A label-free platform for high-throughput, miniaturised electrospray injection mass spectrometry (ESI-MS)

ESI-Mine can test up to 200,000 biomolecular samples (e.g. peptides, enzymes, antibodies, metabolites and small molecules) per day in miniaturized volumes of 500-700pL (picodroplets) facilitating more efficient screening and analysis in bioproduction or synthetic biology processes.

Applying this novel approach, researchers can create a large library of picodroplets containing microorganisms producing proteins or small molecules of interest for analysis. One major drawback of using MS in analysis is that samples are usually destroyed and cannot be retrieved. To overcome this total sample destruction by ESI-MS, we have developed a unique microfluidics workflow where picodroplets are split into two replicate streams with identical clones, one stream is analyzed by ESI‐MS, and the second stream is subsequently ‘held’ and only those ‘hit’ daughter picodroplets sorted based on the result of the MS analysis.

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The Technology

MS offers label-free detection of the presence, absence, and abundance of multiple, specific molecules with high sensitivity and selectivity. However, it is relatively low-throughput and sample destruction during the analysis prevents the direct sorting of ‘hit’ molecules or samples of interest.

The microfluidic-based workflow of ESI-Mine addresses the main challenges in ESI-MS while offering advantages in high speed, increased sample throughput and lower cost over existing solutions.

Cells are encapsulated into picodroplets in a one-droplet-one-cell (OCOD) manner, creating a library of picodroplets that can express and retain novel proteins and/or other hydrophilic entities. The picodroplets are incubated to enable cell growth, protein expression and metabolic processes to occur and are then reinjected into the proprietary microfluidic emitter biochip on the ESI-Mine platform for label-free screening followed by real-time sorting based on MS analysis results. At this stage, each picodroplet is asymmetrically split, producing two daughter picodroplets from the same parent picodroplet. The larger daughter picodroplet is analyzed by ESI-MS. Its smaller sibling picodroplet is processed through microfluidic channels and sorted based on the MS signal. Hits are then collected as a pool for further downstream analysis.

Complete workflow of single cell analysis and sorting on ESI-Mine™ platform

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ESI-Mine™ is suitable for several applications including:

Synthetic biology: Facilitates the study of valuable molecules produced by libraries of engineered microbes.

Bioprocessing: Enables analysis and identification of microbial clones that are high expressors of, e.g. Active Pharmaceutical Ingredients.

Drug and molecular interaction studies: Accurately measures drug or drug fragment interaction with soluble proteins for improved structure-activity relationship studies.

Enzyme evolution/Site-directed mutagenesis: Helps determine the efficiency of engineered enzymes on their native substrates



Recover Rare Variants

ESI-Mine™ uniquely allows live clone retrieval of rare cells producing proteins or other molecules of interest based on the result of the MS analysis.


ESI-Mine™ can selectively sort up to 200,000 biomolecular samples per day for efficient and high-throughput analysis of large cell libraries.


Using picodroplets, the amount of media required is significantly reduced, further reducing costs


ESI-Mine™  can be customized to work with different MS models. We also offer a range of customizable microfluidic biochips enabling the development of complex workflows on a single microfluidic device.


ESI-Mine™ enables a broad range of novel microfluidic workflows and applications.



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