Lateral flow devices (LFDs) are widely used point-of-care (POC) diagnostics. The basic LFD design remains largely unchanged since their first development and this limits their use in clinical applications due to lack of sensitivity. To enhance this, we report the use of laser-patterned geometric control barriers, in the form of a constriction, that leads to a slower flow rate and smaller test zone area. This high sensitivity LFD (HS-LFD) achieved 62% increase in test line colour intensity for the detection of procalcitonin (PCT) and reduced the LOD from 10 ng/ml to 1 ng/ml with contrived human samples
Alzheimer’s disease is caused by neurodegeneration resulting in cognitive decline, that has been linked to heightened systemic inflammation. Identification of the characteristic amyloid-β (Aβ) plaques in the brain is either by positron-emission tomography (PET) imaging or through its measurement in cerebrospinal fluid (CSF). A minimally invasive, cost-effective test that measures blood-based biomarker could predict the onset of Alzheimer’s earlier and therefore start therapies to improve patient prognosis. To this end, we have developed lateral-flow tests that measure vascular biomarkers, ICAM-1 and VCAM-1 and have validated their clinical use with serum samples.
We report a novel solution for semi-quantitative detection of C-reactive protein (CRP), a common inflammatory marker, using a multi-path lateral-flow device (LFD) fabricated via the precise partitioning of the single flow-path of a standard LFD using a laser direct-write technique. The multiple isolated flow-paths allow detection of different concentrations by individually setting different cut-off levels. The semi-quantitative readout is observed via simple appearance/absence of test lines without the need for a reader or further analyses. We have successfully demonstrated the use of these multi-path LFDs for semi-quantitative detection of CRP and will present validation in human samples.
Demand for low-cost alternatives to conventional medical diagnostic tools has been the driving force that has spurred significant developments in the diagnostics field. Lateral flow devices (LFDs) are one of the simplest and most established formats of paper-based devices, and are regarded as ideal point-of-care diagnostic solutions. In recent years, there has been an increasing need for performing multiplexed diagnostics at the point-of-care for rapid and simultaneous detection of different analytes within a single fluidic sample.
Here, we report a novel multiplexing strategy – detection of different analytes individually in the multiple paths of a single LFD. These multi-path LFDs were created via the precise partitioning of the single flow-path of a standard LFD using our previously reported laser direct-write (LDW) technique. Unlike other multiplexing methods, our distinctive approach, presented here, creates multiple parallel flow-paths inside a ‘single’ LFD without increasing its original footprint, and hence does not require larger sample volumes, and, most importantly, eliminates the interference between individual detection sites positioned within the same channel as in the case of other multiplexing strategies.
We show the use of an LDW-patterned dual-channel LFD as an example for the implementation of multiplexed detection of C-reactive protein (CRP) and Serum amyloid A-1 (SAA1), biomarkers commonly used for the diagnosis of bacterial infections. To further validate our multiplexing strategy, we have also tested our LFDs with clinical samples (blood serum from patients with increased systemic inflammation) and the results show a high consistency with those acquired using the gold-standard, an ELISA test.
We report the use of a laser-based direct-write (LDW) technique that allows the fabrication of porous barriers, which enable in-line filtration within a paper-based microfluidic device. The barriers were produced within porous substrates, namely nitrocellulose membranes, via local deposition of a photo-polymer that was subsequently polymerised by exposure from a laser source. Adjustment of the photo-polymer deposition parameters determines the porosity of the barriers, which, when carefully designed and integrated within a fluidic channel, can act as filters that enable either complete blocking, selective flow or controlled separation of particles of different sizes within a fluid travelling through the channel. We have successfully identified the fabrication parameters for the creation of barriers that allow the filtration of two different types of particles, Au-nanoparticles with sizes of 40, 100 and 200 nm and latex microbeads with sizes of 200 nm and 1 μm, dispersed within an aqueous solution. We also report the use of a variable-porosity barrier for selective separation of latex microbeads from Aunanoparticles, thereby showing the usefulness of this technique for enabling in-line filtration in such paper-based microfluidic devices.
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