Abstract
Detection of living microalgae cells is very important for ballast water treatment and analysis. Chlorophyll fluorescence is an indicator of photosynthetic activity and hence the living status of plant cells. In this paper, we developed a novel microfluidic biosensor system that can quickly and accurately detect the viability of single microalgae cells based on chlorophyll fluorescence. The system is composed of a laser diode as an excitation light source, a photodiode detector, a signal analysis circuit, and a microfluidic chip as a microalgae cell transportation platform. To demonstrate the utility of this system, six different living and dead algae samples (Karenia mikimotoi Hansen, Chlorella vulgaris, Nitzschia closterium, Platymonas subcordiformis, Pyramidomonas delicatula and Dunaliella salina) were tested. The developed biosensor can distinguish clearly between the living microalgae cells and the dead microalgae cells. The smallest microalgae cells that can be detected by using this biosensor are 3 μm ones. Even smaller microalgae cells could be detected by increasing the excitation light power. The developed microfluidic biosensor has great potential for in situ ballast water analysis.
Highlights
Ships’ ballast water is one of the common sources of the oceanic biological invasions
This paper presents a novel method of detecting the cell activity and counting the number of single microalgae cells in a microfluidic chip based on non-modulated chlorophyll fluorescence
In order to demonstrate that the method and the system developed in this study can detect the chlorophyll fluorescence of an individual cell, both alive and dead Karenia mikimotoi Hansen cells were tested
Summary
Ships’ ballast water is one of the common sources of the oceanic biological invasions. The detection of algae cell activity (as an indication of cell’s liveliness) and the determination of the concentration of live algae are necessary. Major methods for detecting the activity of single microalgae and counting the algae in ballast water include optical microscopy, fluorescent microscopy, chlorophyll-a fluorometers and flow cytometry. Microfluidic chips or Labs-on-a-Chip (LOCs) are a promising technique for fast in situ detection of small amounts of samples They are applied widely in chemistry, biology, medicine and the environment [12–23]. As the photosynthesis activity of a plant cell indicates the cell’s liveliness, it can be used to determine if the algae cells are alive or dead. This paper presents a novel method of detecting the cell activity and counting the number of single microalgae cells in a microfluidic chip based on non-modulated chlorophyll fluorescence. The detection limit for the minimum size of microalgae using the developed system is explored in this paper
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