The data showed that a reduce concentration of 2nd Ab resulted in reduce signal intensity and a poor correlation. diagnostics and for monitoring highly infectious diseases [1]. Infectious diseases, such as the avian influenza computer virus, severe acute respiratory syndrome (SARS), hand-foot-and-mouth disease, influenza H1N1 and H7N9 are all threats to human being health/existence and collectively cause losses to interpersonal/economic development [2,3]. Consequently, developing methods for the quick on-site assay of these diseases at an early stage is extremely important. The enzyme-linked immunosorbent assay (ELISA) is one of the most widely used approaches in medical diagnostics, food security screening, and environmental monitoring [4,5]. The technique is usually carried out inside a 96-well microtiter plate and involves a series of tedious processes, including sample introduction, incubation and washing. Moreover, substantial amounts of sample are consumed and the method is definitely time-consuming and sometimes suffers from low level of sensitivity [6]. In order to conquer these drawbacks, numerous efforts have been devoted to developing new methods for diagnostic immunoassays. For example, ELISAs have been integrated having a micro/nano system to increase the surface/volume percentage and improve reaction kinetics [7C9]. A variety of materials, such as quantum dots [10], photonic crystals [11], Protopanaxatriol membranes [12] or papers [13], have also been used in conjunction with immunoassays. On the other hand, the microfluidic technique, with its advantages of miniaturization and integration has also been widely exploited for use in immunoassays [14]. However, in Protopanaxatriol the microfluidic-based immunoassay, a single microchannel is usually used as the operating space for an immunoassay [15] and this has the limitation of a small working surface. Similarly, a glass plate or glass capillary, which have also been exploited for use in immunoassays [16,17] also have limitations in that a flat surface or a single channel is used. Interestingly, a MCP with uniformly paralleled microchannels would be an ideal candidate for use in an immunoassay. Such a material has been used for DNA hybridization reactions [18], in which MCP showed substantial advantages over flat glass, in terms of its higher sensitivity and a faster hybridization rates. We previously reported on the use of MCP combined with a microbead-based chemiluminescence immunoassay [19], in which it simply acted as a switch for bonding/free protein separation. However, the use of the inner surface of the MCP, which can increase the immobilization capacity of an antibody to improve the reaction efficiency of an immunoassay, does not appear to have been utilized. We report herein around the development of a compact immunoassay utilizing microchannels within the MCP, which has a large surface area and high surface-to-volume. Thus, the MCP ratio could not only increase coating capacity, but also accelerate an assay. The method would Protopanaxatriol be expected to decrease overall immunoassay time because of the short diffusion distance in the microchannels of the MCP. The compact immunoassay system shows considerable potential in terms of velocity and high-sensitivity for on-site diagnosis and for rapidly monitoring a disease. 2.?Experimental Section 2.1. Reagents and Apparatus A human IgA kit, including affinity purified goat anti-human IgA (1st Ab), a human reference serum answer and goat anti-human IgA HRP conjugated (2nd Ab), was obtained from Bethyl Laboratories (Montgomery, TX, USA). Bovine serum albumin (BSA) was obtained from Merck (Calbiochem, Darmstadt, Germany). 10-Acetyl-3,7-dihydroxyphenoxazine (Amplex? Red reagent) was purchased from Life Technologies (Invitrogen, Eugene, OR, USA). It was dissolved in dimethylsulfoxide (DMSO) to a concentration of 13.8 mmol/L for use as a storage answer and was stored in refrigerator at ?20 C prior to use. The working substrate answer of Amplex? Red was prepared by mixing with phosphate-buffered saline (PBS) buffer (pH = 7.4) and H2O2 answer just before use. Na2HPO4, NaH2PO4 and H2O2 were purchased from Wako Pure Chemical Industries Ltd. (Osaka, Japan). Washing EIF2B buffer (PBST) was prepared with 0.5% (w/v) BSA/0.1% (v/v) Tween-20 (Kanto Chemical Co., Inc., Tokyo, Japan) in 100 mmol/L PBS (pH = 7.4). 10 mmol/L NaOH (Kanto Chemical Co., Inc.) and 10 mmol/L HCl (Wako Pure Chemical Industries Ltd.) were prepared for the cleaning of the MCP. All solutions and buffers were prepared with deionized water purified by Milli-Q system from Nihon Millipore (Tokyo, Japan). All buffers used in the experiments were filtered through 0.45 m membrane filter (Jhwpo 4700, Nihon Millipore). A neutral detergent (TCN-5) used for plate cleaning was obtained from Tomisc Company (Tokyo, Japan) A polydimethylsiloxane (PDMS) kit (Silpot 184) was obtained from Dow Corning Toray (Tokyo, Japan). MCP (1 mm in thickness, effective area 20 20 mm, capillary inner diameter 20 m) was obtained from the Incom Company (Charlton, MA, USA). A Branson.