Bacterial nanocellulose loaded with bromelain and nisin as a promising bioactive material for wound debridement

The bacterial nanocellulose (BnC) membranes were produced extracellularly by a novel aerobic acetic acid bacterium Komagataeibacter melomenusus. The BnC was modified in situ by adding carboxymethyl cellulose (CMC) into the culture media, obtaining a BnC-CMC product with denser fibril arrangement, improved rehydration ratio and elasticity in comparison to BnC. The proteolytic enzyme bromelain (Br) and antimicrobial peptide nisin (N) were immobilized to BnC matrix by ex situ covalent binding and/or adsorption. The optimal Br immobilization conditions towards the maximized specific proteolytic activity were investigated by response surface methodology as factor variables. At optimal conditions, i.e., 8.8 mg/mL CMC and 10 mg/mL Br, hyperactivation of the enzyme was achieved, leading to the specific proteolytic activity of 2.3 U/mg and immobilization efficiency of 39.1 %. The antimicrobial activity was observed against Gram-positive bacteria (S. epidermidis, S. aureus and E. faecalis) for membranes with immobilized N and was superior when in situ modified BnC membranes were used. N immobilized on the BnC or BnC-CMC membranes was cytocompatible and did not cause changes in normal human dermal fibroblast cell morphology. BnC membranes perform as an efficient carrier for Br or N immobilization, holding promise in wound debridement and providing antimicrobial action against Gram-positive bacteria, respectively.

High performance chitosan/nanocellulose-based composite membrane for alkaline direct ethanol fuel cells

Polysaccharide anion exchange membranes (AEMs) containing chitosan (CS), cellulose nanofibrils (CNFs) and CNFs quaternized with poly(diallyldimethylammonium chloride) (CNF(P)s) were developed for use in alkaline direct ethanol fuel cells (ADEFCs). The resulting composite membranes prepared by the solvent casting process based on an experimental design were comprehensively assessed for morphology, KOH uptake, swelling ratio, EtOH permeability, mechanical properties, ionic conductivity, and cell performance. The fabricated CS-based composite membranes with CNF(P) fillers were superior to the commercial Fumatech FAA-3-50 membrane in terms of Young's modulus and tensile strength (69 % and 85 % higher, respectively), ion exchange capacity (169 % higher), and ionic conductivity (228 % higher). Single fuel cell tests have shown excellent performance of the CS-based membranes with CNF and CNF(P) fillers, as they exhibited up to 86 % improvement in power density at 80 °C compared to the commercial membrane (65.1 mW/cm2 vs. 35.1 mW/cm2) and higher maximum power density at all test conditions.

Influence of the Electrode Deposition Method of Graphene-Based Catalyst Inks for ADEFC on Performance

The utilization of graphene as a catalyst support has garnered significant attention due to its potential for enhancing fuel cell performance. However, a critical challenge in electrode production still lies in the electrode preparation technologies and the restacking of graphene sheets, which can greatly impact the fuel cell performance alongside with catalyst development. This study aimed to investigate the impact of different electrode deposition methods for N-rGO-based catalyst inks on catalyst layer morphology, with a specific focus on graphene sheet orientation and its influence on the performance of alkaline direct ethanol fuel cells (ADEFCs). The dispersion behavior and ink stability of the catalysts were assessed using ultraviolet-visible light (UV-vis), ζ potential, and dynamic light scattering techniques. The morphology and physical properties of the gas diffusion electrodes (GDEs) were analyzed through Brunauer-Emmett-Teller measurements, contact angle measurements and scanning electron microscopy (SEM) combined with energy-dispersive spectroscopy. The electrochemical behavior was evaluated both ex-situ, utilizing half-cell GDE measurements, and in situ, through single-cell tests. The N-rGO-based membrane electrode assembly, comprising Pt-free catalysts and a biobased membrane, exhibited outstanding performance in ADEFCs, as evidenced by high maximum power density values and long-term durability. The N-rGO-based membrane electrode assembly has demonstrated remarkable potential for high-performance fuel cells, presenting an exciting avenue for further exploration.

From Nature to Lab: Sustainable Bacterial Cellulose Production and Modification with Synthetic Biology

Bacterial cellulose (BC) is a macromolecule with versatile applications in medicine, pharmacy, biotechnology, cosmetology, food and food packaging, ecology, and electronics. Although many bacteria synthesize BC, the most efficient BC producers are certain species of the genera Komagataeibacter and Novacetimonas. These are also food-grade bacteria, simplifying their utilization at industrial facilities. The basic principles of BC synthesis are known from studies of Komagataeibacter xylinus, which became a model species for studying BC at genetic and molecular levels. Cellulose can also be of plant origin, but BC surpasses its purity. Moreover, the laboratory production of BC enables in situ modification into functionalized material with incorporated molecules during its synthesis. The possibility of growing Komagataeibacter and Novacetimonas species on various organic substrates and agricultural and food waste compounds also follows the green and sustainable economy principles. Further intervention into BC synthesis was enabled by genetic engineering tools, subsequently directing it into the field of synthetic biology. This review paper presents the development of the fascinating field of BC synthesis at the molecular level, seeking sustainable ways for its production and its applications towards genetic modifications of bacterial strains for producing novel types of living biomaterials using the flexible metabolic machinery of bacteria.

Production efficiency and properties of bacterial cellulose membranes in a novel grape pomace hydrolysate by Komagataeibacter melomenusus AV436T and Komagataeibacter xylinus LMG 1518

The microbial production of cellulose using different bacterial species has been extensively examined for various industrial applications. However, the cost-effectiveness of all these biotechnological processes is strongly related to the culture medium for bacterial cellulose (BC) production. Herein, we examined a simple and modified procedure for preparing grape pomace (GP) hydrolysate, without enzymatic treatment, as a sole growth medium for BC production by acetic acid bacteria (AAB). The central composite design (CCD) was used to optimise the GP hydrolysate preparation toward the highest reducing sugar contents (10.4 g/L) and minimal phenolic contents (4.8 g/L). The experimental screening of 4 differently prepared hydrolysates and 20 AAB strains identified the recently described species Komagataeibacter melomenusus AV436^T as the most efficient BC producer (up to 1.24 g/L dry BC membrane), followed by Komagataeibacter xylinus LMG 1518 (up to 0.98 g/L dry BC membrane). The membranes were synthesized in only 4 days of bacteria culturing, 1 st day with shaking, followed by 3 days of static incubation. The produced BC membranes in GP-hydrolysates showed, in comparison to the membranes made in a complex RAE medium 34 % reduction of crystallinity index with the presence of diverse cellulose allomorphs, presence of GP-related components within the BC network responsible for the increase of hydrophobicity, the reduction of thermal stability and 48.75 %, 13.6 % and 43 % lower tensile strength, tensile modulus, and elongation, respectively. Here presented study is the first report on utilising a GP-hydrolysate without enzymatic treatment as a sole culture medium for efficient BC production by AAB, with recently described species Komagataeibacter melomenusus AV436^T as the most efficient producer in this type of food-waste material. The scale-up protocol of the scheme presented here will be needed for the cost-optimisation of BC production at the industrial levels.

Study on Commercially Available Membranes for Alkaline Direct Ethanol Fuel Cells

This study provides a comparison of different commercially available low-cost anion exchange membranes (AEMs), a microporous separator, a cation exchange membrane (CEM), and an anionic-treated CEM for their application in the liquid-feed alkaline direct ethanol fuel cell (ADEFC). Moreover, the effect on performance was evaluated taking two different modes of operation for the ADEFC, with AEM or CEM, into consideration. The membranes were compared with respect to their physical and chemical properties, such as thermal and chemical stability, ion-exchange capacity, ionic conductivity, and ethanol permeability. The influence of these factors on performance and resistance was determined by means of polarization curve and electrochemical impedance spectra (EIS) measurements in the ADEFC. In addition, the influence of two different commercial ionomers on the structure and transport properties of the catalyst layer and on the performance were analyzed with scanning electron microscopy, single cell tests, and EIS. The applicability barriers of the membranes were pointed out, and the ideal combinations of membrane and ionomer for the liquid-feed ADEFC achieved power densities of approximately 80 mW cm^-2 at 80 °C.

Electrode configurations study for alkaline direct ethanol fuel cells

The direct electrochemical conversion of ethanol, a sustainable fuel, is an alternative sustainable technology of the future. In this study, membrane electrode assemblies with different electrode configurations for an alkaline direct ethanol fuel cell were fabricated and tested in a fuel cell device. The configurations include a catalyst-coated substrate (CCS), a catalyst-coated membrane (CCM), and a mixture of these two fabrication options. Two different anion exchange membranes were used to perform a comprehensive analysis. The fabricated CCSs and CCMs were characterized with single cell measurements, electro­chemical impedance spectroscopy and scanning electron microscopy. In addition, the swelling behavior of the membranes in alkaline solution was investigated in order to obtain information for CCM production. The results of the experimental electrochemical tests show that the CCS approach provides higher power densities (42.4 mW cm-2) than the others, regardless of the membrane type.

Argon plasma-modified bacterial cellulose filters for protection against respiratory pathogens

In this work, we present novel, sustainable filters based on bacterial cellulose (BC) functionalized with low-pressure argon plasma (LPP-Ar). The "green" production process involved BC biosynthesis by Komagataeibacter xylinus, followed by simple purification, homogenization, lyophilization, and finally LPP-Ar treatment. The obtained LPP-Ar-functionalized BC-based material (LPP-Ar-BC-bM) showed excellent antimicrobial and antiviral properties against both Gram-positive (S. aureus) and Gram-negative (E. coli) bacteria, and an enveloped bacteriophage phage Φ6, with no cytotoxicity versus murine fibroblasts in vitro. Further, filters consisting of three layers of LPP-Ar-BC-bM had >99 % bacterial and viral filtration efficiency, while maintaining sufficiently low airflow resistance (6 mbar at an airflow of 95 L/min). Finally, as a proof-of-concept, we were able to prepare 80 masks with LPP-Ar-BC-bM filter and ~85 % of volunteer medical staff assessed them as "good" or "very good" in terms of comfort. We conclude that our novel sustainable, biobased, biodegradable filters are suitable for respiratory personal protective equipment (PPE), such as surgical masks and respirators.

Influence of the electrocatalyst layer thickness on alkaline DEFC performance

Determining the optimum layer thickness, for the anode and cathode, is of utmost importance for minimizing the costs of the alkaline direct ethanol fuel cell (DEFC) without lowering the electrochemical performance. In this study, the influence of layer thickness on the performance of the ethanol oxidation reaction (EOR) and oxygen reduction reaction (ORR) in an alkaline medium and resistance was investigated. The prepared gas diffusion electrodes (GDEs) were fully characterized, with scanning electron microscopy to determine the layer thickness and electrochemically in half-cell configuration. Cyclic voltammetry and polarization curve measurements were used to determine the oxidation and reduction processes of the metals, the electrochemical active surface area, and the activity towards the ORR and EOR. It was demonstrated that realistic reaction conditions can be achieved with simple and fast half-cell GDE measurements. Single cell measurements were conducted to evaluate the influence of factors, such as membrane or ethanol crossover. In addition, electrochemical impedance spectra investigation was performed to identify the effect of layer thickness on resistance. This successfully demonstrated that the optimal layer thicknesses and high maximum power density values (120 mW cm^-2) were achieved with the Pt-free catalysts and membranes used.

Dopamine-Assisted Modification of Polypropylene Film to Attain Hydrophilic Mineral-Rich Surfaces

The presented study focuses on the modification of polypropylene (PP) film with tetraethyl orthosilicate (TEOS) under heterogeneous conditions via polydopamine/polyethylene imine (PDA/PEI) chemistry using a facile dip-coating procedure to attain hydrophilic mineral-rich surfaces. Thus, the resulting PP-based films were further immersed in ion-rich simulated body fluid (SBF) to deposit Ca-based minerals onto the film's surfaces efficiently. In addition, the chemical reaction mechanism on PP film was proposed, and mineralisation potential inspected by determination of functional groups of deposits, zeta potential, hydrophilicity and surface morphology/topography using Fourier transform infrared (FTIR) spectroscopy, streaming potential, water contact angle (WCA), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The obtained results show the improved wettability of samples on account of PDA inclusion (WCA was reduced from 103° for pure PP film to 28° for PDA-modified film), as well as the presence of functional groups, due to the PDA/PEI/TEOS surface functionalisation, increased the ability of minerals to nucleate on the PP film's surface when it was exposed to an SBF medium. Moreover, the higher surface roughness due to the silica coatings influenced the enhanced anchoring and attachment of calcium phosphate (CaP), revealing the potential of such a facile approach to modify the chemically inert PP films, being of particular interest in different fields, including regenerative medicine.

GO-Enabled Bacterial Cellulose Membranes by Multistep, In Situ Loading: Effect of Bacterial Strain and Loading Pattern on Nanocomposite Properties

This paper presents the results of research on the preparation and properties of GO/BC nanocomposite from bacterial cellulose (BC) modified with graphene oxide (GO) using the in situ method. Two bacterial strains were used for the biosynthesis of the BC: Komagataeibacter intermedius LMG 18909 and Komagataeibacter sucrofermentans LMG 18788. A simple biosynthesis method was developed, where GO water dispersion was added to reinforced acetic acid-ethanol (RAE) medium at concentrations of 10 ppm, 25 ppm, and 50 ppm at 24 h and 48 h intervals. As a result, a GO/BC nanocomposite membrane was obtained, characterized by tensile strength greater by 150% as compared with the pure BC (̴ 50 MPa) and lower volume resistivity of ~4 ∙ 10⁹ Ω × cm. Moreover, GO addition increases membrane thickness up to ~10% and affects higher mass production, especially with low GO concentration. All of this may indicate the possibility of using GO/BC membranes in fuel cell applications.

Bromelain and Nisin: The Natural Antimicrobials with High Potential in Biomedicine

Infectious diseases along with various cancer types are among the most significant public health problems and the leading cause of death worldwide. The situation has become even more complex with the rapid development of multidrug-resistant microorganisms. New drugs are urgently needed to curb the increasing spread of diseases in humans and livestock. Promising candidates are natural antimicrobial peptides produced by bacteria, and therapeutic enzymes, extracted from medicinal plants. This review highlights the structure and properties of plant origin bromelain and antimicrobial peptide nisin, along with their mechanism of action, the immobilization strategies, and recent applications in the field of biomedicine. Future perspectives towards the commercialization of new biomedical products, including these important bioactive compounds, have been highlighted.

Efficient Chitosan/Nitrogen-Doped Reduced Graphene Oxide Composite Membranes for Direct Alkaline Ethanol Fuel Cells

Herein, we prepared a series of nanocomposite membranes based on chitosan (CS) and three compositionally and structurally different N-doped graphene derivatives. Two-dimensional (2D) and quasi 1D N-doped reduced graphene oxides (N-rGO) and nanoribbons (N-rGONRs), as well as 3D porous N-doped graphitic polyenaminone particles (N-pEAO), were synthesized and characterized fully to confirm their graphitic structure, morphology, and nitrogen (pyridinic, pyrrolic, and quaternary or graphitic) group contents. The largest (0.07%) loading of N-doped graphene derivatives impacted the morphology of the CS membrane significantly, reducing the crystallinity, tensile properties, and the KOH uptake, and increasing (by almost 10-fold) the ethanol permeability. Within direct alkaline ethanol test cells, it was found that CS/N rGONRs (0.07 %) membrane (Pmax. = 3.7 mWcm-2) outperformed the pristine CS membrane significantly (Pmax. = 2.2 mWcm-2), suggesting the potential of the newly proposed membranes for application in direct ethanol fuel cells.

Consolidation of cellulose nanofibrils with lignosulphonate bio-waste into excellent flame retardant and UV blocking membranes

The use of biomass to produce value-adding materials is a core objective of the circular economy, which has attracted great research interest in recent decades. In this context, we present here a simple dispersion-casting process for consolidation of cellulose nanofibrils (CNF), lignosulphonate (LS)-rich bio-waste and CaCl₂ in composite membranes. The addition of CaCl₂ to CNF and LS dispersions reduces the ζ potential, due to an electrostatic screening, which promotes the aggregation of CNF, increases its moisture content and promotes LS deposition on CNFs already in the dispersion phase. Addition of both the LS and CaCl₂ to CNF dispersion has an adverse effect on the mechanical properties of the final membranes. The effectiveness of the new composite membranes has been described in terms of their passive (charring) flame retardancy and 100 % UVA/UVB shielding capacity, both identified for membranes with the highest LS content, as well as high electronic resistance.

Efficiency of Differently Processed Membranes Based on Cellulose as Cationic Dye Adsorbents

In order to minimize the pollution caused by the reuse of textile dyes, technologies and materials have been developed that purify waste water in an efficient and cost-effective manner before it is discharged into a water body. In this context, the presented research investigates the potential of two types of fully cellulose-based membranes as adsorbents for cationic dyes used in the textile industry. The first type combines cellulose nanofibrils (CNFs) and carboxymethylated cellulose (CMC) using the solvent casting process and an esterification coupling reaction, while the second type uses commercial bacterial cellulose (BC) in a native and sodium periodate-treated form (BCox). The corresponding membranes were comprehensively evaluated by means of Fourier Transform Infrared (FTIR) Spectroscopy. Results confirm the esterification process within the CNF/CMC membranes, as well as BC oxidation after periodate treatment, as shown by bands at 1726.2 cm⁻¹ and 895 cm⁻¹, respectively. The Potentiometric Titration shows the highest total negative charge of 1.07 mmol/g for 4CNF/4CMC, which is assigned to the presence of COO⁻ within CMC polymers, and lowest (0.21 mmol/g) for BCox. The Contact Angle Goniometry data confirm the hydrophilicity of all membranes, and the angle increased from 0 ° (in pure BC) to 34.5 ° in CMC-rich and to 31.4 ° in BCox membranes due to the presence of CH₂COO⁻ and CHO groups, respectively. Confocal Fluorescent Microscopy (CFM) demonstrated the highest µ-roughness in 4CNF/4CMC, while Scanning Electron Microscopy (SEM) depicted diverse morphological features between the membranes, from ultrafine nanofiber networks (in BC and BCox) to larger fiber bundles connected within the polymer phase in CNF/CMC membranes. The adsorption experiment followed by UV–VIS spectroscopy, showed ~100% dye removal efficiency in both CNF/CMC-based membranes, while BC and BCox adsorbed only 24.3% and 23.6%, respectively, when anthraquinone dye was used. Azo dye was only adsorbed with an efficiency of 7–9% on CMC/CNF-based membranes, compared with 5.57% on BC and 7.33% on BCox membranes. The adsorption efficiency at equilibrium was highest for BC (1228 mg/g) and lowest for 7CNF/1CMC (419.24 mg/g) during anthraquinone dye adsorption. In the case of azo dye, the BCox was most effective, with 445.7 mg/g. Applicability of a pseudo second-order model was confirmed for both dyes and all membranes, except for BCox in combination with azo dye, showing the fastest adsorption rate in the case of the 7CNF/1CMC membrane.

Bacterial Cellulose: Production, Modification and Perspectives in Biomedical Applications

Bacterial cellulose (BC) is ultrafine, nanofibrillar material with an exclusive combination of properties such as high crystallinity (84%-89%) and polymerization degree, high surface area (high aspect ratio of fibers with diameter 20-100 nm), high flexibility and tensile strength (Young modulus of 15-18 GPa), high water-holding capacity (over 100 times of its own weight), etc. Due to high purity, i.e., absence of lignin and hemicellulose, BC is considered as a non-cytotoxic, non-genotoxic and highly biocompatible material, attracting interest in diverse areas with hallmarks in medicine. The presented review summarizes the microbial aspects of BC production (bacterial strains, carbon sources and media) and versatile in situ and ex situ methods applied in BC modification, especially towards bionic design for applications in regenerative medicine, from wound healing and artificial skin, blood vessels, coverings in nerve surgery, dura mater prosthesis, arterial stent coating, cartilage and bone repair implants, etc. The paper concludes with challenges and perspectives in light of further translation in highly valuable medical products.

Microstructured and Degradable Bacterial Cellulose⁻Gelatin Composite Membranes: Mineralization Aspects and Biomedical Relevance

Bacterial cellulose (BC)⁻gelatin (GEL) membranes were processed by successive periodate oxidation and a freeze-thawing/carbodiimide crosslinking procedure, first facilitating a Schiff-base reaction among respective aldehyde and hydroxyl groups, and later GEL stabilization and microstructuring. The formation of highly microporous structures within the GEL portion, with significant differences between bottom and top, was elucidated, and pores in the 27.6 ± 3 µm⁻108 ± 5 µm range were generated, exceeding the threshold value of ~10 µm sufficient for cell trafficking. During a relatively short (6 h) exhaustion procedure in supersaturated simulated body fluid solution, the membranes accommodated the combination of biologically relevant minerals, i.e., flake-like octacalcium phosphate (OCP) and (amorphous) apatite, onto their surface, forming a membrane with intensive swelling (650⁻1650%) and up to 90% weight loss in a 4-week period. The membranes´ 6-day eluates did not evoke any cytotoxic effects toward human fibroblast, MRC-5 cells. The same type of cells retained their morphology in direct contact with the membrane, attaching to the GEL porous site, while not attaching to the GEL thin-coated BC side, most probably due to combined, ablation effect of dominant β-sheet conformation and carbodiimide crosslinking. Together with arrested proliferation through the BC side, the membranes demonstrated beneficial properties for potential guided tissue regeneration (GTR) applications.

Rapid Water Softening with TEMPO-Oxidized/Phosphorylated Nanopapers

Water hardness not only constitutes a significant hazard for the functionality of water infrastructure but is also associated with health concerns. Commonly, water hardness is tackled with synthetic ion-exchange resins or membranes that have the drawbacks of requiring the awkward disposal of saturated materials and being based on fossil resources. In this work, we present a renewable nanopaper for the purpose of water softening prepared from phosphorylated TEMPO-oxidized cellulose nanofibrils (PT-CNF). Nanopapers were prepared from CNF suspensions in water (PT-CNF nanopapers) or low surface tension organic liquids (ethanol), named EPT-CNF nanopapers, respectively. Nanopaper preparation from ethanol resulted in a significantly increased porosity of the nanopapers enabling much higher permeances: more than 10,000× higher as compared to nanopapers from aqueous suspensions. The adsorption capacity for Ca²⁺ of nanopapers from aqueous suspensions was 17 mg g^-1 and 5 mg g^-1 for Mg²⁺; however, EPT-CNF nanopapers adsorbed more than 90 mg g^-1 Ca²⁺ and almost 70 mg g^-1 Mg²⁺. The higher adsorption capacity was a result of the increased accessibility of functional groups in the bulk of the nanopapers caused by the higher porosity of nanopapers prepared from ethanol. The combination of very high permeance and adsorption capacity constitutes a high overall performance of these nanopapers in water softening applications.

Antibacterial activity and cytotoxycity of gelatine-conjugated lysine-based peptides

The effect of the coupling approach (chemical by using carbodiimide chemistry, and enzymatic by using transglutaminase) of a hydrophilic ɛ-poly-L-lysine (ɛPL) and a structurally-hydrophobic oligo-acyl-lysyl (OAK) to a gelatine (GEL) macromolecule, and their antibacterial activity against Gram-negative E. coli and Gram-positive S. aureus bacteria, as well as cytotoxicity to human osteoblast cells was studied as potential macromolecules for biomedical applications. Different spectroscopic (ultraviolet-visible, infrared, fluorescence, and electron paramagnetic resonance) and separation (size-exclusion chromatography and capillary zone electrophoresis) techniques, as well as zeta-potential analysis were performed to confirm the ɛPL/OAK covalent coupling and to determine their amount and orientation of the immobilization. The highest and kinetically the fastest reduction of bacteria (≥77% against E. coli vs. ≥82% against S. aureus) was achieved with GEL functionalized with ɛPL/OAK by the chemical grafting-to approach being correlated with conformationally the highly-flexible ˝brush-like˝ orientation linkage of peptides, enable its targeted and rapid interactions with bacteria membrane. The up to 400-fold lower yield of OAKs being immobilized may be related also to its cationic charge and hydrophobic alkyl chain moieties, compared to more hydrophilic ɛPL easily causing random polymerization and self-conjugation. The ɛPL/OAK-functionalized GEL did not induce citotoxicity to osteoblasts, even at ∼25-fold higher concentration than bacterial minimum inhibitory (MIC) concentration of ɛPL/OAK. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 3110-3126, 2017.

Mineralization potential of cellulose-nanofibrils reinforced gelatine scaffolds for promoted calcium deposition by mesenchymal stem cells

Cellulose-nanofibrils (CNFs) enriched gelatine (GEL) scaffolds were fabricated in-situ by the combined freeze-thawing process and carbodiimide crosslinking chemistry. The original- and variously surface anionised CNFs (carboxylated/CNF-COOH/, and phosphonated with 3-AminoPropylphosphoric Acid/CNF-COOH-ApA/) were used in order to tune the scaffolds' biomimetic structure towards a more intensive mineralization process. The pore size reduction (from 208±35μm to 91±35μm) after 50% v/v of CNFs addition to GEL was identified, while separated pore-walls' alignment vs. shorter, dense and elongated pores are observed when using 80% v/v of original-CNFs vs. anionised-CNFs, all of them possessed osteoid-like compressive strength (0.025-0.40MPa) and elasticity (0.04-0.15MPa). While randomly distributed Ca²⁺-deficient hydroxyapatite/HAp/(Ca/P≈1.4) aggregates were identified in the case of original-CNF prevalent scaffolds after four weeks of incubation in SBF, the more uniform and intensified deposition with HAp-like (Ca/P≈1.69) structures were established using CNF-COOH-Apa. The growth of Mesenchymal Stem Cells (MSCs) was observed on all CNF-containing scaffolds, resulting in more extensive Ca²⁺ deposition compared to the positive control or pure GEL scaffold. Among them, the scaffold prepared with the 50% v/v CNF-COOH-ApA showed significantly increased mineralization kinetic as well as the capacity for bone-like patterning in bone tissue regeneration.

Correction: Mechanically strong, flexible and thermally stable graphene oxide/nanocellulosic films with enhanced dielectric properties

Correction for ‘Mechanically strong, flexible and thermally stable graphene oxide/nanocellulosic films with enhanced dielectric properties’ by Yasir Beeran P. T. et al., RSC Adv., 2016, 6, 49138–49149.

Mechanically strong, flexible and thermally stable graphene oxide/nanocellulosic films with enhanced dielectric properties

Mechanically strong and flexible films with dielectric properties and energy storage ability have been fabricated from ammonia-functionalized graphene oxide (NGO) nanoplatelets and cellulose nanofibrils (CNFs) vs. TEMPO pre-oxidized CNFs (TCNFs).

Molecular mobility of scaffolds' biopolymers influences cell growth

Understanding biocompatibility of materials and scaffolds is one of the main challenges in the field of tissue engineering and regeneration. The complex nature of cell-biomaterial interaction requires extensive preclinical functionality testing by studying specific cell responses to different biomaterial properties, from morphology and mechanics to surface characteristics at the molecular level. Despite constant improvements, a more general picture of biocompatibility is still lacking and tailormade scaffolds are not yet available. The scope of our study was thus the investigation of the correlation of fibroblast cell growth on different gelatin scaffolds with their morphological, mechanical as well as surface molecular properties. The latter were thoroughly investigated via polymer molecular mobility studied by site-directed spin labeling and electron paramagnetic resonance spectroscopy (EPR) for the first time. Anisotropy of the rotational motion of the gelatin side chain mobility was identified as the most correlated quantity with cell growth in the first days after adhesion, while weaker correlations were found with scaffold viscoelasticity and no correlations with scaffold morphology. Namely, the scaffolds with highly mobile or unrestricted polymers identified with the cell growth being five times less efficient (N(cells) = 60 ± 25 mm(-2)) as compared to cell growth on the scaffolds with considerable part of polymers with the restricted rotational motion (N(cells) = 290 ± 25 mm(-2)). This suggests that molecular mobility of scaffold components could play an important role in cell response to medical devices, reflecting a new aspect of the biocompatibility concept.

Processing of gelatin-based cryogels with improved thermomechanical resistance, pore size gradient, and high potential for sustainable protein drug release

Porous gelatin (GEL) cryogels were processed by spatiotemporal and temperature-controlled gelation and freezing-lyophilizaton process, followed by zero-length crosslinking, using different molarities of reagents (EDC and NHS) and reaction media (100% PBS or 20/80% PBS/EtOH mixture) for variable time extensions (1-24 h). In this way, tuneable cryogels with gradient microporosity (from 100 µm to 1000 µm) were formed, being mainly influenced by crosslinkers' concentration and EtOH addition. Later affect the pore morphology (from round to ellipsoid), consequently modulating the steady-state physiological swelling profile toward twice lower values (∼ 600%) comparing to stepwise swelling of in 100% PBS media crosslinked cryogels. While the presence of EtOH decelerate the crosslinking kinetic by retaining cryogels' microstructure formed during freezing, the 100% PBS and higher EDC molarity resulted in approximately 40% crosslinking degree, being expressed as a thermal resistance of cryogels up to approximately 73°C. Finally, the tuneable enzymatic resistance allow time-dependent poly-L-Lysine (pL) release profile in up to month period. The processed GEL cryogels have potential in broad range biomedical applications, especially as sustainable, protein-based drug delivery systems.

Preparation, characterization, and in vitro enzymatic degradation of chitosan-gelatine hydrogel scaffolds as potential biomaterials

The crosslinking of chitosan (CHT) and gelatin (GEL) accomplished with N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) was investigated and optimized in relation to hydrogels stability by varying the CHT/GEL mass ratio and the EDC/NHS molar ratio at different and constant EDC concentrations. Hydrogels were also fabricated in the presence of α-tocopherol to assess the release mechanism of a lipophilic drug from a highly-hydrophilic CHT/GEL hydrogel network. Alterations in the physico-chemical properties of hydrogels were characterized by differential scanning calorimetry (DSC) and fourier transform infrared spectroscopy (FTIR), and their biostability was studied within a simulated body-fluid solution (PBS of pH 7.4) at 37 °C for 24 h by evaluating the degree of swelling, followed by topography and morphology characterization using scanning electron microscopy (SEM). The analysis confirmed the formation of a modulated hydrogels porosity using different freezing temperatures prior to lyophilization. The in vitro degradation behaviors of the hydrogels were investigated for up to 5 weeks using collagenase, lysozyme, and N-acetyl-β-D-glucosaminidase by monitoring the weight-losses of hydrogels and their degradation products, being identified by UV-Vis spectroscopy and high-performance liquid chromatography (HPLC) as well as the pH monitoring of degraded solutions. It was observed that an inner morphological hydrogel structure influences their swelling and degradation behavior, which is additionally reduced by in-gel-embedded α-tocopherol because of hydrophobic interactions with their constituents, and hindering the effect on collagenase activity.