Anionic Surface Charge Research Articles

Tuning the surface charge of rice straw-derived cellulose nanofibril membrane separator for electrochemical performance enhancement of supercapacitors

The electrochemical performance of supercapacitors has often overlooked the effect of surface charge on cellulose-based separators. Cellulose nanofibrils (CNFs) produced by 2,2,6,6-tetramethylpipridine-1-oxyl (TEMPO) oxidation possess a high anionic surface charge due to the presence of carboxylate groups, which could affect the transport of electrolyte ions. In this work, the surface of CNFs is modified with a cationic polyelectrolyte, namely polydiallydimethylammonium chloride (PDADMAC), to yield a nearly-zero surface charge CNF membrane derived from rice straw. The surface modification of CNFs using 20 wt% PDADMAC results in CNF-M2, with a surface charge of +5.3 mV, notable porosity (64 %), excellent electrolyte uptake (225 %), and improved ionic conductivity (5.0 mS cm−1). A symmetric supercapacitor assembled with CNF-M2 as a separator, exhibits enhanced specific capacitance (185.3 F g−1 at 0.1 A g−1), energy density (37.1 Wh kg−1 at a power density of 0.24 kW kg−1), and is able to maintain 100 % capacitance retention over 10,000 cycles in 1.0 M Na2SO4 aqueous electrolyte solution. This surface modification leads to 1.2–1.4 times increase in energy and power densities compared to the unmodified CNF membrane. Thus, the nearly-zero surface charge of the modified CNF membrane holds promise as a separator that elevates the performance of supercapacitors.

Cationic-motif-modified exosomes for mRNA delivery to retinal photoreceptors.

Topical treatment of vitreoretinal diseases remains a challenge due to slow corneal uptake and systemic clearance. Exosomes are emerging nanocarriers for drug delivery due to biocompatibility and cellular targeting properties. To apply them for retinal targeting via the topical route, exosomes must traverse various ocular barriers including the cornea, lens, vitreous humor (VH), and the retina itself. Here we engineered high-purity milk-derived exosomes by anchoring arginine-rich cationic motifs via PEG2000 lipid insertion on their surface. Modification enabled exosomes to use weak-reversible electrostatic interactions with anionic glycosaminoglycan (GAG) and water content of the tissue to enhance their transport rate and retention. Addition of cationic motifs neutralized the anionic surface charge of exosomes (-24 to -2 mV) without impacting size or morphology. Cationic-motif-modified exosomes exhibited two-fold faster steady state diffusivity through bovine corneas compared to unmodified exosomes. Fluorescence recovery after photobleaching confirmed that cationic-motif-modified exosomes can diffuse through VH without steric hindrance. In healthy VH, cationic-motif-modified exosomes demonstrated stronger binding resulting in three-fold lower average diffusivity that enhanced by six-fold in 50% GAG-depleted VH recapitulating advanced liquefaction. Cationic-motif-modified exosomes penetrated through the full-thickness of porcine retinal explants resulting in ten-fold higher uptake in photoreceptors and three-fold greater transfection with encapsulated eGFP mRNA compared to unmodified exosomes. Cationic-motif-modified exosomes are safe to use as they did not adversely affect the mechanical swelling properties of the cornea or lens nor impact retinal cell viability. Cationic-motif-modified exosomes, therefore, offer themselves as a cell-free nanocarrier platform for gene delivery to retinal photoreceptors potentially via the topical route.

Dual function of ultra-laminated hydrotalcite in environmental remediation: Adsorption of water contaminant BP-4 and reutilization of the adsorption product for photocatalytic NOx air decontamination

UV filters are a class of emerging water pollutants used in cosmetics to protect the skin from ultraviolet radiation. This work appraises the uptake of benzophenone-4 (BP-4), widely used and highly soluble sunscreen agent, by its adsorption on hydrotalcite based compounds. The studied adsorbents were hydrotalcite Mg3Al-CO3 (HT), ultra-laminated hydrotalcite (UHT) prepared by “Aqueous Miscible Organic Solvent Treatment” and their calcined products (HT500 and UHT500, respectively). Adsorbents were characterised by different techniques such as XRD, TEM, FT-IR, BET, XRF and TGA. The most remarkable feature was the enhancement in the specific surface area (SSA) of the ultra-laminated hydrotalcite samples, UHT and UHT500 with values of 212 m2·g─1 and 247 m2·g─1, respectively. Adsorption capacities decreased from very high for UHT500 to low values for HT in order UHT500 > HT500 > UHT > HT. The results showed that not only the SSA values were relevant for adsorbing BP-4, but also other factors such as anionic exchange capacity (AEC) and surface charge. In addition, the adsorption product (UHT-BP4) was evaluated as a photocatalyst for air purification, exhibiting good efficiency for the removal of atmospheric pollutants such as NOx gases.

Charge-adhered microfibrillar cellulose multilayer as a flow-modulating membrane coating: Solute separation by shape

Functional microfibrillar cellulose coatings for ultrafiltration membranes were prepared and characterized. For this purpose, a strategy for converting cotton cellulose into microfibres by incubation in a deep eutectic solvent of choline chloride and malonic acid, with no mechanical disintegration step, was created. The microfibres were furthermore modified to possess either cationic or anionic surface charges to allow charge-assisted adhesion of the fibres on ultrafiltration membrane surface. The adhesion was significantly improved by the electrostatic attraction, and it allowed building durable multilayer coatings by Layer-by-Layer methodology for membrane filtration purposes. The polyelectrolyte-inspired Layer-by-Layer strategy for depositing microfibrillar celluloses onto a membrane makes it possible to create coatings out of pure, only slightly derived cellulose, with no need for incorporating hazardous cross-linkers or synthetic polymers into the matrix. The deposited multilayer introduces a shear-force modulating functionality to the membrane which furthermore allows the permeation of molecules that have larger Stokes-Einstein radii than the membrane pore radius. This permeation is selective towards a linear polymer (poly(ethylene glycol)), while a more globular model substance with a similar molar mass (lignin) is highly rejected. The resulting filtration properties can furthermore be easily tuned by controlling the coating thickness.

Polyelectrolyte brushes affect the adsorption kinetics of nanoparticles onto lipid membranes

This article explores the adsorption kinetics of positively charged hard and soft silica nanoparticles (NPs) on supported lipid bilayers (SLBs) with an anionic surface charge. The softness of the NPs is adjusted by varying the grafting density of covalently bound Poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) brushes. The adsorption process, which is irreversible, can be described by a Langmuir-like adsorption model, where the desorption term is replaced by a term representing repulsive interactions, while the adsorption term is the classical one governed by its rate constant that quantifies how quickly a particle becomes bound to the SLBs. This occurs because further NP adsorption leads to a surface charge conversion that prevents additional particles from covering the SLB interface. NP adsorption is favored by electrostatic attraction and increases the adsorption kinetics. However, the latter decreases with increasing grafting density of the polyelectrolyte layer, ultimately preventing adsorption at a critical grafting density. This results from the interaction between the brush-grafted particle and the supported lipid bilayer depends on the counterion density in the contact area. This reduces the polymer flexibility in the brush, preventing it from making direct contact. Overall, the NP adsorption is favored, but counterions limit the extent of adsorption on a molecular scale, reaching the osmotic limit regime.

Enhanced-release of phenolic-enriched grape seed antioxidants through innovative cholesterol doped phytosomes

Grape seed (GS) is a predominant food by-product in the wine industry and a valuable source of antioxidants due to its high content of polyphenols and fiber. This study aimed to develop an antioxidant-rich GS fraction and formulate appropriate delivery systems for oral administration. A hydroethanolic extract of GS was enriched in phenolic compounds using adsorbent resin column chromatography, resulting in a 4-fold increase in phenolic content compared to the crude extract. The phenolic-enriched fraction was loaded into cholesterol-incorporated phytosomes to improve stability, gut absorption, and oral bioavailability. Different polysaccharide-based polymers were tested as natural-based coatings to improve stability and protection against gastrointestinal degradation while providing a modified-release profile. The phytosomes were evaluated for product yield, particle size, surface charge, surface morphology, and release profile under simulated gastrointestinal conditions. Cholesterol-incorporated phytosomes exhibited an anionic surface charge and a mean hydrodynamic particle size of 168 nm. Both molecular docking and FTIR analyses confirmed the interaction between the lipid bilayer and phenolic compounds. Mathematical fitting models confirmed the modified release profile of the polysaccharide-coated phytosomes. Our enriched phytosomes have potential as smart nutraceuticals for dietary supplements.

Sulfonation of HwBKP by Sulfur Trioxide Pyridine Complex and Preparation of Anionic Cellulose Beads Using the Same

To expand the applications of cellulose beads, sulfonated cellulose beads were prepared by chemically modifying HwBKP fibers with sulfur trioxide pyridine complex (STP), dissolving in tetraethylammonium hydroxide (TEAOH)/urea solvent, and dropping into acetic acid solution. The effect of the amount of STP added on the properties of sulfonated cellulose solution and cellulose beads was investigated. It was observed that the sulfonated cellulose beads exhibited anionic surface charge in a fairly wide pH range, and the degree of substitution of sulfonic acid groups and the zeta potential of the cellulose beads could be controlled by adjusting the amount of added STP. In addition, as the amount of STP added increased, the crystallinity of the cellulose decreased, the viscosity and surface tension of the sulfonated cellulose/TEAOH/urea solution decreased, and the size of the cellulose beads increased.

Triphenylphosphonium conjugated gold nanotriangles impact Pi3K/AKT pathway in breast cancer cells: a photodynamic therapy approach

Although gold nanoparticles based photodynamic therapy (PDT) were reported to improve efficacy and specificity, the impact of surface charge in targeting cancer is still a challenge. Herein, we report gold nanotriangles (AuNTs) tuned with anionic and cationic surface charge conjugating triphenylphosphonium (TPP) targeting breast cancer cells with 5-aminoleuvinic acid (5-ALA) based PDT, in vitro. Optimized surface charge of AuNTs with and without TPP kill breast cancer cells. By combining, 5-ALA and PDT, the surface charge augmented AuNTs deliver improved cellular toxicity as revealed by MTT, fluorescent probes and flow cytometry. Further, the 5-ALA and PDT treatment in the presence of AuNTs impairs cell survival Pi3K/AKT signaling pathway causing mitochondrial dependent apoptosis. The cumulative findings demonstrate that, cationic AuNTs with TPP excel selective targeting of breast cancer cells in the presence of 5-ALA and PDT.

Column-free purification of an artificial protein nanocage, TIP60

Protein nanocages, which have inner cavities and surface pores, are attractive materials for various applications, such as in catalysts and medicine. Recently, we produced an artificial protein nanocage, TIP60, and demonstrated its potential as a stimuli-responsive nanocarrier. In the present study, we report a simple purification method for TIP60 that can replace time-consuming and costly affinity chromatography purification. TIP60, which has an anionic surface charge, aggregated at mildly acidic pH and redissolved at neutral pH, maintaining its cage structure. This pH-responsive reversible precipitation allowed us to purify TIP60 from soluble fractions of the E. coli cell lysate by controlling the pH. Compared with conventional Ni-NTA column purification, the pH-responsive precipitation method provided purified TIP60 with similar purity (∼80%) and higher yield. This precipitation purification method should facilitate the large-scale investigation and practical use of TIP60 nanocages.

Water-redispersible and high-yield α-chitin nanocrystals isolated using electron-beam irradiation as adsorbents to remove heavy metals and dye.

An innovative approach to fabricate transparent and redispersible α-chitin nanocrystals (ChNCs) with high overall yields was developed in this work for eventual commercial use. The nanomanufacturing process included electron-beam irradiation (EBI) of chitin for oxidation and degradation in the dried state, high-pressure nanoscale homogenization via swelling, CO2 absorption, and spray-drying to obtain dehydrated products. The resulting EBI-disassociated chitins contained increased amounts of carboxylate (0.19-0.27 mmol g-1) and a negligible fraction of D-glucosamine moiety (from ca. 6.5 to <1.0%) with an intrinsic structure identical to α-chitin derived from shrimp shell prior to purification by conventional methods, such as deproteination. The resulting EBI-induced ChNC series exhibited nano-sized and rod-like morphology with tunable lengths averaging 608-259 nm, uniform widths of ca. 16-12 nm, a high isolation yield of max. 81%, and sufficient anionic surface charges, as zeta potentials of -32 to -34 mV indicate that it is homogenously water-dispersible and stable with background transparency. Unlike ChNC prepared by HCl-hydrolysis, the dehydrated particles of EBI-induced ChNCs were clearly redispersible in water and retained the characteristics of the original nanomaterials. We also tested the redispersible EBI-induced ChNCs as effective adsorbents. Their anionic groups interacted with cationic heavy metals (Cu2+ and Fe3+) and organic blue dye via electrostatic attraction, forming robust hydrogels, which were self-supporting after centrifugation. The EBI-induced ChNCs produced with low environmental impact in this work offer a promising choice of adsorbents for the removal of undesirable chemicals during wastewater treatment.

Major Development in Cotton Coloration: A Review

Most cotton fabrics are dyed with reactive dyes because they produce a full range of bright fashion colours with a high degree of wash fastness.Reactive dyes are frequently considered as king of dyes for cotton owing to their simple application techniques. However, reactive dyes are anionic and cotton fibers gain anionic surface charge in water, the charge repulsion adversely affects the dye bath exhaustion. Large quantity of electrolyte is added to overcome this problem. Some problems such as low dye utilization, high degree of salt utilization and colored effluent due to unexhausted, unfixed, and hydrolyzed dyestuffs, and high volume of waste water discharged, always exist in the application of reactive dyes.These electrolytes are neither exhausted nor destroyed and hence remain in the discharge dye liquor which leads to enormous environmental problem. Due to these problems this class of dyes is the most unfavorable one from the ecological point of view, these effluents produced gives high values of BOD/COD and increases salinity of the rivers affects the delicate biochemistry of aquatic life.A number of more environmentally sustainable approaches for reactive dyeing of cotton have been proposed to overcome the polluted effluent problem. This paper reviews options to improve the sustainability of the colouration process through development in dye structure, modification of dyeing machinery and processes, chemical modification of cotton fibre prior to dyeing, and use of organic compounds in place of inorganic chemicals.

Intracellular pH-Regulating Nanoparticles to Improve Anticancer Drug Efficacy for Cancer Treatment.

Here, we describe an intracellular pH-regulating nanoparticle (IPRN), coencapsulated with chemosensitizers and anticancer agents for effective and safe cancer treatment. IPRN contains a tubulysin derivative (TUB), a hydrophobic anticancer drug, and pantoprazole (PTZ), a hydrophilic proton-pump inhibitor. IPRN with a size of 62 nm has an anionic surface charge and is stable for at least two weeks under storage conditions, though PTZ and TUB encapsulated in IPRN showed different drug release patterns. PTZ was released before TUB, controlling the cancer's intracellular pH, maintaining a pH at which TUB can work well. The encapsulated PTZ increased the pH of endolysosomes and inhibited ion trapping, with TUB ionization, thereby exhibiting increased cytotoxicity compared with free TUB observed in various cancer cell lines, such as human liver adenocarcinoma, human glioblastoma, and human pancreatic carcinoma. IPRN exhibited a 1.9-fold improved tumor growth inhibitory effect in a human liver adenocarcinoma-bearing mouse model, while minimizing the hepatotoxicity of free TUB. Thus, nanomedicines that contain both a chemosensitizer and an anticancer agent, such as IPRN, are expected to be next-generation anticancer agents that reduce the side effects of anticancer drugs and increase the therapeutic effect.

Interaction of negatively and positively capped gold nanoparticle with different lipid model membranes

The use of functionalised gold nanoparticles in biomedical applications is expanding. Here we explore the interaction of gold nanoparticles with lipid membranes using readily available equipment and basic techniques to explore how the charge on the nanoparticles, and the nature of the lipid, influences the interaction. Gold nanoparticles were synthesised with two different surface functionalisations, negatively charged citrate groups and positively charged cetyltrimethylammonium groups from CTAB, to determine how surface charge affects the interaction of the nanoparticles with the Zwitterionic lipid POPC and the anionic lipid POPG. It was observed that the surface pressure/area isotherms of POPG monolayers on exposure to citrate capped nanoparticles were not shifted to higher molecular areas as much as those of POPC, suggesting that the anionic headgroups of the POPG lipid repel the anionic surface charge of the citrate capped nanoparticles to some extent limiting inclusion. In contrast, the surface pressure/area isotherms of the POPG monolayers exposed to CTAB capped nanoparticles are shifted to higher molecular areas more than for the POPC monolayers. The interaction of anionic nanoparticles with lipid bilayers was measured by the mass change of the bilayer deposited on the surface of a quartz crystal microbalance (QCM) exposed to nanoparticles in an aqueous phase flow. The QCM frequency changes show that bilayers of unsaturated phosophocholine lipids readily took up particles, whereas for the saturated lipid DPPC significant uptake was only observed when the bilayer was warmed to above its gel-to-fluid transition temperature, Tm. This is possibly due to an increase in the molecular mobility and bilayer bending modulus, κ, of the bilayer.

Multi-ionic interaction with magnesium doped hydroxyapatite-zeolite nanocomposite porous polyacrylonitrile polymer bead in aqueous solution and spiked groundwater

Removal of multi-ionic contaminants from water resources has been a major challenge faced during the treatment of water for drinking and industrial applications. In the present study, varying composition of magnesium doped hydroxyapatite (Mg-HAp) and zeolite nanocomposite embedded porous polymeric beads were synthesized using solvent displacement method and its sorption efficiency towards multi-ion contaminant (such as Ag, Al, As, Ba, Be, Cd, Co, Cr, Cu, Mn, Ni, Pb, Se, Tl, Th, U, V and Zn) was investigated in aqueous solution and spiked groundwater. The prepared beads were characterized using suitable techniques like high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) equation. The surface area and pore radius of the beads varied from 6.996 to 66.469 m2/g and 1.698–3.960 nm respectively according to the composition of the bead. The control bead without nanocomposite showed maximum surface area. Multi-ion adsorptions onto beads were confirmed using an inductively coupled plasma-optical emission spectrophotometer (ICP-OES) and X-ray photoelectron spectrophotometer (XPS). The sorption efficiency was high at pH 5 owing to its anionic surface charge leading to an increase in affinity towards the cations. For validating field application, selected high performance beads were tested in multi-ion spiked groundwater. The results indicated that the Mg-HAp nanocomposite bead dominate all the other bead compositions with more than 90% removal efficiency for most of the multi-ion contaminants. The feasible adsorption mechanism has been discussed. This adsorption study revealed that the Mg-HAp nanocomposite bead is a promising material that is cost-effective, non-toxic, biodegradable, eco-friendly and highly efficient towards the removal of multi-ionic contaminants from groundwater.

Flame retardant high-power Li-S flexible batteries enabled by bio-macromolecular binder integrating conformal fractions

Polymer binders for sulfur cathodes play a very critical role as they prerequisites for an in-situ immobilization against polysulfide shuttle and volume change, while ensuring good adhesion within active materials for ion conduction along with robust mechanical and chemical stability. Here, we demonstrate anionic surface charge facilitated bio-polymer binder for sulfur cathodes enabling excellent performance and fire safety improvement. The aqueous-processable tragacanth gum-based binder is adjusted to house high sulfur loading over 12 mg cm−2 without compromising the sulfur utility and reversibility, imparting high accessibility for Li-ions to sulfur particles about 80%. The intrinsic rod and sphere-like saccharidic conformal fraction’s multifunctional polar units act as active channels to reach the sulfur particles. As a result, the binder entraps polysulfides with 46% improvement and restrains the volume changes within 16 % even at 4 C. Moreover, the flexible Li-S battery delivers a stack gravimetric energy density of 243 Wh kg–1, demonstrating high reactivity of sulfur along with good shape conformality, which would open an avenue for the potential development of the compact and flexible high-power device.

Formulation of Nano/Micro-Carriers Loaded with an Enriched Extract of Coffee Silverskin: Physicochemical Properties, In Vitro Release Mechanism and In Silico Molecular Modeling.

Designing strategies for an effective transformation of food waste into high-value products is a priority to address environmental sustainability concerns. Coffee silverskin is the major by-product of the coffee roasting industry, being rich in compounds with health benefits. Such composition gives it the potential to be transformed into high-value products. In this study, coffee silverskin extracts were enriched, regarding caffeine and chlorogenic acid contents, by adsorbent column chromatography. The compounds content increased 3.08- and 2.75-fold, respectively, compared to the original extract. The enriched fractions were loaded into nano-phytosomes or cholesterol-incorporated nano-phytosomes (first coating layers) to improve the physiochemical properties and permeation rate. These nano-lipid carriers were also subjected to a secondary coating with different natural polymers to improve protection and stability against degradation. In parallel, and for comparison, different natural polymers were also used as first coating layers. The produced particles were evaluated regarding product yield, encapsulation efficiency, loading capacity, particle size, surface charge, and in vitro release simulating gastrointestinal conditions. All samples exhibited anionic surface charge. FTIR and molecular docking confirmed interactions between the phytoconstituents and lipid bilayers. The best docking score was observed for 5-caffeoylquinic acid (chlorogenic acid) exhibiting a stronger hydrogen binding to the lipid bilayer. Among several kinetic models tested, the particle release mechanism fitted well with the First-order, Korsmeyer–Peppas, and Higuchi models. Moreover, most of the formulated particles followed the diffusion-Fick law and anomalous transport.

Antimicrobial multi-component lipid-based nanoemulsion of Eucalyptus globulus and Mentha piperita as natural preservative

Natural preservatives were predominantly developed to eliminate the use of synthetic preservatives for food and agriculture industries. Multi-component nanoemulsions (MCN) with significant antibacterial activity should be proper candidates as natural preservatives. This research aimed to formulate a multi-component phospholipid-based nanoemulsion (PNE) with prolonged shelf-life loaded with a mixture of Eucalyptus globulus and Mentha piperita essential oils (EOs). The effects of different chemical and mechanical conditions (ultrasonication) on the stability of MCN were evaluated. The emulsions were monitored from day 1 to 730, and stable formulae were investigated for around two years. The Zeta potential confirmed the anionic surface charge. Dynamic light scattering and transmission light scattering revealed a droplet size ranging between 93.40 and 100.00 nm. A homogeneous formula was stable for more than 730 days. Ultrasonication treatment and 1% v/v of food-grade castor oil as co-emulsifier were critical in fabricating stable formulae. Minimum inhibitory concentration (MIC) values of 31, 8, and 63 µg/ml were observed against Escherichia coli, Staphylococcus aureus and Salmonella enteritidis, respectively. The results showed a significant reduction in MIC values of 32-, 250-, 15-fold against E. coli, S. aureus and S. enteritidis, respectively, compared to an original mixture of essential oils. The mass transfer followed a case-I transfer (Fick law diffusion) evaluated by Koresmeyer-Peppas kinetic model (R 2 = 0.88). In conclusion, MCN could be a promising candidate for natural preservatives to be used in the food, agriculture and cosmetic industries.

Surfactant tail length dependence of the photophysics and dynamics of a chemotherapeutic drug within anionic micellar aggregates

The present work reports a photophysical study of norfloxacin (NOF), an efficient chemotherapeutic antibacterial drug, in well-characterized biomimetic micellar aggregates of anionic surfactants. The major focus of the present investigation lies in deciphering the effect of the surfactant chain length on the structural dynamics of the drug within a micelle-encapsulated state through steady-state and time-resolved fluorescence spectroscopic techniques. The anionic surfactants employed for the purpose are decyl sodium sulfate (S10S), dodecyl sodium sulfate (S12S) and tetradecyl sodium sulfate (S14S). Our experimental results evince that increasing hydrophobic surfactant tail length exerts a profound influence on promoting a specific prototropic form of NOF within the micellar aggregates; an apparently enigmatic observation is that increasing hydrophobicity of the micellar microheterogeneous system indeed favors the cationic species of the drug. This is interpreted on the basis of electrostatic stabilization between the drug (cationic form) and anionic surface charge of the as-employed micellar assemblies, while the micellar hydration model fails to rationalize the experimental findings. Particular emphasis is also given on delineating the probable location and the modulated rotational-relaxation dynamics of the drug molecule within the micellar aggregates. The interaction thermodynamics and dynamics of norfloxacin within anionic micelles is critically dependent on the tail length of the surfactant such that the micellar hydration model is found to be inadequate to explain the photophysics of the drug whereas electrostatic interaction appears to play the governing role.

Hyaluronate siRNA nanoparticles with positive charge display rapid attachment to tumor endothelium and penetration into tumors

A cationizable sequence-defined lipo-oligoaminoamide (lipo-OAA) conferring stable assembly of siRNA into ~200 nm sized complexes contains an N-terminal azidolysine for covalent coating of formed nanoparticles with dibenzocyclooctyne-amine (DBCO)-modified hyaluronic acid (HA). Depending on the applied equivalents of DBCO-HA, stable nanoparticles with either cationic or anionic surface charge can be formed. The unmodified and two types of covalent HA-modified siRNA nanoparticles differ in their biological characteristics. Both types of HA coated siRNA complexes show an enhanced cellular uptake over uncoated complexes and facilitate efficient gene silencing, but differ in intracellular uptake pathways and distribution. Upon intravenous administration in mice, beyond our expectation and in contrast to the in vitro findings, only the cationic HA nanoparticles but neither the non-coated cationic nor the anionic HA complexes were able to target subcutaneous Huh 7 tumors and exert potent (78%) gene silencing. The favorable and very fast accumulation of cationic HA nanoparticles was confirmed in another subcutaneous tumor model. As evidenced by 3D nanoparticle distribution within Huh 7 tumors evaluated at early time points of 5 min and 45 min, only the cationic HA-based nanoparticles rapidly attach to the tumor endothelium and subsequently penetrate into tumor, in contrast to the analogous anionic HA coated or the cationic non-coated formulation.

Impact of incubation conditions and post-treatment on the properties of bacterial cellulose membranes for pressure-driven filtration

Bacterial cellulose (BC) has shown potential as a separation material. Herein, the performance of BC in pressure-driven separation is investigated as a function of incubation conditions and post-culture treatment. The pure water flux of never-dried BC (NDBC), was found to be 9 to 16 times higher than that for dried BC (DBC), in a pressure range of 0.25 to 2.5 bar. The difference in pressure response of NDBC and DBC was observed both in cross-flow filtration and capillary flow porometry experiments. DBC and NDBC were permeable to polymers with a hydrodynamic radius of ∼60 nm while protein retention was possible by introducing anionic surface charges on BC. The results of this work are expected to expand the development of BC-based filtration membranes, for instance towards the processing of biological fluids.