Thread-Based Bioluminescent Sensor for Detecting Multiple Antibodies in a Single Drop of Whole Blood

Abstract

Antibodies are important biomarkers in clinical diagnostics in addition to being increasingly used for therapeutic purposes. Although numerous methods for their detection and quantification exist, they predominantly require benchtop instruments operated by specialists. To enable the detection of antibodies at point-of-care (POC), the development of simple and rapid assay methods independent of laboratory equipment is of high relevance. In this study, we demonstrate microfluidic thread-based analytical devices (μTADs) as a new platform for antibody detection by means of bioluminescence resonance energy-transfer (BRET) switching sensor proteins. The devices consist of vertically assembled layers including a blood separation membrane and a plastic film with a sewn-in cotton thread, onto which the BRET sensor proteins together with the substrate furimazine have been predeposited. In contrast to intensity-based signaling, the BRET mechanism enables time-independent, ratiometric readout of bioluminescence signals with a digital camera in a darkroom or a smartphone camera with a 3D-printed lens adapter. The device design allows spatially separated deposition of multiple bioluminescent proteins on a single sewn thread, enabling quantification of multiple antibodies in 5 μL of whole blood within 5 min. The bioluminescence response is independent of the applied sample volume within the range of 5–15 μL. Therefore, μTADs in combination with BRET-based sensor proteins represent user-friendly analytical tools for POC quantification of antibodies without any laboratory equipment in a finger prick (5 μL) of whole blood.

Applications of bioluminescence in biotechnology and beyond

“…of blood (B5 mL) by depositing the biological machinery on cotton threads. 293 As discussed earlier, whole cell bioluminescent bacterial biosensors are widely used to detect heavy metal concentrations such as mercury, zinc and chromium in ecotoxicology studies. [294][295][296] For more details on this please refer to Section 4.3.…”

Point-of-Care Diagnoses and Assays Based on Lateral Flow Test

“…Problems with lens quality can also play a role when a cheap camera is used for point-ofcare testing. Nevertheless, the use of digital cameras in personal diagnosis is considered as the next direction of research and application into praxis [70][71][72][73][74][75].…”

Smartphone-Enabled Quantification of Potassium in Blood Plasma

“…There are already several smartphone-enabled PoCT devices that have been applied to medical diagnostics. Examples include smartphone-enabled PoCT for dry eye diagnosis [ 26 ], kidney diagnosis [ 27 ], cortisol quantification [ 28 ], bilirubin diagnosis [ 29 ], detection of antibodies and RNA in blood [ 30 , 31 ], and detection of HIV or hepatitis [ 32 ]. Smartphone fluorescence platforms for potassium detection in urine have recently been described [ 33 ].…”