Ultra-absorptive nanofiber swabs developed by researchers at the University of Nebraska Medical Center could reduce the number of false-negative tests for covid-19 by improving sample collection and test sensitivity.1

Reverse transcriptase-polymerase chain reaction (RT-PCR) tests to detect SARS-CoV-2 RNA often require a long swab to collect a specimen from deep inside a patient’s nasal cavity. But if the viral load is low, which can occur early in the course of infection, the swab might not pick up enough virus to be detectable. 

The Nebraska researchers wanted to develop a nanofiber swab that could absorb and then release more viruses and other biological specimens, improving the sensitivity of diagnostic tests. The researchers used an electrospinning technique to make 1-cm-long cylinders composed of aligned nanofiber layers, which they coated with a thin layer of gelatin and bonded to plastic swab sticks. 

“Using nanoscale fibers, instead of micro scale fibers, we have created extremely absorptive swabs that can detect SARS-CoV-2 at very low concentrations and reduce false negative tests,” says Jingwei Xie, PhD, associate professor, UNMC Department of Surgery-Transplant and Mary and Dick Holland Regenerative Medicine Program. “We have been investigating the use of these materials and noting their remarkable absorptive properties and our ability to control their shape, and we thought to repurpose them as swabs.”

In lab tests, the porous nanofiber cylinders absorbed and released more proteins, cells, bacteria, DNA, and viruses from liquids and surfaces than the cotton or flocked swabs commonly used for covid-19 testing. The team made dilutions of SARS-CoV-2 virus, swabbed the liquid samples and tested for viral RNA with RT-PCR. Compared with the two other types of swabs, the nanofiber ones reduced the false-negative rate and detected SARS-CoV-2 at a 10-times lower concentration. 

In addition to allowing more accurate and sensitive COVID-19 testing, the nanofiber swabs have far-reaching potential in diagnosing other diseases, testing for foodborne illnesses and helping forensic teams identify crime suspects from miniscule biological specimens, the researchers say.

“If there is interest in commercialization of the swabs, they may be used to detect trace amounts of biological samples,” Xie says. “The largest potential for the swabs is in early detection of pathogens and in forensics; both avenues are viable for research and commercialization.”


1. McCarthy A, Saldana L, Ackerman DN, et al. Ultra-absorptive nanofiber swabs for improved collection and test sensitivity of sars-cov-2 and other biological specimens. Nano Lett. 2021;21(3):1508-1516. doi: 10.1021/acs.nanolett.0c04956.

Featured image: A new type of nanofiber swab could improve sample collection and test sensitivity for SARS-CoV-2 and other biological specimens; ruler shows centimeters. Adapted from Nano Letters 2021, DOI: 10.1021/acs.nanolett.0c04956.