Cation-exchange performance of a citric-acid esterified cellulose nanofibrous membrane for highly-selective proteins' permeability and adsorption capacity

The usage of low-cost, readily available, or even disposable, single-use membranes in macromolecules' purification and separation is still in the development phase. In this research, highly porous (>95 %), water- and compression stable cation-exchange membranes were prepared by freeze-casting using cellulose nanofibrils (CNF) and citric acid (CA) acting as a crosslinker and source of weak anionic (carboxylic) surface groups arising from the mono-esterified CA. The membranes were characterized by different analytical techniques, and evaluated for the ionic adsorption efficacy of different proteins in dead-end filtration mode using a Tri-buffer of pH 8. The membrane's internal microstructure (porosity and density) with the available (quantity and access) carboxylic groups was confirmed, to determine not only the proteins' specific (related to the net charged and molecular weight) adsorption dynamic (>52 % of positive Lysozyme/Cytochrome, <8 % of negative BSA/Myoglobin; ≤0.5 g/L) at extremely high flow rates (>3.000 hL/h*MPa*m2), but also their desorption (>97 %) and re-equilibration (using NaCl) with flux recovery (>80 %). Such efficiency was achieved with up to 5 consecutive filtering cycles. The high permeability (>87 %) of the spherical and negatively surface charged microparticles (used as models) also suggests the likelihood of removing larger microbial species, which, while retaining relatively smaller and positively charged proteins, further increases their potential in biopharma applications.

Using Different Surface Energy Models to Assess the Interactions between Antiviral Coating Films and phi6 Model Virus

High molecular weight chitosan (HMWCh), quaternised cellulose nanofibrils (qCNF), and their mixture showed antiviral potential in liquid phase, while this effect decreased when applied to facial masks, as studied in our recent work. To gain more insight into material antiviral activity, spin-coated thin films were prepared from each suspension (HMWCh, qCNF) and their mixture with a 1:1 ratio. To understand their mechanism of action, the interactions between these model films with various polar and nonpolar liquids and bacteriophage phi6 (in liquid phase) as a viral surrogate were studied. Surface free energy (SFE) estimates were used as a tool to evaluate the potential adhesion of different polar liquid phases to these films by contact angle measurements (CA) using the sessile drop method. The Fowkes, Owens-Wendt-Rabel-Kealble (OWRK), Wu, and van Oss-Chaudhury-Good (vOGC) mathematical models were used to estimate surface free energy and its polar and dispersive contributions, as well as the Lewis acid and Lewis base contributions. In addition, the surface tension SFT of liquids was also determined. The adhesion and cohesion forces in wetting processes were also observed. The estimated SFE of spin-coated films varied between mathematical models (26-31 mJ/m²) depending on the polarity of the solvents tested, but the correlation between models clearly indicated a significant dominance of the dispersion components that hinder wettability. The poor wettability was also supported by the fact that the cohesive forces in the liquid phase were stronger than the adhesion to the contact surface. In addition, the dispersive (hydrophobic) component dominated in the phi6 dispersion, and since this was also the case in the spin-coated films, it can be assumed that weak physical van der Waals forces (dispersion forces) and hydrophobic interactions occurred between phi6 and the polysaccharide films, resulting in the virus not being in sufficient contact with the tested material during antiviral testing of the material to be inactivated by the active coatings of the polysaccharides used. Regarding the contact killing mechanism, this is a disadvantage that can be overcome by changing the previous material surface (activation). In this way, HMWCh, qCNF, and their mixture can attach to the material surface with better adhesion, thickness, and different shape and orientation, resulting in a more dominant polar fraction of SFE and thus enabling the interactions within the polar part of phi6 dispersion.

Screen-printing of chitosan and cationised cellulose nanofibril coatings for integration into functional face masks with potential antiviral activity

Masks proved to be necessary protective measure during the COVID-19 pandemic, but they provided a physical barrier rather than inactivating viruses, increasing the risk of cross-infection. In this study, high-molecular weight chitosan and cationised cellulose nanofibrils were screen-printed individually or as a mixture onto the inner surface of the first polypropylene (PP) layer. First, biopolymers were evaluated by various physicochemical methods for their suitability for screen-printing and antiviral activity. Second, the effect of the coatings was evaluated by analysing the morphology, surface chemistry, charge of the modified PP layer, air permeability, water-vapour retention, add-on, contact angle, antiviral activity against the model virus phi6 and cytotoxicity. Finally, the functional PP layers were integrated into face masks, and resulting masks were tested for wettability, air permeability, and viral filtration efficiency (VFE). Air permeability was reduced for modified PP layers (43 % reduction for kat-CNF) and face masks (52 % reduction of kat-CNF layer). The antiviral potential of the modified PP layers against phi6 showed inhibition of 0.08 to 0.97 log (pH 7.5) and cytotoxicity assay showed cell viability above 70 %. VFE of the masks remained the same (~99.9 %), even after applying the biopolymers, confirming that these masks provided high level of protection against viruses.

Enzymatic, Antioxidant, and Antimicrobial Activities of Bioactive Compounds from Avocado (Persea americana L.) Seeds

The aim of this research was to identify and quantify biologically active compounds from avocado (Persea americana L.) seeds (AS) utilizing different techniques with the use of ultrasound (US), ethanol (EtOH), and supercritical carbon dioxide (scCO₂) for possible applications in (bio)medicine, pharmaceutical, cosmetic, or other relevant industries. Initially, a study of the process efficiency (η) was carried out, which revealed yields in the range of 2.96-12.11 wt%. The sample obtained using scCO₂ was found to be the richest in total phenols (TPC) and total proteins (PC), while the sample obtained with the use of EtOH resulted in the highest content of proanthocyanidins (PAC). Phytochemical screening of AS samples, quantified by the HPLC method, indicated the presence of 14 specific phenolic compounds. In addition, the activity of the selected enzymes (cellulase, lipase, peroxidase, polyphenol oxidase, protease, transglutaminase, and superoxide dismutase) was quantified for the first time in the samples from AS. Using DPPH radical scavenging activity, the highest antioxidant potential (67.49%) was detected in the sample obtained with EtOH. The antimicrobial activity was studied using disc diffusion method against 15 microorganisms. Additionally, for the first time, the antimicrobial effectiveness of AS extract was quantified by determination of microbial growth-inhibition rates (MGIRs) at different concentrations of AS extract against three strains of Gram-negative (Escherichia coli, Pseudomonas aeruginosa, and Pseudomonas fluorescens) bacteria, three strains of Gram-positive (Bacillus cereus, Staphylococcus aureus, and Streptococcus pyogenes) bacteria, and fungi (Candida albicans). MGIRs and minimal inhibitory concentration (MIC₉₀) values were determined after 8 and 24 h of incubation, thus enabling the screening of antimicrobial efficacy for possible further applications of AS extracts as antimicrobial agents in (bio)medicine, pharmaceutical, cosmetic, or other industries. For example, the lowest MIC₉₀ value was determined for B. cereus after 8 h of incubation in the case of UE and SFE extracts (70 μg/mL), indicating an outstanding result and the potential of AS extracts, as the MIC values for B. cereus have not been investigated so far.

Cationised Fibre-Based Cellulose Multi-Layer Membranes for Sterile and High-Flow Bacteria Retention and Inactivation

Low-cost, readily available, or even disposable membranes in water purification or downstream biopharma processes are becoming attractive alternatives to expensive polymeric columns or filters. In this article, the potential of microfiltration membranes prepared from differently orientated viscose fibre slivers, infused with ultrafine quaternised (qCNF) and amino-hydrophobised (aCNF) cellulose nanofibrils, were investigated for capturing and deactivating the bacteria from water during vacuum filtration. The morphology and capturing mechanism of the single- and multi-layer structured membranes were evaluated using microscopic imaging and colloidal particles. They were assessed for antibacterial efficacy and the retention of selected bacterial species (Escherichia coli, Staphylococcus aureus, Micrococcus luteus), differing in the cell envelope structure, hydrodynamic biovolume (shape and size) and their clustering. The aCNF increased biocidal efficacy significantly when compared to qCNF-integrated membrane, although the latter retained bacteria equally effectively by a thicker multi-layer structured membrane. The retention of bacterial cells occurred through electrostatic and hydrophobic interactions, as well as via interfibrous pore diffusion, depending on their physicochemical properties. For all bacterial strains, the highest retention (up to 100% or log 6 reduction) at >50 L/h∗bar∗m² flow rate was achieved with a 4-layer gradient-structured membrane containing different aCNF content, thereby matching the performance of industrial polymeric filters used for removing bacteria.

Antibacterial and degradation properties of dialdehyded and aminohexamethylated nanocelluloses

Dialdehyde cellulose nanofibrils (CNF) and nanocrystals (CNC) were prepared via periodate oxidation (CNF/CNC-ox) and subsequently functionalized with hexamethylenediamine (HMDA) via a Schiff-base reaction, resulting in partially crosslinked micro-sized (0.5-10 μm) particles (CNF/CNC-ox-HMDA) with an aggregation and sedimentation tendency in an aqueous media, as assessed by Dynamic Light Scattering and Scanning Electron Microscopy. The antibacterial efficacy, aquatic in vivo (to Daphnia magna) and human in vitro (to A594 lung cells) toxicities, and degradation profiles in composting soil of all forms of CNF/CNC were assessed to define their safety profile. CNF/CNC-ox-HMDA exhibited higher antibacterial activity than CNF/CNC-ox and higher against Gram-positive S. aureus than Gram-negative E. coli, yielding a bacteria reduction of >90 % after 24 h of exposure at the minimum (≤2 mg/mL), but potentially moderately/aquatic and low/human toxic concentrations (≥50 mg/L). The presence of anionic, un/protonated amino-hydrophobized groups in addition to unconjugated aldehydes of hydrodynamically smaller (<1 μm) CNC-ox-HMDA increased the reduction of both bacteria to log 9 at ≥4 mg/mL and their bactericidal activity. While only CNF/CNC-ox can be considered as biosafe and up to >80 % biodegradable within 24 weeks, this process was inhibited for the CNF/CNC-ox-HMDA. This indicated their different stability, application and disposal after use (composting vs. recycling).

Phosphonate-Modified Cellulose Nanocrystals Potentiate the Th1 Polarising Capacity of Monocyte-Derived Dendritic Cells via GABA-B Receptor

Purpose

Phosphonates, like 3-AminoPropylphosphonic Acid (ApA), possess a great potential for the therapy of bone tumours, and their delivery via cellulose nanocrystals (CNCs) seems a promising approach for their increased efficacy in target tissues. However, the immunological effects of CNC-phosphonates have not been investigated thoroughly. The main aim was to examine how the modification of CNCs with phosphonate affects their immunomodulatory properties in human cells.

Methods

Wood-based native (n) CNCs were modified via oxidation (ox-CNCs) and subsequent conjugation with ApA (ApA-CNCs). CNCs were characterised by atomic force microscopy (AFM) and nanoindentation. Cytotoxicity and immunomodulatory potential of CNCs were investigated in cultures of human peripheral blood mononuclear cells (PBMCs) and monocyte-derived dendritic cells (MoDCs)/T cells co-cultures by monitoring phenotype, cytokines production, allostimulatory and Th/Treg polarisation capacity.

Results

AFM showed an increase in CNCs' thickens, elasticity modulus and hardness during the modification with ApA. When applied at non-toxic doses, nCNCs showed a tolerogenic potential upon internalisation by MoDCs, as judged by their increased capacity to up-regulate tolerogenic markers and induce regulatory T cells (Treg), especially when present during the differentiation of MoDCs. In contrast, ox- and ApA-CNCs induced oxidative stress and autophagy in MoDCs, which correlated with their stimulatory effect on the maturation of MoDCs, but also inhibition of MoDCs differentiation. ApA-CNC-treated MoDCs displayed the highest allostimulatory and Th1/CTL polarising activity in co-cultures with T cells. These effects of ApA-CNCs were mediated via GABA-B receptor-induced lowering of cAMP levels in MoDCs, and they could be blocked by GABA-B receptor inhibitor. Moreover, the Th1 polarising and allostimulatory capacity of MoDCs differentiated with ApA-CNC were largely preserved upon the maturation of MoDCs, whereas nCNC- and ox-CNC-differentiated MoDCs displayed an increased tolerogenic potential.

Conclusion

The delivery of ApA via CNCs induces potent DC-mediated Th1 polarisation, which could be beneficial in their potential application in tumour therapy.

Solidification of Gelatine Hydrogels by Using a Cryoplatform and Its Validation through CFD Approaches

In this work, we developed a numerical approach based on an experimental platform to determine the working conditions on a cryoplatform and to predict and evaluate the cryogenic printing of hydrogels. Although hydrogels have good biocompatibility, their material properties make it difficult to print them with high precision and shape fidelity. To overcome these problems, a cryogenic cooling platform was introduced to accelerate the physical stabilisation of each deposited layer during the printing process. By precisely controlling solidification (crystallisation), each printed material can withstand its own weight to maintain shape fidelity, and the porosity of the scaffolds can also be controlled more selectively. The thermophysical properties of gelatine hydrogels were investigated to gain a better understanding of the phase change upon freezing. The corresponding material properties and experimental observations of gelatine solidification served as the basis for developing a computational fluid model (CFD) to mimic the solidification of gelatine hydrogels using a cryoplatform at different process conditions and extruder speeds. The goal was to develop a tool simple enough to predict acceptable process conditions for printing gelatine hydrogels using a cryoplatform.

Synergistic Effect of Screen-Printed Single-Walled Carbon Nanotubes and Phosphorylated Cellulose Nanofibrils on Thermophysiological Comfort, Thermal/UV Resistance, Mechanical and Electroconductive Properties of Flame-Retardant Fabric

Single-walled carbon nanotubes (SWCNTs) and phosphorylated nanocellulose fibrils (PCNFs) were used as functional screen-print coatings on flame-retardant (FR) fabric, to improve its thermal resistance and thermophysiological comfort (wetting, water vapour and heat transmission) properties, while inducing it with electrical conductivity and UV protection. The effect of PCNF printing, followed by applying a hydrophobic polyacrylate (AP), on the same (back/B, turned outwards) or other (front/F, turned towards skin) side of the fabric, with and without the addition of 0.1–0.4 wt% SWCNTs, was studied by determining the amount of applied coating and its distribution (microscopic imaging), and measuring the fabric’s colour, air permeability, thickness, mechanical, flame and abrasion resistance properties. Due to the synergistic effect of PCNF and SWCNTs, both-sided printed fabric (front-side printed with PCNF and back-side with SWCNTs within AP) resulted in an increased heat transfer (25%) and an improved thermal resistance (shift of degradation temperature by up to 18 °C towards a higher value) and UV protection (UPF of 109) without changing the colour of the fabric. Such treatment also affected the moisture management properties with an increased water-vapour transfer (17%), reduced water uptake (39%) and asymmetric wettability due to the hydrophilic front (Contact Angle 46°) and hydrophobic back (129°) side. The increased tensile (16%) and tear (39%) strengths were also assessed in the warp direction, without worsening the abrasion resistance of the front-side. A pressure-sensing electrical conductivity (up to 4.9∙10⁻⁴ S/cm with an increase to 12.0∙10⁻⁴ S/cm at 2 bars) of the SWCNT-printed side ranks the fabric among the antistatic, electrostatic discharge (ESD) or electromagnetic interference (EMI) shielding protectives.

Nanocellulose in Drug Delivery and Antimicrobially Active Materials

In recent years, nanocellulose (NC) has also attracted a great deal of attention in drug delivery systems due to its unique physical properties, specific surface area, low risk of cytotoxicity, and excellent biological properties. This review is focused on nanocellulose based systems acting as carriers to be used in drug or antimicrobial delivery by providing different but controlled and sustained release of drugs or antimicrobial agents, respectively, thus showing potential for different routes of applications and administration. Microorganisms are increasingly resistant to antibiotics, and because, generally, the used metal or metal oxide nanoparticles at some concentration have toxic effects, more research has focused on finding biocompatible antimicrobial agents that have been obtained from natural sources. Our review contains the latest research from the last five years that tested nanocellulose-based materials in the field of drug delivery and antimicrobial activity.

Mechanical Properties and Cytotoxicity of Differently Structured Nanocellulose-hydroxyapatite Based Composites for Bone Regeneration Application

The nanocomposites were prepared by synthesizing (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO)-oxidized cellulose nanofibrils (TCNFs) or cellulose nanocrystals (CNCs) with hydroxyapatite (HA) in varying composition ratios in situ. These nanocomposites were first obtained from eggshell-derived calcium and phosphate of ammonium dihydrogen orthophosphate as precursors at a stoichiometric Ca/P ratio of 1.67 with ultrasonication and compressed further by a uniaxial high-pressure technique. Different spectroscopic, microscopic, and thermogravimetric analyses were used to evaluate their structural, crystalline, and morphological properties, while their mechanical properties were assessed by an indentation method. The contents of TCNF and CNC were shown to render the formation of the HA crystallites and thus influenced strongly on the composite nanostructure and further on the mechanical properties. In this sense, the TCNF-based composites with relatively higher contents (30 and 40 wt %) of semicrystalline and flexible TCNFs resulted in smoother and more uniformly distributed HA particles with good interconnectivity, a hardness range of 550-640 MPa, a compression strength range of 110-180 MPa, an elastic modulus of ~5 GPa, and a fracture toughness value of ~6 MPa1/2 in the range of that of cortical bone. Furthermore, all the composites did not induce cytotoxicity to human bone-derived osteoblast cells but rather improved their viability, making them promising for bone tissue regeneration in load-bearing applications.

Effect of Selected Comonomers on the Transition Temperature of Thermosensitive NIPA Derivatives Synthesized with an Anionic Initiator

The present study evaluates the effect of the cationic initiator on the hydrodynamic diameter of copolymers of N-isopropylacrylamide nanogels synthesized via a surfactant-free precipitation polymerization at 70 °C in the presence of the cationic initiator 2,2'-azobis[2- methylpropionamidine] dihydrochloride. Three types of polymeric nanoparticles were synthesized using N, N'-methylenebisacrylamide as a crosslinker. The first batch was used as a reference. The second type of particles included a poly(ethylene glycol) methyl ether-acrylate monomer, while the third type used an N-tert-butylacrylamide comonomer. The hydrodynamic diameters of the synthesized particles were between 160 and 970 nm at 18 °C. The chemical composition and morphology of the synthesized co-polymeric nanoparticles were confirmed using infrared spectroscopy, nuclear magnetic resonance and scanning electron microscopy. The zeta potentials measured via dynamic light scattering were 20.0, 17.0, -0.1 mV for the three types, respectively. The volume phase transition temperature was between 22 and 41 °C. The polydispersity index of particles synthesized with N-tert-butylacrylamide varied depending on the measurement temperature.

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.

UV-Induced reduction of graphene oxide in cellulose nanofibril composites

We report on an effective dry method to reduce graphene oxide (GO) in films of cellulose nanofibrils (CNF) by UV irradiation in the presence of nitrogen gas.

Functionalization-dependent effects of cellulose nanofibrils on tolerogenic mechanisms of human dendritic cells

Background

Cellulose nanofibrils (CNF) are attractive nanomaterials for various biomedical applications due to their excellent biocompatibility and biomimetic properties. However, their immunoregulatory properties are insufficiently investigated, especially in relation to their functionalization, which could cause problems during their clinical application.

Methods

Using a model of human dendritic cells (DC), which have a central role in the regulation of immune response, we investigated how differentially functionalized CNF, ie, native (n) CNF, 2,2,6,6-tetramethylpiperidine 1-oxyl radical-oxidized (c) CNF, and 3-aminopropylphosphoric acid-functionalized (APAc) CNF, affect DC properties, their viability, morphology, differentiation and maturation potential, and the capacity to regulate T cell-mediated immune response.

Results

Nontoxic doses of APAcCNF displayed the strongest inhibitory effects on DC differentiation, maturation, and T helper (Th) 1 and Th17 polarization capacity, followed by cCNF and nCNF, respectively. These results correlated with a specific pattern of regulatory cytokines production by APAcCNF-DC and their increased capacity to induce suppressive CD8⁺CD25⁺IL-10⁺ regulatory T cells in immunoglobulin-like transcript (ILT)-3- and ILT-4- dependent manner. In contrast, nCNF-DC induced predominantly suppressive CD4⁺CD25^hiFoxP3^hi regulatory T cells in indolamine 2,3-dioxygenase-1-dependent manner. Different tolerogenic properties of CNF correlated with their size and APA functionalization, as well as with different expression of CD209 and actin bundles at the place of contact with CNF.

Conclusion

The capacity to induce different types of DC-mediated tolerogenic immune responses by functionalized CNF opens new perspectives for their application as well-tolerated nanomaterials in tissue engineering and novel platforms for the therapy of inflammatory T cell-mediated pathologies.

Incorporation of antimicrobial peptides on electrospun nanofibres for biomedical applications

The aim of this work was to immobilize antimicrobial peptides onto a fibrous scaffold to create functional wound dressings. The scaffold was produced by electrospinning from a mixture of the water soluble polymers poly(acrylic acid) and poly(vinyl alcohol) and subsequently heat cured at 140 °C to produce a stable material with fibre diameter below micron size. The peptides were incorporated into the negatively charged scaffold by electrostatic interaction. The best results were obtained for lysozyme impregnated at pH 7, which rendered a loading of up to 3.0 × 10⁻⁴ mmol mg⁻¹. The dressings were characterized using SEM, ATR-FTIR, elemental analysis, ζ-potential and confocal microscopy using fluorescamine as an amine-reactive probe. The dressings preserved their fibrous structure after impregnation and peptides were distributed homogeneously throughout the fibrous network. The antibacterial activity was assessed by solid agar diffusion tests and growth inhibition in liquid cultures using Staphylococcus aureus, a pathogenic strain generally found in infected wounds. The antibacterial activity caused clear halo inhibition zones for lysozyme-loaded dressings and a 4-fold decrease in S. aureus viable colonies after two weeks of contact of dressings with bacterial liquid cultures. The release profile in different media showed sustained release in acidic environments, and a rapid discharge at high pH values. The incorporation of lysozyme resulted in dressing surfaces essentially free of microbial growth after 14 days of contact with bacteria at pH 7.4 attributed to the peptide that remained attached to the dressing surface.

The aim of this work was to immobilize antimicrobial peptides onto a fibrous scaffold to create functional wound dressings.

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.

INFLUENCE OF LIPOPHILIC AND HYDROPHILIC CO-MONOMERS ON THE HYDRODYNAMIC DIAMETER OF THERMOSENSITIVE NIPA DERIVATIVES FOR THERMALLY CONTROLLED DRUG DELIVERY

For modem drug delivery, new drug carriers sensitive to various factors and with size in the range of micro- and nanometers are required. The aim of this work was to evaluate the influence of hydrophilic and hydrophobic co-monomers on the hydrodynamic diameter of three co-polymers of N-isopropylacrylamide (NIPA) nanogels synthesized at 70*C in the presence of potassium persulfate (KPS) as the initiator and N.N'-methylene bis-acrylamide (MBA) as the cross-linker. The first batch of nanoparticles was synthesized without co-monomer, whereas poly(ethylene glycol) methyl ether acrylate (PEG-MEA), and N-teii-butylacrylamide (NTB), were implemented as co-monomers for the second and third batch. Hydrodynamic diameter of nanoparticles was in the range 550-800 rn. The compositions of the synthesized co-polymer nanoparticles were con- firmed via IR and NMR analyses. The SFPP conditions resulted in hydrodynamic diameters ranging from approximately 550 to 800 nm at temperatures lower than the volume phase transition temperature (VPTT) and diameters ranging from 250 to 600 nm at temperatures above the VPTT, where the VPTT was between 26 and 41'C. The polydispersity index (PDI) showed a maximum or a minimum value at the VPTT, which was an important indicator of the volume phase transition. According to the PDI observation during thermal cycling, the addition of NTB into the polymeric chain resulted in maximal values of the PDI at the VPIT, similar to the case of nanoparticles without any additional co-monomers. In contrast, in the case of PEG-MEA, the PDI presented a minimal value. Dynamic light scattering (DLS) volume measurements, performed simultaneously with spectral methods, may lead to a fast evaluation of nanoparticles prepared by SFPP.

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.

Native cellulose nanofibrills induce immune tolerance in vitro by acting on dendritic cells

Cellulose nanofibrills (CNFs) are attractive biocompatible, natural nanomaterials for wide biomedical applications. However, the immunological mechanisms of CNFs have been poorly investigated. Considering that dendritic cells (DCs) are the key immune regulatory cells in response to nanomaterials, our aim was to investigate the immunological mechanisms of CNFs in a model of DC-mediated immune response. We found that non-toxic concentrations of CNFs impaired the differentiation, and subsequent maturation of human monocyte-derived (mo)-DCs. In a co-culture with CD4⁺T cells, CNF-treated mo-DCs possessed a weaker allostimulatory and T helper (Th)1 and Th17 polarizing capacity, but a stronger capacity to induce Th2 cells and CD4⁺CD25^hiFoxP3^hi regulatory T cells. This correlated with an increased immunoglobulin-like transcript-4 and indolamine dioxygenase-1 expression by CNF-treated mo-DCs, following the partial internalization of CNFs and the accumulation of CD209 and actin bundles at the place of contacts with CNFs. Cumulatively, we showed that CNFs are able to induce an active immune tolerance by inducing tolerogenic DCs, which could be beneficial for the application of CNFs in wound healing and chronic inflammation therapies.

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.

High-flux affinity membranes based on cellulose nanocomposites for removal of heavy metal ions from industrial effluents

Fully biobased affinity membranes based on cellulose nanocrystal functional layer for removal of heavy metal ions from industry effluents were successfully demonstrated.

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).

Enhanced catalytic activity of the surface modified TiO2-MWCNT nanocomposites under visible light

Fusing multiwall carbon nanotubes (MWCNTs) with TiO2 at the nano-scale level promotes the separation of those electron-hole charges generated upon UV and daylight irradiation. In this study, we investigated facile sonochemical synthesis, combined with the calcination process for the preparations of TiO2-MWCNT composites with different mole ratios of titanium and carbon. In order to produce stable nano dispersions we exploited an innovative biotechnology-based approach for the covalent functionalizations of TiO2-MWCNTs with in-situ synthesized soluble phenoxazine dye molecules. The none and functionalized TiO2-MWCNTs composites were analyzed by a range of analytical techniques including XRD, Raman, XPS, SEM and UV-vis diffuse reflectance spectroscopy (DRS), and dynamic light scattering (DLS). The photocatalytic activity was evaluated toward the liquid-phase degradation of MB in aqueous solution under both UV and visible light irradiation. TiO2-MWCNTs with optimized mole ratio exhibit much higher photocatalytic activity and stability than bare TiO2. The as-prepared TiO2-MWCNTs photocatalyst possessed good adsorptivity of dyes, extended light absorption range and efficient charge separation properties simultaneously. The results indicated that the soluble phenoxazine dyes and amino-benzenesulfonic acid monomers were covalently grafted on to the surfaces of TiO2-MCNTs, which promoted good aquatic dispersibility and extended light absorption, resulting in increased photocatalytic efficiency.

Nanocelluloses and their phosphorylated derivatives for selective adsorption of Ag(+), Cu(2+) and Fe(3+) from industrial effluents

The potential of nanoscaled cellulose and enzymatically phosphorylated derivatives as bio-adsorbents to remove metal ions (Ag(+), Cu(2+) and Fe(3+)) from model water and industrial effluents is demonstrated. Introduction of phosphate groups onto nanocelluloses significantly improved the metal sorption velocity and sorption capacity. The removal efficiency was considered to be driven by the high surface area of these nanomaterials as well as the nature and density of functional groups on the nanocellulose surface. Generally, in the solutions containing only single types of metal ions, the metal ion selectivity was in the order Ag(+)>Cu(2+)>Fe(3+), while in the case of mixtures of ions, the order changed to Ag(+)>Fe(3+)>Cu(2+), irrespective of the surface functionality of the nanocellulose. In the case of industrial effluent from the mirror making industry, 99% removal of Cu(2+) and Fe(3+) by phosphorylated nanocellulose was observed. The study showed that phosphorylated nanocelluloses are highly efficient biomaterials for scavenging multiple metal ions, simultaneously, from industrial effluents.

Effect of Low-Density Static Magnetic Field on the Oxidation of Ammonium by Nitrosomonas europaea and by Activated Sludge in Municipal Wastewater

Ammonium removal is a key step in biological wastewater treatment and novel approaches that improve this process are in great demand. The aim of this study is to test the hypothesis that ammonium removal from wastewater can be stimulated by static magnetic fields. This was achieved by analysis of the effects of static magnetic field (SMF) on the growth and activity of Nitrosomonas europaea, a key ammonia-oxidising bacterium, where increased growth and increased ammonia oxidation rate were detected when bacteria were exposed to SMF at 17 mT. Additionally, the effect of SMF on mixed cultures of ammonia oxidisers in activated sludge, incubated in sequencing batch bioreactors simulating wastewater treatment process, was assessed. SMFs of 30 and 50 mT, but not of 10 mT, increased ammonium oxidation rate in municipal wastewater by up to 77% and stimulated ammonia oxidiser growth. The results demonstrate the potential for use of static magnetic fields in increasing ammonium removal rates in biological wastewater treatment plants.

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.

The influence of supramolecular structure of cellulose allomorphs on the interactions with cellulose-binding domain, CBD3b from Paenibacillus barcinonensis

The interaction of recombinant cellulose-binding domains (CBDs) of endoglucanase Cel9B from Paenibacillus barcinonensis with different cotton cellulose allomorphs (I, II and III) has been investigated, in order to bring new insights regarding the CBD adsorption and desorption processes. The highest CBD adsorption capacity was recorded for cellulose I, confirming the affinity of proteins to the most crystalline substrate. The weakening and splitting of the hydrogen bonds within cellulose structure after CBD adsorption, as well as a decrease of the crystallinity degree were identified by ATR-FTIR spectroscopy and XRD. The CBD's adsorption kinetic was shown to be rendered by properties as, specific surface area and porosity, being confirmed by dynamic vapor sorption measurements. An important influence of temperature (25, 37 and 50°C) and/or pH medium (4, 5.5, 7 and 10) on the CBD desorption capacity was confirmed, being related to the hydrophobic interactions formed between the CBD and the cellulose allomorphs.

Effects of low-density static magnetic fields on the growth and activities of wastewater bacteria Escherichia coli and Pseudomonas putida

The aim of this study was to explore the influence of a moderate static magnetic field (SMF) of different densities on Escherichia coli and Pseudomonas putida that are commonly found in wastewater treatment plants. In line with literature reports that SMF increases the efficiency of wastewater treatment the findings of this study indicated that SMF negatively influenced the growth but positively influenced the enzymatic activities and ATP levels of the two model bacteria. The inhibitory effect of SMF on growth of E. coli and P. putida was most pronounced at their optimal growth temperature (37°C and 28°C respectively) and was reversible shortly after the SMF had been terminated. Finally, the results suggested that the induced energy metabolism reflected in higher dehydrogenase activities and ATP levels may be more important for survival, and adaptation to SMF induced stress than the increase in the expression of the rpoS gene.

The study of release of chlorhexidine from preparations with modified thermosensitive poly-N-isopropylacrylamide microspheres

The aim of this study was to investigate and compare the release rates of chlorhexidine (CX) base entrapped in the polymeric beads of modified poly-N-isopropylacrylamides (pNIPAMs) at temperatures below and over the volume phase transition temperature (VPTT) of synthesized polymers: pNIPAM-A with terminal anionic groups resulting from potassium persulfate initiator, pNIPAM-B with cationic amidine terminal groups, and pNIPAM-C comprising anionic terminals, but with increased hydrophobicity maintained by the N-tert-butyl functional groups. The preparations, assessed in vitro below the VPTT, release an initial burst of CX at different time periods between 120 and 240 min, followed by a period of 24 h, when the rate of release remains approximately constant, approaching the zero-order kinetics; the release rates for the polymers beads are as follows: pNIPAM-C>pNIPAM-B>pNIPAM-A. The pattern of release rates at temperature over the VPTT is as follows: pNIPAM-C>pNIPAM-A>pNIPAM-B. In the presence of pNIPAM-C, the duration between the start of the release and the attained minimal inhibitory concentration (MIC) for most of the microbes, in conditions over the VPTT, increased from 60 to 90 min. The release prolongation could be ascribed to some interactions between the practically insoluble CX particle and the hydrophobic functional groups of the polymer.

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.