Bifunctional Laser-Induced Graphene Platforms for Integrated Electrochemical Sensing and Matrix-Free LDI-MS Quantitation of Sarcosine
Wimala Karintrithip, Pumidech Puthongkham, Pranee Rattanawaleedirojn, Narong Praphairaksit, Richard W. Vachet, Andrew J. DeMello, Nadnudda RodthongkumAbstract
This work introduces a dual-modality analytical platform based on laser-induced graphene (LIG) for the label-free, noninvasive detection of the prostate cancer biomarker sarcosine in human urine. The tunable porosity and high conductivity of LIG enable its bifunctional application as both a sensitive electrochemical electrode and an efficient matrix for laser desorption/ionization mass spectrometry (LDI-MS). Functionalized with sarcosine oxidase and gold nanoparticles (AuNPs), the platform leverages the strengths of both modalities: the AuNPs/LIG electrode provides rapid electrochemical screening with a low limit of detection (LOD) of 2 μM, while the LDI-MS modality offers highly selective, matrix-free confirmation with an enhanced ultralow LOD of 500 nM. Both modalities share a wide linear range (5–50 μM), falling well below the clinical urinary threshold of 20 μM. By combining speed and simplicity from electrochemical sensing with the high sensitivity and molecular specificity of MS analysis on a single device, this platform demonstrates the orthogonal capabilities of LIG for robust, pretreatment-free cancer biomarker diagnostics.