Designing a high performance, stable spectroscopic biosensor for the binding of large and small molecules

Area of Science:

• Surface chemistry
• Biosensor technology
• Spectroscopic analysis

Background:

• Stable organic layers are crucial for optimal Fourier-transform infrared attenuated total reflectance (FTIR ATR)-based sensor performance.
• Previous self-assembled coverings were thought stable due to hydrophobic barriers, but stability limits were identified.
• Surface etching of germanium (Ge)-polyethylene glycol-N-hydroxysuccinimide (PEG-NHS) devices was observed upon bovine serum albumin (BSA) injection.

Purpose of the Study:

• To investigate the stability and reactivity of functionalized germanium devices for biosensing applications.
• To develop a more robust and stable organic layer for FTIR ATR sensors.
• To improve the binding capabilities for molecules of various sizes.

Main Methods:

• Simultaneous measurement of stability and reactivity using FTIR ATR.
• Development and characterization of a new functionalized germanium device (Ge-APS-PEG-NHS) using a three-step in situ procedure.
• Evaluation of sensor sensitivity towards BSA and ethanolamine.

Main Results:

• Observed surface etching of Ge-PEG-NHS devices due to molecular chain deformation upon binding large molecules like BSA.
• Identified network deprotection and hydrogen bond disruption in single-barrier networks.
• Demonstrated that the new Ge-APS-PEG-NHS device provides a robust dual-barrier network with homogeneous NHS distribution.
• Achieved exceptional sensitivity for BSA and ethanolamine detection with the new device.

Conclusions:

• Single-barrier networks are susceptible to deformation and deprotection when binding large molecules.
• A dual-barrier network, as achieved with Ge-APS-PEG-NHS, offers superior stability and robustness.
• The new functionalized germanium device exhibits high sensitivity and is suitable for detecting various sized molecules, advancing FTIR ATR-based sensing.