Laser-patterned paper-based flow-through filters and lateral flow immunoassays to enable the detection of C-reactive protein

We report the use of a laser-based fabrication process in the creation of paper-based flow-through filters that when combinedwith a traditional lateral flow immunoassay provide an alternative pathway for the detection of a pre-determined analyte overa wide concentration range. The laser-patterned approach was used to create polymeric structures that alter the porosity of thepaper to produce porous flow-through filters, with controllable levels of porosity. When located on the top of the front end ofa lateral flow immunoassay the flow-through filters were shown to block particles (of known sizes of 200 nm, 500 nm, 1000nm and 3000 nm) that exceed the effective pore size of the filter while allowing smaller particles to flow through onto a lateralflow immunoassay. The analyte detection is based on the use of a size-exclusive filter that retains a complex (~3 µm in size)formed by the binding of the target analyte with two antibodies each of which is tagged with different-sized labels (40 nm Aunanoparticles and 3 µm latex beads), and which is larger than the effective pore size of the filter. This method was tested forthe detection of C-reactive protein in a broad concentration range from 10 ng/ml to 100,000 ng/ml with a limit-of-detectionfound at 13 ng/ml and unlike other reported methods used for analyte detection, with this technique we are able to counter theHook effect which is a limiting factor in many lateral flow immunoassays

Local photo-polymer deposition-assisted fabrication of multilayer paper-based devices

In this paper, we report on the use of a local acrylate-based negative photo-polymer deposition technique for the fabrication of 3D microfluidic paper-based analytical devices (3D-μPADs) where the sample flows in both the lateral and vertical directions through multiple stacked layers of porous materials. A simple and inexpensive manufacturing method was used, which is based on the local deposition of a photo-polymer (deposition speed 30 mm/s) on a porous cellulose paper substrate followed by the subsequent exposure (scanning speed 30 mm/s) to a laser source (fibre coupled continuous wave at 405 nm with maximum power of 60 mW), to stack four layers of cellulose paper and make 3D multilayer μPADs. With this technique, we provide a pathway to eliminate the limitations that other reported methods have during the fabrication of μPADs such as the need for multiple sophisticated alignments between adjoining layers and the use of additional tools to ensure adequate contact between the layers. In this study, we demonstrate the usefulness of our four-layer 3D-μPAD for simultaneous detection of three analytes, namely BSA, glucose, nitrite spiked in artificial urine and also the pH of the tested sample, through single step colorimetric assays with the limit of detection found at 0.4 mg/mL for BSA, 14.5 μg/mL for glucose and 2.5 μg/mL for nitrite. Our 3D-μPAD fabrication methodology can also be adapted in more complex analytical assays where multiple steps are needed for applications in point-of-care diagnostics

Laser-patterned paper-based sensors for rapid point-of-care detection and antibiotic-resistance testing of bacterial infections

Antimicrobial resistance (AMR) has been identified by the World Health Organisation as a global threat that currently claims at least 25,000 deaths each year in Europe and 700,000 globally; the number is projected to reach 10 million per year between 2015 and 2050. Therefore, there is an urgent need for low-cost but reliable point-of-care diagnostics for early screening of infections especially in developing countries lacking in basic infrastructure and trained personnel. This work is aimed at developing such a device, a paper-based microfluidic device for infection testing by an unskilled user in a low resource setting. Here, we present our work relating to the use of our laser-patterned paper-based devices for detection and susceptibility testing of Escherichia coli, via a simple visually observable colour change. The results indicate the suitability of our integrated paper devices for timely identification of bacterial infections at the point-of-care and their usefulness in providing a hugely beneficial pathway for accurate antibiotic prescribing and thus a novel route to tackling the global challenge of AMR.</p

Transverse momentum spectra of charged particles in proton-proton collisions at 1as=900 GeV with ALICE at the LHC

The inclusive charged particle transverse momentum distribution is measured in proton-proton collisions at s=900 GeV at the LHC using the ALICE detector. The measurement is performed in the central pseudorapidity region (|\u3b7|<0.8) over the transverse momentum range 0.15<10 GeV/c. The correlation between transverse momentum and particle multiplicity is also studied. Results are presented for inelastic (INEL) and non-single-diffractive (NSD) events. The average transverse momentum for |\u3b7|<0.8 is \u3008pT\u3009INEL=0.483\ub10.001 (stat.)\ub10.007 (syst.) GeV/c and \u3008pT\u3009NSD=0.489\ub10.001 (stat.)\ub10.007 (syst.) GeV/c, respectively. The data exhibit a slightly larger \u3008pT\u3009 than measurements in wider pseudorapidity intervals. The results are compared to simulations with the Monte Carlo event generators PYTHIA and PHOJET. \ua9 2010