Segment fusion chip calorimetry: a new method for the investigation of fast reactions

The development of the segment-flow technology has considerably extended the application range of miniaturized calorimeters. The transport of samples in aqueous µL segments by a water-immiscible carrier liquid enables the investigation of aggregated, complex biological samples in flow-through. The protection from contaminations of the fluidics of the calorimeter by the carrier liquid is an excellent precondition for the design of efficient automatic experiment protocols. In this paper, a new operation mode of this technique is presented, which allows the measurement of fast transient heat-dissipating processes using a chip calorimeter. Heat dissipation is initiated by the merging of separate µL-sample-segments arriving successively at the measuring chamber. The potential of the segment fusion technique was demonstrated here using two different applications. First, we showed the use of this method for an automatic screening of the strength of receptor–substrate interactions by the measurement of the heat of the adduct formation of carbohydrate octyl s-d-glucopyranoside and three different receptor molecules. Next, we used the method for the determination of transient heat effects in the seconds range allowing the investigation of metabolic processes in Trypanosoma cruzi cells induced by Ca2+ ions.