Abstract-Monitoring of metabolic compounds in cell cultures can provide real-time information of cell line status. This is particularly important in those lines not fully known, as the case of embryonic and mesenchymal cells. On the other hand, such approach can pave the way to fully automated systems for growing cell cultures, when integrated in Petri dishes. To date, the main efforts emphasize the monitoring of few process variables, like pH, pO , electronic impedance, and temperature in bioreactors. Among different presented strategies to develop biosensors, carbon nanotubes exhibit great properties, particularly suitable for high-sensitive detection. In this work, nanostructured electrodes by using multiwalled carbon nanotubes are presented for the detection of lactate and glucose. Some results from simulations are illustrated in order to foresee the behavior of carbon nanotubes depending on their orientation, when they are randomly dispersed onto the electrode surface. A comparison between nonnanostructured and nanostructured electrodes is considered, showing that direct electron-transfer between the protein and the electrode is not possible without nanostructuration. Such developed biosensors are characterized in terms of sensitivity and detection limit, and are compared to previously published results. Lactate production is monitored in a cell culture by using the developed biosensor, and glucose detection is also performed to validate lactate behavior.

a b s t r a c tCarbon nanotubes have been attracting a lot of interest as electron transfer mediators to enhance electrochemical biosensing. The main reason behind this is usually recognized in terms of augmented electrochemical active surface area. The aim of this paper is to review other phenomena that occur at the electrochemical interface. Three distinct features of these phenomena mainly appear in electrochemical biosensing. We introduce the Cottrell, Randle-Sevčick, and Nernst effects to address these features. By using these features, several electrochemical biosensing systems are investigated. Differences among the proposed systems are presented and analyzed in light of these effects. We finally have demonstrated that carbon nanotubes may induce completely opposite effects when dealing with different biosensing systems. This paper also shows that even seemingly small differences (e.g., changing metabolite as detected by the same enzyme) might result in opposite effects on the same carbon nanotube based sensor. Nevertheless, it is shown that carbon nanotubes, in some cases, confirm their exceptional nature in enhancing the sensor performance by orders of magnitude. The sensitivity increases from 87 ± 62 to 3718 ± 73 nA/M ×cm 2 and detection limit decreases from 7.5 ± 5.3 mM to 84 ± 2 M in case of cyclophosphamide detected by the cytochromes P450 3A4.

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Abstract-The objective of this work is the systematic study of the use of electrochemical readout for advanced diagnosis and drug monitoring. Whereas to date various electrochemical principles have been studied and successfully tested, they typically operate on a single target molecule and are not integrated in a full data analysis chain. The present work aims to view various sensing approaches and explore the design space for integrated realization of multi-target sensors and sensor arrays.

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a b s t r a c tMicrodevices dedicated to monitor metabolite levels have recently enabled many applications in the field of cell analysis, to monitor cell growth and development of numerous cell lines. By combining the traditional technology used for electrochemical biosensors with nanoscale materials, it is possible to develop miniaturized metabolite biosensors with unique properties of sensitivity and detection limit. In particular, enzymes tend to adsorb onto carbon nanotubes and their optical or electrical activity can perturb the electronic properties. In the present work we propose multi-walled carbon nanotube-based biosensors to monitor a cell line highly sensitive to metabolic alterations, in order to evaluate lactate production and glucose uptake during different cell states. We achieve sensors for both lactate and glucose, with sensitivities of 40.1 A mM −1 cm −2 and 27.7 A mM −1 cm −2 , and detection limits of 28 M and 73 M, respectively. This nano-biosensing technology is used to provide new information on cell line metabolism during proliferation and differentiation, which are unprecedented in cell biology.

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Abstract. An investigation on nano-structured electrodes to detect different metabolites is proposed in this paper. Three different metabolites are considered: glucose, lactate, and cholesterol. The direct detection of hydrogen peroxide is also considered since it does not involve any enzyme. The metabolites and the peroxide were detected by using screen-printed electrodes modified by using multi-walled carbon nanotubes. In all cases, improvements of orders of magnitude were registered both on detection sensitivity and on detection limit. A close comparison with data recently published in literature has shown the existence of an inverse linear correlation between detection sensitivity and detection limit when sensor performances improve due to nanostructured materials. This inverse linear relationship seems to be a general law as it is here demonstrated for all the considered detections on glucose, lactate, chlesterol, and hydrogen peroxide.