Biopolymer-based Materials Research Articles

Conformations and Intermolecular Interactions in Cellulose/Silk Fibroin Blend Films: A Solid-State NMR Perspective.

Fabricating materials with excellent mechanical performance from the natural renewable and degradable biopolymers has drawn significant attention in recent decades due to the environmental concerns and energy crisis. As two of the most promising substitutes of synthetic polymers, silk fibroin (SF), and cellulose, have been widely used in the field of textile, biomedicine, biotechnology, etc. Particularly, the cellulose/SF blend film exhibits better strength and toughness than that of regenerated cellulose film. Herein, this study is aimed to understand the molecular origin of the enhanced mechanical properties for the cellulose/SF blend film, using solid-state NMR as a main tool to investigate the conformational changes, intermolecular interactions between cellulose and SF and the water organization. It is found that the content of the β-sheet structure is increased in the cellulose/SF blend film with respect to the regenerated SF film, accompanied by the reduction of the content of random coil structures. In addition, the strong hydrogen bonding interaction between the SF and cellulose is clearly elucidated by the two-dimensional (2D) 1H-13C heteronuclear correlation (HETCOR) NMR experiments, demonstrating that the SF and cellulose are miscible at the molecular level. Moreover, it is also found that the -NH groups of SF prefer to form hydrogen bonds with the hydroxyl groups bonded to carbons C2 and C3 of cellulose, while the hydroxyl groups bonded to carbon C6 and the ether oxygen are less favorable for hydrogen bonding interactions with the -NH groups of SF. Interestingly, bound water is found to be present in the air-dried cellulose/SF blend film, which is predominantly associated with the cellulose backbones as determined by 2D 1H-13C wide-line-separation (WISE) experiments with spin diffusion. This clearly reveals the presence of nanoheterogeneity in the cellulose/SF blend film, although cellulose and SF are miscible at a molecular level. Without doubt, these in-depth atomic-level structural information could help reveal the molecular origin of the enhanced mechanical properties of the blend film, and thus to establish the structure-property relationship, which could further provide guidance for the fabrication of high performance biopolymer-based materials.

Rapid Brownian Motion Primes Ultrafast Reconstruction of Intrinsically Disordered Phe-Gly Repeats Inside the Nuclear Pore Complex.

Conformational behavior of intrinsically disordered proteins, such as Phe-Gly repeat domains, alters drastically when they are confined in, and tethered to, nan channels. This has challenged our understanding of how they serve to selectively facilitate translocation of nuclear transport receptor (NTR)-bearing macromolecules. Heterogeneous FG-repeats, tethered to the NPC interior, nonuniformly fill the channel in a diameter-dependent manner and adopt a rapid Brownian motion, thereby forming a porous and highly dynamic polymeric meshwork that percolates in radial and axial directions and features two distinguishable zones: a dense hydrophobic rod-like zone located in the center, and a peripheral low-density shell-like zone. The FG-meshwork is locally disrupted upon interacting with NTR-bearing macromolecules, but immediately reconstructs itself between 0.44 μs and 7.0 μs, depending on cargo size and shape. This confers a perpetually-sealed state to the NPC, and is solely due to rapid Brownian motion of FG-repeats, not FG-repeat hydrophobic bonds. Elongated-shaped macromolecules, both in the presence and absence of NTRs, penetrate more readily into the FG-meshwork compared to their globular counterparts of identical volume and surface chemistry, highlighting the importance of the shape effects in nucleocytoplasmic transport. These results can help our understanding of geometrical effects in, and the design of, intelligent and responsive biopolymer-based materials in nanofiltration and artificial nanopores.

In Situ Generation of Cellulose Nanocrystals in Polycaprolactone Nanofibers: Effects on Crystallinity, Mechanical Strength, Biocompatibility, and Biomimetic Mineralization

Post-electrospinning treatment is a facile process to improve the properties of electrospun nanofibers for various applications. This technique is commonly used when direct electrospinning is not a suitable option to fabricate a nonwoven membrane of the desired polymer in a preferred morphology. In this study, a representative natural-synthetic hybrid of cellulose acetate (CA) and polycaprolactone (PCL) in different ratios was fabricated using an electrospinning process, and CA in the hybrid fiber was transformed into cellulose (CL) by post-electrospinning treatment via alkaline saponification. Scanning electron microscopy was employed to study the effects of polymer composition and subsequent saponification on the morphology of the nanofibers. Increasing the PCL content in the PCL/CA blend solution caused a gradual decrease in viscosity, resulting in smoother and more uniform fibers. The saponification of fibers lead to pronounced changes in the physicochemical properties. The crystallinity of the PCL in the composite fiber was varied according to the composition of the component polymers. The water contact angle was considerably decreased (from 124° to less than 20°), and the mechanical properties were greatly enhanced (Young's Modulus was improved by ≈20-30 fold, tensile strength by 3-4 fold, and tensile stress by ≈2-4 fold) compared to those of PCL and PCL/CA membranes. Regeneration of cellulose chains in the nanofibers increased the number of hydroxyl groups, which increased the hydrogen bonding, thereby improving the mechanical properties and wettability of the composite nanofibers. The improved wettability and presence of surface functional groups enhanced the ability to nucleate bioactive calcium phosphate crystals throughout the matrix when exposed to a simulated body fluid solution. Experimental results of cell viability assay, confocal microscopy, and scanning electron microscopy imaging showed that the fabricated nanofibrous membranes have excellent ability for MC3T3-E1 cell proliferation and growth. Given the versatility and widespread use of cellulose-synthetic hybrid systems in the construction of tissue-engineered scaffolds, this work provides a novel strategy to fabricate the biopolymer-based materials for applications in tissue engineering and regenerative medicine.

Gellan gum—Ionic liquid membranes for electrochromic device application

Biopolymer-based materials have been of particular interest and they are alternatives to synthetic polymers based on the decreasing oil resources. The polymer electrolytes were doped with choline-based IL N,N,N-trimethyl-N-(2-hydroxyethyl)ammonium bis(trifluoromethylsulfonyl)imide ([N1 1 1 2(OH)][NTf2]), or Er (CF3SO3)3 or both. The polymer electrolytes were employed in the production of glass/ITO/WO3/electrolyte/CeO2–TiO2/ITO/glass electrochromic devices (ECDs). The lowest onset temperature for the degradation of all the SPEs is at ~130°C for the Gellan Er (CF3SO3)3 (10:1) this temperature range of stability is wide enough for a material to be applied as an electrolyte/separator component in electrochemical devices.The three ECDs displayed fast switching speed (ca. 15s). Gellan [N1 1 1 2(OH)][NTf2] Er (CF3SO3)3 (5:1:10) exhibited an electrochromic contrast of 4.2% in the visible region, the coloration efficiency attained at 555nm was 3.5 and 0.90cm-2C-1 in the “colored” and “bleached” states, respectively, and the open circuit memory was 48h. Preliminary tests performed with a prototype electrochromic device (ECD) incorporating WO3 as cathodic electrochromic layer, are extremely encouraging.

Eco-Friendly Luminescent Hybrid Materials Based on EuIIIand LiICo-Doped Chitosan

Biopolymer-based materials have been of particular interest as alternatives to synthetic polymers due to their low toxicity, biodegradability and biocompatibility. Among them, chitosan is one of the most studied ones and has recently been investigated for the application as solid state polymer electrolytes. Furthermore, it can serve as a host for luminescent species such as rare earth ions, opening up the possibility of combined electro-optical functionality, of particular interest for electroluminescent devices. In this study, we perform a fundamental, initial, investigation of chitosan based luminescent materials doped with EuIII and LiI triflate salts, from the structural, photophysical and conducting points of view. Because the host presents a broad emission band in the blue to green, while EuIII emits in the red, fine-tuning of emission colour and/or generation of white light is proven possible, by proper combination of optimized composition and excitation scheme. Europium lifetimes (5D0) are in the range 270-350 µs and quantum yields are up to 2%. Although LiI does not interfere with the luminescent properties, it grants ion-conducting properties to the material suggesting that a combination of both properties could be useful in the development of electro-luminescent devices.

3D-Printed Biopolymers for Tissue Engineering Application

3D printing technology has recently gained substantial interest for potential applications in tissue engineering due to the ability of making a three-dimensional object of virtually any shape from a digital model. 3D-printed biopolymers, which combine the 3D printing technology and biopolymers, have shown great potential in tissue engineering applications and are receiving significant attention, which has resulted in the development of numerous research programs regarding the material systems which are available for 3D printing. This review focuses on recent advances in the development of biopolymer materials, including natural biopolymer-based materials and synthetic biopolymer-based materials prepared using 3D printing technology, and some future challenges and applications of this technology are discussed.

Electro-optical properties of the DNA-Eu3+ bio-membranes

Biopolymer-based materials have particular interest and they are alternatives to synthetic polymers based on the decreasing oil resources. In this report they may be viewed as innovative materials for optics area. The incorporation of Eu3+ into natural macromolecules hosts with purpose of producing highly efficient emitting phosphors is of widespread interest in materials science, due to their important roles in display devices. This paper describes studies of the DNA and europium triflate luminescent membranes and its potential technological applications are expanded to electroluminescent devices. The most conductive sample of DNA50Eu, exhibited an ionic conductivity equal to 1.02×10−4Scm−1 and 1.55×10−3Scm−1 at 25°C and 90°C, respectively. Techniques like DSC, XRD and POM, demonstrated that the inclusion of the guest salt does not change significantly the amorphous nature morphology of the samples. Moreover, the overall redox stability of 2.0V was an indication that this material has an acceptable stability window for an application in a solid state electrochemical devices.

Biopolymer-based hydrogels as injectable materials for tissue repair scaffolds

The progress in tissue regeneration is strongly dependent on the development of biocompatible materials with properties resembling those of a native tissue. Also, the application of noninvasive methods of delivering the scaffold into the tissue defect is of great importance. In this study we present a group of biopolymer-based materials as potential injectable scaffolds. In contrast to other studies involving collagen neutralization or additional incubation of gel in genipin solution, we propose collagen and collagen–chitosan gels crosslinked in situ with genipin. Since some parameters of the cells should be considered in the microscale, the steady-state fluorescence anisotropy was applied to study the microenvironment of the gels. To our knowledge we are the first to report on microrheological properties, such as gel time and microviscosity, for this group of hydrogels. Rapid gelation at physiological temperatures found makes these materials of special interest in applications requiring gel injectability. Physico-chemical investigation showed the influence of the crosslinking agent concentration and chitosan addition on the crosslinking degree, swelling ratio, gel microviscosity, and the degradation rate. Strong correlation was revealed between the surface wettability and the viability of cultured mesenchymal stem cells. Cytotoxicity studies indicated that the collagen–chitosan hydrogels showed the best biocompatibility.

Modification of hydrophilic cellulose fibers by monolayer growth of polystyrene chains using ATRP

The chemical modification of biopolymer-based materials by grafting synthetic polymers has received considerable attention in recent years, inasmuch as there are wide varieties of monomers available. Nowadays, the most abundant biomacromolecule, cellulose, has attracted considerable attention due to its biodegradable, biocompatible, and renewable characteristics. In this study, the surface of hydrophilic cellulose microfibers was successfully modified by polymerization of hydrophobic polystyrene using atom transfer radical polymerization (ATRP) technique in dispersion medium. In this medium, only the outer surface of the macroinitiator is available for the polymerization, so the grown polymer chains are formed as monolayer on the surface of the macroinitiator. This type of modification not only increases the mechanical properties of the cellulose backbone, but also turns the hydrophilic characteristics of cellulose into hydrophobic state. For this purpose, in the first part of this research, chloroacetylated cellulose was synthesized as macroinitiator. In the second part, the acyl content of the macroinitiator and the degree of substitution, which show the efficiency of the esterification reaction, have been determined by basic hydrolysis of the macroinitiator with KOH and back-titration of the excess alkali with HCl. Finally, the chloroacetylated cellulose was modified by graft copolymerization of styrene using ATRP method. The polystyrene chain growth is confirmed by the atomic force microscopy images.

Recent Advances in Biopolymers and Biopolymer-Based Nanocomposites for Food Packaging Materials

Plastic packaging for food and non-food applications is non-biodegradable, and also uses up valuable and scarce non-renewable resources like petroleum. With the current focus on exploring alternatives to petroleum and emphasis on reduced environmental impact, research is increasingly being directed at development of biodegradable food packaging from biopolymer-based materials. The proposed paper will present a review of recent developments in biopolymer-based food packaging materials including natural biopolymers (such as starches and proteins), synthetic biopolymers (such as poly lactic acid), biopolymer blends, and nanocomposites based on natural and synthetic biopolymers. The paper will discuss the various techniques that have been used for developing cost-effective biodegradable packaging materials with optimum mechanical strength and oxygen and moisture barrier properties. This is a timely review as there has been a recent renewed interest in research studies, both in the industry and academia, towards development of a new generation of biopolymer-based food packaging materials with possible applications in other areas.

Synthesis and in vitro studies of biodegradable modified chitosan nanoparticles for photodynamic treatment of cancer

The main aim of this research is to study the in vitro photocytotoxicity and cellular uptake of biodegradable polymeric nanoparticles loaded with photosensitizer mTHPP. As the first part of a continued research on conversion of N-sulfonato-N,O-carboxymethylchitosan (NOCCS) to useful biopolymer-based materials, large numbers of carboxylic functional groups were introduced onto NOCCS by grafting with polymethacrylic acid (PMAA). The free radical graft copolymerization was carried out at 70°C, bis-acrylamide as a cross-linking agent and persulfate as an initiator. These results show that the nanoparticles have high loading capacity and stability. These nanoparticles are suitable as carriers for photodynamic therapy in vivo.

Tuneable thickness barriers for composite o/w and w/o capsules, films, and their decoration with particles

Oil-in-water and water-in-oil capsules, and flat membranes of tuneable thickness and composition were prepared in one single facile step, based on the interfacial complexation between chitosan and anionic phosphatidic fatty acids. The phosphatidic acid molecules were introduced via the oil phase. The thickness of the capsule shell or the membrane grows by a diffusion-controlled mechanism, hence can be tuned using e.g. concentration and formation time parameters. A mechanism is proposed to explain the observed behavior. The capsule size is set by the emulsification conditions applied. Microfluidic methods proved useful for the generation of hollow capsules of uniform size and thickness in one step. The capsules and membranes display remarkable integrity over several years in a pH window 2–14. The thickness can easily reach several micrometres within an hour for the wet capsule shell or membrane, which explains the high interfacial rheological properties measured. Hence various processes can be envisaged after their formation. The simple preparation opens the way to tailored, environment-responsive composite systems for fabricating biopolymer-based materials for various applications. The capsules could be washed from the surrounding continuous phase and placed into one of arbitrary choice. Furthermore, the surface of the w/o capsules and of the membranes could be decorated by particles that attach to the water/oil interface with a high energy. The choice of the particle functionality is left open.

Design and characterization of chitosan nanoparticles as delivery systems for paclitaxel

The main objective of this research is to design a new extended release multiparticulate delivery system by incorporation into nanoparticles made of chitosan-polymethacrylic acid copolymers. As the first part of a continued research on conversion of chitosan to useful biopolymer-based materials, by grafting polymethacrylic acid (PMAA), free radical graft copolymerization was carried out at 70 °C, with bis-acrylamide as a cross-linking agent and persulfate as an initiator. Equilibrium swelling studies were carried out in enzyme-free simulated gastric and intestinal fluids. Also, the paclitaxel as a model drug was entrapped in these nano-gels and in vitro release profiles were established separately in both enzyme-free SGF and SIF. The drug release was found to be faster in SIF.

Synthesis and characterization of biodegradable chitosan beads as nano-carriers for local delivery of satranidazole

Abstract The main aim of this research is to design a new extended release gastroretentive multiparticulate delivery system by incorporation of the hydrogel beads made of chitosan. As the first part of a continued research on conversion of N-sulfonato-N,O-carboxymethylchitosan(NOCCS) to useful biopolymer-based materials, large numbers of carboxylic functional groups were introduced onto NOCCS by grafting with polymethacrylic acid (PMAA). The free radical graft copolymerization was carried out at 70 °C, bis-acrylamide as a cross-linking agent and persulfate as an initiator. The equilibrium swelling studies were carried out in enzyme-free simulated gastric and intestinal fluids (SGF and SIF, respectively). Also, the satranidazole as a model drug was entrapped in nano-gels and in vitro release profiles were established separately in both enzyme-free SGF and SIF. The drug release was found to be faster in SIF. The drug-release profiles indicate that the drug release depends on their degree of swelling and cross-linking.

Assembling Vanadium(V) Oxide and Gelatin into Novel Bionanocomposites with Unexpected Rubber-like Properties

A new kind of bionanocomposites is prepared for the first time in soft conditions by a complex coacervation process and consists of an assembly of decavanadate polyanions and gelatin chains in triple helices and coils conformation. Before drying, well-defined homogeneous monoliths with a striking rubber-like behavior were obtained. These mechanical properties were thoroughly characterized by tensile measurements at large strain revealing a complex behavior (strain hardening, large hysteresis during cycling experiments, Mullins effect) associated with characteristics (E = 0.27 MPa, λbreak = 8.6, and σbreak = 1.4 MPa) that were never reported for gelatin based materials. These results were discussed in the frame of classical biopolymer-based materials and in the emerging field of rubbery polyelectrolyte hydrogels. Compared to gelatin based composites which depict a ductile behavior, the improved strain properties of decavanadate-gelatin composite may be attributed to an adequate gelatin triple helices/coils ratio which depends strongly on gelatin concentration, aging time, temperature, and also on the charge matching between decavanadate and gelatin. Upon aging, the nucleation and growth of V2O5 ribbon like particles occurs in situ in the gelatin matrix that exerts a significant control on vanadium condensation from a kinetics and structural point of view.

Study of the amplified spontaneous emission in a dye-doped biopolymer-based material

In this paper we investigate the amplified spontaneous emission (ASE) phenomenon in the system based on a dye dissolved in a modified deoxyribonucleic acid (DNA). The system consisted of a biopolymeric matrix made of DNA blended with cationic surfactant molecule cetyltrimethyl-ammonium chloride (CTMA) and doped with a well-known rhodamine (Rh 6G) laser dye. Thin films of the DNA–CTMA : Rh6G were excited at λ = 532 nm wavelength with 8 ns laser pulses. We report on ASE intensity as a function of the laser power, dependence of polarization state of the excitation beam, ASE gain and temporal stability of the signal for the investigated system.

PH-sensitive starch hydrogels via free radical graft copolymerization, synthesis and properties

Natural polymers are considered high value polymeric materials because of their potential as biocompatible materials with medical applications. The chemical modification of natural polymers by grafting has received considerable attention in recent years because of the wide variety of monomers available. As the first part of a continued research on conversion of carboxymethyl starch (CMS) to useful biopolymer-based materials, large numbers of carboxylic functional groups were introduced onto CMS by grafting with polymethacrylic acid (PMAA). Free radical graft copolymerization was carried out at 70 °C, bis-acrylamide as a crosslinking agent and persulfate as an initiator. Equilibrium swelling studies were carried out in enzyme-free simulated gastric and intestinal fluids (SGF and SIF, respectively). Also, the sodium dicofenac as a model drug was entrapped in these nano-gels and the in vitro release profiles were established separately in both enzyme-free SGF and SIF. The drug release was found to be faster in SIF. The drug-release profiles indicate that amount drug release depends on their degree of swelling, and crosslinking. This hydrogel converted to nano by freeze-drying method and characterized by scanning electron microscopy, differential scanning calorimetry and FT-IR spectrometry.

Modification of collagen in vitro with respect to formation of N ɛ-carboxymethyllysine

Developing new biopolymer-based materials with bio-identical properties is a significant challenge in modern science. One interesting route to this goal involves the biomineralization of collagen, a pre-structured and widely available protein, into a material with interesting properties. A prerequisite for biomineralization is the ability of cations (e.g., calcium) to bind to the protein and to result in concert with appropriate anions (e.g., phosphate) in composite material with e.g., bone-like properties. In order to increase the number of binding sites it is necessary to modify the protein prior to mineralization. For this glucuronic acid (GA) was used due to its carbonyl and carboxyl groups to derivatize proteinogenic amino groups transferring them into negatively charged carboxyl groups. Our experiments showed for the first time, that N ɛ-carboxymethyllysine is the major product of in vitro non-enzymatic glycosylation of collagen by glucuronic acid. For an unequivocal determination of the reaction products, the lysine residues of collagen and of the model peptide were carboxymethylated through a reductive alkylation with glyoxalic acid and compared to the glucuronic acid derivatives. Beside their identical mass spectra the common structure elements could be confirmed with FTIR. Thus, in the context of matrix engineering, by producing N ɛ-carboxymethyllysine, glucuronic acid offers a convenient way of introducing additional stable acidic groups into protein matrices.

Biopolymer-based material used in optical image correlation

We investigate the possible application of a modified deoxyribonucleic acid (DNA)-dye system for dynamic processing of optical information, e.g., optical correlation. The system consists of a biopolymeric matrix made of DNA substituted with the cationic surfactant molecule cetyltrimethyl-ammonium chloride (CTMA) and doped with a photochromic Disperse Red 1 dye. Fast dynamics (millisecond range of rise and fall times) of output correlation signal formation was measured in a joint Fourier transform optical correlator experimental setup. Full reversibility of the correlation signal and reproducibility were observed even after long-time exposures.

Steam exploded biomass for the preparation of conventional and advanced biopolymer-based materials

Lignocellulosic materials treated by the steam explosion technique alone, or in the presence of chemical reagents, undergo remarkable modifications at the level of both the chemical composition and supramolecular structure, developing features suitable for the production of conventional and advanced materials with improved properties. Experience in the production of high yield pulps, composite materials with microbial (PHB) and synthetic (polypropylene) thermoplastic matrices and high modulus lignocellulosic fibers is reported.