The press release from Tokushima University and Kochi University of Technology, Japan, discusses the development of a new optical biosensor that uses dual optical combs for high sensitivity and rapid detection of biomolecules. This biosensor, which has potential applications in detecting infectious pathogens, health monitoring, and environmental hormones, is based on the principle of signal conversion using optical methods.
The researchers used optical frequency combs to overcome limitations in traditional sensing methods. The optical frequency comb has a highly discrete multi-spectrum, which allows it to be used as a reference for optical frequency guaranteed by an electrical frequency standard. This makes electrical frequency-readout optical biosensing feasible, enabling high-precision measurements and offering advantages such as speed and simplicity.
The research also addressed a significant challenge in optical biosensors: temperature drift, which affects the sensor signal due to variations in ambient temperature. To mitigate this, the researchers used active-dummy temperature compensation, a method commonly used in strain gauge temperature compensation. This involved preparing two identical biosensing optical combs in a dual-comb configuration, with one measuring both sample concentration and temperature changes (active), and the other measuring only temperature changes (dummy).
The experimental setup involved preparing pairs of fiber-optic comb resonators and placing fiber biosensors within these resonators. The electrical frequency signals from the active and dummy sensing optical combs were measured with high precision relative to a rubidium frequency standard. The difference frequency signal was then calculated.
The researchers applied this technique to the detection of the novel coronavirus N protein antigen. The results showed that it was possible to measure sample concentration changes without the influence of temperature drift. The detection limit of 37 aM could be achieved within the measurement time of 10 minutes.
In summary, the researchers achieved a world-first by developing an optical comb-based biosensor with high sensitivity and rapid detection capabilities. The use of active-dummy temperature compensation significantly mitigated temperature drift, enabling the development of a SARS-CoV-2 biosensor with a balance between high sensitivity and rapidity.
1. The press release is from Tokushima University and Kochi University of Technology, Japan. It discusses a successful optical biosensing technique using dual optical combs, demonstrating high sensitivity and rapid detection of biomolecules.
2. A biosensor is a device capable of quantitatively or selectively measuring biomolecules by mimicking the molecular recognition abilities of living organisms. It has applications in detecting infectious pathogens like SARS-CoV-2, health monitoring like blood glucose measurement, and the detection of environmental hormones.
3. Biosensors typically consist of a sensing component for molecular recognition and a transducer component for signal conversion. Optical biosensors perform signal conversion using optical methods and possess characteristics like environmental robustness, high precision, and high sensitivity.
4. The detection in Surface Plasmon Resonance (SPR) sensors involves measuring a shift in the reflected light spectrum dependent on sample concentration. This is achieved by directing light onto a thin gold film coated prism, surface-modified with a biomolecular recognition layer.
5. In traditional methods, high-sensitivity sensing was carried out using light, and the readout was accomplished through optical signals. However, device resolution constrained sensing performance due to the optical spectrum shift being often minute compared to the spectral width.
6. To address these limitations, this research performed high-sensitivity sensing using light and high-precision readout using electrical signals. It focused on optical frequency combs as a means to overcome these limitations.
7. The optical frequency comb (optical comb) possesses a highly discrete multi-spectrum characterized by numerous optical frequency mode sequences arranged at equal intervals in a comb-like pattern.
8. By phase-synchronizing the carrier-envelope offset frequency and the frequency spacing to an electrical frequency standard through laser control, it becomes possible to transfer their uncertainties to the left-hand optical frequency signal, allowing the optical comb to be utilized as a reference for optical frequency guaranteed by an electrical frequency standard.
9. When optical fiber sensors are placed within the fiber optic comb resonator, the sample concentration-dependent optical spectrum shift is converted into an electrical frequency signal based on the equation. The optical comb functions as a frequency converter from light to electricity, making electrical frequency-readout optical biosensing feasible.
10. One remaining challenge in optical biosensors is the temperature drift of sensor signals. To mitigate this temperature drift, active-dummy temperature compensation was employed. This concept was applied to the biosensing optical comb. Identical biosensing optical combs were prepared in a dual-comb configuration.
11. The experimental setup involved pairs of fiber-optic comb resonators and fiber biosensors placed within these resonators. The electrical frequency signals from the active sensing optical comb and the dummy sensing optical comb were measured with high precision relative to a rubidium frequency standard as a reference.
12. The difference frequency signal was then calculated. The study showed that it is possible to measure sample concentration changes without the influence of temperature drift.
13. The relationship between sample concentration and sensor signal was plotted using red dots. Fitting was performed on this plot using a theoretical model function, and the detection limit was calculated. It was confirmed that a detection limit of 37 aM could be achieved within the measurement time of 10 minutes in this study.
14. The optical-to-electrical frequency conversion capability of the optical comb enabled the application of optical comb-based biosensors (a world-first achievement). Active-dummy temperature compensation using a dual optical comb configuration significantly mitigated temperature drift.
15. In the SARS-CoV-2, a balance between high sensitivity and rapidity was achieved.