The development of a continuous, minimally invasive, real-time sensor for glucose and lactate sensing using surface-enhanced Raman spectroscopy

The rapid and accurate identification of biomolecules is vital for patients with a need to monitor chronic or acute conditions. Despite years of innovation in sensor technology there remains a need for accurate real-time, continuous sensors to manage chronic conditions and reduce secondary health complications. The work presented in this dissertation is focused on efforts towards the development of a biosensor based on surface-enhanced Raman spectroscopy for glucose and lactate sensing. In the future, this sensor also has the potential to be applied to a greater number of other biological molecules simply by changing the sensor platform.;Surface-enhanced Raman Spectroscopy (SERS) is a highly selective analytical tool that permits the unambiguous identification of molecules based on their unique vibrational signatures and shows great promise for the detection of important biological molecules such as glucose and lactate. SERS amplifies the intensity of Raman scattering a factor of 106--10 8 by utilizing a nanostructured noble metal surface. Additionally, SERS provides spatial selectivity by probing only those molecules confined within ∼ 2 nm of the metal surface.;The sensor design relies on a self-assembled monolayer (SAM) which partitions and departitions the analyte of interest, prevents non-specific binding, and brings the analyte of interest closer to the noble metal surface. In this work, two SAMs are explored, a glycosylated alkane thiol (1-mercaptoocta-8-yl tri(ethylene) (EG3)) and a mixed decanethiol (DT) and mercaptohexanol (MH) SAM. Although the EG3 SAM successfully detects glucose and is known to be biocompatible, its synthesis is challenging and, therefore its availability is limited. The mixed DT/MH-functionalized AgFON SERS sensing platform overcomes the limitations of the EG3 SAM and creates a pocket for improved glucose partitioning, bringing glucose even closer to the SERS-active surface than was possible with EG3. The DT/MH-functionalized AgFON substrate was also subcutaneously implanted in a rat model to demonstrate successful quantitative detection in intestinal fluid. The experiments demonstrate the first in vivo application of SERS. Lactate sensing is also demonstrated using the mixed DT/MH partition layer. In addition multi-analyte detection is demonstrated by testing the reversibility for sequential glucose and lactate exposures. The experiments demonstrate reversibility, temporal response of < 30 s, 10-day stability and successful quantitative detection capabilities of this sensing platform for both glucose and lactate in vitro and for glucose in vivo.