The collection of blood for diagnostic tests is common practice in clinical settings. However, technicians often need to separate plasma from serum, which adds additional time and complexity to the process. Also, many patients are terrified of needles being stuck in their veins. Therefore, when it comes to diagnostic testing, a simple new method that avoids using needles and drawing blood would benefit the field of clinical diagnostics. New research out of the George Institute of Technology and Washington University published in ACS Sensors details the development of a microneedle patch that painlessly attaches to the patient’s skin and collects interstitial fluid (ISF) for on-patch point-of-care diagnostic testing.
ISF is a bodily fluid that fills the interstitial space between cells. ISF contains many of the same biomarkers that are also present in the blood. However, ISF can be simpler to use in diagnostic testing than blood because it does not contain any cells or clotting agents. Patches that contain microneedles can collect ISF from the skin. Remarkably, the needles are so small that patients do not feel any pain when it is attached to their skin. Until now, the ISF collected from microneedles needs to undergo complicated multistep processes, such as biomarker extraction, centrifugation, sample loading, and analysis for diagnostic testing.
The microneedle patch developed by Srikanth Singamaneni, Mark Prausnitz, and colleagues collects ISF from the skin and delivers it to plasmonic paper containing gold nanorods. Diagnostic testing can be performed directly on the patch’s plasmonic paper in a single step. This improvement dramatically reduces the time and complexity of ISF diagnostic testing. The mechanism of detection is called surface-enhanced Raman scattering (SERS), a phenomenon in which absorbed molecules modulate the scattering of light by metal nanostructures. SERS has the capability to enhance the signal of the molecule of interest greater than 10 billion times, which makes single-molecule detection a possibility in the future. As a proof-of-principle, the researchers were able to detect dye that was injected into rats in their ISF using SERS.