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Biomonitoring is a research topic that has largely relied on cell culture systems. Recently, the development of “Organ-on-a-Chip” (OC) platforms and the need for a continuous monitoring of these systems has increased its interest. However, the biomonitorization in these systems is still at its infancy due to the difficulty to adapt the sensors to microfluidic OC systems. In this work we have fabricated a modular, versatile, scalable, multi-analyte sensing platform, which integrates dissolved oxygen (DO), Na, K and pH sensors for monitoring their concentrations in small volume of biological fluids. The platform is fabricated by means of rapid prototyping techniques using polymeric substrates, and incorporates all the necessary elements to measure the four analytes. It was designed with four gold sensing electrodes, and integrates a gold counter electrode and an Ag/AgCl pseudo-reference electrode for the electrochemical measurements in small volumes (0.83 μL) of samples. The sensors featured good sensitivities of 3.60 ± 0.2 nA (mg L) for DO and 69 ± 1 mV decade for pH. Na and K μISE exhibited sensitivities of 57 ± 1 mV decade and 52 ± 2 mV decade, and low limits of detection 5 × 10 M and 0.5 × 10 M respectively. This platform allows the dynamic measurement of the biological fluids parameters simultaneously, in real time and with a rapid response. The versatility of the platform allows its adaptation in any microfluidic cells culture systems. The novel multi-sensor platform has been validated in controlled buffers and with artificial urine (AU). A proof-of-concept using real mice urine (RU) has been carried out, demonstrating the good behaviour of the multi-sensing platform.

WO 3 –Cr, SnO 2 –Pd and TiO 2 –Cr nanoparticles have been prepared following a sol–gel route. The additive-modified nanostructured metal oxides have been deposited on hotplate platforms by microdropping. Functional gas test of the sensitive layers to ammonia has been performed in stationary and pulsed mode of operation. The pulsed mode fastened the regeneration of the surface yielding an enlargement of the sensor response and a decrease of the transient time. The improved sensing response to ammonia was particularly marked for the WO 3 –Cr based gas sensor.