David R. Walt

The Walt lab pioneered the use of microwell arrays for ultra-sensitive biomarker detection and analysis, such as proteins and microRNAs. The technique, known as Single Molecule Arrays (Simoa), is based on digital enzyme-linked immunosorbent assay (ELISA) and can improve the limit of detection of conventional ELISA by between 100- and 1000-fold. Using Simoa, the lab is currently developing blood-based tests for early diagnosis of various diseases including breast cancer, Parkinson’s Disease, Tuberculosis, and sepsis as well as for treatment regimens such as Immuno-oncology. Another application of this effort is an integrated diagnostic platform for performing medical diagnostics using saliva as a sample matrix instead of blood; for example, in the study of neonatal oral feeding and sepsis. The Simoa platform can also be used to study living cells, both as cell populations and as individual cells when integrated with microfluidics. The lab is interested in studying the behavior of large numbers of cells to understand the distribution of cell behaviors in a population.

In addition to these clinical and biological projects, the lab pursues technology development to enhance diagnostics capabilities. The Simoa limit of detection is typically about a factor of 100 to 1000 times more sensitive than the traditional method of protein analysis—the enzyme-linked immunosorbent assay (ELISA) technique. Simoa opens up the potential for being able to measure proteins at concentrations that have never been detected before in various kinds of samples including blood, which is the main focus for Simoa-based assays. However, we still cannot detect certain proteins when measuring blood samples because the Simoa technology does not provide the requisite sensitivity to measure some of the molecules present at lower expression levels. Currently, we are attempting to push the boundary of sensitivity to detect even lower concentrations using nanotechnology. Nanomaterials modified with enzymes or DNA are utilized for signal amplification to further improve the sensitivity of the digital ELISA method.

Finally, the lab is exploring fundamental enzymology by using our single molecule platform to observe individual enzyme molecules.  We are using in vitro transcription and translation systems to study fundamental aspects of enzyme structure and activity such as measuring translation error rates. This work enables us to resolve phenomena that cannot be observed using traditional ensemble measurements.