Ultrasensitive immunoassays are important tools for detecting low-abundance protein biomarkers in biological matrices, both in research and therapeutic settings.
Technologies such as electrochemiluminescence immunoassay (ECLIA), digital ELISA, and nucleic acid-linked immuno-sandwich assay (NULISA™) have femtomolar or even attomolar sensitivity.
These heterogeneous assay approaches require solid-surface capture and have disadvantages, including dependence on high-affinity antibodies, non-specific binding to solid surfaces, high variability due to complex procedures, and the need for proprietary apparatus.
SPEAR is a revolutionary immunoassay technology that solves the sensitivity limits of existing heterogeneous immunoassay methods. SPEAR offers highly specific and robust protein detection in a totally homogenous, wash-free format by incorporating nucleic acid amplification into a novel two-factor authentication process.
This novel approach delivers the first ultra-sensitive immunoassay platform that combines increased specificity, workflow simplicity, and minimal sample input, while relying on standard qPCR for readout.
Mechanism and benefits of SPEAR technology
SPEAR employs two target-specific antibodies, each coupled to a distinct DNA device. One is mostly double-stranded with two toeholds, whereas the other is single-stranded and contains a short sequence complementary to one of the toeholds.
After binding to the target, proximity allows for hybridization and polymerase extension, resulting in the addition of a first extended sequence to the single-stranded DNA device.
A second hybridization-extension step occurs only when the probes co-localize for an extended period of time, resulting in an amplifiable DNA sequence. This two-factor authentication reduces background and non-specific signals while providing exceptional sensitivity and specificity.
Target-specific signals are quantified using conventional qPCR, which has strong consistency across a wide range of qPCR devices.
SPEAR’s two-factor authentication mechanism
Image Credit: Spear Bio
A unique homogeneous immunoassay technology
SPEAR's homogeneous nature eliminates nonspecific binding associated with solid-phase capture, thereby increasing specificity.
SPEAR's reaction happens fully in solution, eliminating the need for wash steps. This simplifies the workflow, allows for easy automation, and improves precision, with mean CVs <5 % from as little as 1 μL of diluted samples.
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About Spear Bio
Spear Bio is an innovative leader in providing scalable solutions for ultra-sensitive protein biomarker measurements. Spear Bio’s proprietary technology, Successive Proximity Extension Amplification Reaction (SPEAR), employs a unique 2-factor authentication mechanism to precisely measure protein biomarkers at attomolar level from sub-microliter sample volume. Spear Bio is focused on leveraging its technology’s unprecedented sensitivity to transform protein research and early disease diagnosis.
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