Dear Colleagues,

Any developments or updates related to biosensors are welcome for publication in our Special Issue, whether in the form of research article, review, or scientific communication. Below are just a few examples of recent developments in the field of biosensors. Rapid antigen tests can quickly and conveniently tell a person that they are positive for COVID-19, though antibody-based tests are not very sensitive. The first molecular electronics chip has been developed, representing the realization of a 50-year-old goal of integrating single molecules into circuits to reach the ultimate scaling limits of Moore’s law. Developed by Roswell Biotechnologies and a multidisciplinary team of leading academic scientists, the chip uses single molecules as universal sensor elements in a circuit to create a programmable biosensor with real-time, single-molecule sensitivity and unlimited scalability in sensor pixel density. This innovation, appearing this week in a peer-reviewed article in the Proceedings of the National Academy of Sciences (PNAS), will power advances in diverse fields that are fundamentally based on observing molecular interactions, including drug discovery, diagnostics, DNA sequencing, and proteomics. “Biology works by single molecules talking to each other, but our existing measurement methods cannot detect this,” stated co-author Jim Tour, Ph.D., a Rice University chemistry professor and a pioneer in the field of molecular electronics. “The sensors demonstrated in this paper for the first time let us listen in on these molecular communications, enabling a new and powerful view of biological information.” Scientists discovered nuclear magnetic resonance, a physical phenomenon where nuclei absorb and re-emit energy when placed in a magnetic field, in 1938. However, it took almost 30 years for this fundamental discovery in physics to find its most widely known application: MRI imaging, a crucial diagnostic tool in medical and biological research.

Now in the 21st century, researchers can make quantum devices precise enough to sense single ions—and University of Chicago chemistry professor Greg Engel does not want to wait 30 years to find their most useful applications. “It’s rapidly becoming clear that quantum sensing could be transformative in the next phases of biology research,” Engel says. The advantage of superposition: Quantum technology takes advantage of scientific phenomena that are only accessible on the smallest of scales, such as the concept of superposition—where a system exists in a combination of possible states rather than in a single state. This unique characteristic of quantum systems is quite fragile—when a quantum system in superposition interacts with its environment in any way, its superposition “collapses”, and it exists in one state instead of many. This incredible fragility is what makes quantum communication and computing technologies so difficult to implement. Keeping something as tiny as an atom isolated enough to exist in superposition takes a lot of energy, funding, and logistics.
Quantum sensing, however, takes that fragility and turns it into an advantage. If the superposition of a system can be disturbed by a single molecule, atom, or even photon, that system can be turned into a sensor to monitor these individual particles. Many important phenomena in biology originate from single atoms, such as the motion of an individual ion or a small change in the electric charge of a protein. These processes, however, are currently incredibly difficult or even impossible to measure. Quantum biosensing offers a way to investigate these biological events with unprecedented sensitivity. “With the convergence between the sensitivity that is possible with quantum measurement, and the absolute need in biology to understand things on exactly these scales: it’s just a match made in heaven,” says Engel, who is also the director of the new $25 million Quantum Leap Challenge Institute for Quantum Sensing for Biophysics and Bioengineering (QuBBE). The potential applications of quantum biosensing range from tracking a drug through the membrane and across the cytoplasm of a single cell, to precise demarcation of tumor margins during surgery. Noninvasive glucose monitoring devices are not currently commercially available in the United States, so people with diabetes must collect blood samples or use sensors embedded under the skin to measure their blood sugar levels. Now, with a new wearable device created by Penn State researchers, less intrusive glucose monitoring could become the norm. Led by Huanyu “Larry” Cheng, Dorothy Quiggle Career Development Professor in Penn State’s Department of Engineering Science and Mechanics, the researchers published the details of the noninvasive, low-cost sensor that can detect glucose in sweat in Biosensors and Bioelectronics. The paper, available online, will be published in the journal’s December print issue. The researchers constructed the device first with laser-induced graphene (LIG), a material consisting of atom-thick carbon layers in various shapes. With high electrical conductivity and a convenient fabrication time of just seconds, LIG appears to be an ideal framework for sensing devices—but with a significant caveat. “The challenge here is that LIG is not sensitive to glucose at all,” Cheng said. “So, we needed to deposit a glucose-sensitive material onto the LIG.” The team chose nickel because of its robust glucose sensitivity, according to Cheng, and combined it with gold to lower the potential risks of an allergic reaction. The researchers hypothesized that the LIG outfitted with the nickel–gold alloy would be able to detect low concentrations of glucose in sweat on the skin’s surface.

Prof. Dr. Florian Ion Tiberiu Petrescu
Dr. Gang Shi
Guest Editors

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