Evaluation of single molecule array digital immunoassay technology to quantitate neurofilament light chain.

Aim: Globally, neurodegeneration accounts for significant morbidity and mortality among the elderly. Millions of people are afflicted with neurodegenerative diseases, with the most notable cases attributed to Alzheimer's, Huntington's, amyotrophic lateral sclerosis and Parkinson's diseases. Sensitive assays that can detect proteopathic anomalies indicative of early neurodegeneration have remained elusive. Therefore, there is an urgent need for sensitive diagnostic and prognostic biomarker assays that can guide the therapeutic regimen in the clinic. Materials & methods: Single molecule array digital immunoassay platform has sensitivity about 1000-fold higher than traditional ligand binding assays. Consequently, we are now beginning to implement ultrasensitive techniques in bioanalysis. Conclusion: In the current study, we evaluated single molecule array technology and report specifications to quantitate neurofilament light chain, a bona-fide biomarker for neurodegeneration. Preliminary neurofilament light screening results from 100 human geriatric cerebrospinal fluid samples displayed huge biological variation and warrants further investigation.

The importance of chromatographic resolution when analyzing steroid biomarkers.

The analyses of endogenous substances as biomarkers presents challenges that are distinctly different from the analyses of drugs or other xenobiotic substances. This is particularly true for estrogens. When no matrix is available which does not contain some level of the biomarker of interest, specificity cannot be demonstrated. Therefore it cannot be known whether the analyte signal includes a response from another substance. This uncertainty is increased by the fact that biomarkers are often created as part of a complex biosynthetic process that also creates a large number of substances with very similar structures and sometimes the same mass. Because of this, the two most powerful selectivity tools in the analysis of drugs, mass selective detection and MS/MS, are often rendered ineffective. The only remaining selectivity tool is chromatography and as will be demonstrated these separations can be very challenging. Failure to achieve specificity is perhaps the leading cause for inaccuracy of biomarker data and inter-laboratory variability.