Hua Cai

A novel biomimetic olfactory-based biosensor for single olfactory sensory neuron monitoring

This paper presents a novel biomimetic olfactory biosensor for the study of olfactory transduction mechanisms on the basis of light addressable potentiometric sensor (LAPS), in which rat olfactory sensory neurons (OSNs) are used as sensing elements. Rat OSNs are cultured on the surface of LAPS chip. To validate the origin of the electrical signals recorded by LAPS, the inhibitory effect of MDL12330A to the olfactory signals of OSNs is tested, which is the specific inhibitor of adenylyl cyclase. The enhancive effect of LY294002 to the responses of OSNs is also investigated, which is the specific inhibitor of phosphatidylinositol 3-kinase (PI3K). The results show that this hybrid biosensor can record the responses of OSNs to odours efficiently in a non-invasive way for a long term, and the responses can be inhibited by MDL12330A and enhanced by LY294002. All these results demonstrate that this hybrid biosensor can be used to monitor electrophysiology of OSNs in a non-invasive way and suggest it could be a promising tool for the study of olfactory transduction mechanisms.

A novel design of multifunctional integrated cell-based biosensors for simultaneously detecting cell acidification and extracellular potential.

The paper discussed a novel design of multifunctional cell-based biosensors for simultaneously detecting cell acidification and extracellular potential. Employing living cells such as cardiac myocytes as a source for the light addressable potentiometric sensor (LAPS) array, this cell-based biosensor was able to monitor both the acidification and extracellular potential in parallel. For LAPS array fabrication, part of the silicon base was heavily doped with boron to form separate testing areas. Detecting system was built involving lock-in amplifier and digital demodulation with FFT methods. This LAPS array showed a good sensitivity of 53.9 mV/pH to H(+) with good linearity. Each testing area for extracellular potential detection was decreased to 200 microm x 200 microm in size to obtain a better sensitivity. Experiment results showed that this LAPS array could monitor the acidification of cells as well as the extracellular potential with good sensitivity. This novel integrated biosensor will be useful for multi-parameter extracellular monitoring and can possibly be a platform for drug screening.

Olfactory receptor cells respond to odors in a tissue and semiconductor hybrid neuron chip

Olfactory systems of human beings and animals have the abilities to sense and distinguish varieties of odors. In this study, a bioelectronic nose was constructed by fixing biological tissues onto the surface of light-addressable potentiometric sensor (LAPS) to mimic human olfaction and realize odor differentiation. The odorant induced potentials on tissue-semiconductor interface was analyzed by sensory transduction theory and sheet conductor model. The extracellular potentials of the receptor cells in the olfactory epithelium were detected by LAPS. Being stimulated by different odorants, such as acetic acid and butanedione, olfactory epithelium activities were analyzed on basis of local field potentials and presented different firing modes. The signals fired in different odorants could be distinguished into different clusters by principal component analysis (PCA). Therefore, with cellular populations well preserved, the epithelium tissue and LAPS hybrid system will be a promising neuron chip of olfactory biosensors for odor detecting.

Extracellular recording of spatiotemporal patterning in response to odors in the olfactory epithelium by microelectrode arrays.

In olfactory biosensors, microelectronic sensor chips combined with biological olfactory cells are a promising platform for odor detection. In our investigation, olfactory epithelium stripped from rat was fixed on the surface of microelectrode arrays (MEAs). Electrophysiological activities of olfactory receptor neurons in intact epithelium were measured in the form of extracellular potentials. Based on multi-channel recording performance of MEA and structural and functional integrality of native olfactory epithelium, the spatiotemporal analysis was carried out to study the extracellular activity pattern of neurons in the tissue. The variation of spatiotemporal patterns corresponding to different odors displayed the signals firing image characteristic intuitionally. It is an effective method in the form of patterns for monitoring the state of tissue both in time and space domain, promoting the platform for olfactory sensing mechanism research.

High spatial resolution impedance measurement of EIS sensors for light addressable cell adhesion monitoring.

In this paper, impedance measurement of electrolyte-insulator-semiconductor (EIS) structure with high spatial resolution was proposed to monitor cell adhesion. The light addressing ability of this work overcomes the geometrical restrict of cell culture on conventional impedance detection devices such as interdigitated electrode (IDE) and electric cell-substrate impedance sensing (ECIS). Instead of studying cells on predetermined sites of IDE and ECIS, cells cultured anywhere on EIS sensor surface can be addressed and selected as target cells. Principle and primary models for high resolution impedance detection were described and tested by experiments. The EIS sensor was investigated in terms of its intrinsic characteristics, like impedance behavior, voltage characteristic, frequency dependency and photovoltaic effect. Optimized working condition was studied for cell experiments. Cell adhesion under treatment of 0.1% Triton X-100 was monitored using rat kidney cells as the source. Results showed good sensitivity (10% change of impedance) and resolution (40 μm) for cell adhesion impedance detection and suggested this work should be suitable for monitoring cell impedance. Further improvements on sensitivity, spatial resolution were discussed as well as the further applications for single cell monitoring and cell adhesion imaging.

Embryonic Stem Cells Biosensor and Its Application in Drug Analysis and Toxin Detection

To investigate the use of stem cells as biosensor elements, a novel cell-based light-addressable potentiometric sensor (LAPS) was developed for monitoring cellular beating. Mouse embryonic stem cells were induced to differentiate into cardiomyocytes in vitro. Extracellular field potentials of spontaneously beating cardiomyocytes induced from stem cells were recorded by LAPS in the potential and frequency ranges of 25-45 muV and 0.5-3 Hz, respectively. Due to its capability of monitoring important physiological parameters such as potential and frequency in vitro, the sensor can be used in drug analysis and toxin detection in a long-term and noninvasive way. The pharmacological and toxicological researches make it possible to use stem cells-based biosensor for biomedical assays.

The development of taste transduction and taste chip technology

The intrinsic perception process of taste is obviously far less known than those of vision, audition, touch and olfaction. Despite that taste cells utilize a variety of sensory mechanisms to translate plenty of gustatory sensations such as sour, sweet, bitter, salty and umami into cellular signals, gustatory perception mechanisms are still under exploration due to the lack of effective methods on cellular and molecular level. Recently the development of molecular biological and electrophysiological studies has promoted exploration of olfactory and gustatory transduction and coding mechanisms dramatically. Based on the studies of artificial olfaction, artificial taste and cell-based biosensor in our laboratory, this paper reviews the current research on taste transduction mechanism. We introduce the recent advances in cell chip that combined biology with microelectronics, discuss taste cell chip as well as its potential of prospective application in taste transduction mechanism in detail and propose the research trends of taste chip in future.

DESIGN OF MICROPHYSIOMETER BASED ON MULTIPARAMETER CELL-BASED BIOSENSORS FOR QUICK DRUG ANALYSIS

Cellular metabolism arouses the changes of substance in extracellular physiological micro-environment, and the metabolic level reflects the physiological state of cells. This paper developed a novel microphysiometer automatic analysis instrument based on multiparameter cell-based biosensors for quick drug analysis. This study included the multiparameter cell-based biosensors, cell culture chamber, drug auto-injection detection and analysis. The analysis instrument was capable of real-time detection for the acidic product and other chemical parameters generated by the cellular metabolism in the micro-volume. Finally, the paper employs human breast cancer cell line MCF-7 and drug experiments to verify the performance of microphysiometer, and study effects of different drugs on cell metabolism. Further, the research explores drug analysis method of the multiparameter microphysiometer. The results showed that the cell-based microphysiometer system provides a utility platform for rapid, long-term and automatic cell physiological environment detection and drug analysis.

A photovoltage-based integrated sensor for nephrotoxicity evaluation under drug stimulation

A monolithically integrated sensor based on photovoltage technique is developed for kidney metabolism detection under drug toxicity. The sensor utilizes the light-addressable potentiometric sensor with an electrolyte-insulator-semiconductor (EIS) structure for measuring cellular metabolic rate, and a gold metal layer is deposited on partial surface of silicon dioxide for extracellular redox (reduction-oxidation) potential detection. The neonatal rats kidney cells are confined to a flow chamber with a volume of 50 µl, in which the constructed sensor continuously monitoring the rate of acid metabolites, and the redox potential in extracellular microenvironment. The synthesis parameters detected reflect the cellular metabolic and active condition after drug stimulation, which demonstrates the potentials for nephrotoxicity evaluation and preclinical drug screening.

The Study on Bionic Olfactory Neurochip Based on Light-addressable Potentiometric Sensor

Olfactory system can distinguish thousands of odors. In order to utilize biological olfactory neurons as sensitive material of electronic nose, this article reports an olfactory neurochip as real bionic technique for odorants detection. Effective cultures of olfactory receptor neurons and olfactory bulb cells on the chip have been achieved. Using light-addressable potentiometric sensor (LAPS) as sensing chip to monitor extracellular potential of the neurons, we tested the response under stimulations of the odorants or neurotransmitters, such as acetic acid and glutamic acid. The results demonstrate that this kind of the LAPS and olfactory neurons hybrid system is sensitive to environmental changes, which has potential to be used as a novel bioelectrical nose for detecting odors