Paper-based Sensor Detects COVID-19 in Five minutes

As the COVID-19 pandemic continues to spread across the world, testing remains a key strategy for tracking and containing the virus. Bioengineering graduate student, Maha Alafeef, has co-developed a rapid, ultrasensitive test using a paper-based electrochemical sensor that can detect the presence of the virus in less than five minutes. The team led by professor Dipanjan Pan reported their findings in ACS Nano

“Currently, we are experiencing a once-in-a-century life-changing event,” said Alafeef. “We are responding to this global need from a holistic approach by developing multidisciplinary tools for early detection and diagnosis and treatment for SARS-CoV-2.” 

There are two broad categories of COVID-19 tests on the market. The first category uses reverse transcriptase real-time polymerase chain reaction (RT-PCR) and nucleic acid hybridization strategies to identify viral RNA. Current FDA-approved diagnostic tests use this technique. Some drawbacks include the amount of time it takes to complete the test, the need for specialized personnel and the availability of equipment and reagents. The second category of tests focuses on the detection of antibodies. However, there could be a delay of a few days to a few weeks after a person has been exposed to the virus for them to produce detectable antibodies.

n recent years, researchers have had some success with creating point-of-care biosensors using 2D nanomaterials such as graphene to detect diseases. The main advantages of graphene-based biosensors are their sensitivity, low cost of production and rapid detection turnaround. “The discovery of graphene opened up a new era of sensor development due to its properties. Graphene exhibits unique mechanical and electrochemical properties that make it ideal for the development of sensitive electrochemical sensors,” said Alafeef. The team created a graphene-based electrochemical biosensor with an electrical read-out setup to selectively detect the presence of SARS-CoV-2 genetic material.

There are two components to this biosensor: a platform to measure an electrical read-out and probes to detect the presence of viral RNA. To create the platform, researchers first coated filter paper with a layer of graphene nanoplatelets to create a conductive film. Then, they placed a gold electrode with a predefined design on top of the graphene as a contact pad for electrical readout. Both gold and graphene have high sensitivity and conductivity which makes this platform ultrasensitive to detect changes in electrical signals.


How To Early Detect Prostate Cancer

For the first time, a team of scientists at the University of Central Florida has created functional nanomaterials with hollow interiors that can be used to create highly sensitive biosensors for early cancer detection. Xiaohu Xia, an assistant professor of chemistry with a joint appointment in the NanoScience Technology Center, and his team developed the new method and recently published their work in the journal ACS Nano.

These advanced hollow nanomaterials hold great potential to enable high-performance technologies in various areas,” says Xia. “Potentially we could be talking about a better and less expensive diagnostic tool, sensitive enough to detect biomarkers at low concentrations, which could make it invaluable for early detection of cancers and infectious diseases.”

Because hollow nanomaterials made of gold and silver alloys display superior optical properties, they could be particularly good for developing better test strip technology, similar to over-the-counter pregnancy tests. Currently the technology used to indicate positive or negative symbols on the test stick is not sensitive enough to pick up markers that indicate certain types of cancer. But Xia’s new method of creating hollow nanomaterials could change that. More advance warning could help doctors save more lives.

In conventional test strips, solid gold nanoparticles are often used as labels, where they are connected with antibodies and specifically generate color signal due to an optical phenomenon called localized surface plasmon resonance. Under Xia’s technique, metallic nanomaterials can be crafted with hollow interiors. Compared to the solid counterparts, these hollow nanostructures possess much stronger LSPR activities and thus offer more intense color signal. Therefore, when the hollow nanomaterials are used as labels in test strips they can induce sensitive color change, enabling the strips to detect biomarkers at lower concentrations.

Test-strip technology gets upgraded by simply replacing solid gold nanoparticles with the unique hollow nanoparticles, while all other components of a test strip are kept unchanged,” says Xia. “Just like the pregnancy test, the new test strip can be performed by non-skilled persons, and the results can be determined with the naked eye without the need of any equipment. These features make the strip extremely suitable for use in challenging locations such as remote villages.”

The UCF study focused on prostate-specific antigen, a biomarker for prostate cancer. The new test strip based on hollow nanomaterials was able to detect PSA as low as 0.1 nanogram per milliliter (ng/mL), which is sufficiently sensitive for clinical diagnostics of prostate cancer. The published study includes electron microscope images of the metallic hollow nanomaterials.

“I hope that by providing a general and versatile platform to engineer functional hollow nanomaterials with desired properties, new research with the potential for other applications beyond biosensing can be launched,” Xia says.


Safe Stem Cells Therapies To Fight Alzheimer’s, Parkinson’s Diseases

A Rutgers-led team has created better biosensor technology that may help lead to safe stem cell therapies for treating Alzheimer’s and Parkinson’s diseases and other neurological disorders.

The technology, which features a unique graphene and gold-based platform and high-tech imaging, monitors the fate of stem cells by detecting genetic material (RNA) involved in turning such cells into brain cells (neurons), according to a study in the journal Nano Letters.

Stem cells can become many different types of cells. As a result, stem cell therapy shows promise for regenerative treatment of neurological disorders such as Alzheimer’s, Parkinson’s, stroke and spinal cord injury, with diseased cells needing replacement or repair. But characterizing stem cells and controlling their fate must be resolved before they could be used in treatments. The formation of tumors and uncontrolled transformation of stem cells remain key barriers.

This unique biosensing platform consists of an array of ultrathin graphene layers and gold nanostructures. The platform, combined with high-tech imaging (Raman spectroscopy), detects genetic material (RNA) and characterizes different kinds of stem cells with greater reliability, selectivity and sensitivity than today’s biosensors.

A critical challenge is ensuring high sensitivity and accuracy in detecting biomarkers – indicators such as modified genes or proteins – within the complex stem cell microenvironment,” said senior author KiBum Lee, a professor in the Department of Chemistry and Chemical Biology in the School of Arts and Sciences at Rutgers UniversityNew Brunswick.Our technology, which took four years to develop, has demonstrated great potential for analyzing a variety of interactions in stem cells.”