Filtration Of Nanoparticles Research Articles

Short cellulose acetate nanofibers: A novel and scalable coating for enhancing nanoparticles filtration efficiency of filter media

This study introduces a novel and scalable approach to significantly enhance the filtration efficiency of automotive cabin air filters using short cellulose acetate nanofibers applied via a spray coating method. The short nanofibers, produced through the mechanical fragmentation of electrospun mats, enable uniform dispersion and application onto microfibrous filter media, addressing a key limitation in nanofiber technology. This innovative process enhances the capture of ultrafine particles (7.4 to 250 nm), which are critical for improving air quality in confined environments such as vehicle cabins. The filters, coated with nanofiber weights ranging from 1 to 13 mg, showed a prominent improvement in filtration efficiency, achieving quality factors (Qf) from 0.01 to 0.0221 Pa−1, outperforming both uncoated filters (0.0025 Pa−1) and commercial HEPA filters (0.0212 Pa−1). Filtration efficiency increased from 18 % to 99.8 %, with corresponding pressure drops between 44.5 and 620 Pa. Remarkably, a filter with 9 mg of nanofibers achieved a superior quality factor of 0.0221 Pa−1, effectively optimizing both efficiency and pressure drop while outperforming HEPA filters. This method addresses the common challenge in conventional filters of balancing filtration efficiency with pressure drop. The scalable spray coating process, combined with the advantages of electrospinning, offers a practical, industrially viable solution to improve air filtration in automotive HVAC systems and other environments requiring high filtration efficiency and low-pressure drop.

Cordierite ceramic membrane preparation using gas solid reaction growth for nanoparticles filtration

Mullite whiskers have been successfully grown on the surface of cordierite honeycomb ceramics by the gas-phase growth method. The cilia-like structure can significantly improve the filtration precision. The acicular mullite whiskers grew on the cordierite present nanometer-sized (200–300 nm) diameters and micrometer-sized (1–2 μm) lengths. Owing to mullite whiskers growth on surface of pores, the morphology of pores is changed and the microstructure change will lead to filtration precision increasing. The composites with the largest ratio of length/diameter mullite whiskers possess the highest filtration precision, which can reach 122.42 nm, 255.00 nm and 458.67 nm in intercepting different particle size of nano-SiO2, respectively. Moreover, the bending strength of the cordierites were enhanced due to the generation of mullite whiskers, these generated whiskers intersected with each other forming many unfixed lap-jointing points. The porous ceramics membrane with the unique microstructure has great potential application in gas-solid separation field and liquid-solid separation field.

Impact of pH, ionic strength, and operating conditions on capture mechanisms in nanoparticle filtration

Filtration of biopharmaceutical streams can be complex due to the variety of components in the stream and their interactions among themselves and with the filter pore surfaces. This work used a variety of measurements to study the filtration of model silica nanoparticles through asymmetric hydrophilized polyethersulfone (mPES) membrane in solutions covering a range of pH and ionic strengths. Measurements included particle size, particle concentration, zeta potential, particle-particle and particle-membrane surface intermolecular forces. These measurements were used to rationalize observed particle capture behavior under various filtration conditions. We found that increasing ionic strength and decreasing pH resulted in higher particle aggregation and higher particle retention due to adsorption of model silica nanoparticles to the membrane and sieving of aggregates within the membrane. In addition, captured particles can be eluted from the membrane in some cases, depending on the operating conditions, extent of particle loading, buffer flush pressure, and buffer pH and conductivity conditions. These findings provide insight into methods to improve filtration performance and particle capture or release, including product recovery, in filtration processes.

Physiological principles underlying the kidney targeting of renal nanomedicines.

Kidney disease affects more than 10% of the global population and is associated with considerable morbidity and mortality, highlighting a need for new therapeutic options. Engineered nanoparticles for the treatment of kidney diseases (renal nanomedicines) represent one such option, enabling the delivery of targeted therapeutics to specific regions of the kidney. Althoughthey are underdeveloped compared with nanomedicines for diseases such as cancer, findings from preclinical studies suggest that renal nanomedicines may hold promise. However, the physiological principles that govern the in vivo transport and interactions of renal nanomedicines differ from those of cancer nanomedicines, and thus a comprehensive understanding of these principles is needed to design nanomedicines that effectively and specifically target the kidney while ensuring biosafety in their future clinical translation. Herein, we summarize the current understanding of factors that influence the glomerular filtration, tubular uptake, tubular secretion and extrusion of nanoparticles, including size and chargedependency, and the role of specific transporters and processes such as endocytosis. We also describe how the transport and uptake of nanoparticles is altered by kidney disease and discuss strategic approaches by which nanoparticles may be harnessed for the detection and treatment of a variety of kidney diseases.

Effect of static electricity and thickness of solution blow spun polyamide 6/AgNP nanofibrous membrane on nanoparticle filtration and microbiological activity

The efficient filtration of particulate matter smaller than 0.3 µm is crucial for preventing microbial and viral infections. Nanofiber membranes (NFMs) produced by solution blow spinning (SBS) modified with antimicrobial nanoparticles have emerged as a promising technology for filtration technology. In this context, here we developed novel NFMs produced by SBS using Polyamide 6 (PA6) which was surface functionalized with different types of silver nanoparticles (AgNPs) using a simple immersion procedure. The NFMs thickness was customized to evaluate their performance towards the filtration of NP (nanoparticle) from 30 to 300 nm. The incorporation of AgNPs onto the NFMs was also investigated to test their bactericidal activity against E. coli and S. aureus. The NFMs were physically and chemically characterized using distinct techniques. The filtration efficiency of 30–300 nm NP reached around 93.5 %, where the NFMs thickness played a key role in the filtration efficiency and pressure drop. Furthermore, the presence of static electricity in the NFM inherent to the SBS process also contributed to the greater filtration efficiency of smaller particles. Our results demonstrated that NFMs can be produced through SBS in an easy and scalable way, leading to highly efficient filtration systems, with implications for diverse fields such air purification systems and protective clothing.

Comparison of microfiltration performances of ePTFE and PCTE membranes in IPA and deionized water

Isopropyl alcohol (IPA) is widely used as a cleaning and drying agent in semiconductor manufacturing. The purity of chemicals is becoming increasingly stricter as the leading-edge node sizes become smaller. The microfiltration of nanoparticles (NPs) in water has been extensively studied by many research groups. However, studies on microfiltration in IPA are rare. In this study, we conducted experiments to determine the filtration of nanoparticles using expanded polytetrafluoroethylene (ePTFE) and polycarbonate track-etched (PCTE) membranes in both deionized water (DIW) and IPA. The zeta potentials (ZP) of the polymers and particles were measured. The Hamaker constant and its effect on particle capture were estimated using Derjaguin–Landau–Verwey–Overbeek theory. The results show that the retention efficiency of the two membranes (five different pore sizes) for Ag NPs (size: 20–100 nm) in IPA was much higher than that in DIW. However, the retention efficiencies of the two membranes in IPA and DIW increase monotonically upon increasing the particle size, which was completely different from the U-shaped curve for aerosol filtration predicted using the previous liquid model. In addition, the absolute ZP value of the NPs and membrane surface in IPA was found to be much smaller than that of DIW.

Characterization and associated pressure-dependent behavior of deposits formed during sterile filtration of mRNA-Lipid nanoparticles

The recent success of mRNA vaccines has generated increased interest in the use of Lipid Nanoparticles (LNPs) for delivery of nucleic acids. The objective of this study was to characterize the deposit formed on the surface of membranes during sterile filtration of mRNA-LNPs using a combination of scanning electron microscopy (SEM), environmental scanning electron microscopy (ESEM), atomic force microscopy (AFM), and hydraulic resistance measurements. The microscopic characterizations showed an amorphous deposit fouling the surface of the filter and blocking the membrane pores. The resistance of the deposit showed an unusual biphasic behavior, increasing at low pressure (consistent with a compressible filtration medium) but decreasing at high pressure, in a reversible manner. The surprising reduction in resistance at high pressure has not previously been identified in the filtration literature. The pressure corresponding to the maximum resistance (Pcritical) was found to be proportional to the inverse of the membrane pore size, as described by the Young-Laplace relationship. The hydraulic resistance measurements and microscopic characterization are consistent with a mechanism whereby an amorphous fouling deposit intrudes through membrane pores at high transmembrane pressures. These results provide important insights into the physical properties of the fouling deposit that governs the sterile filtration of LNPs.

Temperature-Responsive Nanoporous Membranes from Self-Assembly of Poly(N-isopropylacrylamide) Hairy Nanoparticles.

Nanoporous membranes play a critical role in numerous separations on laboratory and industrial scales, ranging from water treatment to biotechnology. However, few strategies exist that allow for the preparation of mechanically robust nanoporous membranes whose separation properties can be easily tuned. Here, we introduce a new family of tunable nanoporous membranes based on nanoparticles decorated with temperature-responsive polymer brushes. We prepared mechanically robust membranes from hairy nanoparticles (HNPs) carrying PNIPAM polymer brushes. We assembled the HNPs into thin films through pressure-driven deposition of nanoparticle suspensions and measured the permeability and filtration cutoff of these membranes at different temperatures. The membrane pore diameter at room temperature varied between 10 and 30 nm depending on the polymer length. The water permeability of these membranes could be controlled by temperature, with the effective pore diameter increasing by a factor of 3-6 (up to 100 nm) when the temperature was increased to 60 °C. The size selectivity of these membranes in the filtration of nanoparticles could also be attenuated by temperature. Molecular dynamics computer simulations of a coarse-grained HNP model show that temperature-sensitive pores sizes are consistent with our experimental results and reveal the polymer configurations responsible for the observed filtration membrane permeability. We expect that these membranes will be useful for separations and in the preparation of responsive microfluidic devices.

Single-Pass Tangential Flow Filtration (SPTFF) of Nanoparticles: Achieving Sustainable Operation with Dilute Colloidal Suspensions for Gene Therapy Applications.

Recent approval of several viral-vector-based therapeutics has led to renewed interest in the development of more efficient bioprocessing strategies for gene therapy products. Single-Pass Tangential Flow Filtration (SPTFF) can potentially provide inline concentration and final formulation of viral vectors with enhanced product quality due. In this study, SPTFF performance was evaluated using a suspension of 100 nm nanoparticles that mimics a typical lentivirus system. Data were obtained with flat-sheet cassettes having 300 kDa nominal molecular weight cutoff, either in full recirculation or single-pass mode. Flux-stepping experiments identified two critical fluxes, one based on boundary-layer particle accumulation (Jbl) and one based on membrane fouling (Jfoul). The critical fluxes were well-described using a modified concentration polarization model that captures the observed dependence on feed flow rate and feed concentration. Long-duration filtration experiments were conducted under stable SPTFF conditions, with the results suggesting that sustainable performance could potentially be achieved for as much as 6 weeks of continuous operation. These results provide important insights into the potential application of SPTFF for the concentration of viral vectors in the downstream processing of gene therapy agents.

Development of reusable cloth mask with nanoparticle filtration efficiency greater than 95%

Development of reusable cloth mask with nanoparticle filtration efficiency greater than 95%

Precoating Effects in Fine Steelmaking Dust Filtration

Particle emissions into the atmosphere can cause extensive damage to the environment and human health. To improve the efficiency in the collection of submicronic particles, new filtration media appeared on the market due to new textile technologies and equipment, such as filter media developed with polytetrafluoroethylene (PTFE) membranes; however, these are more expensive. A filter coating technique called precoating is a more economical alternative that could enhance filtration efficiency. This paper aimed to evaluate the operational parameters of precoating for micro- and nanoparticle filtration and compare the results with those obtained from the PTFE membrane. For this purpose, filtration cycles were performed, using precoated polyester with hydrated lime and dolomitic limestone, polyester with a PTFE membrane, and steel industry ultrafine dust. The results showed that the precoated polyester had a longer cycle duration and lower pressure drop than the polyester with a PTFE membrane. Therefore, precoating was shown to be a great alternative to be used in bag filters in steel mills because it presented high collection efficiency for submicronic particles, in addition to increasing the bag lifespan with less energy expenditure.

Influence of electrospinning parameters on the morphology and performance of filter media

Nanofibrous filter media used for filtration of nanoparticles dispersed in air can be produced by electrospinning of polymer solutions. However, this process is influenced by many operating variables, including the solution feed conditions. In this work, a 2³ factorial design was used to evaluate the influence of electrospinning variables on the morphology and performance characteristics of filter media composed of polyvinyl alcohol (PVA) nanofibers. The variables considered were needle-collector distance, collector rotation speed, and spinning time. The dependent variables were the median and geometric standard deviation of the fiber diameter distribution, the overall efficiency for collection of NaCl particles (5.94–224.7 nm), and the initial pressure drop. It was found that the needle-collector distance had the most significant influence on the output variables, especially for the median fiber diameter and the initial pressure drop. For these variables, the fitted curves provided coefficient of determination (R²) values of 0.98 and 0.96, respectively.

Pressure-dependent fouling behavior during sterile filtration of mRNA-containing lipid nanoparticles.

The COVID-19 pandemic has generated growing interest in the development of mRNA-based vaccines and therapeutics. However, the size and properties of the lipid nanoparticles (LNPs) used to deliver the nucleic acids can lead to unique phenomena during manufacturing that are not typical of other biologics. The objective of this study was to develop a more fundamental understanding of the factors controlling the performance of sterile filtration of mRNA-LNPs. Experimental filtration studies were performed with a Moderna mRNA-LNP solution using a commercially available dual-layer polyethersulfone sterile filter, the Sartopore 2 XLG. Unexpectedly, increasing the transmembrane pressure (TMP) from 2 to 20 psi provided more than a twofold increase in filter capacity. Also surprisingly, the effective resistance of the fouled filter decreased with increasing TMP, in contrast to the pressure-independent behavior expected for an incompressible media and the increase in resistance typically seen for a compressible fouling deposit. The mRNA-LNPs appear to foul the dual-layer filter by blocking the pores in the downstream sterilizing-grade membrane layer, as demonstrated both by scanning electron microscopyand derivative analysis of filtration data collected for the two layers independently. These results provide important insights into the mechanisms governing the filtration of mRNA-LNP vaccines and therapeutics.

Penetration and aerosolization of cough droplet spray through face masks: A unique pathway of transmission of infection

The advent of the COVID-19 pandemic has necessitated the use of face masks, making them an integral part of the daily routine. Face masks occlude the infectious droplets during any respiratory event contributing to source control. In the current study, spray impingement experiments were conducted on porous surfaces like masks having a different porosity, pore size, and thickness. The spray mimics actual cough or a mild sneeze with respect to the droplet size distribution (20–500 μm) and velocity scale (0–14 m/s), which makes the experimental findings physiologically realistic. The penetration dynamics through the mask showed that droplets of all sizes beyond a critical velocity penetrate through the mask fabric and atomize into daughter droplets in the aerosolization range, leading to harmful effects due to the extended airborne lifetime of aerosols. By incorporating spray characteristics along with surface tension and viscous dissipation of the fluid passing through the mask, multi-step penetration criteria have been formulated. The daughter droplet size and velocity distribution after atomizing through multi-layered masks and its effects have been discussed. Moreover, the virus-emulating particle-laden surrogate respiratory droplets are used in impingement experiments to study the filtration and entrapment of virus-like nanoparticles in the mask. Furthermore, the efficacy of the mask from the perspective of a susceptible person has been investigated.

Retention and Fouling during Nanoparticle Filtration: Implications for Membrane Purification of Biotherapeutics.

One major challenge in the development of nanoparticle-based therapeutics, including viral vectors for the delivery of gene therapies, is the development of cost-effective purification technologies. The objective of this study was to examine fouling and retention behaviors during the filtration of model nanoparticles through membranes of different pore sizes and the effect of solution conditions. Data were obtained with 30 nm fluorescently labeled polystyrene latex nanoparticles using both cellulosic and polyethersulfone membranes at a constant filtrate flux, and both pressure and nanoparticle transmission were evaluated as a function of cumulative filtrate volume. The addition of NaCl caused a delay in nanoparticle transmission and an increase in fouling. Nanoparticle transmission was also a function of particle hydrophobicity. These results provide important insights into the factors controlling transmission and fouling during nanoparticle filtration as well as a framework for the development of membrane processes for the purification of nanoparticle-based therapeutics.

Analysis and Filtration of Nanoparticles during Heating of Spherical Simulators of Fuel Elements in Helium

A technique is described and analysis of radioactive nanoaerosols formed during heating of spherical simulators of fuel elements for high-temperature gas-cooled reactors in helium to 1500 K has been carried out. It was found that upon high-temperature gas corrosion and leakage of radioactive fission products from fuel elements, nanoaerosols of graphite with iodine and tellurium isotopes can be formed. More than 80% of their γ-activity is accounted for by particles ranging in size from 0.002 to 0.5 μm. Their filtration by highly efficient fiberglass and membrane cermet filters with multilayer and regenerable nanostructure at increased temperatures has been studied.

Effectiveness of Different Cellulose-Based Filtration Materials against Inhalation of SARS-CoV-2-Like Particles

The respiratory protection equipment (RPE) used by health professionals consists of an essential device to prevent infectious diseases, especially those caused by biological agents such as the coronavirus (SARS-CoV-2). The current epidemiological panorama is worrying, and the context of creation and production of the mask has emerged as an alternative to RPE to face the public health crisis worldwide. The aim of this work is to present a low-cost alternative as an FFP2-like filter for a reusable respirator face mask. This study presents the comparison of different cellulose-based filtering materials performed by retention testing, time saturation testing, aerosol penetration testing, nanoparticle (~140 nm) filtration testing, bacterial filtration efficiency (BFE), analysis of material morphology and usability. The reusable respirator face mask used in this study is an open-source innovation, using 3D printing. Cotton disc proved to be the best filter material for the reusable mask, with satisfactory results and a performance similar to that shown by the N95-type mask. The cotton disc ensured effectiveness over 6 h of use, and after that, the reusable respirator face mask (here, Delfi-TRON®) needed to be sanitized and replenished with a new cotton disc. Upon preliminary analyses of filtration efficiency, the selected filter was shown to be a low-cost biodegradable and biocompatible alternative.

Fabrication of flexible graphene oxide paper-like adsorbent doped with magnetite nanoparticles for removal of dyes

Organic dyes are used in many industries, e.g., textile, cosmetics and food. Hence, contamination of organic dyes to water sources is a critical issue. To reduce water pollution by organic dyes, we propose a paper-like adsorbent with a practical and economical production procedure. Subsequently, a flexible adsorbent was produced using a one-step approach by vacuum filtration of graphene oxide (GO) and iron oxide nanoparticles (Fe3O4-NPs) containing dispersion through a membrane and quoted as GO/Fe3O4 paper. For comparison, GO paper was also prepared using the same procedure. Both papers were characterized using UV–VIS absorption spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, electron diffraction X-ray analysis, X-ray photoelectron spectroscopy, and powder X-ray diffraction techniques. At the steady-state conditions, GO/Fe3O4 and GO papers were performed as adsorbent for cationic dyes of methylene blue, neutral red, and anionic dyes of methyl orange and fluorescein. In general, the removal efficiency of GO/Fe3O4 paper was higher than that of GO paper for adsorption of all dyes and this adsorbent revealed satisfactory adsorption properties for cationic dyes when compared to anionic dyes.

Development of Filter Media by Electrospinning for Air Filtration of Nanoparticles from PET Bottles.

Air pollution and solid pollution are considered global problems, and endanger human health mainly due to the emission of fine particulate matter released into the atmosphere and improper disposal of post-consumer plastic bottles. Therefore, it is urgent to develop filter media to effectively protect the public. The properties of plastics make them potential candidates for nanofiber mat formers due to their attractive structural and mechanical characteristics. This work aims to produce and evaluate novel PET electrospun fibers dispensed with the use of support materials to be used as filter media to remove nanoparticles from the air. The electrospinning process was carried out by changing the concentration of the polymer solution, the needle diameter, and the electrospinning processing time at two rotation speeds. The average diameters of the micro- and nanofibers of the filter media produced ranged from 3.25 μm to 0.65 μm and it was possible to conclude that, as the size of the fibers decreased, the mechanical strength increased from 3.2 to 4.5 MPa. In filtration tests, a collection efficiency of up to 99% with low-pressure drops (19.4 Pa) was obtained for nanoparticles, demonstrating high quality factor filter media, which could be applicable in gas filtration.

Examination of Nanoparticle Filtration by Filtering Facepiece Respirators During the COVID-19 Pandemic.

The onset of the COVID-19 pandemic in spring 2020 resulted in a spike in the demand for face masks and respirators. Due to their effectiveness at filtering aerosols that could potentially contain viruses, the N95-type filtering facepiece respirators (FFRs) are frequently used by healthcare workers and first responders. However, due to a shortage of domestic N95 FFRs in the US at the beginning of the pandemic, internationally produced respirators were imported and deployed under an Emergency Use Authorization by the Food and Drug Administration. Due to concerns raised at the time, there was an urgent need to verify their effectiveness and usability. In this study, we summarize our characterization of the nanoparticulate filtration performances of 136 such respirators, measured between April 1 and June 30, 2020. Our results indicate that about 42% of the respirators showed filtration efficiencies better than 90% (≤10% penetration), but only 17% performed better than 95% (≤5% penetration). On the other hand, about 35% showed filtration efficiencies below 80% (≥20% penetration). A representative subset of devices was analyzed for the origin of such variations in filtration performance. We found that filtration efficiency increased with the level of electrostatic charge on the FFRs and that the poor performance of the internationally sourced FFRs could be traced to a lack of electrostatic filtration mechanisms. Furthermore, electrostatics shifted the particle size at which aerosol penetration through the FFR was maximal from around 200 nm to less than 100 nm for the highest-performing FFRs, a size range that largely goes undetected in standardized tests.