O.S. Larionovad, V.A. Feodorovaa Amplification of output signal of laser scanning speckle-microscope using gold nanoparticles: detection of a single chlamydial cell in a clinical sample O.V. Ulianovaa, N.N. Filonovaa, I.A. Subbotinaa, S.S. Ulyanova, b, L.A. Dykmanc, S.S. Zaytseva, Yu.V. Saltykova, O.S. Larionovad, V.A. Feodorovaa

AFFILIATION a Federal Research Center for Virology and Microbiology, Branch in Saratov RUSSIA b Saratov State University, RUSSIA c Institute of Biochemistry and Physiology of Plants and Microorganisms, Russian Academy of Sciences (IBPPM RAS), RUSSIA D Saratov State Agrarian University, RUSSIA

ABSTRACT Combined system “Chlamydia trachomatis bacterial cell”-“monoclonal antibody”-“gold nanoparticle” has been used as a complicated scattering element in the case of formation of biospeckles with a small number of scatterers. It has been demonstrated theoretically and experimentally, that signal of speckle microscope is increased drastically in the presence of gold nanoparticles. It has been demonstrated the unique possibility of detection of a single C. trachomatis cell in a clinical sample.

Demonstration of principles of speckle-microscopy

General view of speckle-microscope

Sample (with C. trachomatis bacterial cell, fixed on the microscope slide) on the speckle-microscope

Seria of three realizations of output signal of scanning microscope Scanning samples (fixed on the glass) containing C. trachomatis cells, connected with the conjugate “Chlamydial monoclonal antibody + gold nanopartickles (diameter = 20 nm)” (CT-Mab-Au)

#1 Appearance of peaks corresponds to the moment of scanning of immune nanocomplex CT-Mab-Au by strongly focused laser beam

#2 Appearance of peaks corresponds to the moment of scanning of immune nanocomplex CT-Mab-Au by strongly focused laser beam

#3 Appearance of peaks corresponds to the moment of scanning of immune nanocomplex CT-Mab-Au by strongly focused laser beam

Seria of three smoothed spectra obtained for three realizations of output signal of scanning microscope. Shapes of spectra are identical. Scanning samples (fixed on the glass) containing with C. trachomatis cells, connected with conjugate Mab-Au of 20 nm

#1

#2

#3

Testing of complexes, which contain and do not contain nanoparticles/(CT-Mab-Au)

Motionless sample, containing only CT cells (without immune complexes of chlamydial monoclonal antibody (Mab) with gold nanoparticles (Au)) This signal can be considered as a pure noise of measuring set-up. No any peaks, generated as a result of light scattering by Mab labelled with Au, are shown up in output signal.

Scanning of CT cells, connected with Mab and nanoparticles Peaks, produces by laser light scattering by CT-Mab-Au, are shown up in output signal

Scanning of CT cells, which do not bind with Mab and gold nanopatickes No peaks, produces by laser light scattering by CT-Mab-Au, are observable

Summary It is clearly demonstrated, that in the case when CT cells are by Mab labelled with gold nanoparticles, output signal of speckle microscope is essentially enhanced. It opens the way of detection of a single CT bacterial cell in the analyzing samples.

This research has been supported by Russian Science Foundation, ACKNOWLEDGEMENT This research has been supported by Russian Science Foundation, grant # 17-16-01099

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