Two-step PEG-based surface functionalization of gold nanoparticles enables specific SERS imaging of EGFR in an...

Surface-Enhanced Raman Scattering (SERS)-based cancer imaging is of significant interest for histopathological examination, molecular analysis, and intraoperative guidance of tumor tissues due to its sensitive and specific detection of multiple cancer-associated biomarkers and stable signal over time. However, synthesis of SERS nanotags targeting cancer biomarkers is limited by the complexity in achieving a balance between Raman sensitivity, binding specificity, and nanoparticle stability. Here, we established a two-step PEG-based surface modification for 60 nm spherical gold nanoparticles to enable the SERS imaging of various ovarian cancer cell models expressing the epidermal growth factor receptor (EGFR). In contrast to conventional surface modification of gold-based SERS nanotags, our approach enables the simultaneous optimization of Raman activity, colloidal stability, and targeting specificity directly on gold nanoparticles. PEG-conjugated ⍺EGFR antibodies were successfully immobilized on 75.4 ± 4.6% of nanoparticles, with proof of accessible, active surface binding sites. Surface coverage with carboxyl-terminated poly(ethylene glycol)-1,4 benzenedithiol conjugate provided simultaneous SERS signal and steric stabilization, overcoming limitations associated with insufficient surface coverage of one or more functional groups. Colloidal stability during the two-step surface modification was maintained by the addition of surfactant Tween 80. Finally, SERS imaging demonstrated the specificity of our SERS nanotags toward EGFR-positive ovarian cancer cells (OVCAR5 and OVCAR8). Evaluation of ΔEGFR-OVCAR8 cells further confirmed that nanoparticle binding is primarily driven by specific antigen-antibody recognition, independent of cell line-specific effects. Overall, this work provides a promising strategy for effective SERS-based imaging of cancer, with potential for future clinical applications.