with a Fluorescent Polymer

From the ACS Press Room Illuminating Invisible Bloody Fingerprints with a Fluorescent Polymer

“Highly Stable, Nondestructive, and Simple Visualization of Latent Blood Fingerprints Based on Covalent Bonding Between the Fluorescent Conjugated Polymer and Proteins in Blood” ACS Applied Materials & Interfaces

addition, some textured surfaces, such as wood, pose challenges for an identification. Fluorescent compounds can enhance the contrast between fingerprints and the surface on which they are deposited. However, to get a good and stable image, these molecules need to form strong bonds with molecules in the .Careful criminals usually clean a scene, wip- blood. So, Li-Juan Fan, Rongliang Ma and ing away visible blood and fingerprints. colleagues wanted to find a simple way to However, prints made with trace amounts of bind a fluorescent polymer to blood proteins blood, invisible to the naked eye, could re- so that they could detect clear fingerprints on main. Dyes can detect these hidden prints, many different surfaces. but the dyes don’t work well on certain surfaces. Now, researchers reporting in ACS Ap- The researchers modified a yellow-green fluplied Materials & Interfaces have developed orescent polymer they had previously devela fluorescent polymer that binds to blood in a oped by adding a second amino group, which fingerprint — without damaging any DNA allowed stable bonds to form between the also on the surface — to create high-contrast polymer and blood serum albumin proteins. images. They dissolved the polymer and absorbed it into a cotton pad, which was placed on top of Fingerprints are critical prints made with chicken blood on various pieces of forensic evi- surfaces, such as aluminum foil, multicolored dence because their plastic and painted wood. After a few whorls, loops and arches minutes, they peeled off the pad, and then let are unique to each per- Fingerprint patterns it air-dry. All of the surfaces showed high son, and these patterns don’t change as people made in blood are clearly visible on aluminum foil (left) and contrast between the blood and background under blue-violet light and revealed details, age. When violent painted wood (right) including ridge endings, short ridges, whorls crimes are committed, a culprit’s fingerprints when developed with a fluorescent polymer. and sweat pores. These intricate patterns were distinguishable when the researchers inked in blood can be hard to see, especially contaminated the prints with mold and dust, if they tried to clean the scene. So, scientists and they lasted for at least 600 days in storusually use dyes to reveal this type of evi- age. In another set of experiments, a piece of dence, but some of them require complex human DNA remained intact after being techniques to develop the images, and busy backgrounds can complicate the analysis. In

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From the ACS Press Room Personalized Sweat Sensor Reliably Monitors Blood Glucose without Finger Pricks

“Touch-Based Fingertip Blood-Free Reliable Glucose Monitoring: Personalized Data Processing for Predicting Blood Glucose Concentrations”

ACS Sensors

.Many people with diabetes endure multiple, painful finger pricks each day to measure their blood glucose. Now, researchers reporting in ACS Sensors have developed a device that can measure glucose in sweat with the touch of a fingertip, and then a personalized algorithm provides an accurate estimate of blood glucose levels. According to the American Diabetes Association, more than 34 million children and adults in the U.S. have diabetes. Although self-monitoring of blood glucose is a critical part of diabetes management, the pain and inconvenience caused by finger-stick blood sampling can keep people from testing as often as they should. Scientists have developed ways to measure glucose in sweat, but because levels of the sugar are much lower than in blood, they can vary with a person’s sweat rate and skin properties. As a result, the glucose level in sweat usually doesn’t accurately reflect the value in blood. To obtain a more reliable estimate of blood sugar from sweat, Joseph Wang and colleagues wanted to devise a system that could collect sweat from a fingertip, measure glucose and then correct for individual variability. The researchers made a touch-based sweat glucose sensor with a polyvinyl alcohol hydrogel on top of an electrochemical sensor, which was screen-printed onto a flexible plastic strip. When a volunteer placed their fingertip on the sensor surface for 1 minute, the hydrogel absorbed tiny amounts of sweat. Inside the sensor, glucose in the sweat underwent an enzymatic reaction that resulted in a small electrical current that was detected by a hand-held device. The researchers also measured the volunteers’ blood sugar with a standard finger -prick test, and they developed a personalized A hand-held device combined with a algorithm that touch sweat sensor (strip at right) could translate measures glucose in sweat, while a pereach person’s sonalized algorithm converts that data into a blood glucose level. sweat glucose Credit: Adapted from ACS Sensors to their blood 2021, DOI: 10.1021/acssensors.1c00139 glucose levels. In tests, the algorithm was more than 95% accurate in predicting blood glucose levels before and after meals. To calibrate the device, a person with diabetes would need a finger prick only once or twice per month. But before the sweat diagnostic can be used to manage diabetes, a large-scale study must be conducted, the researchers say. The authors acknowledge funding from the University of California San Diego Center for Wearable Sensors and the National Research Foundation of Korea.