Development of Microfluidic Dilution Network-Based System for Lab-on-a-Chip Microalgal Bioassays.

Because of the crucial ecological significance of microalgae, microalgal bioassays have become one of the most demanding tests from all classic aquatic toxicity tests in regulatory frameworks. However, conventional algal tests tend to be lab-intensive and time- and space-consuming, and they have not been utilized to their full potential for routine toxicity assessments. Microfluidics should be a user-friendly alternative. Particularly, dilution to generate gradients that are appropriate for screening experiments can be precisely attained by microfluidic network in a simple and cost-/time-/space-saving way. Here, we demonstrate a microfluidics series toward routine microalgal bioassays, including pretest, single, and joint toxicity test. The chip mainly consists of upstream dilution network (single serial dilution module (logarithmic/linear gradient generator) or multiple (binary/ternary/quaternary) mixing serial dilution module) and downstream diffusible culturing module. It allows the processes of chemical liquid dilution and diffusion, microscale microalgal culture, cell stimulation, and online screening to be integrated into a single device. Electric theorems with the aid of EDA (electronic design automation) simulation were innovatively introduced to minimize design effort for such systems. Using the device, microalgae were successfully cultured and stressed on-chip. The simple assay provides multibiological trait assessments of cell division rate, autofluorescence, esterase activity, and mobile capacity. This work showed promise in developing a high-throughput microfluidic platform for microalgal bioassays as well as lab-on-a-chip screening experiments in the cell-based quantitative assessment of environmental health risks.