Portable and economical plasmonic capillary sensor for biomolecular detection

We present here, a label-free and non-destructive plasmonic capillary sensor based on embedded gold nanoparticles on a glass capillary. The gold nanoparticles were embedded into the glass capillary by the thermal annealing process. Our proposed plasmonic capillary sensor simultaneously acted as a sensing chip as well as a flow cell. It also provides mechanical support for easy integration with light source and detector. Based on theoretical analysis, we have found that electromagnetic field confinement in embedded gold nanoparticles was much stronger as compared to the freestanding case. However, the strength of the optical field depends upon how large gold nanoparticles is embedded into the substrate. The calculated bulk refractive index sensitivity of proposed sensor is 127 ± 10 nm/RIU. Further, we have demonstrated the application of our proposed sensor towards biomolecular detection by monitoring the specific interactions between bovine serum albumin (BSA) proteins and anti-BSA proteins. Based on wavelength shifting interrogation, a detection limit of 90 pg/mm2 was obtained with our proposed sensor. Therefore, we believe that our plasmonic capillary sensor could be a promising candidate to develop a simple, low-cost, label-free and portable biosensor.