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Nanoparticles are heavily researched for environmental applications, such as photocatalytic water treatment, however practical separation of nanoparticles from colloidal dispersions remains a critical challenge. Here, we demonstrate a new approach to nanoparticle recovery, combining the advantages of flocculation with magnetic separation to enable simple collection of non-magnetic nanoparticles. Flocculant polymers were coated onto magnetic nanoparticles (Fe3O4@SiO2) to prepare reusable magnetic flocculants (MFs). When added to colloidal nanoparticle dispersions, MFs aggregate with the suspended nanoparticles to form magnetically responsive flocs, which upon separation can be reversibly deflocculated for nanoparticle release, and reused in a closed loop process. High separation efficiency was attained in a variety of nanoparticle suspensions, including Au, Ag, Pd, Pt, and TiO2, stabilized by different coatings and surface charge. The MFs were shown to be recyclable for photocatalytic treatment of naphthenic acids in oil sands process-affected water (OSPW) and selenate in flue gas desulfurization wastewater (FGDW). Magnetic flocculation thus represents a general platform and alternative paradigm for nanoparticle separation, with potential applications in water treatment and remediation of nanoparticle pollution. Furthermore, given that flocculant chemicals can be recovered and reused in this process, magnetic flocculation may also serve as an environmentally sustainable solution to conventional flocculation challenges.

The response to the COVID-19 epidemic is generating severe shortages of personal protective equipment around the world. In particular, the supply of N95 respirator masks has become severely depleted, with supplies having to be rationed and health care workers having to use masks for prolonged periods in many countries. We sought to test the ability of 7 different decontamination methods: autoclave treatment, ethylene oxide gassing (ETO), low temperature hydrogen peroxide gas plasma (LT-HPGP) treatment, vaporous hydrogen peroxide (VHP) exposure, peracetic acid dry fogging (PAF), ultraviolet C irradiation (UVCI) and moist heat (MH) treatment to decontaminate a variety of different N95 masks following experimental contamination with SARS-CoV-2 or vesicular stomatitis virus as a surrogate. In addition, we sought to determine whether masks would tolerate repeated cycles of decontamination while maintaining structural and functional integrity. All methods except for UVCI were effective in total elimination of viable virus from treated masks. We found that all respirator masks tolerated at least one cycle of all treatment modalities without structural or functional deterioration as assessed by fit testing; filtration efficiency testing results were mostly similar except that a single cycle of LT-HPGP was associated with failures in 3 of 6 masks assessed. VHP, PAF, UVCI, and MH were associated with preserved mask integrity to a minimum of 10 cycles by both fit and filtration testing. A similar result was shown with ethylene oxide gassing to the maximum 3 cycles tested. Pleated, layered non-woven fabric N95 masks retained integrity in fit testing for at least 10 cycles of autoclaving but the molded N95 masks failed after 1 cycle; filtration testing however was intact to 5 cycles for all masks. The successful application of autoclaving for layered, pleated masks may be of particular use to institutions globally due to the virtually universal accessibility of autoclaves in health care settings. Given the ability to modify widely available heating cabinets on hospital wards in well-resourced settings, the application of moist heat may allow local processing of N95 masks.

A growing understanding of the fundamental role of proteins in diseases has advanced the development of quantitative protein assays in the medical field. Current techniques for protein analysis include enzyme-linked immunosorbent assays (ELISA), flow cytometry, mass spectrometry, and immunohistochemistry. However, many of these conventional strategies require specialized training, expensive antibodies, or sophisticated equipment, raising assay costs and limiting their application to laboratory analysis. Here, we present the application of a "chemical nose" type colorimetric gold nanoparticle sensor for detection, quantification, and identification of single proteins, protein mixtures, and proteins within the complex environment of human serum. The unique interactions between a mixture of two different gold nanoparticle morphologies (spherical and branched) and six separate proteins (bovine serum albumin, human serum albumin, immunoglobulin G, fibrinogen, lysozyme, and hemoglobin) generated distinguishable protein- and concentration-dependent absorption spectra, even at nanomolar concentrations. Furthermore, we show that this response is sensitive to the relative abundance of different proteins in solution, permitting analysis of protein mixtures. Finally, we demonstrate the ability to distinguish human serum samples with and without a clinically relevant two-fold increase in immunoglobulin G, without the use of expensive reagents or complicated sample processing.

Surface fouling remains an exigent issue for many biological implants. Unwanted solutes adsorb to reduce device efficiency and hasten degradation while increasing the risks of microbial colonization and adverse inflammatory response. To address unwanted fouling in modern implants in vivo, surface modification with antifouling polymers has become indispensable. Recently, zwitterionic self-assembled monolayers, which contain two or more charged functional groups but are electrostatically neutral and form highly hydrated surfaces, have been the focus of many antifouling coatings. Reports using various compositions of zwitterionic polymer brushes have demonstrated ultralow fouling in the ng/cm2 range. These coatings, however, are thick and can hinder the target application of biological devices. Here, we report an ultrathin (8.52 A) antifouling self-assembled monolayer composed of cysteine that is amenable to facile fabrication. The antifouling characteristics of the zwitterionic surfaces were evaluated against bovine serum albumin, fibrinogen, and human blood in real time using quartz crystal microbalance and surface plasmon resonance imaging. Compared to untreated gold surfaces, the ultrathin cysteine coating reduced the adsorption of bovine serum albumin by 95% (43 ng/cm2 adsorbed) after 3 h and 90% reduction after 24 h. Similarly, the cysteine self-assembled monolayer reduced the adsorption of fibrinogen as well as human blood by >90%. The surfaces were further characterized using scanning electron microscopy: protein-enhanced adsorption and cellular adsorption in human blood was found on untreated surfaces but not on the cysteine SAM-protected surfaces. These findings suggest that surfaces can be functionalized with an ultrathin layer of cysteine to resist the adsorption of key proteins, with performance comparable to zwitterionic polymer brushes. As such, cysteine surface coatings are a promising methodology to improve the long-term utility of biological devices.

The adhesion properties of Staphylococcus aureus on palladium–cobalt (Pd–Co) alloy nanostructures with various cross-sectional geometries have been characterised. They include solid core, hollow, c-shaped, and x-shaped pillars. These pillars have unique funnel-shaped geometric features on the top surfaces with average included angles between ∼142o and ∼149o. The success rates of cell attachment on these pillar tops were quantified by using field emission scanning electron microscopy techniques. Results show the Staphylococcus aureus attachment rates of Pd–Co solid core, hollow, and x-shaped pillars are statistically indistinguishable with success rate up to 82%. X-shaped pillars have the lowest attachment rate among the four geometries of 46 ± 5%.

A new methodology was developed to trap polystyrene or latex nanospheres in nanocrystalline nickel columnar nanostructures with various cross-sectional geometries. After filling the column interiors with polystyrene or latex nanospheres with diameters of ∼300 and 500 nm, respectively, the top openings of these small metallic nanopillars were capped with Staphylococcus aureus (S. aureus) bacterial cells. High resolution scanning electron microscopy inspection revealed that these bacterial cells were able to cover the top openings of C-shaped pillars within an hour of incubation at 37 °C. Results also demonstrated that capping S. aureus adhesive strengths to the nickel structures are greater than the cell wall cohesive strengths.

Rapid detection of pathogenic bacteria is challenging because conventional methods require long incubation times. Nanoparticles have the potential to detect pathogens before they can cause an infection. Gold nanostars have recently been used for colorimetric biosensors but they typically require surface modification with antibodies or aptamers for cellular detection. Here, CTAB-coated gold nanostars have been used to rapidly (

To evaluate the ability of trastuzumab (Herceptin) Fab, labelled with (99m)Tc through introduced hydrazinenicotinamide (HYNIC) functionalities, to image HER2/neu-overexpressing human breast cancer xenografts in athymic mice.Fab fragments were produced by immobilized papain digestion of trastuzumab immunoglobulin G (IgG), followed by purification by ultrafiltration. The immunoreactivity of trastuzumab Fab was evaluated by receptor-binding assays against HER2/neu-positive SK-BR-3 human breast cancer cells. Trastuzumab Fab fragments were labelled with (99m)Tc following modification with HYNIC N-hydroxysuccinimide ester. Biodistribution and tumour imaging studies were performed in athymic mice bearing subcutaneous HER2/neu-overexpressing BT-474 human breast cancer xenografts following intravenous injection of 1.1 or 25 MBq of [(99m)Tc]-trastuzumab Fab (30 microg), respectively. The specificity of tumour uptake was assessed by comparison with that of [(99m)Tc]-labelled irrelevant anti-CD33 HuM195 Fab.Trastuzumab Fab was pure and exhibited preserved immunoreactivity towards SK-BR-3 cells (K(d) = 1.6 x 10(-8) M). Modification with HYNIC diminished its receptor-binding affinity fourfold. [(99m)Tc]-trastuzumab Fab localized avidly and specifically in BT-474 xenografts, achieving a tumour uptake of 10.7% of the injected dose (ID) per gram and a tumour to blood (T/B) ratio of 3 : 1 at 24 h. The tumour uptake and T/B ratio for [(99m)Tc]-trastuzumab Fab were significantly higher than those for control [(99m)Tc]-HuM195 Fab (2.6% ID x g(-1) and 0.9 : 1, respectively; P0.05). Tumours were imaged as early as 2 h post-injection of [(99m)Tc]-trastuzumab Fab, but were more clearly visualized at 6 and 24 h post-injection.[(99m)Tc]-HYNIC-trastuzumab Fab localized specifically in HER2/neu-overexpressing human breast cancer xenografts in athymic mice, allowing imaging of the tumours within the useful lifetime of the radionuclide.

This chapter provides a review of thermodynamics of liquid films. In particular, film thermodynamics based on the film excess convention is presented. Both the fundamental equation and mechanical equilibrium condition are similar to those of a surface phase in the well-known Gibbsian thermodynamics of surfaces. Experimental techniques for measuring film tension are also reviewed; in particular, Axisymmetric Drop Shape Analysis-Profile (ADSA-P) is introduced. ADSA-P is the only existing technique which is not restricted to spherical drops or bubbles. With ADSA-P, film tension can be measured under both static and dynamic conditions. As a demonstration of ADSA-P, film tension and film rupture of alkanes (hexadecane, tetradecane, and dodecane) at the air–water interface are presented. The film tension measured is found to be equal to the sum of alkane-water interfacial tension and alkane surface tension for hexadecane and tetradecane films. In the case of dodecane films, a slight difference between the film tension and the sum of two surface (interfacial) tensions is observed and can be attributed to the interactions between the two surfaces of the film, which may be quantified by disjoining pressure.

Recently, Joos proposed a new kinetic model for transfer-controlled surfactant adsorption at liquid interfaces. His model is general, in the sense that the change in interfacial tension is incorporated into adsorption rate descriptions, and its governing kinetic equation can be reduced to various specific expressions for individual situations, such as the Langmuir kinetic equation. Joos developed his kinetic model by simply drawing analogies between adsorption and electrode kinetics, where the rate expression was obtained by using conventional chemical reaction theory. In this paper, we present a quantum statistical formulation for surfactant adsorption kinetics. With the assumption of excited states for molecular adsorption, we derive a rate equation by using Statistical Rate Theory (SRT), which gives the expression for transition probabilities from a first-order perturbation analysis of the Schrodinger equation. This new derivation avoids using the principle of mass action and the law of Arrhenius–Eyring, and hence many empirical assumptions in conventional chemical reaction theory are not needed for describing adsorption kinetics. The resulting rate expression can be reduced to Joos's kinetic equation and hence serves as a confirmation of it. Simplifications of the general rate expression are also presented for specific interfacial situations of near equilibrium and far from equilibrium. A combination of these rate expressions with a surface tension–adsorption relation, e.g. the Frumkin equation, can result in equations that are experimentally accessible. Future work will be concentrated on experimental investigations that may provide further validation of the theory and estimates for the parameters used in the rate expressions, especially the symmetry factor α .

In connection with interfacial tension measurements for n-hexadecane−water under conditions of mutual saturation, we accidentally found an extremely high tension value for the aqueous phase of approximately 80 mJ/m2, using axisymmetric drop shape analysis−profile (ADSA-P) for an air bubble formed in the water phase. This high tension value is that of an alkane film at the air−water interface. From static measurements (the drop surface area kept constant) at 25 ± 0.2 °C, we observed this film tension value to be 80.67 ± 0.06 and 77.20 ± 0.02 mJ/m2 at the 95% confidence level for hexadecane and dodecane films at the air−water interface, respectively. These film tension values were also confirmed in dynamic measurements (the drop surface area continuously increased) for both alkane systems. In addition, film rupture has been demonstrated both in the sudden change in the bubble profile and in the abrupt decrease in the tension value. The alkane film tension measured is approximately equal to the sum of the in...

Line tension is calculated by applying the contact line quadrilateral relation to a dodecane-water-air liquid lens system, where two contact angles are measured through an image analysis scheme. To complement previous measurements on individual lenses [1], contact angles were determined as a function of lens diameter. In order to exclude the possibility of any fluid mechanics or other dynamic effects, the change of lens size was performed at three different rates. No apparent rate dependence of contact angle and line tension can be observed for the three speeds. By reformulating the quadrilateral relation, the lens-size dependence of contact angles can be used in the calculation of line tension. To compute line tension with this scheme, three derivatives need to be obtained in addition to two contact angles and three surface tensions. No computational advantage can be gained over the direct application of the quadrilateral relation; however, the approach used here provides a potentially important approximation in term of a single surface tension and a lens-size dependent contact angle. For the water-dodecane system studied here, the line tension values calculated, by the quadrilateral relation, its reformulation and the simplified quadrilateral relation, are negative and between −1 and −4 × 10−6 J m−1.

The pulsating bubble and the film balance techniques are classical methods for measuring the dynamic surface tension response of surfactant solutions to area changes. Both techniques have advantages and disadvantages, and have been employed to study a variety of surfactant systems. Recently, a motor-controlled syringe has been developed in our laboratory which, when used in conjunction with a drop shape technique known as axisymmetric drop shape analysis (ADSA), is capable of performing many of the experiments traditionally conducted using either the pulsating bubble surfactometer or the film balance. In addition, ADSA has a number of distinct advantages over more conventional approaches. A comparison of these three methodologies is made and new data relating the surface tension response of three concentrations (8, 12 and 16 mM) of sodium dodecyl sulfate (SDS) solutions to surface area changes is reported.

Axisymmetric Drop Shape Analysis has been employed to measure the dynamic surface tension response to a sawtooth-shaped variation in the surface area. Four systems were studied: (a) bovine serum albumin (BSA) aqueous solution; (b) dimethyl sulfoxide (DMSO) added to the BSA aqueous solution; (c) ethyl alcohol (ethanol) added to the BSA aqueous solution; and (d) hepoxilin methyl ester, a lipidic hydroxy epoxide derived from arachidonic acid, dissolved in DMSO and then added to the BSA aqueous solution. In the mixtures of the solutions, competitive adsorption to the surface is revealed between the smaller molecules and the protein molecules, through the change of the pattern in the dynamic surface tension response to the surface area change. In the initial stage of the adsorption, the smaller organic molecules (DMSO, ethanol) diffuse to the surface at a faster rate than the protein molecules, impeding protein adsorption. However, in the cases of DMSO/BSA and ethanol/BSA solutions, the experiment indicates that the small organic molecules are squeezed out of the surface because of the compression/dilation process. After steady state is established, the surface tension pattern shows a skewed shape suggesting a conformational change in the protein. When hepoxilin, a naturally occurring biologically active C20 fatty acid containing a hydroxyl epoxide functionality, is present in the BSA solution, a rather symmetric shape is found in the dynamic surface tension changes, different from the skewed shape found in that of the pure BSA solution. This suggests that hepoxilin molecules interact with the protein, leading to a stabilization of one conformation of the protein molecules at the surface.

Molecular imaging of the expression of key genes which determine the response to DNA damage following cancer treatment may predict the effectiveness of a particular treatment strategy. A prominent early response gene for DNA damage is the gene encoding p21(WAF-1/CIP-1), a cyclin-dependent kinase inhibitor that regulates progression through the cell cycle. In this study, we explored the feasibility of imaging p21(WAF-1/CIP-1) gene expression at the mRNA level using an 18-mer phosphorothioated antisense oligodeoxynucleotide (ODN) labeled with (111)In. The known induction of the p21(WAF-1/CIP-1) gene in MDA-MB-468 human breast cancer cells following exposure to epidermal growth factor (EGF) was used as an experimental tool. Treatment of MDA-MB-468 cells in vitro with EGF (20 n M) increased the ratio of p21(WAF-1/CIP-1) mRNA/beta-actin mRNA threefold within 2 h as measured by the reverse transcription polymerase chain reaction (RT-PCR). A concentration-dependent inhibition of EGF-induced p21(WAF-1/CIP-1) protein expression was achieved in MDA-MB-468 cells by treatment with antisense ODNs with up to a tenfold decrease observed at 1 microM. There was a fourfold lower inhibition of p21(WAF-1/CIP-1) protein expression by control sense or random sequence ODNs. Intratumoral injections of EGF (15 microg/dayx3 days) were employed to induce p21(WAF-1/CIP-1) gene expression in MDA-MB-468 xenografts implanted subcutaneously into athymic mice. RT-PCR of explanted tumors showed a threefold increased level of p21(WAF-1/CIP-1) mRNA compared with normal saline-treated tumors. Successful imaging of EGF-induced p21(WAF-1/CIP-1) gene expression in MDA-MB-468 xenografts was achieved at 48 h post injection of (111)In-labeled antisense ODNs (3.7 MBq; 2 microg). Tumors displaying basal levels of p21(WAF-1/CIP-1) gene expression in the absence of EGF treatment could not be visualized. Biodistribution studies showed a significantly higher tumor accumulation of (111)In-labeled antisense ODNs in the presence of EGF induction of the p21(WAF-1/CIP-1) gene (0.32%+/-0.06% injected dose/g) compared with normal saline-treated control mice (0.11%+/-0.07% injected dose/g). The tumor/blood ratio for antisense ODNs in the presence of EGF induction of the p21(WAF-1/CIP-1) gene (4.87+/-0.87) was also significantly higher than for control random sequence ODNs (2.14+/-0.69) or for mice receiving antisense ODNs but not treated with EGF (2.07+/-0.37). We conclude that antisense imaging of upregulated p21(WAF-1/CIP-1) gene expression is feasible and could represent a promising new molecular imaging strategy for monitoring tumor response in cancer patients. To our knowledge, this study also describes the first report of molecular imaging of the upregulated expression of a downstream gene target of the EGFR, a transmembrane tyrosine kinase receptor.

In a recent paper,(1) we demonstrated that molecular interactions between biopolymers and other smaller molecules can be detected by means of dynamic surface tension measurements. In the present paper, we demonstrate that the same methodology can be employed for investigating dose effects and specificity of molecular interactions. Three similar lipids were chosen for this study: 12(S)-hydroxy-5(Z), 8(Z),10(E),14(Z)-eicosatetraenoic acid (12(S)-HETE-free acid), methyl 12(S)-hydroxy-5(Z),8(Z),10(E),14(Z)-eicosatetraenoate (12(S)-HETE-methyl ester), and 5(Z),8(Z),11(Z), 14(Z)-eicosatetraenoic acid (arachidonic acid-free acid). These substances were added to a fatty acid free bovine serum albumin (BSA) aqueous solution at different lipid concentrations. The characteristic tension response indicates that molecular interactions between 12(S)-HETE-free acid and BSA exist. The detected interactions are concentration dependent: at a molecular ratio of lipid to protein of 1:1, the binding of 12(S)-HETE-free acid to BSA is hydrophobic in nature; at the molecular ratio of lipid to protein of 10:1, a secondary binding occurs and is hydrophilic in nature. Similar molecular interactions were not detected between 12(S)-HETE-methyl ester or arachidonic acid-free acid and BSA, indicating that the interactions between 12(S)-HETE-free acid and BSA are specific. As an independent means, surface elasticity is used to probe the molecular interactions at the interface. In the case of 12(S)-HETE-free acid but not its methyl ester or arachidonic acid, distinct higher surface elasticities were observed at lipid concentrations in excess of a molecular ratio of lipid to protein of 1:1. This finding reinforces the above stipulations.

Publisher Summary This chapter discusses axisymmetric drop shape analysis (ADSA) and its application. It provides an account of these ADSA methodologies. It contains a description of the numerical algorithms and their implementation. The applicability of ADSA is illustrated extensively for the investigation of surface tension measurements with pendant and sessile drops and contact angle experiments with sessile drops using both axisymmetric drop shape analysis - profile (ADSA-P) and axisymmetric drop shape analysis - diameter (ADSA-D). The advantages of pendant and sessile drop methods are numerous. In comparison with a method such as the Wilhelmy plate technique, only small amounts of the liquid are required. Drop shape methods easily facilitate the study of both liquid-vapor and liquid-liquid interfacial tensions. Also, the methods have been applied to materials ranging from organic liquids to molten metals and from pure solvents to concentrated solutions. There is no limitation to the magnitude of surface or interracial tension that can be measured: The methodology presented in this chapter works as well at 103 mJ/m 2 as at 10 -3 mJ/m 2.

Conventional lock-and-key biosensors often only detect a single pathogen because they incorporate biomolecules with high specificity. “Chemical nose” biosensors are overcoming this limitation and identifying multiple pathogens simultaneously by obtaining a unique set of responses for each pathogen of interest, but the number of pathogens that can be distinguished is limited by the number of responses obtained. Herein, we use a gold nanoparticle-based “chemical nose” to show that changing the shapes of nanoparticles can increase the number of responses available for analysis and expand the types of bacteria that can be identified. Using four shapes of nanoparticles (nanospheres, nanostars, nanocubes, and nanorods), we demonstrate that each shape provides a unique set of responses in the presence of different bacteria, which can be exploited for enhanced specificity of the biosensor. Additionally, the concentration of nanoparticles controls the detection limit of the biosensor, where a lower concentration provides better detection limit. Thus, here we lay a foundation for designing “chemical nose” biosensors and controlling their characteristics using gold nanoparticle morphology and concentration. Keywords: Morphology, Color change, Staphylococcus aureus, Point-of-care, Nanocubes, Nanorods