Jeffrey Randall

Single-molecule enzyme-linked immunosorbent assay detects serum proteins at subfemtomolar concentrations

The ability to detect single protein molecules in blood could accelerate the discovery and use of more sensitive diagnostic biomarkers. To detect low-abundance proteins in blood, we captured them on microscopic beads decorated with specific antibodies and then labeled the immunocomplexes (one or zero labeled target protein molecules per bead) with an enzymatic reporter capable of generating a fluorescent product. After isolating the beads in 50-fl reaction chambers designed to hold only a single bead, we used fluorescence imaging to detect single protein molecules. Our single-molecule enzyme-linked immunosorbent assay (digital ELISA) approach detected as few as ∼10–20 enzyme-labeled complexes in 100 μl of sample (∼10−19 M) and routinely allowed detection of clinically relevant proteins in serum at concentrations (<10−15 M) much lower than conventional ELISA. Digital ELISA detected prostate-specific antigen (PSA) in sera from patients who had undergone radical prostatectomy at concentrations as low as 14 fg/ml (0.4 fM).

Tau proteins in serum predict neurological outcome after hypoxic brain injury from cardiac arrest: Results of a pilot study

OBJECTIVE To conduct a pilot study to evaluate the prognostic potential of serum tau protein measurements to predict neurological outcome 6 months following resuscitation from cardiac arrest. METHODS In this retrospective observational study, we employed a new ultra sensitive digital immunoassay technology to examine serial serum samples from 25 cardiac arrest patients to examine tau release into serum as a result of brain hypoxia, and probe for its significance predicting six-month neurological outcome. Serial blood samples were obtained from resuscitated cardiac arrest survivors during their first five days in an intensive care unit, and serum total tau was measured. Cerebral function assessments were made using Cerebral Performance Categorization (CPC) at discharge from the ICU and six months later. Tau data were analyzed in the context of 6-month CPC scores. RESULTS Tau elevations ranged from modest (<10 pg/mL) to very high (hundreds of pg/mL), and exhibited unexpected bi-modal kinetics in some patients. Early tau elevations appeared within 24h of cardiac arrest, and delayed elevations appeared after 24-48 h. In patients with delayed elevations, areas under the curves of tau concentration vs. hours since cardiac arrest were highly predictive of 6-month outcome (P<0.0005). CONCLUSION High-sensitivity serum tau measurements combined with an understanding of tau release kinetics could have utility for hypoxic brain injury assessment and prediction of cerebral function outcome.

Olympic boxing is associated with elevated levels of the neuronal protein tau in plasma

Objectives: The aim of this study was to investigate if olympic (amateur) boxing is associated with elevation of brain injury biomarkers in peripheral blood compared to controls. Materials and methods: Thirty olympic boxers competing in at least 47 bouts were compared to 25 controls. Blood was collected from the controls at one occasion and from the boxers within 1–6 days after a bout and after a rest period of at least 14 days. Tau concentration in plasma was determined using a novel single molecule ELISA assay and S-100B, glial fibrillary acidic protein, brain-derived neurotrophic factor and amyloid β 1–42 were determined using standard immunoassays. Results: None of the boxers had been knocked-out during the bout. Plasma-tau was significantly increased in the boxers after a bout compared to controls (mean ± SD, 2.46 ± 5.10 vs. 0.79 ± 0.961 ng L−1, p = 0.038). The other brain injury markers did not differ between the groups. Plasma-tau decreased significantly in the boxers after a resting period compared to after a bout (p = 0.030). Conclusions: Olympic boxing is associated with elevation of tau in plasma. The repetitive minimal head injury in boxing may lead to axonal injuries that can be diagnosed with a blood test.