Green synthesis of κ-carrageenan@Ag submicron-particles with high aqueous stability, robust antibacterial activity and low cytotoxicity

Electron Beam-Supported Fabrication of Biocompatible Silver/iota-Carrageenan for Wound Healing Application

Silver nanoparticles (AgNPs) are a potent antibacterial agent, especially when used to treat bacteria that are multidrug resistant. However, it is challenging to eliminate the hazardous reducing agents that remain in AgNPs produced by the conventional chemical reduction process. To overcome these challenges, the presented research demonstrates the fabrication of AgNPs using iota-carrageenan (ι-carra) as a carbohydrate polymer using electron beam (EB) irradiation. Well-characterized ι-carra@AgNPs have a face-centered cubic (FCC) structure with spherical morphology and an average size of 26 nm. Herein we explored the approach for fabricating ι-carra@AgNPs that is suitable for scaling up the production of nanoparticles that exhibit excellent water stability. Further, the optimized ι-carra@AgNPs exhibited considerable antibacterial activity of 40% and 30% inhibition when tested with Gram-negative Escherichia coli ATCC 43895 and Gram-positive Staphylococcus aureus (S. aureus) (ATCC 6538), respectively, and low cytotoxicity at 10-50 μg/mL. To establish the potential biomedical application, as proof of the concept, the ι-carra@AgNPs showed significant antibiofilm activity at 20 μg/mL and also showed 95% wound healing abilities at 50 μg/mL compared to the nontreated control groups. Electron beam assisted ι-carra@AgNPs showed significant beneficial effects against specific bacterial strains and may provide a guide for the development of new antibacterial materials for wound dressing for large-scale production for biomedical applications.

Photocatalytic Ag/AgBr-MBG for Rapid Antibacterial and Wound Repair

In daily life and during surgery, the skin, as the outermost organ of the human body, is easily damaged to form wounds. If the wound was infected by the bacteria, especially the drug-resistant bacteria such as methicillin-resistant staphylococcus aureus (MRSA), it was difficult to recover. Therefore, it was important to develop the safe antimicrobial strategy to inhibit bacterial growth in the wound site, in particular, to overcome the problem of bacterial drug resistance. Here, the Ag/AgBr-loaded mesoporous bioactive glass (Ag/AgBr-MBG) was prepared, which had excellent photocatalytic properties under simulated daylight for rapid antibacterial activity within 15 min by generating reactive oxygen species (ROS). Meanwhile, the killing rate of Ag/AgBr-MBG against MRSA was 99.19% within 15 min, which further reduced the generation of drug-resistant bacteria. In addition, Ag/AgBr-MBG particles could disrupt bacterial cell membranes, showing the broad-spectrum antibacterial properties and promoting tissue regeneration and infected wound healing. Ag/AgBr-MBG particles might have potential applications as a light-driven antimicrobial agent in the field of biomaterials.

Green Synthesis of Flower-Like Carrageenan-Silver Nanoparticles and Elucidation of Its Physicochemical and Antibacterial Properties

Herein, we report the green synthesis of flower-like carrageenan-silver nanoparticles (c-AgNPs) through a facile hydrothermal reaction at 90 °C for 2 h. The reduction of silver nitrate (AgNO₃) to c-AgNPs was evident by the colour change of the solution from colourless to dark brown and further confirmed by a UV-Vis surface plasmon resonance (SPR) peak at ~420 nm. The FTIR spectra showed that the abundance of functional groups present in the carrageenan were responsible for the reduction and stabilisation of the c-AgNPs. The XRD pattern confirmed the crystalline nature and face-centred cubic structure of the c-AgNPs, while the EDX analysis showed the presence of a high composition of elemental silver (85.87 wt%). Interestingly, the morphological characterisations by SEM and FE-SEM revealed the formation of flower-like c-AgNPs composed of intercrossed and random lamellar petals of approximately 50 nm in thickness. The growth mechanism of flower-like c-AgNPs were elucidated based on the TEM and AFM analyses. The c-AgNPs displayed promising antibacterial properties against E. coli and S. aureus, with zones of inhibition ranging from 8.0 ± 0.0 to 11.7 ± 0.6 mm and 7.3 ± 0.6 to 9.7 ± 0.6 mm, respectively, as the concentration of c-AgNPs increased from 0.1 to 4 mg/mL.

Retrospective analysis of the key molecules involved in the green synthesis of nanoparticles

Emerging nanotechnology leads to success in synthesizing and applying nanoparticles (NPs) using the green-chemistry approach. NPs synthesized using naturally derived materials are a potential alternative to chemical and physical methods because they are simple, cost-effective, eco-friendly, and lower the possibility of hazardous residues being released into the environment. Furthermore, NPs synthesized using the green synthesis approach are stable and biocompatible. However, because natural extracts contain a diverse spectrum of bioactive components, it is difficult to pinpoint the specific component involved in NP formation. Furthermore, the bioactive component contained in the extract changes based on a number of environmental factors; therefore, several studies began with the synthesis of NPs using a pure compound isolated from diverse natural sources. Hence, the present review paper makes an effort to retrospectively analyze the key compounds of the extracts which are responsible for the synthesis of the NPs. The analysis was carried out based on the physicochemical characteristics and biological activities of NPs synthesized from either the extract or the pure compounds. These pure-compound-based NPs were studied for their antimicrobial, antibiofilm, anti-inflammatory, anticancer, and antioxidant properties. In addition, the present review also describes progress in the study of pure compound-based numerous biological activities and the underlying mechanisms of action.

Green Extraction of Carrageenans from Mastocarpus stellatus

The recovery of biopolymers from natural resources using eco-friendly extraction technologies that enhance their mechanical properties has gained attention in recent years. In this context, this work deals with the isolation of hybrid carrageenans from Mastocarpus stellatus red seaweed using subcritical water extraction operating in a wide range of thermal conditions (70–190 °C). The extracted biopolymers were analyzed by means of either Fourier-Transform infrared, nuclear magnetic resonance, rheological or cell viability assays. In parallel, the fundamental chemical composition of the seaweed used as raw material, as well as the main phytochemical properties of the soluble liquid extracts, were also studied. Results indicated that thermal extraction conditions significantly affected the rheological behavior of the recovered hybrid carrageenans. The hybrid carrageenan extraction yields varied, with results between 10.2 and 30.2% being the highest values obtained at hydrothermal treatment of 130 °C. A wide palette of viscous features was identified for recovered hybrid carrageenans, with the strongest rheology properties observed at the same temperature. It should be remarked that the maximum inhibitory effect was also obtained at 130 °C for both the ovarian carcinoma cell line (A2780) (65%, IC₅₀: 0.31 mg/mL) and lung carcinoma cell line (A549) (59%, IC₅₀: 0.41 mg/mL).

Silver ion loaded 3-aminopropyl trimethoxysilane -modified Fe3O4 nanoparticles for the fabrication of carrageenan-based active packaging films

Fe₃O₄ nanoparticle loaded with silver ion was prepared as a more efficient, safer, and less environmentally hazardous silver-based antibacterial nanomaterial. The Fe₃O₄ nanoparticle was modified using 3-aminopropyl trimethoxysilane (APTMS) to enhance the silver ion adsorption capacity and antibacterial activity. Silver ions were adsorbed on pristine Fe₃O₄ and Fe₃O₄@NH₂ to enhance antibacterial activity. Energy dispersive spectroscopy (EDS) results showed that Fe₃O₄ adsorbed 2.74 wt% of Ag, whereas Fe₃O₄@NH₂ adsorbed 9.88 wt%. Pristine Fe₃O₄NP, silver ion loaded Fe₃O₄ (Fe₃O₄-Ag), and silver ion loaded Fe₃O₄@NH₂ (Fe₃O₄@NH₂-Ag) were used to manufacture carrageenan-based composite films. Compared with Fe₃O₄-Ag, Fe₃O₄@NH₂-Ag exhibited stronger antimicrobial activity against E. coli (8.82 vs. 5.02 log reduction) and L. monocytogenes (10.09 vs. 3.93 log reduction). While the addition of Fe₃O₄ significantly reduced the WCA of the carrageenan films from 61.1 ± 5.4 ° to 37.2 ± 2.1 °, the additions of Fe₃O₄-Ag and Fe₃O₄@NH₂-Ag reduced the WCA of the film to a lesser extent (56.9 ± 4.6 ° and 56.9 ± 4.6 °, respectively). Fe₃O₄NP also improved the thermal stability of carrageenan over Fe₃O₄@NH₂-Ag (22 °C vs. 13 °C) and UV blocking properties (T₂₈₀, 0.1 ± 0.0 % vs. 3.3 ± 1.5 %).

Functionalization of an Electroactive Self-Healing Polypyrrole-Grafted Gelatin-Based Hydrogel by Incorporating a Polydopamine@AgNP Nanocomposite

Hydrogels are considered a promising wound dressing owing to their ability to absorb wound exudates and their moist network structure for skin regeneration. It is of great significance to give added multiple functions to hydrogels for wound healing. In this paper, we present a gelatin-based hydrogel with self-healing ability, conductivity, and antibacterial and antioxidant activities. Dopamine was added into an alkaline solution to polymerize into polydopamine (PDA), which was used to reduce AgNO₃ into Ag nanoparticles (AgNPs) to gain a PDA@AgNP composite. Polypyrrole-grafted gelatin (PPyGel) was dissolved in a PDA@AgNP solution and ferric ions were used as a cross-linking agent to form PDA@AgNPs-PPyGel-Fe hydrogels. The as-prepared hydrogels are soft and ductile and exhibit porous structures with pore sizes from 20 to 50 μm. The hydrogels have high water absorption ability, indicating the potential to absorb wound exudates. PPy and Fe³⁺ endow the hydrogels with slightly higher conductivity than that of skin tissue, indicating the ability to effectively transmit bioelectric signals for skin regeneration. The ionic interactions and hydrogen bonding in hydrogels make them possess self-healing ability, and the self-healing process can be completed in 30 min. PDA confers hydrogels with effective antioxidant activities, while AgNPs endow hydrogels with good antibacterial activities. Moreover, the hydrogels possess good blood compatibility and cytocompatibility. In sum, the developed hydrogel has potential applications as wound dressings.

Ultrasonically developed silver/iota-carrageenan/cotton bionanocomposite as an efficient material for biomedical applications

In this approach, we assembled AgNps on cotton by using iota-carrageenan as a carbohydrate polymer under ultrasonic waves. UV-Vis spectroscopy revealed that iota-carrageenan free radicals increased the absorbance values of AgNps at 438 nm under ultrasonic vibration. We also observed an effective reduction of AgNps by color hue changes in the colloidal dispersions, ranging from pale to dark yellow. Interestingly, the zeta potential values for the AgNps changed from -8.5 to -45.7 mV after incorporation with iota-carrageenan. Moreover, iota-carrageenan reduced the average particle sizes of AgNps/iota-carrageenan nanocomposite particles. Fourier transform infrared (FTIR) spectra proved the successful fabrication of AgNps/iota-carrageenan/cotton nanocomposites by shifting two bands at 3257 and 990 cm^-1. Quantum Chemistry and Molecular Dynamics demonstrated strong interactions between AgNps and iota-carrageenan by changes in the bond lengths for CC, CH, CO, SO. Furthermore, new energy levels were generated in iota-carrageenan's molecules by exciting electrons under ultrasonic vibration. According to the thermal gravimetric analysis (TGA) results, fabrication of AgNps/iota-carrageenan on cotton reduced the thermal stability of the resultant AgNps/iota-carrageenan/cotton nanocomposites. The average friction coefficient values of nanocomposite samples were increased in weft-to-warp direction that can be an advantage for wound healing, antimicrobial treatment and drug delivery applications. We did not observe reduction in the mechanical properties of our AgNps incorporated nanocomposites. Furthermore, the samples were tested for possible cytotoxicity against primary human skin fibroblast cells and no toxicity was observed.

Nanofibrous ε-polycaprolactone scaffolds containing Ag-doped magnetite nanoparticles: Physicochemical characterization and biological testing for wound dressing applications in vitro and in vivo

Skin wounds can lead to numerous complications with dangerous health consequences. In this work, magnetite nanoparticles were doped with different concentrations of antimicrobial silver (Ag) ions and incorporated into the electrospun nanofibrous ε-polycaprolactone (PCL) scaffolds. Nanoparticles and scaffolds with various Ag contents were characterized using a range of physicochemical techniques. Ag entered magnetite as cations and preferentially positioned at tetrahedral sites, introducing lattice distortions and topographic irregularities. Amorphization of the structure due to accommodation of Ag expanded the lattice in the bulk and contracted it on the surface, where broadened distribution of Fe–O coordinations was detected. Promoting spin canting and diminishing the double exchange interaction through altered distribution of ferric and ferrous ions, Ag softened the magnetism of magnetite. By making the nanoparticle structure more defective, Ag modified the interface with the polymer and promoted the protrusion of the nanoparticles from the surface of the polymeric nanofibers, thus increasing their roughness and hydrophilicity, with positive repercussions on cell adhesion and growth. Both the viability of human melanocytes and the antibacterial activity against E. coli and S. aureus increased with the concentration of Ag in the magnetite phase of the scaffolds. Skin wound healing rate in rats also increased in direct proportion with the concentration of Ag in the magnetite phase, and no abnormalities in the dermal and epidermal tissues were visible on day 10 in the treatment group. These results imply an excellent potential of these composite nanofibrous scaffolds for use as wound dressings and in other reconstructive skin therapies.

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Electrospun nanofibrous polymeric wound dressings interspersed with magnetite nanoparticles doped with Ag ions were fabricated.

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Detailed physicochemical characterization is provided with aid of diffractometric, spectroscopic and microscopic techniques.

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Both the viability of melanocytes and the antibacterial activity increased with the addition of Ag ions.

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Skin wound healing rate in rats increased to 51 and 92 % on day 10 for dressings without and with Ag, respectively, relative to control.

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Animals treated with Ag-doped dressings displayed no atrophy of sebaceous glands and necrosis of hair follicles of control animals.

The role of deep eutectic solvents and carrageenan in synthesizing biocompatible anisotropic metal nanoparticles

Plasmonic metal nanoparticles are widely used for many applications due to their unique optical and chemical properties. Over the past decade, anisotropic metal nanoparticles have been explored for imaging, sensing, and diagnostic applications. The variations and flexibility of tuning the size and shape of the metal nanoparticles at the nanoscale made them promising candidates for biomedical applications such as therapeutics, diagnostics, and drug delivery. However, safety and risk assessment of the nanomaterials for clinical purposes are yet to be made owing to their cytotoxicity. The toxicity concern is primarily due to the conventional synthesis route that involves surfactants as a structure-directing agent and as a capping agent for nanoparticles. Wet chemical methods employ toxic auxiliary chemicals. However, the approach yields monodispersed nanoparticles, an essential criterion for their intended application and a limitation of the green synthesis of nanoparticles using plant extracts. Several biocompatible counterparts such as polymers, lipids, and chitosan-based nanoparticles have been successfully used in the synthesis of safe nanomaterials, but there were issues regarding reproducibility and yield. Enzymatic degradation was one of the factors responsible for limiting the efficacy. Hence, it is necessary to develop a safer and nontoxic route towards synthesizing biocompatible nanomaterials while retaining morphology, high yield, and monodispersity. In this regard, deep eutectic solvents (DESs) and carrageenan as capping agent for nanoparticles can ensure the safety. Carrageenan has the potential to act as antibacterial and antiviral agent, and adds enhanced stability to the nanoparticles. This leads to a multidimensional approach for utilizing safe nanomaterials for advanced biomedical and clinical applications.

Carrageenan: Drug Delivery Systems and Other Biomedical Applications

Marine resources are today a renewable source of various compounds, such as polysaccharides, that are used in the pharmaceutical, medical, cosmetic, and food fields. In recent years, considerable attention has been focused on carrageenan-based biomaterials due to their multifunctional qualities, including biodegradability, biocompatibility, and non-toxicity, in addition to bioactive attributes, such as their antiviral, antibacterial, antihyperlipidemic, anticoagulant, antioxidant, antitumor, and immunomodulating properties. They have been applied in pharmaceutical formulations as both their bioactive and physicochemical properties make them suitable biomaterials for drug delivery, and recently for the development of tissue engineering. This article provides a review of recent research on the various types of carrageenan-based biomedical and pharmaceutical applications.

Direct Investigation of Synthesis of Gold Nanoparticles Using Polyscias scutellaria Leaf Extract in the Hexane-Water System Using the Centrifugal Liquid Membrane-Spectrophotometry Method

The Centrifugal liquid Membrane (CLM) method, which provides an ultra-thin two-phase liquid membrane system in a rotating glass cell, was successfully applied to Green Synthesis from Polyscias scutellaria (PS) capped gold nanoparticles (AuNPs-PS) using a Mangkokan leaf (Polyscias scutellaria) extract as a reducing agent and stabilizer in the hexane-water system. PS extract in hexane fraction as the organic phase has a UV absorption spectrum at the maximum wavelength, λmax of 220 nm, while the precursor of HAuCl4 solution as an aqueous phase has an λmax of 214 nm. Investigation of AuNPs-PS formation was carried out at various concentrations of Mangkokan leaf extract concentration; i.e., 0.001 0.003; 0.005; 0.007 and 0.009%, while the reaction was carried out at various rotational speeds of 5,000-9,000 rpm. The formation and stability of AuNPs-PS were observed from the phenomenon of surface plasmon resonance (SPR) and absorbance changes as measured by a UV-Vis spectrophotometer. The results of measurements using CLM-Spectrophotometry shows the formation of AuNPs-PS in the hexane-water system at λmax of 534 nm.

In-situ synthesis of metal nanoparticles@metal-organic frameworks: Highly effective catalytic performance and synergistic antimicrobial activity

M-NP@Zn-BIF (M-NP = Ag or Cu nanoparticle; Zn-BIF is a zinc-based boron imidazolate framework, Zn₂(BH(2-mim)₃)₂(obb); 2-mim = 2-methylimidazole; obb = 4,4'-oxybis(benzoate)) composites were successfully in-situ synthesized by utilizing the reducing ability of the BH bond contained in the Zn-BIF at room temperature without any additional chemical reduction reagents. These composites (225 μg/mL) exhibited excellent catalytic activity to convert 4-nitrophenol to 4-aminophenol in 2.5 min and 6 min with a conversion rate of 99.9 %, respectively. In addition, Ag@Zn-BIF (50 μg/mL) showed highly synergistic antibacterial activity against both Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) with a bactericidal rate of approximately 99.9 %. An antibacterial mechanism was proposed for the generation of intracellular reactive oxygen species (ROS) levels. Superoxide radicals (O^2-) and hydroxyl radicals (OH) formed during the antibacterial process were shown to accelerate the death of bacteria. They also exhibited highly photocatalytic activity for Rhodamine B (RhB). When the concentration of the composites is 1000 μg/mL, the photocatalytic efficiency of Ag@Zn-BIF and Cu@Zn-BIF increased by 31.62 and 18.13 times compared with Zn-BIF, respectively. All in all, this study developed a simple and versatile integrated platform for the removal of nitrophenols, organic dyes, and the effective inactivation of bacteria in water.

Synthesis of silver nanoparticles using oxidized amylose and combination with curcumin for enhanced antibacterial activity

Many kinds of multi-drug-resistant microorganisms have appeared. Moreover, monotherapy is increasingly no longer adequate for many complicated bacterial infections. Therefore, development of efficient combination antibacterial agent is becoming crucial. Herein, we present a hybrid antibacterial agent with enhanced antibacterial activity and high aqueous dissolubility based on silver nanoparticles and curcumin. The silver nanoparticles were firstly synthesized using oxidized amylose as an environmentally friendly reducing agent and stabilizer. Then, curcumin was added into the above mixture to get the hybrid antibacterial agent. The hybrid antibacterial agent presented high dissolubility in aqueous solution and enhanced antibacterial activity. In addition, the hybrid antibacterial agent presented good antioxidant activity and cell compatibility. Overall, the developed hybrid antibacterial agent has a potential to combat multiple bacteria-induced infections of wound surfaces.