Cellular biochemical parameters can be used to reveal the physiological and functional information of various cells. Pepstatin A in cell monitoring are covered. Driven by the need for high throughput and multi-parameter detection proposed by biomedicine the development trends of electrochemical cell-based biosensors are also introduced including newly developed integrated biosensors and the application of nanotechnology and microfluidic technology. monitoring 1 Introduction A living cell can be properly described as an electrochemical dynamic system . Due to various reduction-oxidation (redox) reactions and changes of ionic composition Pepstatin A and concentration  in biological processes cellular life activities are accompanied with electron generation and charge transfer which can be exploited using electrochemical methods to reveal information about changes in cell function as well as cell growth and development. In this case cell biochemical parameters such as concentrations of inorganic ions (H+ K+ Na+ Ca2+ Cl? [17 18 The ECIS technique  which has matured in cell morphology study  is greatly promoted by the microfabrication technology and thus diversification of electrode design is facilitated [21 22 23 Semiconductor technology stimulates the development of new cell-semiconductor hybrid biosensor systems such as the ion-selective field effect transistor (ISFET)  based on the properties of the electrolyte insulator semiconductor (EIS) system and another type of promising field effect transistor utilizing the electrolyte-semiconductor interface for achieving biosensing [25 26 Pepstatin Rabbit Polyclonal to BRP44L. A Among these LAPS  based on the photovoltage technique received extensive attention because of its good sensitivity stability and high signal-to-noise ratio. Using LAPS the response of cells to chemical substances is studied by monitoring the acidification of living cells  and changes in concentration of other inorganic ions . These miniaturized cell-based biosensor systems are capable of real-time noninvasive label-free measurements which guarantees the potential in on-line biochemical analysis of living cells and facilitates the development of new analytical instruments based on these biosensors. Here we start with the presentation of principles of biochemical cell-based biosensors including MEA ECIS and LAPS. Then their applications in biochemical monitoring of living cells are introduced combined with descriptions of MEMS technology and photovoltage technology. Finally we survey the developing trends of biochemical cell-based biosensors including the integration and multifunction requirements combined with hot topics about microfluidic technology and nanotechnology. 2 Principles of Electrochemical Cell-Based Biosensors 2.1 Theory and Structure of Microelectrode Array MEA is an electrochemical biosensor developed to detect the action potential (AP) in the extracellular microenvironment of cells. On an MEA a thin metallic film is fabricated Pepstatin A between a substrate of glass or silicon and a passivation layer with several electrode sites exposed for sensing the extracellular field potential changes generated by the objective cells. When spreading on the microelectrodes cultured cells adhere to the substrate. But there is still a minute volume of electrolyte between the cells and the microelectrodes; thus a solid-liquid Pepstatin A interface on the electrode surfaces is formed. The electrochemical properties of the interface are the basis of the sensing mechanism of MEA. According to the electric double layer (EDL) theory when a metal is placed into ionic liquid an equilibrium condition is established once the charge transfer between the metal and the solution is equal. The electric field on the interface generated by electron transfer causes the formation of an inner Helmholtz plane (IHP) and an outer Helmholtz plane (OHP). The net reaction induces the creation of an electric double layer which is also an electrified interface Pepstatin A describing the interphase region at the electrolyte boundary . The equivalent circuit of metal-electrolyte interface can be explained with the Randles model as shown in Figure 1(a). In the circuit an interfacial capacitance (CI) is in parallel with charge transfer resistance (Rt) and diffusion related Warburg element (RW and CW). The spreading resistance (RS) represents the effect of current spreading from the localized electrode to a distant counter electrode..