Negatively-charged Nanoparticles Research Articles

Auricularia auricula Anionic Polysaccharide Nanoparticles for Gastrointestinal Delivery of Pinus koraiensis Polyphenol Used in Bone Protection under Weightlessness.

Auricularia auricula polysaccharides used in Pinus koraiensis polyphenol encapsulation and delivery under weightlessness are rarely reported. In this study, an anionic polysaccharide fragment named AAP Iα with a molecular weight of 133.304 kDa was isolated and purified to construct a polyphenol encapsulation system. Nanoparticles named NPs-PP loaded with a rough surface for Pinus koraiensis polyphenol (PP) delivery were fabricated by AAP Iα and ε-poly-L-lysine (ε-PL). SEM and the DLS tracking method were used to observe continuous changes in AAP Iα, ε-PL and PP on the nanoparticles' rough surface assembly, as well as the dispersion and stability. Hydrophilic, monodisperse and highly negative charged nanoparticles can be formed at AAP Iα 0.8 mg/mL, ε-PL 20 μg/mL and PP 80 μg/mL. FT-IR was used to determine their electrostatic interactions. Release kinetic studies showed that nanoparticles had an ideal gastrointestinal delivery effect. NPs-PP loaded were assembled through electrostatic interactions between polyelectrolytes after hydrogen bonding formation in PP-AAP Iα and PP-ε-PL, respectively. Colon adhesion properties and PP delivery in vivo of nanoparticles showed that NPs-PP loaded had high adhesion efficiency to the colonic mucosa under simulated microgravity and could enhance PP bioavailability. These results suggest that AAP Iα can be used in PP encapsulation and delivery under microgravity in astronaut food additives.

Construction of SERS substrates by gold nanoparticles assembly on polymeric matrices

This study reported the fabrication of stable and reproducible large-area SERS substrates based on the assembly of pre-synthesized gold nanoparticles on reconstructed poly(styrene-block-2-vinylpyridine) (PS-b-P2VP) films with different molecular weights and PS/P2VP volume fractions. PS-b-P2VP films on a glass substrate were submitted to different reconstruction procedures: immersion in deionized water or ethanol, exposure to toluene/THF vapor, or thermal annealing. These reconstructed films were immersed in citrate-stabilized gold NPs suspension for different time intervals. P2VP microdomains acted selectively as a binding site for the negatively-charged nanoparticles through electrostatic interactions. The substrates were characterized by UV–vis spectroscopy and atomic force microscopy. The SERS activity was tested using the Nile Blue (NB) dye as a molecular probe. The results demonstrated that the annealing treatment and the molecular weight of the copolymers strongly influence the NPs dispersion and, consequently, the SERS enhancements. Moreover, we established that water and ethanol swelling of the micelles allowed a high uniformity of nanoparticle deposition over the films. In contrast, more efficient SERS enhancement was observed in the nanocomposites treated with toluene/THF vapor annealing and thermal annealing.

Accelerated activation of H2O2 and persulfate by Sm-doped ZnO@highly-defective layered yttria nanocomposite under visible-light irradiation for dyeing wastewater treatment: Comprehensive dominance of oxygen vacancies in photocatalytic advanced oxidation processes

Herein, innovative visible-light-driven nano-photocatalysts for accelerated-activation of H2O2 and persulfate (PS) are explored towards degradation of ionic-dyes from wastewater. Highly-defective yttria-layers (D-Y2O3) are customized and used for stabilization of ZnO and Sm-doped ZnO (Sm-ZnO) nanoparticles. Comparing to ZnO@D-Y2O3, Sm-ZnO@D-Y2O3 nanocomposite possesses advanced surface-area and porosity with significant surface-heterogeneity, elevated negatively-charged nanoparticles (ζav = −36.3 mV), large populations of oxygen vacancies, and enhanced visible-light absorptivity. PS-activation over visible-light-driven Sm-ZnO@D-Y2O3 photocatalyst (Sm-ZnO@D-Y2O3/PS/Vis) displays superior degradation efficiency (~100 %) of isosulfan-blue, Bismarck-brown, and methylene-blue dyes within 10 min, near-complete mineralization performance, and great cyclability. Such excellent photodegradability results from (i) synergistic combination of nanocomposite-PS-visible light, yielding highly-developed synergy-index values (SI = 3–20), (ii) abundant generation of reactive-oxidizing-species (SO4•-/h+/•OH synergistic ratio 1:1.8:1.9), and (iii) facilitated transference of photoexcited-electrons across oxygen vacancies in yttria-moiety, prohibiting electron-hole pairs recombination. Hence, Sm-ZnO@D-Y2O3/PS/Vis system is an extraordinarily candidate for complete destruction of organic-pollutants via newly photocatalytic-mechanism, whatever it treats it degrades.

Effect of different charged Fe3O4 nanoparticles on methane production for anaerobic digestion of wheat straw

Anaerobic digestion (AD) is an effective measure to deal with organic waste, and biogas can be recovered from waste as clean energy. China is mainly an agricultural country, and a large amount of wheat straw is produced every year, which needs to be treated innocuously and resourcefully. In this context, the purpose of this study was to evaluate the effect of exogenous conductive material Fe3O4 nanoparticles on AD of wheat straw and to further evaluate the effect of the charge of nanoparticles on AD. The effects of different charged Fe3O4 nanoparticles on AD of wheat straw were studied. Fe3O4 nanoparticles with positive, negative, and no charge were successfully prepared and used them in the AD of wheat straw. The experiments were carried out in a 500-mL glass bottle with an effective volume of 350 mL and a total solid (TS) concentration of 6%. The results showed that Fe3O4 nanoparticles with positive, negative, and no charge could increase the cumulative methane production of AD, and the pure ligands used to modify Fe3O4 nanoparticles had no considerable effect on AD of wheat straw. The negatively charged nanoparticles (NNPs) had the greatest positive effects on the AD of wheat straw, which was 51.33% higher than that of the blank control group and reached 333.14 mL CH4/g·TS. The peak concentration of volatile fatty acids (VFAs) in the negative experiment was 31.65% higher than that of the blank control group at the beginning of the experiment and 30.57% lower than that of the blank control group at the end of the experiment. The cyclic voltammetry curve showed that the NNPs improved the redox performance in the AD process, and the maximum value was reflected in the methane production. NNPs can increase the metabolic rate of VFAs and the content of active substances catalyzing biochemical reactions. The charge properties of Fe3O4 nanoparticles play an important role in improving the efficiency of AD, which is of great significance for nano-electron transfer mediators to improve the efficiency of AD. These results show that NNPs have the most significant effect on AD. The addition of this material is helpful in regulating the indices in the process of AD and can be applied to the AD of more substrates.

Surface functionalization of cellulose fibers via aza-Michael addition for CO2-assisted water remediation

The remediation of water that polluted by organic dyes and nanoparticles (NPs) remains a great challenge. However, second pollution of solid waste may produce if the adsorbents are not degradable or recyclable. The stimuli-responsive materials were regarded to be able to resolve this problem by reversible adsorption-desorption under stimuli. Here in this work, the surface of cellulose fibers was modified with CO2-responsive molecules through a simple esterification followed by an aza-Michael addition reaction. The chemical structure was confirmed with Fourier transform infrared spectra (FT-IR), X-ray photoelectron spectroscopy (XPS), x-ray diffractometer (XRD) and thermal analysis. The gas-responsiveness was demonstrated by monitoring of the pH, conductivity and surface zeta potential. Anionic dyes and negative charged NPs in water can be selectively and reversibly captured by the CO2-responsive surface on cellulose fibers, suggesting the inexpensive, readily available and smart cellulose fibers may find great potential in water remediation.

Direct translocation of a negatively charged nanoparticle across a negatively charged model cell membrane.

Nanoparticles have attracted much attention as a carrier for drug, gene, and macromolecule delivery in next-generation biomedical and therapeutic technologies. In delivery applications, nanoparticles tend to have negative charge due to the negative charge of biomolecules used as delivery cargo, while biological cell membranes are also negatively charged. This means that negatively charged nanoparticles (NC-NPs) are required to translocate across these negatively charged cell membranes (NC-CMs). However, this translocation is unlikely to occur because of electrostatic interactions. Here, we investigated the translocation of a NC-NP across a NC-CM under a transmembrane electric potential through coarse-grained molecular dynamics simulations. To model the transmembrane potential, two approaches were adopted: externally applied electric field and ionic charge imbalance. We showed that a NC-NP can directly translocate across a NC-CM via a non-disruptive pathway under a weak external electric field with an ionic charge imbalance. It was also found that the ionic charge imbalance contributes to the membrane crossing of a NC-NP as well as the self-resealing of the cell membrane after a NC-NP translocation. Our findings imply that NC-NPs can be delivered into a cell by combining applied electric field with membrane hyperpolarization/depolarization induced by an external stimulus.

Biological behavior of nanoparticles with Zr-89 for cancer targeting based on their distinct surface composition.

Nano-sized materials with properties that enable their internalization into target cells using passive targeting systems have been utilized with radioisotopes to track their pharmacokinetics in the body. Here, we report the incorporation of novel chelator-free Zr-89 using a hierarchical iron oxide nanocomposite (89Zr-IONC). Characterization revealed that it had a rice-shape with a mean width of 160 nm. The surface of the 89Zr-IONCs was coated by polyethyleneimine (PEI) and polyvinylpyrrolidone (PVP) to improve the cancer target efficacy. The biological behavior of the nanoparticles coated with the polymers differed significantly by the surface composition. Positron emission tomography measurements by the labeled Zr-89 effectively confirmed the cancer target capability and the fate of distribution in the body. We found that only PVP coated 89Zr-IONC reached the tumor region while non-coated and PEI coated 89Zr-IONC tended to be undesirably entirely cleared in the liver and spleen. The 89Zr-incorporated iron oxide nanocomposite is significantly stable for radiolabeling despite various surface modifications, allowing the potential carrier to specifically target cancer cells. The strategy of utilizing the biocompatible PEI and PVP surface coating system for negative charged nanoparticles such as iron oxide will afford enhanced biological application.

Effect of superparamagnetic nanoparticles coated with various electric charges on α-synuclein and β-amyloid proteins fibrillation process.

BackgroundMost of nanoparticles are nontoxic and have high absorption capability. Therefore, nanoparticles binding can effectively restrain fibrillation of β-amyloid and α-synuclein proteins and eventually prevent the toxicity of pathogenesis peptide of Alzheimer. Super paramagnetic iron oxide nanoparticles (SPIONs) contain iron oxide core which can be connected to a special part through magnetic coating.Materials and methodsIn this study, the effect of SPIONs with different charges was simultaneously examined on the fibrillation of both β-amyloid and α-synuclein proteins by applying Thioflavin-T assay.ResultsAccording to the results of the investigation on amyloid-fibrillation mechanism in both β-amyloids and α-synucleins, it was revealed that negatively-charged nanoparticles encoded to –COOH by dextran-coating were able to have a considerable absorption decrease from 17,000–12,000 after 320 minutes delay to lag phase and decrease in binding level of thioflavin-T particles to β-sheets.ConclusionThe different concentrations of these nanoparticles and special coating of each particle had an effect on the kinetics of β-amyloid and α-synuclein fibrillations.

Directed Nanoscale Self-Assembly of Low Molecular Weight Hydrogelators Using Catalytic Nanoparticles.

The work presented here shows that the growth of supramolecular hydrogel fibers can be spatially directed at the nanoscale by catalytic negatively charged nanoparticles (NCNPs). The NCNPs with surfaces grafted with negatively charged polymer chains create a local proton gradient that facilitates an acid-catalyzed formation of hydrogelators in the vicinity of NCNPs, ultimately leading to the selective formation of gel fibers around NCNPs. The presence of NCNPs has a dominant effect on the properties of the resulting gels, including gelation time, mechanical properties, and network morphology. Interestingly, local fiber formation can selectively entrap and precipitate out NCNPs from a mixture of different nanoparticles. These findings show a new possibility to use directed molecular self-assembly to selectively trap target nano-objects, which may find applications in therapy, such as virus infection prevention, or engineering applications, like water treatment and nanoparticle separation.

Designing solid-electrolyte interphases for lithium sulfur electrodes using ionic shields

Lithium metal is among the most sought-after anode chemistries for next-generation electrical energy storage due to its high theoretical capacity (3860mAhg−1) and low reduction potential (− 3.04V vs S.H.E.). To realize its promise, reactive Li anodes must be paired with high-energy conversion cathodes, such as sulfur or oxygen. Chemical and physical instability at both electrodes pose formidable challenges to development of practical lithium metal batteries. These instabilities are compounded by problems with active material loss and anode passivation when Li is paired with conversion cathodes, such as elemental sulfur. Here, we report on design principles and a process for creating artificial solid electrolyte interphases composed of ionic shields that are able to stabilize electrochemical processes at both the anode and cathode of Li-S electrochemical cells. We show that ASEI composed of negatively-charged nanoparticles on Li stabilize deposition of Li at the anode by multiple fundamental mechanisms. A similar concept is used to design interphases composed of positively charged conductive nanoparticles at the cathode and shown to be effective at intercepting dissolved polysulfide anions and for enhancing sulfur reutilization. We combine the two ASEI design strategies to create Li-S cells based on high-loading sulfur cathodes and demonstrate their long-term cycling stability.

Chitosan as stabilizing agent for negatively charged nanoparticles

Chitosan is a biocompatible polysaccharide with positive Z potential which can stabilize negative charged nanoparticles. Silk fibroin nanoparticles and citrate gold nanoparticles, both with negative Z potential, but they form aggregates at physiological ionic strength. In this work, we study the behavior of chitosan in solution when the ionic strength of the medium is increased and how the concentration of chitosan and the proportion of the two components (chitosan and AuNP or SFN) significantly affect the stability and size of the nanocomposites formed. In addition to experimental measurements, molecular modeling were used to gain insight into how chitosan interacts with silk fibroin monomers, and to identify the main energetic interactions involved in the process. The optimum values for obtaining the smallest and most homogeneous stable nanocomposites were obtained and two different ways of organization through which chitosan may exert its stabilizing effect were suggested.

Carrier particle design for stabilization and isolation of drug nanoparticles

Nanoparticles of poorly water-soluble drugs were prepared in suspension via antisolvent precipitation in order to improve their dissolution behaviour. Insoluble, surface-functionalized, micron-range, clay carrier particles were employed for the dual purpose of stabilizing the nanoparticles in suspended state, and facilitating their unhindered isolation to solid state; often a challenging step in nanoparticle production. The carrier particles, which were functionalized with an optimal level of cationic polymer (protamine), attracted negatively-charged nanoparticles to their surface as a uniform and segregated nanoparticle layer, at drug loadings up to 9% w/w. By using carrier particles to stabilise the nanoparticles on their surface, the traditionally used solubilised nanosuspension stabilisers could be eliminated, thus avoiding time-consuming stabiliser screening tests. The carrier particle system facilitated stabilisation of nanoparticles in suspension, isolation of nanoparticles to the solid state via filtration, and preservation of fast nanoparticle-induced dissolution rates of the dried nanoparticle-carrier composites, indicating preservation of their high surface area during drying. The process was validated with two poorly water-soluble BCS Class II drugs, fenofibrate and mefenamic acid, both of which demonstrated negative surface charge in aqueous suspension.

Controlled Fluxes of Silicon Nanoparticles to a Substrate in Pulsed Radio-Frequency Argon–Silane Plasmas

It has been hypothesized that high-energy impact of very small silicon nanoparticles on a substrate may lead to epitaxial growth of silicon films at low substrate temperature. A possible means for producing such energetic nanoparticle fluxes involves pulsing an RF silane-containing plasma, and applying a positive DC bias to the substrate during the afterglow phase of each pulse so as to collect the negatively charged particles generated during the RF power on phase. We here report numerical modeling to provide a preliminary assessment of the feasibility of this scheme. The system modeled is a parallel-plate capacitively-coupled RF argon–silane plasma at pressures around 100 mTorr. Simulation results indicate that it is possible to achieve a periodic steady state in which each pulse delivers a controlled flux of nanoparticles to the biased substrate, that average particle sizes can be kept below 2–3 nm, that impact energies of the negatively-charged nanoparticles that are attracted by the applied bias can be maintained in the ~1 eV/atom range thought to be conducive to epitaxial growth without causing film damage, and that the volume fraction of neutral nanoparticles that deposit by low-velocity diffusion can be kept well below 1 %. The effects of several operating parameters are explored, including RF voltage, pressure, the value of the applied DC bias, and RF power on and off time during each pulse.

Tumor stroma-containing 3D spheroid arrays: A tool to study nanoparticle penetration

Nanoparticle penetration through tumor tissue after extravasation is considered as a key issue for tumor distribution and therapeutic effects. Most tumors possess abundant stroma, a fibrotic tissue composed of cancer-associated fibroblasts (CAFs) and extracellular matrix (ECM), which acts as a barrier for nanoparticle penetration. There is however a lack of suitable in vitro systems to study the tumor stroma penetration of nanoparticles. In the present study, we developed and thoroughly characterized a 3D co-culture spheroidal array to mimic tumor stroma and investigated the penetration of silica and PLGA nanoparticles in these spheroids. First, we examined human breast tumor patient biopsies to characterize the content and organization of stroma and found a high expression of alpha-smooth muscle actin (α-SMA; 40% positive area) and collagen-1 (50% positive area). Next, we prepared homospheroids of 4T1 mouse breast cancer cells or 3T3 mouse fibroblasts alone as well as heterospheroids combining 3T3 and 4T1 cells in different ratios (1:1 and 5:1) using a microwell array platform. Confocal live imaging revealed that fibroblasts distributed and reorganized within 48h in heterospheroids. Furthermore, immunohistochemical staining and gene expression analysis showed a proportional increase of α-SMA and collagen in heterospheroids with higher fibroblast ratios attaining 35% and 45% positive area at 5:1 (3T3:4T1) ratio, in a good match with the clinical breast tumor stroma. Subsequently, we studied the penetration of high and low negatively charged fluorescent silica nanoparticles (30nm; red and 100 or 70nm; green; zeta potential: −40mV and −20mV) and as well as Cy5-conjugated pegylated PLGA nanoparticles (200nm, −7mV) in both homo- and heterospheroid models. Fluorescent microscopy on spheroid cryosections after incubation with silica nanoparticles showed that 4T1 homospheroids allowed a high penetration of about 75–80% within 24h, with higher penetration in case of the 30nm nanoparticles. In contrast, spheroids with increasing fibroblast amounts significantly inhibited NP penetration. Silica nanoparticles with a less negative zeta potential exhibited lesser penetration compared to highly negative charged nanoparticles. Subsequently, similar experiments were conducted using Cy5-conjugated pegylated PLGA nanoparticles and confocal laser scanning microscopy; an increased nanoparticle penetration was found in 4T1 homospheroids until 48h, but significantly lower penetration in heterospheroids. Furthermore, we also developed human homospheroids (MDA-MB-231 or Panc-1 tumor cells) and heterospheroids (MDA-MB-231/BJ-hTert and Panc-1/pancreatic stellate cells) and performed silica nanoparticle (30 and 100nm) penetration studies. As a result, heterospheroids had significantly a lesser penetration of the nanoparticles compared to homospheroids. In conclusion, our data demonstrate that tumor stroma acts as a strong barrier for nanoparticle penetration. The 30-nm nanoparticles with low zeta potential favor deeper penetration. Furthermore, the herein proposed 3D co-culture platform that mimics the tumor stroma, is ideally suited to systematically investigate the factors influencing the penetration characteristics of newly developed nanomedicines to allow the design of nanoparticles with optimal penetration characteristics.

Nanotoxicological Effects of SiO2 Nanoparticles on Spodoptera frugiperda Sf9 Cells.

The application of silica nanoparticles (NPs) in the biomedical field experienced a great development. The driving forces for these and future developments are the possibility to design NPs with homogeneous size and structure amenable to specific grafting. Moreover, it is possible to tune the characteristics of the NPs to meet the requirements of each specific cell and desired application. Herein, we analyzed the effect of silica NPs of various sizes and surface charge on the viability of Spodoptera frugiperda cells (Sf9 cell line) with the aim of extending the knowledge of possible toxicity of the NPs in the environment and development of new tools for insect control. Moreover, these results will also contribute to develop more effective systems for gene vectors delivery and recombinant proteins expression. Bare silica NPs of 14 nm, 380 nm and 1430 nm as well as amine-modified silica NPs of 131 nm and 448 nm were obtained by the Stöber method. The NPs were characterized by DLS and zeta potential measurements. The cell viability was assessed by the MTT test. It was observed that the 14 nm NPs possess the highest toxic effect. Indeed, after 24 h, the viability of the cells exposed to the lower concentration of NPs (0.12 mg/ml) was about 40% of the value obtained for the control cells not exposed to NPs. Moreover, the exposure to other negative charged NPs also causes a lower activity when compared with the control. Alternatively, lower concentrations of positive charged NPs (i.e.: 0.12 or 0.6 mg/ml) demonstrated to stimulate the proliferation of the cells and higher concentrations (i.e.: 7.2 mg/ml) did not present significant differences with the control. In conclusion, we have demonstrated that the NPs possess an effect that is highly influenced by the size, charge and concentration. Although, silica NPs are being used in the biomedical field, these results contribute to further understanding the risk that could be associated to nanoparticles and how these can be modified in order to meet the requirements of each desired application.

Generation of Charged Nanoparticles During Thermal Evaporation of Silver at Atmospheric Pressure.

The generation of charged silver nanoparticles in the gas phase during thermal evaporation of silver at atmospheric pressure was confirmed by the nano-differential mobility analyzer (DMA). Effects of the evaporation temperature, the nitrogen gas flow rate and the amount of silver to be evaporated on the size distribution of charged nanoparticles (CNPs) were examined. Both positively and negatively-charged nanoparticles were generated under all processing conditions adopted in this study. The deposition behavior of CNPs was affected by the gas flow, which is affected by the temperature gradient in the reactor and by the applied electric bias. The electric bias, which not only enhanced the film growth rate but also produced a much denser film surface, turned out to be an important process parameter under the condition where an appreciable amount of CNPs is generated.

Curcumin Nanoparticles Attenuate Production of Pro-inflammatory Markers in Lipopolysaccharide-Induced Macrophages.

The surface charge of nanoparticles is an important factor that controls efficiency and cellular uptake. The aim of this study was to investigatethe efficacy of curcumin nanoparticles (Cur-NPs) with different surface charges, in terms of toxicity, internalization, anti-inflammatory and anti-oxidant activities towards alveolar macrophages cells. The surface charge of curcumin nanoparticles (positive, negative and neutral), with an average diameter of 30nm, were synthesized and characterized. Polyvinyl-alcohol, polyvinylpyrrolidone and dextran were used as coatings to confer negative, positive and neutral charges. The synthesized Cur-NPs were evaluated for particle size, encapsulation efficiency, surface charge, qualitative and quantitative cellular uptakes, anti-oxidant and anti-inflammatory activities. Positively charged nanoparticles showed higher cytotoxicity effects compared to negative and neutral particles. The same trend was observed in antioxidant activity, which included radical scavenging and nitric oxide production. In addition, the anti-inflammatory activity (interleukin-1β, IL-6 and TNF-α) depleted in the order: positive>negative>neutral. The void neutral-, positively- and negatively-charged nanoparticles did not show any cytotoxic effects. The difference in activity for different surface charges of Cur-NPs may be due to the internalization rate of the particles by alveolar macrophages. Intracellular uptake measurements demonstrated that Cur-NPs with positive surface charges possessed the strongest interaction with alveolar macrophages.

Comparison of charged nanoparticle concentrations near busy roads and overhead high-voltage power lines

Overhead high-voltage power lines are known sources of corona ions. These ions rapidly attach to aerosols to form charged particles in the environment. Although the effect of ions and charged particles on human health is largely unknown, much attention has focused on the increasing exposure as a result of the expanding power network in urban residential areas. However, it is not widely known that a large number of charged particles in urban environments originate from motor vehicle emissions. In this study, for the first time, we compare the concentrations of charged nanoparticles near busy roads and overhead power lines. We show that large concentrations of both positive and negative charged nanoparticles are present near busy roadways and that these concentrations commonly exceed those under high-voltage power lines. We estimate that the concentration of charged nanoparticles found near two freeways carrying around 120 vehicles per minute exceeded the corresponding maximum concentrations under two corona-emitting overhead power lines by as much as a factor of 5. The difference was most pronounced when a significant fraction of traffic consisted of heavy-duty diesel vehicles which typically have high particle and charge emission rates.

Cellulose nanofibre composite membranes – Biodegradable and recyclable UF membranes

Polymeric membranes are widely used in filtration applications because of their excellent mechanical properties and chemical resistance. Unfortunately they pose environmental problems during the production and particularly in the disposal stages of their life cycle. Cellulose nanofibre membranes, which are recyclable, have the potential to mitigate these problems. In this work cellulose nanofibre composite membranes are prepared using suspensions of cellulose nanofibres, silica nanoparticles (22nm) and polyamide-amine-epichlorohydrin (PAE) via filtration. Here silica nanoparticles act as spacers to the control pore size of the nanofibre network. PAE was added to adhere the negatively-charged nanoparticles to the nanofibres and also to improve the wet strength of the membrane. Membranes prepared with nanofibres alone showed high flux but low rejection due to large pore size. In contrast, nanofibre composite membranes showed water flux of 80LMH and MWCO of 200kDa. Addition of silica nano particles controlled the pore size. These results demonstrate the potential of cellulose nanofibre composite membranes in ultrafiltration. The produced membranes are readily recyclable as a feed stock to a conventional paper making process.

Cylindrical Silicon on Insulator Solid State Nanopores for Charge Selective Nanoparticle Filtering

Rapid separation of specific biomolecules like virions and other nanoparticles through a solid state nanopore is of vital importance to various biomedical applications and bioanalytical studies. Several factors such as external applied transmembrane voltages, particle size and surface charge density of the nanopore are being investigated to improve the separation efficiency. However, in most cases the transmembrane electric field is not strong enough to pull the particles into the pore. Our goal is to use a voltage bias applied to the substrate of our specific silicon-on-insulator nanopore to significantly increase the nanoparticle translocation rate through the aperture, enhancing the performance of the device as a particle-selective filter.The ability to apply a substrate bias to single silicon-on-insulator cylindrical nanopores via the top silicon layer offers a tremendous advantage over regular silicon nitride nanopores. Moreover, the nanopore process flow is compatible with standard cleanroom facilities allowing a similar high throughput fabrication. The buried oxide layer provides a robust etch stop for the nanopore membrane and the sub-100nm aperture size is precisely controlled by electron beam lithography and thermal oxidation.The applied substrate bias changes the transverse conductance of the nanopore at low electrolyte concentrations (<10-4M HCl) when the Debye length is comparable to the dimensions of the nanopore. The bias depletes or attracts the H+ ions, being theions contributing to the ionic current flow within the nanopore, thereby decreasing or increasing the ionic current. When a positive substrate bias is applied to silicon device layer, it attracts negative charged nanoparticles such as polystyrene beads, which subsequently pass through the pore and repel positively charged particles away from the aperture entrance, acting as a charge-selective filter.