A tunable nanopore sensor for the detection of metal ions using translocation velocity and biphasic pulses

A Tunable Resistive Pulse Sensor utilising a Polyurethane nanopore, has been used to characterise nanoparticles as they traverse the pore opening. Here we demonstrate that the translocation speed, conductive and resistive pulse magnitude, can be used to infer the surface charge of a nanoparticle, and act as a specific transduction signal for the binding of metal ions to ligands on the particles surface. Surfaces of silica nanoparticles were modified with a ligand to demonstrate the concept, and used to extract copper (II) ions (Cu2+) from solution. By tuning the pH and ionic strength of the solution, a biphasic pulse, a conductive followed by a resistive pulse is recorded. Biphasic pulses are becoming a powerful way to characterise materials, and provide an insight into the translocation mechanism, and here we present their first use to detect the presence of metal ions in solution. We demonstrate how combinations of translocation speed and/ or biphasic pulse behaviour are used to detect Cu2+ with quantitative responses across a range of pH and ionic strengths. Using a generic ligand this assay allows a clear signal for Cu2+ as low as 1 ppm with short 5 minute incubation time, and capable of measuring 10 ppm Cu2+ in the presence of 5 other ions. The method has potential for monitoring heavy metals in biological and environmental samples

Protein detection using tunable pores: resistive pulses and current rectification

We present the first comparison between assays that use resistive pulses or rectification ratios on a tunable pore platform. We compare their ability quantify the cancer biomarker Vascular Endothelial Growth Factor (VEGF). The first assay measures the electrophoretic mobility of aptamer modified nanoparticles as they traverse the pore. By controlling the aptamer loading on the particles surface, and measuring the speed of each translocation event we are able to observe a change in velocity as low as 18 pM. A second non-particle assay exploits the current rectification properties of conical pores. We report the first use of Layer-by-Layer, (LbL) assembly of polyelectrolytes onto the surface of the polyurethane pore. The current rectification ratios demonstrate the presence of the polymers, producing pH and ionic strength dependent currents. The LbL allows the facile immobilisation of DNA aptamers onto the pore allowing a specific dose response to VEGF. Monitoring changes to the current rectification allows for a rapid detection of VEGF 5 pM. Each assay format offers advantages in preparation but comparable sensitivitie

Real-time polarimetric biosensing using macroporous alumina membranes

We report the first demonstration of real-time biosensing in free standing macroporous alumina membranes. The membranes with their 200 nm diameter pores are ideal candidates for biosensing applications where fast response times for small sample volumes are needed as they allow analytes to flow through the pores close to the bioreceptors immobilized on the pores walls. A bulk refractive index sensitivity of 5.2×10-6 refractive index units was obtained from signal responses to different concentrations of NaCl solutions flowing through the pores. Finally, after functionalizing the alumina pore surfaces with an epoxysilane and then spotting it with β-Lactoglobulin protein, the interactions between the β-lactoglobulin and rabbit anti-β-lactoglobulin, as well as the interaction between the rabbit anti-β-lactoglobulin and a secondary antibody anti-rabbit Immunoglobulin G were monitored in real-time

Maintaining Well-Being During the COVID-19 Pandemic: A Network Analysis of Well-Being Responses from British Youth

COVID-19 has significant impacts on young peoples’ lives and emotions. Understanding how young people maintain well-being in the face of challenges can inform future mental health intervention development. Here we applied network analysis to well-being data gathered from 2532 young people (12-25 years) residing in the UK during the COVID-19 pandemic to identify the structure across well-being and crucially, its central defining features. Gender and age differences in networks were also investigated. Across all participants, items emerged in two clusters: 1) optimism, positive self-perception, and social connectedness, and 2) processing problems and ideas. The two central features of well-being were: “I’ve been dealing with problems well” and “I’ve been thinking clearly”. There were minimal age and gender differences. Our findings suggest that the perception of being able to process problems and ideas efficiently could be a hallmark of well-being, particularly in the face of challenging circumstances. These findings contrast with pre-pandemic studies that point to positive affect as central aspects of well-being networks. Future interventions that encourage problem-solving and mental flexibility could be useful in helping young people maintain well-being during times of stress and uncertainty

The design and characterization of multifunctional aptamer nanopore sensors

Aptamer-modified nanomaterials provide a simple, yet powerful sensing platform when combined with resistive pulse sensing technologies. Aptamers adopt a more stable tertiary structure in the presence of a target analyte, which results in a change in charge density and velocity of the carrier particle. In practice the tertiary structure is specific for each aptamer and target, and the strength of the signal varies with different applications and experimental conditions. Resistive pulse sensors (RPS) have single particle resolution, allowing for the detailed characterization of the sample. Measuring the velocity of aptamer-modified nanomaterials as they traverse the RPS provides information on their charge state and densities. To help understand how the aptamer structure and charge density effects the sensitivity of aptamer-RPS assays, here we study two metal binding aptamers. This creates a sensor for mercury and lead ions that is capable of being run in a range of electrolyte concentrations, equivalent to river to seawater conditions. The observed results are in excellent agreement with our proposed model. Building on this we combine two aptamers together in an attempt to form a dual sensing strand of DNA for the simultaneous detection of two metal ions. We show experimental and theoretical responses for the aptamer which creates layers of differing charge densities around the nanomaterial. The density and diameter of these zones effects both the viability and sensitivity of the assay. While this approach allows the interrogation of the DNA structure, the data also highlight the limitations and considerations for future assays

Normalizing glycosphingolipids restores function in CD4+ T cells from lupus patients

Patients with the autoimmune rheumatic disease systemic lupus erythematosus (SLE) have multiple defects in lymphocyte signaling and function that contribute to disease pathogenesis. Such defects could be attributed to alterations in metabolic processes, including abnormal control of lipid biosynthesis pathways. Here, we reveal that CD4+ T cells from SLE patients displayed an altered profile of lipid raft–associated glycosphingolipids (GSLs) compared with that of healthy controls. In particular, lactosylceramide, globotriaosylceramide (Gb3), and monosialotetrahexosylganglioside (GM1) levels were markedly increased. Elevated GSLs in SLE patients were associated with increased expression of liver X receptor β (LXRβ), a nuclear receptor that controls cellular lipid metabolism and trafficking and influences acquired immune responses. Stimulation of CD4+ T cells isolated from healthy donors with synthetic and endogenous LXR agonists promoted GSL expression, which was blocked by an LXR antagonist. Increased GSL expression in CD4+ T cells was associated with intracellular accumulation and accelerated trafficking of GSL, reminiscent of cells from patients with glycolipid storage diseases. Inhibition of GSL biosynthesis in vitro with a clinically approved inhibitor (N-butyldeoxynojirimycin) normalized GSL metabolism, corrected CD4+ T cell signaling and functional defects, and decreased anti-dsDNA antibody production by autologous B cells in SLE patients. Our data demonstrate that lipid metabolism defects contribute to SLE pathogenesis and suggest that targeting GSL biosynthesis restores T cell function in SLE

Curable sexually transmitted infections among women with HIV in sub-Saharan Africa

OBJECTIVES: Sexually transmitted infections (STIs) cause significant morbidity among women with HIV and increase HIV transmission. We estimated the prevalence of four STIs among women with HIV in sub-Saharan Africa (SSA) and compared prevalence among women with and without HIV. DESIGN: Systematic review and meta-analysis. METHODS: We searched for studies published 1 January 1999 to 19 December 2019 reporting prevalence of gonorrhea, chlamydia, trichomoniasis, or Mycoplasma genitalium among women with HIV in SSA. We excluded studies conducted in high-risk groups (e.g. female sex workers). We extracted data on laboratory-confirmed STIs among women with HIV, and when included, among women without HIV. We estimated pooled prevalence for each STI among women with HIV using inverse variance heterogeneity meta-analysis, compared prevalence to women without HIV, and examined the influences of region, clinical setting, and pregnancy status in subgroup analyses. RESULTS: We identified 3756 unique records; 67 studies were included in the meta-analysis. Prevalence of gonorrhea, chlamydia, trichomoniasis, and M. genitalium was 3.5, 4, 15.6, and 10.2%, respectively. Chlamydia prevalence was lower in Eastern (2.8%) than in Southern (12.5%) and West/Central (19.1%) Africa combined. Prevalence of chlamydia and trichomoniasis was higher among pregnant (8.1%, 17.6%) than nonpregnant (1.7%, 12.3%) women. All STIs were more prevalent among women with than without HIV (relative risks ranging 1.54-1.89). CONCLUSION: STIs are common among women with HIV in SSA, and more common among women with than without HIV. Integrated STI and HIV care could substantially impact STI burden among women with HIV, with potential downstream impacts on HIV transmission

Real time optical immunosensing with flow-through porous alumina membranes

Through the presentation of analytical data from bioassay experiments, measured by polarimetry, we demonstrate for the first time a real time immunoassay within a free standing macroporous alumina membrane. The 200 nm nominal pore diameter of the membrane enables flow-through, thereby providing an ideal fluidic platform for the targeted delivery of analytes to bioreceptors immobilized on the pore walls, enabling fast sensing response times and the use of small sample volumes (<100 μL). For the immunoassay, the pore walls were first coated with the functional copolymer, copoly(DMA-NAS) using a novel coupling process, before immobilization of the allergen protein, β-lactoglobulin, by spotting. The immuno-assay then proceeded with the binding of the primary and secondary antibody cognates, rabbit anti-β-lactoglobulin and anti-rabbit IgG respectively. Through the use of streptavidin coated quantum dots as refractive index signal enhancers, a noise floor for individual measurements of 3.7 ng/mL (25 pM) was obtained, with an overall statistical, or formal assay LOD of 33.7 ng/mL (225 pM), for total assay time below 1 h

Probing expression of E-selectin using CRISPR-Cas9-mediated tagging with HiBiT in human endothelial cells.

E-selectin is expressed on endothelial cells in response to inflammatory cytokines and mediates leukocyte rolling and extravasation. However, studies have been hampered by lack of experimental approaches to monitor expression in real time in living cells. Here, NanoLuc Binary Technology (NanoBiT) in conjunction with CRISPR/Cas9 genome editing, was used to tag endogenous E-selectin in human umbilical vein endothelial cells (HUVECs) with the 11 amino acid nanoluciferase fragment HiBiT. Addition of the membrane impermeable complementary fragment LgBiT, allowed detection of cell surface expression. This allowed the effect of inflammatory mediators on E-selectin expression to be monitored in real-time in living endothelial cells. NanoBiT combined with CRISPR/Cas9 gene editing allows sensitive monitoring of real time changes in cell surface expression of E-selectin and offers a powerful tool for future drug discovery efforts aimed at this important inflammatory protein

Comparison of intranasal versus intravenous midazolam for management of status epilepticus in dogs : a multi‐center randomized parallel group clinical study

Background: The intranasal (IN) route for rapid drug administration in patients with brain disorders, including status epilepticus, has been investigated. Status epilepticus is an emergency, and the IN route offers a valuable alternative to other routes, especially when these fail. Objectives: To compare IN versus IV midazolam (MDZ) at the same dosage (0.2 mg/kg) for controlling status epilepticus in dogs. Animals Client-owned dogs (n = 44) with idiopathic epilepsy, structural epilepsy, or epilepsy of unknown origin manifesting as status epilepticus. Methods: Randomized parallel group clinical trial. Patients were randomly allocated to the IN-MDZ (n = 21) or IV-MDZ (n = 23) group. Number of successfully treated cases (defined as seizure cessation within 5 minutes and lasting for >= 10 minutes), seizure cessation time, and adverse effects were recorded. Comparisons were performed using the Fisher's exact and Wilcoxon rank sum tests with statistical significance set at alpha < .05. Results: IN-MDZ and IV-MDZ successfully stopped status epilepticus in 76% and 61% of cases, respectively (P = .34). The median seizure cessation time was 33 and 64 seconds for IN-MDZ and IV-MDZ, respectively (P = .63). When the time to place an IV catheter was taken into account, IN-MDZ (100 seconds) was superior (P = .04) to IV-MDZ (270 seconds). Sedation and ataxia were seen in 88% and 79% of the dogs treated with IN-MDZ and IV-MDZ, respectively. Conclusions and Clinical Importance: Both routes are quick, safe, and effective for controlling status epilepticus. However, the IN route demonstrated superiority when the time needed to place an IV catheter was taken into account