Nano-biosensor based on the combined use of the dynamic and static light scattering for Aspergillus galactomannan analysis

A biosensor based on the analyte-induced aggregation of functionalized nanoparticles recorded using two optical signals of different physical nature is developed. The hydrodynamic diameter of the conjugates, measured by the dynamic light scattering (DLS) method, and the counting rate of scattered light pulses, proportional to the elastic static scattering intensity are used together as the analytical signals. This improves the accuracy and reliability of the obtained results. Both signals are determined in one measurement on a compact DLS analyzer, specially designed as a detecting device for optical nano-biosensors. The proposed approach was used to detect Aspergillus galactomannan, a marker of an invasive fungal infection that poses a serious threat for the lungs. The results of the determination of galactomannan in the culture fluid of Aspergillus fungi, bronchoalveolar lavage (BAL) as well as in the calibration solutions, prepared on the basis of blood plasma and galactomannan calibrator are presented. A good correlation of the data obtained using nano- biosensor with the results of ELISA is shown, while the sensitivity of the analysis is not inferior to ELISA, and sample preparation is significantly simplified and accelerated by eliminating the washing stage. The detection limit for galactomannan in BAL samples was 3 ng/ml when detecting by the hydrodynamic diameter and 0.4 ng/ml when detecting by the counting rate of scattered light pulses. The total duration of sample preparation and measurements for a set of 10 samples does not exceed 100 min. The developed nano- biosensor can be used for the point of care diagnostics.