Electrospun TiO₂ nanofiber integrated lab-on-a-disc for ultrasensitive protein detection from whole blood

Abstract

ELISA-based devices are promising tools for the detection of low abundant proteins in biological samples. Reductions of the sample volume and assay time as well as full automation are required for their potential use in point-of-care diagnostic applications. Here, we present a highly efficient lab-on-a-disc composed of a TiO2 nanofibrous mat for sensitive detection of serum proteins with a broad dynamic range, with only 10 μL of whole blood within 30 min. The TiO2 nanofibers provide high specific surface area as well as active functional groups to capture large amounts of antibodies on the surface. In addition, the device offers efficient mixing and washing for improving the signal-to-noise ratio, thus enhancing the overall detection sensitivity. We employ the device for the detection of cardiac biomarkers, C-reactive protein (CRP) and cardiac troponin I (cTnI), spiked in phosphate-buffered saline (PBS) as well as in serum or whole blood. The device exhibited a wide dynamic range of six orders of magnitude from 1 pg mL(-1) (~8 fM) to 100 ng mL(-1) (~0.8 pM) and a low detection limit of 0.8 pg mL(-1) (~6 fM) for CRP spiked in CRP-free serum and a dynamic range of 10 pg mL(-1) (~0.4 pM) to 100 ng mL(-1) (~4 nM) with a detection limit of 37 pg mL(-1) (~1.5 pM) for cTnI spiked in whole blood.

A critical insight into the development pipeline of microfluidic immunoassay devices for the sensitive quantitation of protein biomarkers at the point of care

“…In respect to sensitive biomarker quantitation, different approaches have been reported in the literature, including TiO 2 nanofibres treated with GPDES (3-glycidoxypropyl) methyldiethoxysilane (Fig. 1A); 80 inner glass capillary surfaces with ZnO nanorods modified with (3-glycidoxypropyl) trimethoxy silane (GPTS); 65 graphene nanosheets treated with 3-glycidyloxypropyl trimethoxysilane (GOPS); 54 glass slides silanised with epoxysilane surface 75,78 and functionalised graphene nanoplatelets with APTES (3-aminopropyl)triethoxysilane. 79 Silanisation and other surface modification chemistries also use aldehydes as cross-linkers for protein immobilisation.…”

“…2A). 80 This represented a 7-fold reduction in the LLoD for TnI and about a 300-fold reduction in the LLoD for CRP, by simply increasing the overall surface available for immobilising the CapAb. A glass capillary device was able to quantify PSA, AFP and CEA in serum with a LLoD between 1 and 5 ng ml −1 (33.3 pM for PSA, 74 pM for AFP and 25 pM for CEA) based on ZnO nanorods deposited within the glass capillaries (Fig.…”

“…The composition of BSA blocking solution used varies from 0.1 to 3% w/v, with incubation times that can go from seconds to several hours. 33,41,46,49,53,64,65,69,[72][73][74][79][80][81] This suggests that BSA has a broad capacity of surface passivation, which is independent of the surface chemistry and assay reagents. 110 CRP and CEA were quantified with LLoDs of 8 × 10 −4 and 4 × 10 −3 ng ml −1 in different microfluidic surfaces, such as TiO 2 fibres and glass.…”

“…110 CRP and CEA were quantified with LLoDs of 8 × 10 −4 and 4 × 10 −3 ng ml −1 in different microfluidic surfaces, such as TiO 2 fibres and glass. 53,80 BSA is also used in mixtures with other molecules, such as casein 60,68 and sucrose. A paper microfluidic device reported LLoDs of 8 × 10 −4 ng ml −1 for CEA using 0.5% BSA and 0.5% casein for surface passivation.…”

“…Several studies have reported biomarker quantitation in microfluidic devices using pre-treated whole blood samples, with sample preparation structures embedded in the chip. For example, a lab-on-a-disc was capable of quantifying CRP and TnI from whole blood samples by separating the red blood cells through centrifugation, 80 while a silicon porous microarray was integrated with an acoustophoresis system for plasma separation from whole blood samples (Fig. 4A) 67 and other microfluidic devices have incorporated a flow-based blood separation channel for whole blood protein quantitation (Fig.…”