Functional Bionanocomposites Research Articles

Effect of addition of γ-poly glutamic acid on bacterial nanocellulose production under agitated culture conditions.

Bacterial nanocellulose (BNC), a natural polymer material, gained significant popularity among researchers and industry. It has great potential in areas, such as textile manufacturing, fiber-based paper, and packaging products, food industry, biomedical materials, and advanced functional bionanocomposites. The main current fermentation methods for BNC involved static culture, as the agitated culture methods had lower raw material conversion rates and resulted in non-uniform product formation. Currently, studies have shown that the production of BNC can be enhanced by incorporating specific additives into the culture medium. These additives included organic acids or polysaccharides. γ-Polyglutamic acid (γ-PGA), known for its high polymerization, excellent biodegradability, and environmental friendliness, has found extensive application in various industries including daily chemicals, medicine, food, and agriculture. In this particular study, 0.15g/L of γ-PGA was incorporated as a medium additive to cultivate BNC under agitated culture conditions of 120rpm and 30℃. The BNC production increased remarkably by 209% in the medium with 0.15g/L γ-PGA and initial pH of 5.0 compared to that in the standard medium, and BNC production increased by 7.3% in the medium with 0.06g/L γ-PGA. The addition of γ-PGA as a medium additive resulted in significant improvements in BNC production. Similarly, at initial pH levels of 4.0 and 6.0, the BNC production also increased by 39.3% and 102.3%, respectively. To assess the characteristics of the BNC products, scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis were used. The average diameter of BNC fibers, which was prepared from the medium adding 0.15g/L γ-PGA, was twice thicker than that of BNC fibers prepared from the control culture medium. That might be because that polyglutamic acid relieved the BNC synthesis from the shear stress from the agitation. This experiment held great significance as it explored the use of a novel medium additive, γ-PGA, to improve the production and the glucose conversion rate in BNC fermentation. And the BNC fibers became thicker, with better thermal stability, higher crystallinity, and higher degree of polymerization (DPv). These findings lay a solid foundation for future large-scale fermentation production of BNC using bioreactors.

New Functional Bionanocomposites by Combining Hybrid Host-Guest Systems with a Fully Biobased Poly(lactic acid)/Poly(butylene succinate-co-adipate) (PLA/PBSA) Binary Blend.

In this study, we have developed innovative polymer nanocomposites by integrating magnesium-aluminum layered double hydroxide (LDH)-based nanocarriers modified with functional molecules into a fully biobased poly(lactic acid)/poly(butylene succinate-co-adipate) (PLA/PBSA) matrix. These LDH-based hybrid host-guest systems contain bioactive compounds like rosmarinic acid, ferulic acid, and glycyrrhetinic acid, known for their antioxidant, antimicrobial, and anti-inflammatory properties. The bioactive molecules can be gradually released from the nanocarriers over time, allowing for sustained and controlled delivery in various applications, such as active packaging or cosmetics. The morphological analysis of the polymer composites, prepared using a discontinuous mechanical mixer, revealed the presence of macroaggregates and nano-lamellae at the polymer interface. This resulted in an enhanced water vapor permeability compared to the original blend. Furthermore, the migration kinetics of active molecules from the thin films confirmed a controlled release mechanism based on their immobilization within the lamellar system. Scaling-up experiments evaluated the materials' morphology and mechanical and thermal properties. Remarkably, stretching deformation and a higher shear rate during the mixing process enhanced the dispersion and distribution of the nanocarriers, as confirmed by the favorable mechanical properties of the materials.

Supramolecular Assembly of Multifunctional Collagen Nanocomposite Film via Polyphenol-Coordinated Clay Nanoplatelets.

Functional bionanocomposites have evoked immense research interests in many fields including biomedicine, food packaging, and environmental applications. Supramolecular self-assembled bionanocomposite materials fabricated by biopolymers and two-dimensional (2D) nanomaterials have particularly emerged as a compelling material due to their biodegradable nature, hierarchical structures, and designable multifunctions. However, construction of these materials with tunable properties has been still challenging. Here, we report a self-assembled, flexible, and antioxidative collagen nanocomposite film (CNF) via regulating supramolecular interactions of type I collagen and tannic acid (TA)-functionalized 2D synthetic clay nanoplatelets Laponite (LAP). Specifically, TA-coordinated LAP (LAP-TA) complexes were obtained via chelation and hydrogen bonding between TA and LAP clay nanoplatelets and further used to stabilize the triple-helical confirmation and fibrillar structure of the collagen via hydrogen bonding and electrostatic interactions, forming a hierarchical microstructure. The obtained transparent CNF not only exhibited the reinforced thermal stability, enzymatic resistance, tensile strength, and hydrophobicity but also good water vapor permeability and antioxidation. For example, the tensile strength was improved by over 2000%, and the antioxidant property was improved by 71%. Together with the simple fabrication process, we envision that the resulting CNF provides greater opportunities for versatile bionanocomposites design and fabrication serving as a promising candidate for emerging applications, especially food packaging and smart wearable devices.

One-pot green extraction of high charge density cellulose nanocrystals with high yield for bionanocomposites

The use of lignocellulosic materials for extracting functionalized cellulose nanocrystals (FCNs) in a green and sustainable method under mild conditions is limited owing to the strong hydrogen bonding in cellulose. A facile, green, and high-efficient avenue was developed to produce FCNs with high yield through the mechanochemistry synergetic effect of recyclable p-toluenesulfonic acid (PTSA)-catalyzed deep eutectic solvent (PDES) and microwave- solvothermal (MWS). FCNs with a high charge density of 1.59 e nm−2, a crystallinity of 81%, a better thermostability and dispersibility were obtained at a high yield of 87.6% by the one-step processing. The PDES could be easily recycled, and thus was beneficial to cost reduction and waste liquor treatment. Generated FCNs could be used to develop functional bionanocomposites due to their enhanced effect. When a loading of 1 wt% FCNs was added into gelatin matrix, the tensile strength and Young’s modulus of the bionanocomposites increased 188 and 131%, respectively, suggesting their remarkable stress transfer potential. Thus, the study demonstrates a green and cost-effective approach for the mass production of FCNs, contributing to strong potential in building high-performance bionanocomposites.

Development of Functional Bionanocomposites Using Cyanobacterial Polysaccharides.

Cyanobacteria are regarded as very eco-friendly microreactors for the production of various biomolecules such as polysaccharides by fixing not only carbon but also nitrogen in water. Cyanobacterial polysaccharides having various functional groups such as hydroxyls, carboxyls, sulfates, etc. have the ability to interact with metals or inorganics, to create bionanocomposites. Sacran, a supergiant cyanobacterial anionic polysaccharide extracted from the extracellular matrix of Aphanothece sacrum which is mass-cultivated in freshwater, is mainly used to create functional bionanocomposites. Gel-type bionanocomposites of sacran with various metal cations are formed and showed photoresponsive functions. Metal recovery is performed from the sacran bionanocomposite gels. Sacran chains are complexed with multi-wall carbon nanotubes (MWCNT) to give viscose dispersion from which MWCNT bionanocomposites can be collected by electrophoresis. The MWCNT/sacran dispersion retains the capability of adsorbing various metal ions to form hardened hydrogel beads. Finally, natural inorganic sepiolite can be used for sacran bionanocomposites which show an efficient neodymium ion adsorption ability. Thus, cyanobacterial polysaccharides are useful for preparing eco-friendly and functional bionanocomposites with various hard materials.

Building Up Functional Bionanocomposites from the Assembly of Clays and Biopolymers.

Functional bionanocomposites are developed from the assembly of naturally occurring polymers and inorganic solids that show at least one dimension at the nanoscale. Our research group focused on the development of bionanocomposites based on clay minerals, including smectites and fibrous silicates, as well as layered double hydroxides. The resulting materials show interesting properties regarding biocompatibility and biodegradability, together with improved mechanical and thermal properties in comparison to the pristine biopolymer. Besides these characteristics, they offer also other interesting functional properties that allow their potential use in a wide range of applications, including sensors, drug delivery and other health care applications, bioplastics and environmental remediation. For these materials, nature provides not only the components but also the inspiration to develop new combinations that may give rise to nanostructured biomaterials with exceptional features.

Protein-directed gold nanoparticles with excellent catalytic activity for 4-nitrophenol reduction

To explore high-performance noble metal nanomaterials for the reduction of the biotoxin 4-nitrophenol (4-NP) in medicine, we developed a green synthesis strategy of bovine serum albumin-stabilized Au nanoparticles (Au@BSA NPs). The as-synthesized Au@BSA NPs were characterized by ultraviolet-visible absorption spectrum, fourier transformed infrared spectroscopy, transmission electron microscopy and dynamic light scattering. The functional bio-nanocomposites showed Au-protein core-shell structure and uniform distribution, and their sizes were dependent on the additive amount of HAuCl4. Interestingly, Au@BSA NPs showed remarkable catalytic activity for the reduction of 4-NP into 4-aminophenol in the presence of sodium borohydride. Due to the introduction of Au@BSA NPs, the reduction reaction could be conducted at ambient temperature and pressure without any additional conditions. Moreover, the reduction rate was closely related to the sizes of NPs and reaction temperature, and the catalytic mechanism was verified to follow the pseudo-first-order kinetics. Due to the environmentally friendly synthesis process and green reduction strategy of 4-NP, Au@BSA NPs would show great potential in governance of the biotoxin in medicine.

Ultrasound assisted preparation of chitosan–vermiculite bionanocomposite foams for cadmium uptake

The objective of this work was the development of functional bionanocomposites based on the intercalation of the cationic biopolymer chitosan in natural or in organically modified vermiculite samples under experimental conditions involving ultrasound irradiation. The resulting materials were processed as macroporous foams with the aim to apply them in the removal of Cd(II) ions from aqueous solution. Physicochemical characterization confirmed the intercalation of chitosan into the interlayer space of vermiculite, causing the exfoliation of VU layers in those bionanocomposites. They were processed as foams by means of freeze-drying resulting in materials that show interconnected elongated macropores with average diameter around 150–200μm, and the material in the cell walls exhibited a tendency to organize in parallel planes. The adsorption equilibrium data of Cd(II) on the bionanocomposite foams, carried out in batch mode, was interpreted with the Langmuir, Freundlich and Prausnitz–Radke (P–R) isotherm models, and the P-R isotherm showed the best fit to the experimental data. The adsorption capacity was increased by raising the solution pH, which most likely favors a chelation mechanism between the chitosan chains and the Cd(II) cations. The chitosan–vermiculite bionanocomposites with the highest chitosan content showed exceptionally high adsorption capacity values, at least three times higher than those of the individual components.

Mechanical milling as a technology to produce structural and functional bio-nanocomposites

Mechanical milling as an ecological and economical alternative to achieve homogeneous dispersion of nano-fillers into sustainable polymers.

Correlating enzyme density, conformation and activity on nanoparticle surfaces in highly functional bio-nanocomposites.

The biological activity of the immobilized enzyme is crucial for the performance of different nanoparticle mediated enzymatic assays, where enzymatic conversion can be used for label-free analyte detection. In this article we have addressed two significant aspects of enzyme-nanoparticle interactions. First, we have developed copper sulfide (CuS) nanoparticles with an average diameter of 25 nm as a potential enzyme-interface using trypsin protease as a model enzyme. CuS nanoparticles showed high trypsin immobilization capacity of about 14.0 mg m(-2) with the significant retention of native enzymatic activity (75-98%) at room temperature, even beyond the calculated tightly packed monolayer coverage (which is around 4.1 mg m(-2)). Second, we report a quantitative correlation between the structure-functional relationship and the density of immobilized trypsin on a nanoparticle surface. The in situ conformation of immobilized trypsin could be efficiently analyzed by fluorescence, circular dichroism and FT-IR spectroscopic measurements because of the small size of the nanoparticles. Trypsin molecules appear to retain their close-native tertiary and secondary structural features (with a small loss of 1-2% of helical content) in the entire surface density range (2.0-14.0 mg m(-2)) on the CuS nanoparticles. However, interestingly, at a low surface coverage (2.0 mg m(-2)), immobilized trypsin retains almost 98% of its native enzymatic activity, leading to a highly functional bio-nanocomposite. However, at higher surface coverages, the enzyme activity decreases to 77%, indicating the influence of steric crowding. Furthermore, the high functionality of the immobilized trypsin at low surface density on CuS nanoparticle was also confirmed by determining the kinetic parameters of enzymatic activity.

Bionanocomposites based on layered silicates and cationic starch as eco-friendly adsorbents for hexavalent chromium removal

Functional bionanocomposites based on two layered silicates, the commercial montmorillonite known as Cloisite®Na and a natural bentonite from Algeria, were prepared by intercalation of cationic starch, synthesized with two different degrees of substitution, 0.85 and 0.55. After characterization of the prepared bionanocomposites by XRD and zeta potential measurements, batch studies were conducted to evaluate the adsorption capacity of hexavalent chromium anions from aqueous solution. The adsorption isotherms, adsorption kinetics, and the effect of pH on the process were studied. The removal efficiency was evaluated in the presence of competing anions such as NO3(-), ClO4(-), SO4(2-) and Cl(-). In order to regenerate the adsorbent for its repeated use, the regeneration process was studied in two different extractant solutions, 0.1 M NaCl at pH 10 and 0.28 M Na2CO3 at pH 12.

Efficient and stable enzyme immobilization in a block copolypeptide vesicle-templated biomimetic silica support

We report the immobilization of a model enzyme, papain, within silica matrices by combining vesiclization of poly- l-lysine-b-polyglycine block copolypeptides with following silica mineralization. Our novel strategy utilizes block polypeptide vesicles to induce the condensation of orthosilicic acid while trapping an enzyme within and between vesicles. The polypeptide mediated silica-immobilized enzyme exhibits enhanced pH and thermal stability and reusability, comparing with the free and vesicle encapsulated enzyme. The enhanced enzymatic activity in the immobilized enzyme is due to the confinement of the enzyme in the polypeptide mediated silica matrices. Kinetic analysis shows that the enzyme functionality is determined by the structure and property of silica/polypeptide matrices. The proposed novel strategy provides an alternative route for the synthesis of a broad range of functional bionanocomposites entrapped within silica nanostructures.

Assembly of poly(methacrylate)/purple membrane lamellar nanocomposite films by intercalation and in situ polymerisation

Thin films comprising ordered stacks of purple membrane (PM) sheets containing the light-driven proton pump bacteriorhodopsin (BR) were infiltrated with methacrylic acid (MA) monomers to produce lamellar bionanocomposites. Subsequent in situ polymerization and crosslinking of the guest MA molecules resulted in partially intercalated poly(methacrylate)/PM freestanding films, which showed increased stability in water, structural integrity and enhanced resistance to ethanol degradation compared with PM control films or non-polymerized MA/PM layered nanocomposites. Studies on photocycle kinetics confirmed that the polymerized PM films were functionally active, and showed an increase in the lifetime for the M-state intermediate of the photocycle. The results indicate that nanometre-thin layers of crosslinked poly(methacrylate) can be synthesized in situ between the PM sheets to produce novel functional bionanocomposites with proton transfer and photochromic properties.