Make use of digital ELISA
Precise detection of neurological biomarkers in the blood.
Advances in protein biomarker detection technologies, such as digital enzyme-linked immunosorbent assays (ELISAs), are breaking down barriers to neural research and diagnosis. This article will take you through what a digital ELISA is, how it works, and how researchers can use it to improve healthcare for patients with neurological disorders.
Digital ELISA vs. traditional ELISA
Conventional ELISA is a commonly used quantitative immunoassay technique for measuring protein concentration. This technique uses a microplate to immobilize a target antigen or antibody, bind to the target analyte, and measure the signal emitted. However, the sensitivity of conventional ELISAs is often insufficient to detect certain biomarkers, especially those that are important in diseases such as neurological diseases and cancer. Digital ELISA is a development of ultrasensitive immunoassays. Digital ELISAs use magnetic beads to induce enzymatic reactions in soar-sized wells with orders of magnitude higher sensitivity compared to standard sandwich-based immunoassay techniques. With digital ELISAs, researchers can detect ultra-low concentrations of proteins—the same as nanomolar (nm;) found in traditional ELISAs10-9 m) to picomolar (PM, 10-12 m) compared to the detection level, the digital ELISA can be detected at the femtomolar level (FM;10-15m).
Digital ELISAs enable scientists to detect low-concentration neural biomarkers in a variety of sample types.
Increased sensitivity, accuracy, and reduced sample volumes have provided researchers and others with new assays, especially in neurology, to measure brain-derived biomarkers that were previously below the limits of quantification by conventional immunoassays. Digital ELISAs help avoid the need for invasive sampling of cerebrospinal fluid while providing the potential to detect the same biomarkers in blood or other non-invasive biological samples.
Digital ELISA technology revolutionizes neurobiology research.
Biomarkers of Alzheimer's disease.
As the most common form of dementia**, we need a faster, earlier, less invasive, and less costly way to diagnose Alzheimer's disease (AD). Detecting brain-derived biomarkers in the blood is a promising path. The researchers used the SIMOA platform to explore the potential of blood amyloid and tau proteins, based on the results of CSF-derived profiles of patients known to be in different stages of AD. The study found that data from blood phosphorylated tau (p-tau181) and amyloid (A42A40) correlated with CSF-derived biomarker profiles, which have traditionally been used for the staging of Alzheimer's disease. This study demonstrates the ability of blood biomarkers to be used as a basis for accurate diagnosis of AD, and is simple, non-invasive, and cost-effective.
Biomarkers of ALS.
Amyotrophic lateral sclerosis is a degenerative neurological disease. Diagnosis often relies on a complex assessment of physical characteristics, such as walking, speaking, and limb strength. Identifying specific and reliable biomarkers for ALS will improve early diagnosis,** and overall patient care. Falzone et al. utilize SIMOA's digital ELISA technology to address this unmet need. The researchers evaluated four potential biomarkers that may indicate different stages or manifestations of ALS and help distinguish ALS from other neurodegenerative diseases. They assessed GFAP (glial fibrillary acidic protein), UCHL-1 (ubiquitin carboxy-terminal hydrolase isoenzyme L-1), NFL (neurofilament light chain), and total tau levels in the blood. Studies have found that all biomarkers can be reliably detected in serum at levels as low as tens or a few picograms per microliter. While UCHL-1, NFL, and GFAP have all been shown to be promising biomarkers, NFL and UCHL1 have shown strong diagnostic and prognostic value in patients with ALS.
Biomarkers of traumatic brain injury.
Traumatic brain injuries can be caused by workplace or sports injuries, vehicle collisions, and other blunt trauma to the head. Routine evaluations through various scans are costly, time-consuming, and sometimes inconclusive. A simple, fast, and accurate blood test will get you started faster. The researchers found that serum biomarkers have an incremental prognostic value for functional outcomes after traumatic brain injury. They modeled prognosis through demographic, clinical, and radiological features, such as Impact and CRASH, and examined six biomarkers (S100 calcium-binding protein B [S10b], neuron-specific enolase [NSE], GFAP, UCH-L1, NFL, and total TAU). These findings support the good integration of serum biomarkers, particularly uch-L1, in established prognostic models.
Digital ELISA in the future of neurological biomarkers.
The above cases are just a few of the many cases where various biomarkers have been detected and accurately quantified using SIMOA digital ELISA technology. The low detection limits provided by this technology allow researchers and clinicians to measure biomarkers present in peripheral biological samples and biofluids at concentrations that were previously too low to be reliable.
Digital ELISA with SIMOA technology
Quanterix offers SIMOA technology that allows you to harness the power and potential of digital ELISAs to achieve ultra-low detection easily and quickly.
Capture Single Molecule – Single Molecule Detection.
SIMOA is based on paramagnetic bead-based separation, using standard reagents to detect individual immune complexes attached to these beads. The main difference between SIMOA and traditional immunoassays is the ability to trap individual beads in soar-sized wells and condense the fluorescence signal into a small volume, allowing individual beads to be "digitally read" to determine if they bind to the analyte of interest. Each molecule produces a signal that can be counted.
Produces discrete, strong signals.
SIMOA arrays use high-resolution fluorescence imaging to determine the proportion of beads associated with at least one enzyme and the fluorescence intensity of each well. SIMOA is measured in the average number of enzymes (AEB) per bead. Calculations were made using Poisson distribution at ultra-low analyte concentrations (digital mode) or average fluorescence intensity at higher concentrations (analog mode). The system covers all the micropores with a layer of oil, which prevents diffusion and shows a discrete, strong signal.
Detection limit – how low can it be?
With its digital counting algorithms, coupled with powerful imaging technology, SIMOA reduces LODs and LLOQs to the low-fly-mole range.
Singleplex and multiplex assays.
With SIMOA, you can detect single (singleplex) or multiple (multiplex) targets in a single analysis on a high-performance, scalable platform. By using fluorescently labeled beads, you can find up to four biomarkers at once to study complex interactions in clinical samples. Biology is complex. Diseases are complex. Digital immunoassays can help you look at a problem from multiple angles at the same time to reveal its complexity.
Are you ready to test for neurological biomarkers in your blood?
The SIMOA assay can detect neurological biomarkers such as NFL, TAU, GFAP, and several other biomarkers associated with brain injury and disease. With SIMOA, researchers can detect these information markers in serum or plasma, enabling early diagnosis and a better understanding of the pathological process of the disease without the need for invasive measures.
references
1. rissin dm, kan cw, campbell tg, et al. single-molecule enzyme-linked immunosorbent assay detects serum proteins at subfemtomolar concentrations. nat biotechnol. 2010;28(6):595-599. doi:10.1038/nbt.1641
2. delaby c, alcolea d, hirtz c, et al. blood amyloid and tau biomarkers as predictors of cerebrospinal fluid profiles. j neural transm (vienna). 2022;129(2):231-237. doi:10.1007/s00702-022-02474-9
3. falzone ym, domi t, mandelli a, et al. integrated evaluation of a panel of neurochemical biomarkers to optimize diagnosis and prognosis in amyotrophic lateral sclerosis. eur j neurol. 2022;29(7):1930-1939. doi:10.1111/ene.15321
4. helmrich irar, czeiter e, amrein k, et al. incremental prognostic value of acute serum biomarkers for functional outcome after traumatic brain injury (center-tbi): an observational cohort study. lancet neurol. 2022;21(9):792-802. doi:10.1016/s1474-4422(22)00218-6