As shown in Figure  7, Fluo-4 with a concentration of 10 8 μM flo

As shown in Figure  7, Fluo-4 with a concentration of 10.8 μM flowed in channel B in a continuous phase with an apparent velocity of 40 μm/s, while calcium chloride with a concentration of 5 mM was filled in channel A. As soon as the voltage was applied across the nanochannel array, Fluo-4 bonded with the calcium ions resulting in an enhanced fluorescent intensity.

The feeding quantity of the calcium ion was controlled by the effective percentage of the applied voltage with a duty cycle varying from 50% to 100%. In other words, the larger the duty cycles, the brighter (fluorescent intensity) the fluid in channel B, as indicated by comparing Figure  7a to Figure  7c. All optical images taken were at equilibrium state. Figure 7 Still optical images capturing the reaction between Fluo-4 (in channel B) and Ca 2+ (in MM-102 supplier Selleckchem ARS-1620 channel A). The reaction is in a continuous phase and controlled by the square wave with different duty cycles: (a)

50%, (b) 75%, (c) 100%. Calcium ion (Ca2+) is an important intracellular information transfer substance. Intracellular regulation of calcium is an important second messenger, which is widely involved in cell motility, secretion, metabolism, and differentiation of a variety of cellular functions. An accurate control of the extracellular calcium concentration is significant in many biological studies. Therefore, a real-time system with dynamic control of the calcium concentration is of great significance. We herein demonstrated the capability of our nanofluidic device for precise control of calcium concentration for biological systems. Conclusions We have demonstrated that a simple nanofluidic device fabricated on a Si wafer with a thin layer of SiO2 and then sealed by a PDMS thin film has its potential for constructing a picoinjector. The bonding between the Si wafer and ALOX15 PDMS relies on the adhesion force other than chemical bonding. Therefore, it is easy to separate them, and the silicon chip could be cleaned to use repeatedly. The injection process is based on the electroosmotic flow generated by the voltage bias across the nanochannels. The EO pumping rate was measured by analyzing

the fluorescent intensity when the fluorescent probe (FITC) was used in PBS as an indicator. The variations in EO flow rate at different DC voltages and different analyte concentrations were JNK-IN-8 ic50 investigated, and the results exhibited good agreement with the existing theory. The precisely controlled reaction between Fluo-4 and calcium ions was used to demonstrate our device’s potential application in electrochemical reaction, biochemical reaction, DNA/protein analysis, drug delivery, and drug screening. The electroosmotic effect dominates the fluid transport in our picoinjector, and electroosmosis allows our device to attain precision in fluid transport for chemical reaction on a nanoscopic scale using low DC bias voltage.

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