Partially gold-coated tilted FBGs for enhanced surface biosensing.

Area of Science:

• Plasmonics
• Nanotechnology
• Biosensing

Background:

• Gold-coated tilted fiber Bragg gratings (TFBGs) are sensitive plasmonic biosensors but suffer from dual sensitivity to surface and bulk refractive index changes, leading to drift.
• This dual sensitivity complicates accurate analyte detection in complex biological samples.

Purpose of the Study:

• To develop a TFBG biosensor capable of discriminating between surface and bulk refractive index changes.
• To enhance the signal-to-noise ratio in biosensing applications by mitigating environmental drift.
• To demonstrate the detection of human epidermal growth factor receptor (HER2) proteins using the developed biosensor.

Main Methods:

• Utilizing partially gold-coated TFBGs with a functionalized gold surface and a bare area.
• Analyzing transmitted amplitude spectra for changes in surrounding refractive index (SRI).
• Biofunctionalizing the gold surface with HER2 aptamers and detecting HER2 proteins at various concentrations.

Main Results:

• The partially coated TFBGs successfully discriminated between SRI and surface binding events.
• The bare area of the TFBG served as a reference to identify and eliminate environmental perturbations.
• Accurate detection of HER2 proteins at concentrations down to 10^-9 g/mL was achieved, with minimal non-specific drift.

Conclusions:

• Partially gold-coated TFBGs offer a robust platform for biosensing by enabling differentiation between specific binding and environmental changes.
• This approach significantly improves the reliability and accuracy of optical biosensors in complex sample matrices.
• The developed biosensor shows great potential for sensitive and specific detection of cancer biomarkers.