Disposable and versatile optical sensors for real-time SERS analysis of liquid samples by fiber-based spectroscopy

摘要

Optical detection techniques based on surface enhanced Raman spectroscopy (SERS) and capable of providing relevantinformation on molecular and protein composition of biological samples, are gaining rising attention in clinical researchas alternatives to traditional detection assays. Meanwhile, due to the technological advances in compact instrumentationas well as in nanofabrication processes, SERS probes based on portable guided-wave systems, have been implementedthus providing for easier accessibility into complex environments and enabling for real-time in situ detection of lowconcentrated target analytes. In the present study, low-cost fabrication processes were successfully combined withsurface functionalization strategies for the fabrication of disposable SERS-active substrates, engineered to tightly fit thedistal end of portable Raman instruments. Being based on a polymer casting fabrication process, the overall design of thesubstrates can be easily adapted to the varied geometry of the probes to be fit, thus guaranteeing high design versatility.SERS-functionality was achieved by immobilization of gold nanoparticles whose size and shape directly affect theplasmonic properties of the substrates. Moreover, SERS substrates can be further modified by covalently bindingmolecules acting as baits to selectively fish target biomarkers within heterogeneous samples thereby increasing thespecificity of SERS signals. Finally, these sensors represent a powerful tool potentially implementable for the earlydiagnosis of widespread pathologies by real-time SERS analysis of liquid biopsy.