Flexible Ternary Combination of Gellan Gum, Sodium Carboxymethyl Cellulose, and Silicon Dioxide Nanocomposites Fabricated by Quaternary Ammonium Silane: Rheological, Thermal, and Antimicrobial Properties

Fabrication of a novel magnetic nanostructure based on cellulose-gellan gum hydrogel, embedded with MgAl LDH as an efficient catalyst for the synthesis of polyhydroquinoline derivatives

Nanocatalysts play a vital role in chemical reactions, energy conservation, and pollution control. They significantly contribute to organic synthesis by using natural polymers as nanoparticle substrates in nanocatalysts. Natural hydrogels made from polysaccharide and/or protein sources may be used to accomplish this. Recent research has focused on using layered double-hydroxides (LDHs) in composites having catalytic properties. Magnetic features of the catalyst allow its extraction from the environment using a magnet after the reaction, improving product efficiency. This work developed a catalyst for producing physiologically relevant polyhydroquinoline derivatives using a novel magnetic nanocomposite containing natural cellulose-gellan gum hydrogel and MgAl LDH. The Cell-GG hydrogel/MgAl LDH/Fe3O4 nanocomposite showed over 90 % efficiency in one-pot production of polyhydroquinoline derivatives by asymmetric Hantzsch condensation. Dimedone, ammonium acetate, ethyl acetoacetate, and different substituted aldehydes were employed in successive processes to create polyhydroquinoline derivatives. High product efficiency, quick reaction time, room temperature functioning, and easy separation with a magnet suggest a potent catalyst. Interestingly, the catalyst retains 80 % of its original capability after four cycles. Additionally, the Cell-GG hydrogel/MgAl LDH/Fe3O4 nanocomposite was analyzed using several methods, including FT-IR, FE-SEM, EDX, XRD, VSM and TGA, to obtain insight into its chemical and physical characteristics.

Preparation of Liposome Gel by Calcium Cross-Linking Induces the Long-Term Release of DOX to Improve the Antitumor Effect

Doxorubicin (DOX) is one of the most commonly used anticancer drugs; however, its clinical application is greatly limited due to its toxicity and chemotherapy resistance. The delivery of DOX by liposomes (Lipos) can improve the blood circulation time in vivo and reduce toxic side effects, but the drug's accumulation in the tumor is often insufficient for effective treatment. In this study, we present a calcium cross-linked liposome gel for the encapsulation of DOX, demonstrating its superior long-term release capabilities compared to conventional Lipos. By leveraging this enhanced long-term release, we can enhance drug accumulation within tumors, ultimately leading to improved antitumor efficacy. Lipos were prepared using the thin-film dispersion method in this study. We utilized the ion-responsiveness of glutathione-gelatin (GSH-GG) to form the gel outside the Lipos and named the nanoparticles coated with GSH-GG on the outside of Lipos as Lipos@GSH-GG. The average size of Lipos@GSH-GG was around 342.9 nm, with a negative charge of -25.6 mV. The in vitro experiments revealed that Lipos@GSH-GG exhibited excellent biocompatibility and slower drug release compared to conventional Lipos. Further analysis of cellular uptake and cytotoxicity demonstrated that Lipos@GSH-GG loading DOX (DOX&Lipos@GSH-GG) exhibited superior long-term release effects and lower toxic side effects compared to Lipos loading DOX (DOX&Lipos). Additionally, the findings regarding the long-term release effect in vivo and the tumor accumulation within tumor-bearing mice of Lipos@GSH-GG suggested that, compared to Lipos, it demonstrated superior long-term release capabilities and achieved greater drug accumulation within tumors. In vivo antitumor efficacy experiments showed that DOX&Lipos@GSH-GG demonstrated superior antitumor efficacy to DOX&Lipos. Our study highlights Lipos@GSH-GG as a promising nanocarrier with the potential to enhance efficacy and safety by means of long-term release effects and may offer an alternative approach for effective antitumor therapy in the future.

Biomineralization-Inspired Anti-Caries Strategy Based on Multifunctional Nanogels as Mineral Feedstock Carriers

Background

Dentin caries remains a significant public concern, with no clinically viable material that effectively combines remineralization and antimicrobial properties. To address this issue, this study focused on the development of a bio-inspired multifunctional nanogel with both antibacterial and biomineralization properties.

Methods

First, p(NIPAm-co-DMC) (PNPDC) copolymers were synthesized from N-isopropylacrylamide (NIPAm) and 2-methacryloyloxyethyl-trimethyl ammonium chloride (DMC). Subsequently, PNPDC was combined with γ-polyglutamic acid (γ-PGA) through physical cross-linking to form nanogels. These nanogels served as templates for the mineralization of calcium phosphate (Cap), resulting in Cap-loaded PNPDC/PGA nanogels. The nanogels were characterized using various techniques, including TEM, particle tracking analysis, XRD, and FTIR. The release properties of ions were also assessed. In addition, the antibacterial properties of the Cap-loaded PNPDC/PGA nanogels were evaluated using the broth microdilution method and a biofilm formation assay. The remineralization effects were examined on both demineralized dentin and type I collagen in vitro.

Results

PNPDC/PGA nanogels were successfully synthesized and loaded with Cap. The diameter of the Cap-loaded PNPDC/PGA nanogels was measured as 196.5 nm at 25°C and 162.3 nm at 37°C. These Cap-loaded nanogels released Ca2+ and PO43- ions quickly, effectively blocking dental tubules with a depth of 10 μm and promoting the remineralization of demineralized dentin within 7 days. Additionally, they facilitated the heavy intrafibrillar mineralization of type I collagen within 3 days. Moreover, the Cap-loaded nanogels exhibited MIC50 and MIC90 values of 12.5 and 50 mg/mL against Streptococcus mutans, respectively, with an MBC value of 100 mg/mL. At a concentration of 50 mg/mL, the Cap-loaded nanogels also demonstrated potent inhibitory effects on biofilm formation by Streptococcus mutans while maintaining good biocompatibility.

Conclusion

Cap-loaded PNPDC/PGA nanogels are a multifunctional biomimetic system with antibacterial and dentin remineralization effects. This strategy of using antibacterial nanogels as mineral feedstock carriers offered fresh insight into the clinical management of caries.

Biosynthesis and physicochemical properties of low molecular weight gellan produced by a high-yield mutant of Sphingomonas paucimobilis ATCC 31461

Gellan gum (GG) is used in many industries. Here, we obtained a low molecular weight GG (L-GG) directly produced by M155, the high-yield mutant strain of Sphingomonas paucimobilis ATCC 31461, which was selected using UV-ARTP combined mutagenesis. The molecular weight of L-GG was 44.6 % lesser than that of the initial GG (I-GG), and the GG yield increased by 24 %. The monosaccharide composition and Fourier transform-infrared spectroscopic patterns of L-GG were similar to those of I-GG, which indicated that the decrease in the molecular weight of L-GG was probably because of reduction in the degree of polymerization. In addition, microstructural analysis revealed that the surface of L-GG was rougher, with smaller pores and tighter network, than that of I-GG. L-GG showed low hardness, gumminess, and chewiness, which are indicative of better taste. The results of rheological analysis revealed that the L-GG solution is a typical non-Newtonian fluid with low viscoelasticity, which exhibited stable dynamic viscoelasticity within 20-65 °C. To the best of our knowledge, this is the first report of direct biosynthesis of low molecular weight GG during fermentation, which will reduce the manufacturing costs. Our observations provide a reference for precise and expanded applications of GG.

From Antibacterial to Antibiofilm Targeting: An Emerging Paradigm Shift in the Development of Quaternary Ammonium Compounds (QACs)

In a previous development stage, mostly individual antibacterial activity was a target in the optimization of biologically active compounds and antiseptic agents. Although this targeting is still valuable, a new trend has appeared since the discovery of superhigh resistance of bacterial cells upon their aggregation into groups. Indeed, it is now well established that the great majority of pathogenic germs are found in the environment as surface-associated microbial communities called biofilms. The protective properties of biofilms and microbial resistance, even to high concentrations of biocides, cause many chronic infections in medical settings and lead to serious economic losses in various areas. A paradigm shift from individual bacterial targeting to also affecting more complex cellular frameworks is taking place and involves multiple strategies for combating biofilms with compounds that are effective at different stages of microbiome formation. Quaternary ammonium compounds (QACs) play a key role in many of these treatments and prophylactic techniques on the basis of both the use of individual antibacterial agents and combination technologies. In this review, we summarize the literature data on the effectiveness of using commercially available and newly synthesized QACs, as well as synergistic treatment techniques based on them. As an important focus, techniques for developing and applying antimicrobial coatings that prevent the formation of biofilms on various surfaces over time are discussed. The information analyzed in this review will be useful to researchers and engineers working in many fields, including the development of a new generation of applied materials; understanding biofilm surface growth; and conducting research in medical, pharmaceutical, and materials sciences. Although regular studies of antibacterial activity are still widely conducted, a promising new trend is also to evaluate antibiofilm activity in a comprehensive study in order to meet the current requirements for the development of highly needed practical applications.

A Self-Healing, Magnetic and Injectable Biopolymer Hydrogel Generated by Dual Cross-Linking for Drug Delivery and Bone Repair

Injectable hydrogels based on various functional biocompatible materials have made rapid progress in the field of bone repair. In this study, a self-healing and injectable polysaccharide-based hydrogel was prepared for bone tissue engineering. The hydrogel was made of carboxymethyl chitosan (CMCS) and calcium pre-cross-linked oxidized gellan gum (OGG) cross-linked by the Schiff-base reaction. Meanwhile, magnetic hydroxyapatite/gelatin microspheres (MHGMs) were prepared by the emulsion cross-linking method. The antibacterial drugs, tetracycline hydrochloride (TH) and silver sulfadiazine (AgSD), were embedded into the MHGMs. To improve the mechanical and biological properties of the hydrogels, composite hydrogels were prepared by compounding hydroxyapatite (HAp) and drug-embedded MHGMs. The physical, chemical, mechanical and rheological properties of the composite hydrogels were characterized, as well as in vitro antibacterial tests and biocompatibility assays, respectively. Our results showed that the composite hydrogel with 6% (w/v) HAp and 10 mg/mL MHGMs exhibited good magnetic responsiveness, self-healing and injectability. Compared with the pure hydrogel, the composite hydrogel showed a 38.8% reduction in gelation time (196 to 120 s), a 65.6% decrease in swelling rate (39.4 to 13.6), a 51.9% increase in mass residual after degradation (79.5 to 120.8%), and a 143.7% increase in maximum compressive stress (53.6 to 130.6 KPa). In addition, this composite hydrogel showed good drug retardation properties and antibacterial effects against both S. aureus and E. coli. CCK-8 assay showed that composite hydrogel maintained high cell viability (> 87%) and rapid cell proliferation after 3 days, indicating that this smart hydrogel is expected to be an alternative scaffold for drug delivery and bone regeneration. STATEMENT OF SIGNIFICANCE: Biopolymer hydrogels have been considered as the promising materials for the treatment of tissue engineering and drug delivery. Injectable hydrogels with and self-healing properties and responsiveness to external stimuli have been extensively investigated as cell scaffolds and bone defects, due to their diversity and prolonged lifetime. Magnetism has also been involved in biomedical applications and played significant roles in targeted drug delivery and anti-cancer therapy. We speculate that development of dual cross-linked hydrogels basing biopolymers with multi-functionalities, such as injectable, self-healing, magnetic and anti-bacterial properties, would greatly broaden the application for bone tissue regeneration and drug delivery.

Temperature-Ion-pH Triple Responsive Gellan Gum as In Situ Hydrogel for Long-Acting Cancer Treatment

Background: Promising cancer chemotherapy requires the development of suitable drug delivery systems (DDSs). Previous research has indicated that a hydrogel is a powerful DDS for tumor therapy and holds great potential to offer a feasible method for cancer management. Methods: In this study, glutathione-gellan gum conjugate (GSH-GG) was synthesized through chemical reaction. Doxorubicin hydrochloride (DOX) was loaded into GSH-GG to accomplish DOX-loaded GSH-GG. The properties, injectability, drug release, and in vitro and in vivo anticancer effects of DOX-loaded GSH-GG were tested. Results: DOX-loaded GSH-GG showed a temperature-ion dual responsive gelling property with good viscosity, strength, and injectability at an optimized gel concentration of 1.5%. In addition, lower drug release was found under acidic conditions, offering beneficial long-acting drug release in the tumor microenvironment. DOX-loaded GSH-GG presented selective action by exerting substantially higher cytotoxicity on cancer cells (4T1) than on normal epithelial cells (L929), signifying the potential of complete inhibition of tumor progression, without affecting the health quality of the subjects. Conclusions: GSH-GG can be applied as a responsive gelling material for delivering DOX for promising cancer therapy.

Properties of Cellulose Pulp and Polyurethane Composite Films Fabricated with Curcumin by Using NMMO Ionic Liquid

Cellulose pulp (CP), polyurethane (PU), and curcumin-based biocompatible composite films were prepared using a simple cost-effective method. Significant structural and microstructural changes were studied using FT-IR spectroscopy, XRD, and SEM. The 5% and 10% gravimetric losses of the CP/PU/curcumin composite were found to be in the range 87.2–182.3 °C and 166.7–249.8 °C, respectively. All the composites exhibited single T_g values in the range 147.4–154.2 °C. The tensile strength of CP was measured to be 93.2 MPa, which dropped to 14.1 MPa for the 1:0.5 CP/PU composite and then steadily increased to 30.5 MPa with further addition of PU. The elongation at the break of the composites decreased from 8.1 to 3.7% with the addition of PU. The addition of PU also improved the water vapor permeability (3.96 × 10⁻⁹ to 1.75 × 10⁻⁹ g m⁻¹ s⁻¹ Pa⁻¹) and swelling ratio (285 to 202%) of the CP composite films. The CP/PU/curcumin composite exhibited good antioxidant activity and no cytotoxicity when tested on the HaCat cell line. The visual appearance and UV transmittance (86.2–32.9% at 600 nm) of the CP composite films were significantly altered by the incorporation of PU and curcumin. This study demonstrates that CP/PU/curcumin composites can be used for various packaging and biomedical applications.

Montmorillonite clay and quaternary ammonium silane-reinforced pullulan/agar-based nanocomposites and their properties for packaging applications

Synergistic combinations of pullulan, agar, montmorillonite (MMT) clay, and quaternary ammonium silane (QAS)-based (Pullulan/agar/MMT clay/QAS) active nanocomposites were prepared by a simple, cost-effective method. The Pullulan/agar/MMT clay/QAS nanocomposites were studied via Fourier-transform infrared spectroscopy, scanning electron microscopy, and X-ray diffraction analyses. The concentration of MMT clay played a very important role in the properties of the nanocomposites. However, the transparency of the composite was not significantly affected by the addition of MMT clay. The ultraviolet (UV) transmittance of Pullulan/agar/MMT clay/QAS was in the range of 91.4-79.8 at 600 nm. The thermal and mechanical properties were significantly improved by the MMT clay. The tensile strength and elongation at break of the composites were in the range of 23.8-39.7 MPa and 37.2-26.9%, respectively. The long alkyl chain in QAS significantly improved the hydrophobic nature of the Pullulan/agar/MMT clay nanocomposites, impacting the contact angle (66.2-71.2°), water vapor permeability (3.17-2.20 × 10^-9 g/m² Pa·s), and swelling ratio (1837-836%). The combination of Pullulan/agar/MMT clay/QAS had a synergistic effect on the rheological properties. MMT clay and QAS significantly increased the viscosity, storage, and loss modulus of the hydrogel composites. With the addition of QAS, the Pullulan/agar/MMT clay nanocomposites showed good antimicrobial activity against gram-positive and gram-negative pathogens.

Advances in Functional Biopolymer-Based Nanocomposites for Active Food Packaging Applications

Polymeric nanocomposites have received significant attention in both scientific and industrial research in recent years. The demand for new methods of food preservation to ensure high-quality, healthy foods with an extended shelf life has increased. Packaging, a crucial feature of the food industry, plays a vital role in satisfying this demand. Polymeric nanocomposites exhibit remarkably improved packaging properties, including barrier properties, oxygen impermeability, solvent resistance, moisture permeability, thermal stability, and antimicrobial characteristics. Bio-based polymers have drawn considerable interest to mitigate the influence and application of petroleum-derived polymeric materials and related environmental concerns. The integration of nanotechnology in food packaging systems has shown promise for enhancing the quality and shelf life of food. This article provides a general overview of bio-based polymeric nanocomposites comprising polymer matrices and inorganic nanoparticles, and describes their classification, fabrication, properties, and applications for active food packaging systems with future perspectives.

Antimicrobial Properties of Food Nanopackaging: A New Focus on Foodborne Pathogens

Food products contaminated by foodborne pathogens (bacteria, parasites, and viruses) cause foodborne diseases. Today, great efforts are being allocated to the development of novel and effective agents against food pathogenic microorganisms. These efforts even might have a possible future effect in coronavirus disease 2019 (COVID-19) pandemic. Nanotechnology introduces a novel food packaging technology that creates and uses nanomaterials with novel physiochemical and antimicrobial properties. It could utilize preservatives and antimicrobials to extend the food shelf life within the package. Utilizing the antimicrobial nanomaterials into food packaging compounds typically involves incorporation of antimicrobial inorganic nanoparticles such as metals [Silver (Ag), Copper (Cu), Gold (Au)], and metal oxides [Titanium dioxide (TiO2), Silicon oxide (SiO2), Zinc oxide (ZnO)]. Alternatively, intelligent food packaging has been explored for recognition of spoilage and pathogenic microorganisms. This review paper focused on antimicrobial aspects of nanopackaging and presented an overview of antibacterial properties of inorganic nanoparticles. This article also provides information on food safety during COVID-19 pandemic.

Quaternary ammonium silane-reinforced agar/polyacrylamide composites for packaging applications

Agar/polyacrylamide/quaternary ammonium silane-based (A/P/QAS-based) composite films were developed for food and biomedical packaging applications. The structural, optical, and surface morphological properties of the A/P and A/P/QAS composites were characterized by various characterization techniques in terms of thermogravimetric analysis, differential scanning calorimetry analyses, mechanical and rheological properties. Results showed that the 5% gravimetric loss (57.8-139.1 °C), glass transition temperature (179-189.9 °C) and tensile strength (35.2-47.8 MPa) of the prepared composites increased with increasing polyacrylamide content. The contact angle and water barrier properties of the composites were considerably improved by the addition of QAS. To compare WVP values of the A/P/QAS composite with neat AP composite films it reduced nearly 46% (2.45 to 1.32 × 10^-9 g/m² Pas). The A/P/QAS composites showed excellent antimicrobial properties against five different organisms. The Staphylococcus aureus exhibited highest 25 mm for gel and 18.1 mm for film of A/P/QAS composites. All the composites exhibited shear-thinning behavior, and their viscosity increased with increasing polyacrylamide content. The storage moduli of the prepared hydrogel composites were in the range of 5000-10,600 Pa at 1 rad/s and increased continuously over the entire frequency range. The dynamic rheological properties of A/P and A/P/QAS composites indicated that the prepared composites had good mechanical strength. Biopolymer based A/P and A/P/QAS composite films are suitable for green composite packaging applications.

Preparation and Properties of Hydrophobically Modified Nano-SiO2 with Hexadecyltrimethoxysilane

As a common inorganic silicon material, nano-SiO₂ is extremely hydrophilic due to the presence of a large number of hydroxyl groups on its surface, which limits its application in some fields. In this research, hexadecyltrimethoxysilane (HDTMS) was used to modify nano-SiO₂, and the results of water contact angle (WCA), Fourier transform infrared (FTIR), two-dimensional correlation spectroscopy (2D-COS), thermogravimetric (TG) analysis, and scanning electron microscopy (SEM) indicated that the hydrophobic long-chain alkyl of HDTMS was successfully grafted onto the surface of nano-SiO₂. When the ratio of nano-SiO₂ and HDTMS was 0.25:1, the WCA of nano-SiO₂ modified with HDTMS (HDTMS-nano-SiO₂) reached 170.9°, which was about 5.62 times higher than that before modification, and the superhydrophobic property was obtained. The novelty of this work lies in the modified nano-SiO₂ with a WCA of over 170° and the analysis of the modification mechanism with the help of 2D-COS. This study can provide a reference for the hydrophobic modification of nano-SiO₂ and its application field expansion.

Biomacromolecule assembly based on gum kondagogu-sodium alginate composites and their expediency in flexible packaging films

The assembly of bio-based macromolecules of gum kondagogu/sodium alginate (KO/SA) was fabricated using glycerol as a plasticiser and their optimum blending ratio was identified based on their physical and chemical, structural, mechanical, barrier, and morphological properties. The attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) analysis show that both biomacromolecules are well organised due to the hydrogen bond interaction between molecular chains involving the hydroxyl, carbonyl, and acetyl groups. Structural identification was performed by recording X-ray diffraction (XRD) spectra. Field emission scanning electron microscopy (FESEM) was used to identify the distinction between the surface of the films of biopolymers, and their conjugates, where the addition of SA increased the surface homogeneity and smoothness. The water contact angle of the blend films reached up to 81°, although the value for pure biomacromolecule films was very low. The blend films also exhibited high tensile strength (up to 24 MPa) compared to the pure biopolymer films. Investigation of film-forming ability, mechanical strength, permeability, transparency, and biodegradability of the developed KO/SA bio-macromolecular association may be established as green and sustainable food packaging films.