Improved monitoring dynamics through use of a tethered enzyme biosensor to detect and quantify neuron-specific enolase activity levels in biofluids

Abstract

Purpose:

Neuron-specific enolase (NSE) is an isoform of the glycolytic enzyme enolase. For decades, changes in NSE levels in biofluids have been studied for their clinical value in diagnosis, prognosis and monitoring of a plethora of pathologies and conditions, including brain injuries, various kinds of cancers and tumors, and other diseases (eg, Guillain-Barré syndrome and Creutzfeldt-Jakob). However, because of its long 24–30 hours half-life, NSE’s diagnostic and prognostic power, specifically for brain injuries, was found to be limiting in respect to other biomarkers with faster dynamics (eg, S100β). Thus, we hypothesize that measuring NSEs fast decaying enzymatic activity, rather than only amounts of protein, will provide improved resolution of dynamic temporal changes.

Methods:

Our previously reported tethered enzyme-based biosensor was used here to provide rapid measurement of changes in NSE activity as measured in vitro following incubation in canine and human serum or plasma. NSE activity was then compared with total protein amounts to assess the relative changes of these two parameters.

Results:

We find that in serum, recovered plasma, and fresh plasma at 37°C, NSE protein levels (NSE^P) are highly stable, whereas the enzymatic activity (NSE^A) decays at a considerably faster rate.

Conclusion:

Because the decay rate of NSE^A is significantly higher as measured in vitro than its reported half-life in biofluids, and taking into account physiological clearance rates, measuring its enzymatic activity can provide better assessment of dynamic changes in the levels of this biomarker. A convenient and rapid technology for measurement of NSE enzymatic activity would improve understanding of NSE temporal dynamics, in comparison to more commonly used diagnostic methods.

Keywords::

• biomarker
• enzyme activity
• tethered enzymes
• biosensor
• brain injuries
• tumor markers

Disclosure

The authors report no conflicts of interest in this work.