Journal of Chromatography A, 1111 (2006) 228–232 Monitoring of intercellular messengers released from neuron networks cultured in a microchip Kiichi Sato a,1 , Akiko Egami b , Tamao Odake a,2 , Manabu Tokeshi a , Makoto Aihara c , Takehiko Kitamori a,b,d,∗ a Kanagawa Academy of Science and Technology, Sakado, Takatsu, Kawasaki 213-0012, Japan b Department of Applied Chemistry, School of Engineering, The University of Tokyo, Hongo, Bunkyo, Tokyo 113-8656, Japan c Faculty of Medicine, The University of Tokyo, Hongo, Bunkyo, Tokyo 113-0033, Japan d Core Research for Evolutional Science and Technology, Japan Science and Technology Corporation, Honcho, Kawaguchi, Saitama 332-0012, Japan Available online 26 July 2005 Abstract A cellular biochemistry analysis system was integrated on a quartz glass microchip with a microchamber for cell culture followed by a microchannel for detecting with a thermal lens microscope (TLM). Nerve cells from rat hippocampus were successfully cultured to form neural networks in the microchip. An aqueous solution of glutamate, which is known as a neurotransmitter, was introduced to stimulate the cultured neuron to release a retrograde messenger, arachidonate which is considered to be critical for neuronal plasticity, especially for long-term potentiation (LTP). After the introduction, the solution that flowed through the culture chamber was analyzed using the UV-TLM (excitation wavelength, 244 nm). The measured signal intensity was dependent on glutamate solution concentration, and the neurons were considered to release the retrograde messenger according to the glutamate concentration. This system is suitable for time-course monitoring of ultra trace amounts of chemicals released from very small amount of cultured cells. © 2005 Elsevier B.V. All rights reserved. Keywords: Microchip; Cell culture; Neuron network; Thermal lens microscope; Cell response monitoring 1. Introduction Microchip-based systems have desirable characteristics, such as lower consumptions of reagents and samples, smaller space requirements, and shorter analysis time. Applications of these systems, widely known as micro total analysis sys- tems (-TAS) [1] or lab-on-a-chip [2], have been spreading rapidly. We have demonstrated many applications, including flow-injection analyses, solvent extractions, and microreac- tors [3,4]. In these systems, full advantage was taken of the Abbreviation: TLM, thermal lens microscope ∗ Corresponding author. Fax: +81 3 5841 6039. E-mail address: kitamori@icl.t.u-tokyo.ac.jp (T. Kitamori). 1 Present address: Department of Applied Biological Chemistry, School of Agricultural and Life Sciences, The University of Tokyo, Yayoi, Bunkyo, Tokyo 113-8657, Japan. 2 Present address: Chemistry Department, Faculty of Engineering, Gunma University, Tenjin-cho, Kiryu, Gunma 376-8515, Japan. scale merits of the microspace, i.e. a short diffusion distance, a large specific interface area, and a rapid and efficient reaction. Moreover, by combination of the micro unit operations con- nected with pressure-driven flow, a complex chemical system, i.e. continuous flow chemical processing (CFCP), can be con- structed. We have reported that CFCP has a great potential to realize various chemical systems consisting of reaction, extraction and analysis, easily and efficiently, without trou- blesome mechanical operations. The major advantages of these microchip-based systems accrue especially to biochem- ical applications. We have demonstrated rapid and sensitive immunoassay systems for protein analyses [5–8]. Microchip techniques also appear to provide some advan- tages for cellular biochemical analysis systems, because the scale of the liquid microspace inside a microchip is fitted to the size of the cells. For microchambers fabricated on microchips, rapid and secure exchange of media or reagents will be achieved by simple operations under continuous 0021-9673/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.chroma.2005.06.099