Shedding Light on Glucose: Tip-Enhanced Raman Scattering Achieves Complete Vibrational Fingerprint Coverage (400–3200 cm⁻¹) for Non-Invasive Metabolite Detection
Non-invasive glucose monitoring remains a critical unmet clinical need, primarily because glucose exhibits an inherently weak Raman scattering cross-section—approximately five times smaller than that of benzene—and poor affinity for bare metal surfaces. While surface-enhanced Raman spectroscopy (SERS) can amplify weak signals, it suffers from incomplete spectral coverage and interference from linker molecules, preventing reliable comprehensive analysis. A recent study by Xie et al. published in Opto-Electronic Science demonstrates that tip-enhanced Raman scattering (TERS) can record the complete vibrational spectrum of glucose molecules across the 400–3200 cm⁻¹ Raman recording window. By combining a shear-force feedback-controlled scanning probe with a radially polarised vector beam launched through an optical fibre tip, the authors achieve strong near-field confinement and far-field background suppression. The tip concentrates a strong longitudinal electric field along its axis, maximising the localised hotspot at the apex, which boosts near-field enhancement and enables more complete vibrational fingerprints to be captured. This label-free approach overcomes the long-standing barriers of weak signal intensity and incomplete spectral coverage, establishing a viable pathway for highly sensitive metabolite detection and future in vivo biosensing applications. The work represents a significant advance in optical diagnostic techniques for diabetes management and broader clinical metabolite monitoring.