The Challenge of Measuring Proteins in Live Cells
Understanding disease pathways and drug-target interactions often hinges on measuring specific proteins inside cells. Traditionally, scientists tag the protein of interest – for example with a fluorescent reporter or epitope label – which usually requires genetically modifying cells to express a tagged version of the protein. While this works in engineered cell lines, many biologically critical cell types (especially primary cells from patients or blood) are notoriously difficult to modify. And even when it does work the tag can alter the biology of the protein
Electroporation and viral vectors used to introduce tags or genes can severely stress or even fail in these cells: electroporation can cause substantial toxicity and gene dysregulation, and many viruses cannot infect quiescent primary cells1. This leaves researchers in a bind: How do we quantify a protein in live, hard-to-engineer cells without weeks of making custom cell lines or risking cell health?
A Mechanical Solution: Portal’s Mechanoporation Approach
Enter mechanoporation – a physical method to deliver probes into cells by briefly squeezing them through small pores. The concept is simple: force cells through a small constriction to mechanically disrupt the membrane for a brief time, so that large molecules ranging from nanotubes to full-size proteins diffuse directly into the cytosol in dozens of cell types (including hard-to-transfect primary cells)3, 4. Crucially, this technique doesn’t rely on any specific cell-surface markers or custom vectors – it’s a universal, vector-free delivery platform driven by physics rather than biology1.
Directly Measuring Intracellular Proteins without Tags
How does mechanoporation help measure untagged proteins? By allowing the directintroduction of targeted probes (like antibodies) with conjugated detection moieties (like fluorophores) into living cells. Instead of engineering the cell to express a tagged protein, we deliver a tag to the protein inside the cell. Portal’s mechanoporation technology can deliver essentially any membrane-impermeable reagents into the cell cytosol – including antibodies that bind your protein of interest3.
Mechanoporation has shown effective cytosolic delivery of whole antibodies (~150 kDa) into cells alongside other large molecules with high efficiency1. Notably, multiple cargoes can be delivered at once. This multiplexed delivery means researchers could introduce several labeled antibodies in one step – for instance, to label and visualize multiple distinct intracellular proteins in a live cell.
