"Liquid biopsy" on a patch
A patch with microneedles detects extracellular DNA in tissue fluid
Yulia Panchenko, PCR.news
Interstitial (tissue) fluid contains a large number of bi-markers (proteins, cells, nucleic acids). Their real-time tracking using wearable devices can play an important role in monitoring the progression of diseases and the patient's condition. Great hopes are pinned on devices with microneedles that reach the tissue fluid harmlessly and painlessly for the patient.
Researchers from China have created a biosensor based on the CRISPR-Cas9 system, which allows extracting and tracking the presence of extracellular DNA in real time without prior amplification. They tested a new approach for monitoring Epstein-Barr virus (EBV) DNA and other extracellular DNA sequences.
The biosensor consists of a membrane on which a component with a cathode and an anode functionalized by carbon nanotubes is applied, which attracts extracellular DNA by reverse ionophoresis. Detection is performed using the CRISPR-Cas9 system and microneedles. The catalytically inactive Cas9 protein in complex with hydRNA (dRNP) can specifically bind the target DNA. Such hybridization is detected using a graphene interface on microneedles, resulting in an electrical signal.
First, the biosensor was tested on extracellular EBV DNA in solution. The dRNP complex was fixed on a microelectrode. The authors optimized the hydRNA sequence and demonstrated the specificity of EBV DNA recognition compared to sequences of other viruses.
After checking the operability of the idea, the authors received a full-fledged wearable patch with microneedles. The researchers tested the biosafety of the patch: it did not irritate the skin of the volunteers.
After that, the biosensor was demonstrated in vitro on a chip simulating human skin with three layers — the epidermis, dermis and endothelium. The device detected extracellular EBV DNA even in the presence of 60% fetal bovine serum. The signal remained stable for about 30 minutes, and a monitoring time of 75 minutes was considered sufficient.
The authors showed that the biosensor detects other extracellular DNA that may be associated with sepsis or transplantation. The patch was also tested on naked mice: The biosensor detected the extracellular DNA of EBV. The stability of the patch in vivo was demonstrated for 10 days.
Article by Yang et al. The programmable CRISPR-Cas9 microneedle patch for long-term capture and real-time monitoring of universal cell-free DNA is published in the journal Nature Communications.
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