Identification of coexistence of biological and non-biological aerosol particles with DAPI (4′,6-diamidino-2-phenylindole) stain--颗粒学报PARTICUOLOGY

Liu, T., Zhang, J., Cao, J., Zheng, H., Zhan, C., Liu, H., . . . Zhang, D. (2023). Identification of coexistence of biological and non-biological aerosol particles with DAPI (4′,6-diamidino-2-phenylindole) stain. Particuology, 72, 49-57. https://doi.org/10.1016/j.partic.2022.02.009

Identification of coexistence of biological and non-biological aerosol particles with DAPI (4′,6-diamidino-2-phenylindole) stain

Ting Liu ^a *, Jiaquan Zhang ^a, Junji Cao ^b, Han Zheng ^a, Changlin Zhan ^a, Hongxia Liu ^a, Lili Zhang ^a, Kai Xiao ^a, Shan Liu ^a, Dong Xiang ^c, Daizhou Zhang ^d

a School of Environmental Science and Engineering, Hubei Polytechnic University, Hubei Key Laboratory of Mine Environmental Pollution Control and Remediation, Huangshi 435003, China
b Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
c School of Computer Science and Artificial Intelligence, Wuhan University of Technology, Wuhan 430063, China
d Faculty of Environmental and Symbiotic Sciences, Prefectural University of Kumamoto, Kumamoto 862-8502, Japan

10.1016/j.partic.2022.02.009

Volume 72, January 2023, Pages 49-57

Received 23 January 2022, Revised 10 February 2022, Accepted 11 February 2022, Available online 2 May 2022, Version of Record 2 May 2022.

E-mail: tingliu_hbpu@hotmail.com

Highlights

• Specific filter sets can be used to separate signals for the identification of DAPI stained particles.

• Biological particles appeared blue under a DAPI-BP filter set (excitation 350/50 nm, emission 460/50 nm bandpass).

• Mineral particles were transparent under a DAPI-BP filter set.

• Biochar, soot, metal, and fly ash particles were black under a DAPI-BP filter set.

• Two salt particles were yellow under a DAPI-LP filter set (excitation 340–380 nm, emission 425 nm long pass).

Abstract

The fluorescent dye 4′,6-diamidino-2-phenylindole (DAPI) has been widely used to stain microorganisms in various environment media. We applied DAPI fluorescence enumeration to airborne microorganisms and found that non-biological particles, including organic compounds, minerals, and soot, were also visible upon exposure to UV excitation under fluorescence microscope. Using laboratory-prepared biological particles as the control, we investigated the feasibility of identifying both biological and non-biological particles in the same sample with DAPI staining. We prepared biological (bacterial, fungi, and plant detritus) and non-biological (biochar, soot, mineral, metal, fly ash, salt) particles in the laboratory and enumerated the particles and their mixture with DAPI. We found that mineral particles were transparent, and biochar, soot, metals and fly ash particles were black under a filter set at excitation 350/50 nm and emission 460/50 nm bandpass (DAPI-BP), while biological particles were blue, as expected. Particles of the water-soluble salts NaCl and (NH₄)₂SO₄ were yellow under a filter set at excitation 340–380 nm and emission 425 nm long pass (DAPI-LP). Case studies with samples of dustfall, atmospheric aerosols and surface soils could allow for the quantification of the relative number of different types of particles and particles with organic matter or salt coating as well. Fluorescence enumeration with DAPI stain is thus able to identify the co-existence of biological and non-biological particles in the air, at least to the extent of those examined in this study.

Graphical abstract

Keywords

4′,6-diamidino-2-phenylindole (DAPI); Biological particles; Non-biological particles; Atmospheric aerosols

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