Cross-Platform Biosensing of Immune Receptors Using Peptide-Functionalized Graphene

Changes in the composition of specific cell-surface molecules on immune cells are important early markers of directed immune responses. Current biosensors largely focus on detecting soluble disease markers. Here, a peptide-functionalized graphene biosensor is presented capable of platform-independent, highly sensitive detection of specific immune receptors on living cells. Formyl peptide receptor 2 (FPR2) is targeted, a key modulator of innate immune cells, and validated the technology in two complementary formats: i) graphene-enhanced surface plasmon resonance (SPR) as a robust optical benchmark, and ii) graphene field-effect transistors (gFETs) as a compact, cost-effective electrical alternative. Target specificity is first confirmed using HEK293T cells selectively overexpressing FPR2. Detection of FPR2 on primary human neutrophils is achieved with high reproducibility using fewer than 10 000 cells mL^-1, demonstrating both sensitivity and reliability. By demonstrating sensitive and reproducible detection across both optical and electrical platforms, this work bridges materials science and immunology, highlighting the potential of peptide-functionalized graphene biosensors for point-of-care diagnostics, immune monitoring, and early sepsis triage.