Fluorophore microbeads are widely used in biomolecule detection/quantification, flow tracing reference for gases and liquids, pathogen detection, and other life science applications [1, 2]. Often multiple fluorophores need to be simultaneously detected using spectral multiplexing detection system which is typically operated at a single excitation wavelength with multiple fluorescent emission filters or vice versa [3]. However, it significantly limits the use of different fluorophores since they have different absorption and emission peak wavelengths. Here, we propose a portable multi-excitation fluorometer combined with 12 different bandpass emission filters that can a viable option for detecting multiple fluorophores. Six fluorophore microbeads were selected as target subject for this study: Nile blue, FITC, Cy3, Cy5, Quinine, and Rhodamine B.

The sensing system has six excitation light sources for stimulating different fluorophore microbeads in a solution. Each fluorophore bead has different peak absorption and excitation spectra enabling particle differentiation by measuring fluorescent responses under different excitation lights. A PDMS microfluidic chip technology was used to load an aliquot volume of the sample. A highly sensitive silicon photomultiplier tube (SiPM), MicroFC (SensL Inc., Cork, Ireland), was used to detect corresponding fluorescence signals from each fluorophore microbead. A filter wheel containing 12 different bandpass filters controlled by microprocessor was deployed above SiPM to selectively measure corresponding fluorescent signals, as illustrated in the figure.

In summary, we have developed an LED-based portable fluorescent sensing system that is capable of differentiating multiple fluorophore microbeads. Future work includes full characterization of the sensor system and fabrication of integrated electronic circuitry for a standalone and field-deployable fluorometer.

References

[1] Dai, C. et al. American Journal of Infection Control43, (2015), 78-81.

[2] Wu, S., Duan, N., Shi, Z., Fang, C. and Wang, Z. Analytical chemistry86, (2014), 3100-3107.

[3] Wan, Y., Sun, Y., Qi, P., Wang, P. and Zhang, D. Biosensors and Bioelectronics 55, (2014), 289-293.