Printed Paper Substrates with Plasmonic and Magnetic Nanoprobes for SERS Detection of Cancer Biomarkers

Sensitivity and multiplexing capability are essential for developing effective cancer-screening biosensors. This is addressed in this work by coupling plasmonic and magnetic nanoprobes with wax-printed fibrous substrates in direct or microfluidic configurations using a portable Raman spectrometer. Gold nanoparticles and nickel–iron alloyed magnetic cores with gold shells, upon bioconjugation and Raman labeling, are exploited as nanoprobes for the surface-enhanced Raman scattering (SERS) detection of cancer biomarkers. The enrichment of the nanoprobe “hot spots” within the wax-confined fibrous space enables enhanced detection of the targeted biomarkers, such as carcinoembryonic antigen (CEA) and neuron-specific enolase (NSE). The detection is also enhanced by magnetic focusing using plasmonic-magnetic nanoprobes. In the case of wax-printed fibrous substrates, the confined conjugated plasmonic nanoprobes allowed for enhancement of the detection. In the case of magnetic-plasmonic nanoprobes, microfluidic magnetic focusing facilitated effective detection. Both plasmonic and plasmonic-magnetic nanoparticles have successfully detected CEA and NSE, demonstrating the viability of multiplexing using distinct Raman labels. These findings have significant implications for developing effective SERS-based early cancer detection strategies.