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This is a project that aims to expedite research in marine biology using chip-based and state-of-the-art detection technology. The project is a joint effort that will incorporate the expertise of three different groups, Dr. Chih-Ming Ho at UCLA, Dr. David Caron at USC and Dr. Yu-Chong Tai at Caltech. One main focus of the project is to develop Lab-on-a-chip devices that reduce total sample volume and detection time. Also, the chips can be fabricated in large quantities with minimal cost so many experiments can be run in parallel. Here at Caltech, a chip will be developed to culture a small number of algae and screen for factors inducing toxin production. Algal bloom and toxins produced by different algae have always caused problems to the environment and marine ecology. Pseudo-nitzschia is one type of algae that produces a neural toxin called Domoic Acid, which when transferred through the food chain causes sickness and mortality in marine mammals and seabirds. However, during Pseudo-nitzschia bloom, Domoic Acid is not always produced. In another word, growth of algae does not equal Domoic Acid production. Studies done by other groups have suggested that many factors (such as trace metal, macronutrient, or ionic concentration) might induce or suppress algae to produce toxin. Yet, exact causes are unclear. To completely elucidate the causes of toxin production, many potential compounds will have to be screened. This leads to an enormous amount of experiments to be performed and large quantity of reagents and cells to be used. To speed up the process of screening for possible factors inducing toxin production, we would like to make a chip to culture Pseudo-nitzschia under different growing conditions. At the same time, an Ultra Sensitive Electrochemical Sensor will be developed for detection of Domoic Acid at Dr. Chih-Ming Ho’s lab at UCLA. The current state-of-the-art detection technology indicates that per cell toxin load may range over 2 or 3 orders of magnitude but its sensitivity is limited since a sample size of at least 100 cells/mL is required. The new sensor will be able to push the sensitivity to 10 cells/mL or to even single molecules of Domoic Acid. This sensor will not only enable the detection of Domoic Acid produced by algae cells inside the culture chip, such sensor will also have the broad application of detecting Domoic Acid from field samples.

Lab-on-a-Chip aquatic microorganism analysis system is a project that aims to expedite research in marine biology using chip-based technology. The miniaturized device reduces the total sample and detection time. Also, the chips can be fabricated in large quantities with minimal cost so many experiments can be run in parallel. Our project is organized into two main research areas. First, we would like to develop a chip to monitor the content of the sea water and assess the concentration of different algae. The chip will take in sea water sample, separate the cells based on size, and a downstream impedance sensor will count the number of cells. The second main area of this project is to make a chip that can culture algae and screen for factors inducing toxin production. The exact causes for Peudo-nitzschia to produce toxins are unclear, and we would like to make a chip that cultures Pseudo-nitzschia under different growing conditions. The algae will be kept inside an array of micro culture chambers and an integrated combinatorial mixer will deliver eight combinatorial streams to the culture chambers. We developed a monolithic process to integrate the combinatorial mixer with culture arrays. The cell culturing functionality and fluidic testing with the chip have been completed. A laser-induced fluorescence detection system is also being developed to be used to detect domoic acid (DA) downstream of the algae culture chip.

With the confocal Laser induced fluorescent sensor developed in our lab concentrations as low as 5.9 fM can be detected. We will work with Professor Caron at USC and Professor Tai at Caltech to detect Amnestic shellfish poisoning (ASP) caused by ingestion of contaminated shellfish by Domoic Acid (DA) causes death both in human beings and animals when the contamination is higher than 20 ?g (64 ?Mole) of DA per gram of shellfish tissue. DA is produced by a number of algae, including microalgae of the genus Pseudo-nitzschia, and it is accumulated by shellfish filter feeding during Pseudo-nitzschia blooms. Competitive ELISA is used for DA detection down to 0.2 ng/mL. The detection limit not low enough, the confocal Laser induced fluorescent sensor is going to be used to detect lower concentrations of DA. In our sensor optics are used to define a very small detection volume. In this method, molecules of interest are labeled with fluorophores. A droplet of sample is added to the sensor. The target molecules which are conjugated with fluorescent molecules will move in and out of the detection volume by diffusion and Brownian motion. A photon burst is observed when the molecule passes the detection volume and the number of peaks per unit of time indicates the concentration of sample under study. Using the pinhole for confocal microscopy will reduce the background noise coming from the reflection and spurious fluorescence background and going to lower concentration down to single molecules will be made possible. The molecule under study can be easily changed with this sensor.