Lidan Xiao

Impedance studies of bio-behavior and chemosensitivity of cancer cells by micro-electrode arrays

Impedimetric analysis on adherently growing cells by micro-electrodes provides information related to cell number, cell adhesion and cellular morphology. In this study, cell-based biosensor with micro-electrode arrays (MEAs) was used to monitor the culture behavior of mammalian cancer cells and evaluate the chemosensitivity of anti-cancer drugs using electrochemical impedance spectroscopy. The platinum electrode arrays were fabricated by semiconductor technology to a 10 x 10 pattern, with diameter of 80 microm of each electrode. The human oesophageal cancer cell lines (KYSE 30) were cultured on the surface of the electrodes with the pre-coated fibronectin, the connecting protein for tumor cells metastasis and adhesion in extracellular matrix. Morphology changes during cells adhesion, spreading, and proliferation can be detected by impedimetric analysis in a real time and non-invasive way. Cisplatin was added to cells for potential drug screening applications. The experimental results show that this well-known anti-cancer drug has characteristic chemosensitivity effects on KYSE 30 cells which can be detected by MEA. Thus, this cell-based chip provides a useful analytical method for cancer research.

Extracellular potentials recording in intact olfactory epithelium by microelectrode array for a bioelectronic nose

Human beings and animals have sensitive olfactory systems that can sense and identify a variety of odors. The purpose of this study is to combine biological cells with micro-chips to establish a novel bioelectronic nose system for odor detection by electrophysiological sensing measurements of olfactory tissue. In our experiments, 36-channel microelectrode arrays (MEAs) with the diameter of 30 microm were fabricated on the glass substrate, and olfactory epithelium was stripped from rats and fixed on the surface of MEA. Electrophysiological activities of olfactory receptor neurons in intact epithelium were measured through the multi-channel recording system. The extracellular potentials of cell networks could be effectively analyzed by correlation analysis between different channels. After being stimulated by odorants, such as acetic acid and butanedione, the olfactory cells generate different firing modes. These firing characteristics can be derived by time-domain and frequency-domain analysis, and they were different from spontaneous potentials. The investigation of olfactory epithelium can provide more information of olfactory system for artificial olfaction biomimetic design.

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.

Covalently immobilized biomolecule gradient on hydrogel surface using a gradient generating microfluidic device for a quantitative mesenchymal stem cell study

Precisely controlling the spatial distribution of biomolecules on biomaterial surface is important for directing cellular activities in the controlled cell microenvironment. This paper describes a polydimethylsiloxane (PDMS) gradient-generating microfluidic device to immobilize the gradient of cellular adhesive Arg-Gly-Asp (RGD) peptide on poly (ethylene glycol) (PEG) hydrogel. Hydrogels are formed by exposing the mixture of PEG diacrylate (PEGDA), acryloyl-PEG-RGD, and photo-initiator with ultraviolet light. The microfluidic chip was simulated by a fluid dynamic model for the biomolecule diffusion process and gradient generation. PEG hydrogel covalently immobilized with RGD peptide gradient was fabricated in this microfluidic device by photo-polymerization. Bone marrow derived rat mesenchymal stem cells (MSCs) were then cultured on the surface of RGD gradient PEG hydrogel. Cell adhesion of rat MSCs on PEG hydrogel with various RGD gradients were then qualitatively and quantitatively analyzed by immunostaining method. MSCs cultured on PEG hydrogel surface with RGD gradient showed a grated fashion for cell adhesion and spreading that was proportional to RGD concentration. It was also found that 0.107-0.143 mM was the critical RGD concentration range for MSCs maximum adhesion on PEG hydrogel.

An olfactory bulb slice-based biosensor for multi-site extracellular recording of neural networks

Multi-site recording is the important component for studies of the neural networks. In order to investigate the electrophysiological properties of the olfactory bulb neural networks, we developed a novel slice-based biosensor for synchronous measurement with multi-sites. In the present study, the horizontal olfactory bulb slices with legible layered structures were prepared as the sensing element to construct a tissue-based biosensor with the microelectrode array. This olfactory bulb slice-based biosensor was used to simultaneously record the extracellular potentials from multi-positions. Spike detection and cross-correlation analysis were applied to evaluate the electrophysiological activities. The spontaneous potentials as well as the induced responses by glutamic acid took on different electrophysiological characteristics and firing patterns at the different sites of the olfactory bulb slice. This slice-based biosensor can realize multi-site synchronous monitoring and is advantageous for searching after the firing patterns and synaptic connections in the olfactory bulb neural networks. It is also helpful for further probing into olfactory information encoding of the olfactory neural networks.

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.

A transcutaneous controlled magnetic microvalve based on iron-powder filled PDMS for implantable drug delivery systems

This paper reports a magnetic microvalve based on iron-powder filled polydimethysiloxane (PDMS) for implantable drug delivery systems, which allows transcutaneous control when implanted under the skin. It does not require any implanted power source or receiver including batteries, RF coils, piezoelectric materials, etc. Only a magnet is required to open the microvalve for drug delivery. A pressurized balloon reservoir is used to pump the drug when the microvalve is open. This simplifies the structure design and reduces components for implanted devices. Only a single mask is required to define the silicon cavity for valve plug and legs with different width and depth when anisotropic etching with potassium hydroxide (KOH) is used. The defined silicon cavity was then filled with PDMS that has been mixed with iron-powder to form the body of valve plug and legs. After removing the excess material by a blade, the magnetic microvalve is finished. The microvalve was packaged with transparent acrylic for making valve channels for testing with a permanent magnet to open the valve by magnetic force.

An integrated label-free cell-based biosensor for simultaneously monitoring of cellular physiology multiparameter in vitro.

The study presented a novel integrated cell-based biosensor with light-addressable potentiometric sensor (LAPS) and electrical cell-substrate impedance sensor (ECIS). The integrated cell-based biosensor was fabricated in order to monitor the cellular metabolism and growth status by LAPS and ECIS. Moreover, the specific instrument was established for controlling the detection processes. Sensor test and cell experiments were carried out to determine the performance of integrated sensor. The result showed that integrated biosensor can monitor the change of cell electrical impedance and extracellular acidification simultaneously which can be used for drug evaluation by monitoring cell growth status (e.g. cell number, adhesion, and morphology) and cell energy metabolism status (e.g. extracellular acidification) in real time. With the development of sensor technology, the integrated cell-based biosensor will be a utility platform to study the mechanism of cellular metabolism and in vitro drug analysis.

Micro-Electrode Cell-Based Biosensor Using Electrochemical Impedance Spectroscopy for Cancer Research

In this study, cell biosensor chip with microelectrode arrays was used to monitor the culture behaviour of mammalian cancer cells and evaluate the chemosensitivity of anti-cancer drugs using electrochemical impedance spectroscopy. The electrode arrays were fabricated by semiconductor technology with diameter from 50 μm to 10 μm of each electrode. The human oesophageal cancer cell lines (KYSE 30) were cultured on the surface of the electrode with the help of fibronectin. Morphology changes of cells adhesion, spreading, and proliferation can be detected by impedimetric analysis in a real time and non-invasive way. Anti-caner drug of cisplatin was added to cells for potential drug screening applications. The experimental results show that drug’s chemosensitivity effects can be detected by this cell based biosensor.

A strain gauge that uses carbon black and carbon nanotube doped silicone oil encapsulated in a PDMS microchannel

We present a piezoresistive strain gauge fabricated using electrically conductive silicone oil encapsulated in a close volume polydimethylsiloxane (PDMS) microchannel. The conductive silicone oil is made using carbon black and carbon nanotube to dope the silicone oil to become conductive. A characteristic of the electrical resistance versus the applied pulling force was measured. The non-linear behavior was due to the large deformation of the strain gauge, which makes the second order term of the increasing gauge length can not be ignored. An exponentially decrease of the resistance was found when applying a biasing voltage without exerting a force. It is caused by the reorganization of the carbon black particles in the silicone oil with applying electrical field. Temperature change also gave effect on the strain gauge with positive and negative temperature coefficients (PTC and NTC) with turning point at 55degC.