Ζ-potential Measurements Research Articles

Venturi-based rapid expansion of supercritical solution (Vent-RESS): synthesis of liposomes for pH-triggered delivery of hydrophilic and lipophilic bioactives.

Multivitamin-loaded and surface-modified liposomes tailored for simultaneous intestinal delivery of both lipophilic and hydrophilic bioactives were synthesized from sunflower phosphatidylcholine (SFPC). Liposomes (SL) were generated with the aid of a novel, organic solvent free, and environmentally benign process which utilizes venturi-based rapid expansion of supercritical solution (Vent-RESS). Vitamins E and C were used as model lipophilic and hydrophilic bioactives and demonstrated an average encapsulation efficiency of 92 and 70 %, respectively. Synthesized liposomes were coated with a pH-responsive double-wall of chitosan and β-lactoglobulin (βlg-Cs-SL) to develop a biocompatible vehicle for pH-triggered delivery of bioactive cargo(s). To compare the efficacy of this newly developed dual-coating, SL was also coated with a commercially available pH responsive polymer, Eudragit® S100 (Eu-SL). No organic solvent was used during the surface coating of SLs with these two different types of enteric coatings. The performance of these two coatings was studied by conducting morphological characterization through diameter and ζ-potential measurements along with confocal laser scanning and freeze-fracture cryogenic scanning electron microscopies. The stability of coated and uncoated SFPC liposomes was determined in simulated gastrointestinal fluids. For βlg-Cs-SL and Eu-SL, after 2 h of incubation in simulated gastric condition, less than 5 % of the encapsulated vitamins C and E were released, whereas for SL, 41 and 28 % of vitamins C and E were released within 2 h of incubation period. In simulated intestinal fluid, coated liposomes released most of their remaining payload when incubated for 4 h. The newly developed dual coating was found to be as effective as its commercially available counterpart, Eudragit® S100 coating; nevertheless, the biocompatible, non-toxic, and non-synthetic nature of this coating makes it an attractive alternative. Modeling the release kinetics of vitamins from coated liposome showed that the release of payload from surface coated liposomes proceeded through a multistep structural disintegration involving both Fickian and non-Fickian types of diffusion. The ability of these surface-coated liposomes to maintain structural integrity under the gastric condition followed by site-specific, pH-triggered release of encapsulated cargo in the intestine will make them highly suitable for oral administration of bioactive compounds in pharmaceutical and food applications.

Studies into interactions and interfacial characteristics between cellulose nanocrystals and bovine serum albumin

This study investigates the interactions between cellulose nanocrystals (CNCs) and bovine serum albumin (BSA) under different pH conditions. A multiscale technique was employed to characterize the CNCs and BSA at pH 7 and pH 3. ζ-Potential measurement and UV–vis spectroscopy demonstrated strong interactions between CNCs and BSA at pH 3, whereat they have opposite charges. Interfacial tensiometry showed a deficiency in the surface activity of the CNCs and indicated that BSA dominated the interface behavior in their complex. Quartz crystal microbalance with dissipation revealed that the sequential adsorption of BSA and CNCs produced viscoelastic bilayers at pH 3, and the mass adsorbed was ∼ 28 times that adsorbed at pH 7. Molecular dynamics simulations indicated that the key interactions between the two materials were produced between the hydrophobic CNC surface and the BSA domain IIA region. These results provide interesting insights into the design of complex food emulsions and fluid interfaces.

Improved Stability of the Palm Oil-in-Water Emulsion via the Surface Modification of Droplets with a Chitosan-Casein Complex Layer

The stabilization effect of a biopolymer complex layer consisting of sodium caseinate (SC) and chitosan (CHI) formed via electrostatic interaction was investigated using an oil-in-water (O/W) emulsion containing palm oil droplets as the dispersed phase. O/W emulsions containing palm oil droplets with a narrow droplet diameter distribution were successfully prepared using two microchannel emulsification devices using SC as an emulsifier at 60℃. Surface modification of the palm oil droplets was conducted using different CHI/SC ratios. The surface charge of the droplets was negative and positive at CHI/SC ratios of less than 0.025 and more than 2.5, respectively. At an intermediate CHI/SC ratio between 0.025 and 2.5, the droplets formed large aggregates and became polydisperse. The adsorption of CHI on the surface of palm oil droplets at a high CHI/SC ratio was confirmed by fluorescent microscopy and ζ-potential measurement. Improved stability of the O/W emulsions with the CHI-SC complex layer was demonstrated during heating (60℃) and cooling (20℃) treatment, and long-term (7 months) storage at room temperature (20-25℃). Interestingly, separation of the large oil phase on the top of the emulsion samples and the formation of large crystals of palm oil were suppressed in the emulsion samples with the CHI-SC complex layer.

Formation of Shelf-Stable Pickering High Internal Phase Emulsion Stabilized by Sipunculus nudus Water-Soluble Proteins (WSPs).

To form a stable emulsion system, the water-soluble proteins (WSPs) of Sipunculus nudus were prepared as the sole effective stabilizer for the high internal phase emulsion (HIPEs), of which the influence of the WSPs concentration and environmental stability was investigated. The HIPEs were fabricated using a simple one-pot homogenization process (10,000 rpm/min, 3 min) that involved blending the WSPs (0.1, 1, 2, 3, 4, and 5 wt%) with soybean oil (60, 65, 70, 75, 80, 85, and 90%). The microstructure and properties of stable HIPEs were characterized by particle size, ζ-potential, visual observations, optical microscopy, and dynamic rheology property measurements. As the concentration of WSPs increases, the mean particle diameter of HIPEs decreases, on the contrary, the apparent viscosity and storage modulus gradually increase. At a given emulsifier concentration (3 wt%), the stable and gel-like HIPEs were formed at the oil internal phase (ϕ) values of 70–75%, all the pH range in values from 3 to 9, and the ionic strength from 100 to 500 mM. Furthermore, the HIPEs that were stabilized formed a gel-like state that was relatively stable to heat and storage (30 days). And there was a new phenomenon that the destabilized HIPE of the freeze-thaw treatments could still return to a gel-like state again after homogenizing. The study results suggest that the WSPs of S. nudus as a natural emulsifier could be widely used in the food industry.

Characterization of an exopolysaccharide (EPS-3A) produced by Streptococcus thermophilus ZJUIDS-2-01 isolated from traditional yak yogurt

Yak yogurt, one of the naturally fermented dairy products prepared by local herdsmen in the Qinghai-Tibet Plateau, contains a diverse array of microorganisms. We isolated and identified a novel Streptococcus thermophilus strain, ZJUIDS-2-01, from the traditional yak yogurt. We further purified and carried out detailed structural, physiochemical, and bioactivity studies of an exopolysaccharide (EPS-3A) produced by S. thermophilus ZJUIDS-2-01. The weight-average molecular weight (Mw) of EPS-3A was estimated to be 1.38 × 106 Da by High-Performance Gel Permeation Chromatography (HPGPC). The monosaccharide analysis established its composition to be glucose, galactose, N-acetyl-D-galactosamine, and rhamnose in a ratio of 5.2:2.5:6.4:1.0. The molecular structure of EPS-3A was determined by the combination of permethylation analysis, FT-IR, and NMR spectroscopic techniques. The ζ-potential measurements indicated that EPS-3A had a pKa value of ~4.40. The DSC yielded a melting point (Tm) of 80.4 °C and enthalpy change (ΔH) of 578 J/g for EPS-3A, comparable to those of the xanthan gum (XG), a commercial EPS. EPS-3A exhibited better O/W emulsion stability and flocculating capacity than XG. Furthermore, it also demonstrated similar antioxidant activity to XG and promising in vitro antibacterial properties. This work evidenced that EPS-3A derived from S. thermophilus ZJUIDS-2-01 holds the potential for food and industrial applications.

Experimental and COSMO-RS Simulation Studies on the Effects of Polyatomic Anions on Clay Swelling.

Ionic liquids (ILs) can play a vital role in clay swelling inhibition during hydraulic fracturing. Previous studies highlighted the effect of side-chain length attached to the cationic core and different anions possessing almost the same chemical properties on inhibition performance. However, polyatomic anions have the potential to superiorly inhibit swelling compared to monoatomic anions. In this study, three ILs, namely, 1-butyl-3-methylimidazolium chloride (BMIMCl), 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4), and 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6), were utilized to assess the effects of polyatomic anions on clay swelling inhibition. These performances were compared with the performances of a conventional inhibitor, potassium chloride (KCl). X-ray diffraction (XRD) testing was applied to check the mineral components present in the bentonite clay sample studied in this research. Clay swelling inhibition performance and rheological properties of these ILs were evaluated by the bentonite plate soaking test, linear swelling test, and rheological test. The swelling inhibition mechanisms were investigated through ζ-potential measurement, Fourier transform infrared (FT-IR) spectroscopy, and contact angle measurement. Moreover, COSMO-RS computer simulation was conducted to explain the inhibition mechanisms theoretically. The results demonstrated that BMIMPF6 showed superior inhibition performance and reduced the swelling by 21.55%, while only 9.26% reduction was attained by potassium chloride (KCl). The adsorption ability on the bentonite surface through electrostatic attraction, higher activity coefficient, and less electronegativity of PF6– anion played a vital role in attaining such superior inhibition performance by BMIMPF6.

Study of chalcopyrite flotation in the presence of illite using a design of experiments approach

AbstractThe interaction between chalcopyrite and illite particles was analysed using ζ-potential measurements and flotation tests. Statistically designed tests were used to examine the factors controlling flotation (frother concentration, dispersant concentration, froth height, airflow rate and amount of clay). Furthermore, the significance levels of the impacts of these factors on responses (chalcopyrite grade/recovery, pyrite grade/recovery, dynamic froth stability and mean bubble diameter) were determined. Chalcopyrite and pyrite ζ-potentials were measured in the presence of illite. The addition of 15% illite to the chalcopyrite, especially between pH 11 and 12, shifted the ζ-potential values closer to that of pure illite, indicating complete surface coating of chalcopyrite with illite. In the flotation experiments, better results were obtained in terms of chalcopyrite grade at a low airflow rate and a high froth height. With increasing froth height there was a decline in the gangue mineral recovery as the residence time of the froth increased. The most significant factor increasing pyrite recovery was the amount of clay. Although illite is considered to be the least problematic clay mineral for flotation, as reported in the literature, an illite content of as low as 5% in the ore decreased chalcopyrite grade by 3.83%. While K and Na contents of 4% were detected after flotation without the addition of illite, their abundance increased to 5.7% after the addition of illite.

Dynamic gastric stability and in vitro lipid digestion of soybean protein isolate and three storage protein-stabilized emulsions: Effects of ultrasonic treatment

The emulsification of vegetable protein is closely related to solubility. The purpose of this study was to evaluate the effect of ultrasound on protein emulsification and to provide a prospective method for assessing the digestive properties of emulsions. In this article, we investigate the emulsion stability of ultrasonic pretreated soy protein isolate (SPI), and its three storage proteins, namely β-conglycinin (7S), lipophilic protein (LP), and glycinin (11S), under dynamic gastric conditions. The effects of these emulsions on lipolysis during digestion in the small intestine are also assessed using an in vitro dynamic human stomach simulator and a small intestine model. Particle size and ζ-potential measurements, as well as confocal laser scanning microscopy, revealed that during dynamic gastric digestion, the flocculation degree and floc size of 7S and soybean LP emulsions are larger than that of 11S and SPI emulsions. Meanwhile, ultrasound pretreatment of the proteins was found to prevent the agglomeration of the emulsion in a dynamic gastric environment. Moreover, enhanced flocculation delayed oil droplet delivery to the small intestine and subsequently retarded the release of lipophilic nutrients. The droplet size, molecular weight, and protein secondary structures of the ultrasonicated proteins were conducive to relatively higher rates and degrees of lipolysis in intestinal digestion than those of unsonicated proteins. Additionally, the slow-release effect of LP was superior to that of 11S and SPI, whereas 7S was comparatively more difficult to digest. The present study elucidated the fate of soy protein in the digestive tract and may facilitate microstructural food design to regulate physiological responses during digestion.

Freeze-thaw stability and rheological properties of soy protein isolate emulsion gels induced by NaCl

This article focused on the freeze-thaw stability and rheological properties of soy protein isolate (SPI) emulsion gels induced by NaCl. The freeze-thaw stability was characterized by particle size, ζ-potential, and differential scanning calorimetry (DSC) measurements. The salt concentration (200–400 mM) could promote protein aggregation and improve freeze-thaw stability. The study of both linear and nonlinear rheology properties proved that SPI emulsion gels exhibited the maximal gel strength at 300 mM NaCl that could resist structure disruption and oil droplet migration. The nonlinear responses were further analyzed using Lissajous plots. Initial SPI emulsion gels had higher peak stress values at 300 mM NaCl, indicating more resistance to deformation and increased elastic-dominant behavior as well as improved freeze-thaw stability. While the area of the elastic and viscous Lissajous plots narrowed as the salt concentration exceeded 300 mM, suggesting the viscosity and elasticity decreased. Scanning electron microscopy (SEM) images further confirmed that the SPI emulsion gels had smaller pores and denser structures at 300 mM NaCl, resulting in good freeze-thaw stability. Besides, the maximum gel strength emerged in 300 mM NaCl and 100 mM NaCl before and after freeze-thaw cycles, respectively, which was due to moderate dehydration and a small amount of oil leakage from the network. These findings provide valuable information for the relationships between freeze-thaw stability and rheology property of emulsion gels.

Dynamic Duo: Vibrational Sum Frequency Scattering Investigation of pH-Switchable Carboxylic Acid/Carboxylate Surfactants on Nanodroplet Surfaces.

Surfactants containing pH-switchable, carboxylic acid moieties are utilized in a variety of environmental, industrial, and biological applications that require controlled stability of hydrophobic droplets in water. For nanoemulsions, kinetically stable oil droplets in water, surface adsorption of the anionic form of the carboxylic acid surfactant stabilizes the droplet, whereas a dominant surface presence of the neutral form leads to destabilization. Through the use of dynamic light scattering, ζ-potential, and vibrational sum frequency scattering spectroscopy (VSFSS), we investigate this mechanism and the relative surface population of the neutral and charged species as pH is adjusted. We find that the relative population of the two surfactant species at the droplet surface is distinctly different than their bulk equilibrium concentrations. The ζ-potential measurements show that the surface concentration of the charged surfactant stays nearly constant throughout the stabilizing pH range. In contrast, VSFSS shows that the neutral carboxylic acid form increasingly adsorbs to the surface with increased acidity. The spectral features of the headgroup vibrational modes confirm this behavior and go further to reveal additional molecular details of their adsorption. A significant hydrogen-bonding interaction occurs between the headgroups that, along with hydrophobic chain-chain interactions, assists in drawing more carboxylic acid surfactant to the interface. The charged surfactant provides the stabilizing force for these droplets, while the neutral surfactant introduces complexity to the interfacial structure as the pH is lowered. The results are significantly different than what has been found for the planar oil/water studies where stabilization of the interface is not a factor.

Sclerotium oryzae biocontrol in flooded rice fields with floating microcarrier technology: The effect of chitosan molecular weight.

Biocontrol strategies are of significant concern for their application in crops. Various green practices have been designed, but almost all of them had delivery constraints. In particular, to design biocontrol strategies against Sclerotium oryzae in flooded rice fields, the active agent should be retained on the plant leaves by spreading application, nevertheless the direct application onto the water produces the biocontrol agent dilution. An effective delivery model was needed. This work aimed to evaluate the effects of chitosan molecular weight on the formation of positively charged Pseudomonas fluorescens-chitosan complex as a floating microcarrier against Sclerotium oryzae. To this end, three different sizes of chitosan [molecular weights (MWs) 20 000, 250 000, and 1 250 000 g mol-1 ] at different pH values (4, 6, and 7) were tested. The electrostatic interaction was analyzed through ζ-potential measurement. An adjustment of the experimental values was carried out for making predictions. The bacteria antifungal activity into the carrier with different chitosan MWs was analyzed. Our results suggest that it is possible to form a bacteria-chitosan complex with a net positive charge under condition that improve bacteria incorporation to the microcarrier technology without harming bacteria viability and antifungal activity. Thus, high chitosan MW (1250 000 g mol-1 ) at pH6 is preferable for microcarrier technology. Our findings provide relevant information about bacteria-chitosan interaction and may be useful in biocontrol programs that involved these two components as well as situations in which bacteria adsorption to an anionic carrier or anionic surface is desirable.

Preparation of Liposomes from Soy Lecithin Using Liquefied Dimethyl Ether.

We investigated a method to prepare liposomes; soy lecithin was dissolved in liquefied dimethyl ether (DME) at 0.56 MPa, which was then injected into warm water. Liposomes can be successfully prepared at warm water temperatures above 45 °C. The transmission electron microscopy (TEM) images of the obtained liposomes, size distribution, ζ-potential measurements by dynamic light scattering and the amount of residual medium were compared by gas chromatography using the conventional medium, diethyl ether. The size of the obtained liposomes was approximately 60–300 nm and the ζ-potential was approximately −57 mV, which was almost the same as that of the conventional medium. Additionally, for the conventional media, a large amount remained in the liposome dispersion even after removal by depressurization and dialysis membrane treatment; however, liquefied DME, owing to its considerably low boiling point, was completely removed by depressurization. Liquefied DME is a very attractive medium for the preparation of liposomes because it does not have the toxicity and residue problems of conventional solvents or the hazards of ethanol addition and high pressure of supercritical carbon dioxide; it is also environmentally friendly.

Engineered mucoadhesive microparticles of formoterol/budesonide for pulmonary administration

In the present study, a multi-component system comprised of dipalmitylphospatidylcholine (DPPC), Chitosan, Lactose, and L-Leucine was developed for pulmonary delivery. Microparticles were engineered by the spray drying process and the selection of the critical parameters was performed by applying experimental design. The microcarriers with the appropriate size and yield were co-formulated with two active pharmaceutical ingredients (APIs), namely, Formoterol fumarate and Budesonide, and they were further investigated. All formulations exhibited spherical shape, appropriate aerodynamic performance, satisfying entrapment efficiency, and drug load. Their physicochemical properties were evaluated using Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FT-IR), and Differential Scanning Calorimetry (DSC). The aerodynamic particle size characterization was determined using an eight-stage Andersen cascade impactor, whereas the release of the actives was monitored in vitro in simulated lung fluid. Additional evaluation of the microparticles’ mucoadhesive properties was performed by ζ-potential measurements and ex vivo mucoadhesion study applying a falling liquid film method using porcine lung tissue. Cytotoxicity and cellular uptake studies in Calu-3 lung epithelial cell line were conducted to further investigate the safety and efficacy of the developed formulations.

PH-Responsive Chitosan/Alginate Polyelectrolyte Complexes on Electrospun PLGA Nanofibers for Controlled Drug Release.

The surface functionalization of electrospun nanofibers allows for the introduction of additional functionalities while at the same time retaining the membrane properties of high porosity and surface-to-volume ratio. In this work, we sequentially deposited layers of chitosan and alginate to form a polyelectrolyte complex via layer-by-layer assembly on PLGA nanofibers to introduce pH-responsiveness for the controlled release of ibuprofen. The deposition of the polysaccharides on the surface of the fibers was revealed using spectroscopy techniques and ζ-potential measurements. The presence of polycationic chitosan resulted in a positive surface charge (16.2 ± 4.2 mV, pH 3.0) directly regulating the interactions between a model drug (ibuprofen) loaded within the polyelectrolyte complex and the layer-by-layer coating. The release of ibuprofen was slowed down in acidic pH (1.0) compared to neutral pH as a result of the interactions between the drug and the coating. The provided mesh acts as a promising candidate for the design of drug delivery systems required to bypass the acidic environment of the digestive tract.

Structural Characterization and Adsorption Properties of Dunino Raw Halloysite Mineral for Dye Removal from Water.

In this work, raw halloysite mineral from Dunino (Poland) has been characterized and tested as an efficient and low-cost adsorbent for dye removal from water. The morphology and structure of this clay were characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) and the chemical composition was evaluated by means of X-ray fluorescence spectroscopy (XRF), energy dispersive X-ray spectroscopy (EDX), and electron energy loss spectroscopy (EELS). The results showed that it is made up of both platy and tubular structures, mainly composed of Si, Al, and O. Iron oxide particles covering the platy structures were also observed. The surface charge of halloysite was measured by z-potential measurements and by the evaluation of the point of zero charge. The clay was tested as an adsorbent for the removal of positively and negatively charged dye molecules, i.e., methylene blue (MB) and methyl orange (MO), both separately and in a mixed-dye solution. Halloysite showed the ability to efficiently and selectively remove MB molecules by adsorption, both in a single-dye solution and in a mixed one. The adsorption of positive dyes on the clay surface mainly occurred through ion exchange at negatively charged sites on its surface. The possibility of regenerating the clay for further dye removal processes is also shown.

Fabrication of Cationic Poly(vinyl alcohol) Films Cross-Linked Using Copolymers Containing Quaternary Ammonium Cations, Benzoxaborole, and Carboxy Groups.

Water-insoluble cationic poly(vinyl alcohol) (PVA) films were fabricated using a mixed aqueous solution of PVA and poly([2-(methacryloyloxy)ethyl]trimethylammonium chloride (METAC)-co-methacrylic acid (MAAc)-co-5-methacrylamido-1,2-benzoxaborole (MAAmBO)) copolymer (3D). The surface of the PVA film is typically negatively charged, and simple fabrication methods for water-insoluble PVA films with cationic surface charges are required to expand their application fields. METAC, which has a permanent positive charge owing to the presence of a quaternary ammonium cation, was selected as the cationic unit. The MAAc and MAAmBO units were used as two types of cross-linking structures for the thermal cross-linking of the hydroxy and carboxy groups of the MAAc unit (covalent bonding) as well as the diol and benzoxaborole groups of the MAAmBO unit (dynamic covalent bonding). The films were thermally cross-linked at 135 °C for 4 h without the addition of materials. After immersion in surplus water at 80 °C for 3 h, the cross-linked PVA/3D films retained almost 100% of their weights. The ζ-potential of the water-insoluble PVA/3D film was 9.4 ± 0.8 mV. The PVA/3D film was strongly dyed using anionic acid red 1 (AR1) because of its positively charged surface. Interestingly, it could also be slightly dyed using cationic methylene blue (MB) and became transparent (original state) after immersion in water for 2 days. These results suggested that positive and negative charges coexisted in the PVA/3D film, and the surface properties were positively inclined. Moreover, the degree of hemolysis of the PVA/3D films was similar to that of the negative control, which showed high blood compatibility. To our knowledge, this is the first report on the fabrication of water-insoluble cationic PVA films using two types of cross-linking structures containing carboxy and benzoxaborole groups. The cross-linked PVA films were analyzed using Fourier transform infrared (FT-IR) spectroscopy, differential scanning calorimetry (DSC), and contact angle (CA) and ζ-potential measurement, as well as by determining the mechanical properties, adsorption of charged molecules, and biocompatibility. These readily fabricated water-insoluble PVA films with positive charges can show potential applications in sensors, adsorption systems, and antimicrobial materials.

Enhanced photocatalytic performance and reusability of N-doped carbon dots/zinc oxide hybrid nanostructures

We report the fabrication of nitrogen-doped carbon dots-zinc oxide hybrid (NCDs-ZnO) nanostructures utilizing simple chemical procedures. The role of NCDs in ZnO nanostructured matrix has been analyzed through XRD, SEM, FTIR and PL characterization techniques. The introduction of NCDs was found to modify not only their aspect ratio, observed by a reduction in the preferred c-axis growth compared to the a- and b-axis, but also induced an additional emission around 441 nm, which is typical of NCDs. The hybrid nanostructures were utilized as catalyst for methylene blue dye degradation showing a 95% degradation after 2 h of UV irradiation in comparison to the ∼70% degradation obtained by utilizing pristine ZnO, while the dye half-life (t 1/2) was reduced by ∼65% by utilizing NCDs-ZnO hybrid nanostructures when compared to the pristine ZnO. The reusability of the fabricated hybrid structures was tested up to eight times with no significant loss in their photocatalytic performance (>90%). The stability of the hybrid structures was verified through Z-potential measurements prior and after reutilization. Excellent reusability and simple processing presented by NCDs-ZnO hybrid nanostructures makes them promising for industrial level photocatalyst for the waste water treatment.

Virus pH-Dependent Interactions with Cationically Modified Cellulose and Their Application in Water Filtration.

Norovirus and Rotavirus are among the pathogens causing a large number of disease outbreaks due to contaminated water. These viruses are nanoscale particles that are difficult to remove by common filtration approaches which are based on physical size exclusion, and require adsorption-based filtration methods. This study reports the pH-responsive interactions of viruses with cationic-modified nanocellulose and demonstrates a filter material that adsorbs nanoscale viruses and can be regenerated by changing the solution's pH. The bacteria viruses Qbeta and MS2, with diameters below 30nm but different surface properties, are used to evaluate the pH-dependency of the interactions and the filtration process. Small angle X-ray scattering, cryogenic transmission electron microscopy, and ζ-potential measurements are used to study the interactions and analyze changes in their nanostructure and surface properties of the virus upon adsorption. The virus removal capacity of the cationic cellulose-based aerogel filter is 99.9% for MS2 and 93.6% for Qbeta, at pH = 7.0; and desorption of mostly intact viruses occurs at pH = 3.0. The results contribute to the fundamental understanding of pH-triggered virus-nanocellulose self-assembly and can guide the design of sustainable and environmentally friendly adsorption-based virus filter materials as well as phage and virus-based materials.

Improving Fibrin Hydrogels' Mechanical Properties, through Addition of Silica or Chitosan-Silica Materials, for Potential Application as Wound Dressings.

Fibrin is a protein-based hydrogel formed during blood coagulation. It can also be produced in vitro from human blood plasma, and it is capable of resisting high deformations. However, after each deformation process, it loses high amounts of water, which subsequently makes it mechanically unstable and, finally, difficult to manipulate. The objective of this work was to overcome the in vitro fibrin mechanical instability. The strategy consists of adding silica or chitosan-silica materials and comparing how the different materials electrokinetic-surface properties affect the achieved improvement. The siliceous materials electrostatic and steric stabilization mechanisms, together with plasma protein adsorption on their surfaces, were corroborated by DLS and ζ-potential measurements before fibrin gelling. These properties avoid phase separation, favoring homogeneous incorporation of the solid into the forming fibrin network. Young's modulus of modified fibrin hydrogels was evaluated by AFM to quantitatively measure stiffness. It increased 2.5 times with the addition of 4 mg/mL silica. A similar improvement was achieved with only 0.7 mg/mL chitosan-silica, which highlighted the contribution of hydrophilic chitosan chains to fibrinogen crosslinking. Moreover, these chains avoided the fibroblast growth inhibition onto modified fibrin hydrogels 3D culture observed with silica. In conclusion, 0.7 mg/mL chitosan-silica improved the mechanical stability of fibrin hydrogels with low risks of cytotoxicity. This easy-to-manipulate modified fibrin hydrogel makes it suitable as a wound dressing biomaterial.

Role of Anodic Time in Pulse-Reverse Electrocodeposition of Nano-SiC Particles

This work focuses on the significance of the particle’s residence time in composite electrodeposition. Ni-SiC were produced using different pulse-reverse (PR) waveforms based on the average particle diameter (60 nm). The waveform was designed to deposit a metal thickness equivalent to the average diameter during the cathodic pulse and strip half during the anodic pulse. The shape of the waveform was modified to study its effect on particle codeposition by changing the cathodic and anodic pulse current density peaks and cycle time while maintaining the same charge. For benchmark, samples were also produced under direct current (DC), matching the cathodic pulse current density peaks and average. The electrodeposition was done in an additive-free and SDS-Watts bath. ζ-potential measurements were employed to determine the interaction between particles and electrolyte. A relation was established between particle incorporation rate and residence time at the electrode interface, examining. The microhardness of the deposits was also studied. The SiC content was more than doubled by PR compared to DC, from 2 vol.% to 5.5 vol.% even after SDS addition. The increase in codeposition rate was related to the anodic pulse time, supported by the existing models on the mechanisms of particle codeposition.