CRISPR lateral flow: the genome as a paper strip

A CRISPR diagnostic is a bacterial immune system taught to hunt on command. A guide RNA directs a Cas12 or Cas13 enzyme to a chosen sequence; on finding it, the enzyme does something biologically extravagant — it shreds any single-stranded molecule in reach, not just its target. Diagnostic chemistry converts that collateral burst into the readout: reporters clipped by the activated enzyme release a signal, and on a lateral flow strip the signal is a line the eye can see. Recognition by programmable guide, amplification by isothermal chemistry, readout by paper — the architecture removes the thermocycler and the instrument that kept molecular testing in laboratories.

The regulated history ran unusually fast, and it is worth reading as evidence about the platform rather than about the pandemic. Sherlock Biosciences took the first CRISPR-based FDA Emergency Use Authorization for a SARS-CoV-2 assay in May 2020; Mammoth Biosciences — the DETECTR company, with $375 million raised — received its own EUA for the DETECTR BOOST SARS-CoV-2 Reagent Kit in 2022 and runs high-throughput operation at 1,500 tests per 8-hour shift in CLIA laboratories. The platform’s constraint, before and since, is manufacturing and conversion: Sherlock’s ISO 13485-certified facility in Swavesey, UK is sized for 5 million diagnostic devices annually with revenue still primarily grant-funded as of late 2024, and the emergency-era products must graduate into ordinary IVD review — the same conversion the EU gates through IVDR 2017/746.

The engineering that decides field performance is the unglamorous half. Isothermal amplification (LAMP and RPA) feeds the CRISPR step at constant temperature, but sample extraction remains the failure point outside a laboratory — the step no guide RNA can rescue. Lyophilized reaction chemistry is what makes the strip survivable without a cold chain, and manufacturing it is regulated device production: strips made, chemistry dried, lots released against performance standards. BGI’s adjacent experience shows the scale such manufacturing reaches when a health system calls — a factory in Addis Ababa producing 10 million test kits per year, within a group reporting CNY 3.705 billion revenue for fiscal 2025, with NMPA emergency approvals and EU CE certification across its kit lines.

The honest boundary of the platform is specificity management and the conversion clock. Guide design prevents false positives before any chemistry exists, but multiplexing several targets on one strip taxes the readout, and no CRISPR-diagnostics product has yet converted from emergency authorization to routine certified IVD at the scale sequencing-based testing holds. That conversion — IVDR certificates, ordinary FDA clearances, WHO tenders — is the near-term competition, because the platform’s unit economics at paper-strip cost are already what point-of-care testing has wanted for decades.