Graphene-based magnetoelastic biosensor for COVID-19 serodiagnosis

This work presents an innovative magnetoelastic (ME) biosensor using graphene functionalized with the SARS-CoV-2 N protein for antibody detection via magnetoelastic resonance. Graphene was chosen for its biocompatibility and high surface area, enabling efficient antigen adsorption, validated by techniques such as energy-dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM), and micro-Raman spectroscopy. Changes in Raman bands (a $\sim 10~\mathrm{cm}^{-1}$ shift in the 2D band and an increase in the $I_D/I_G$ ratio from 0.03 to 0.60) confirmed non-covalent interactions and enhanced surface coverage with ~100 $\mu$g of N protein. Tests using human plasma (10 RT-PCR-positive and 10 negative samples) demonstrated a clear distinction between groups using graphene sensors functionalized with ~100 $\mu$g of N protein. Enzyme-linked immunosorbent assay (ELISA) validation corroborated the results. Optimization of protein concentration and biofunctionalization time highlighted the importance of homogeneous surface coverage for reproducibility of the graphene-based ME biosensor. The platform combines graphene's advantages with the wireless, real-time detection capabilities of ME sensors, offering low cost, high sensitivity, and potential for automation, with applications in point-of-care diagnostics.