxic chemicals is very necessary for the development of environmentally friendly procedures. Herein, a Komagataeibacter xylinus-based direct biosynthetic method to fabricate D-Saccharic acid potassium salt (SA)-grafted BC (SABC) through in situ bacterial metabolism was firstly explored. Subsequently, the SABC pellicles were immersed in AgNO₃ solution for ion-exchanged process, and the silver nanoparticles (AgNPs) with diameter of ∼25.2 nm were in situ synthesized on SABC nanofiber surfaces by thermal reduction instead of using a reducing agent. The morphology and microstructure of SABC/AgNPs pellicles were analyzed by field-emission scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and X-ray photoelectron spectra. Moreover, antibacterial activity measurement performed against the Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus) by disk diffusion and plate count methods, showed high-efficiency bacteria-killing performance of SABC/AgNPs pellicles. This work proposed a new method by using microbial metabolism to prepare BC pellicles with functional groups, and antimicrobial films containing AgNPs was prepared by thermal reduction, exhibiting valuable prospects in wound healing treatment.