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Selective layer-free blood serum ionogram based on ion-specific interactions with a nanotransistor


Despite being ubiquitous in the fields of chemistry and biology, the ion-specific effects of electrolytes pose major challenges for researchers. A lack of understanding about ion-specific surface interactions has hampered the development and application of materials for (bio-)chemical sensor applications. Here, we show that scaling a silicon nanotransistor sensor down to ~25 nm provides a unique opportunity to understand and exploit ion-specific surface interactions, yielding a surface that is highly sensitive to cations and inert to pH. The unprecedented sensitivity of these devices to Na+ and divalent ions can be attributed to an overscreening effect via molecular dynamics. The surface potential of multi-ion solutions is well described by the sum of the electrochemical potentials of each cation, enabling selective measurements of a target ion concentration without requiring a selective organic layer. We use these features to construct a blood serum ionogram for Na+, K+, Ca2+ and Mg2+, in an important step towards the development of a versatile, durable and mobile chemical or blood diagnostic tool.

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Fig. 1: 0D ISFETs show negligible sensitivity to pH near neutral pH.
Fig. 2: Signatures of ion-specific effects.
Fig. 3: Additive contribution of multiple species on ψ0.
Fig. 4: Selective-layer-free blood ionogram.
Fig. 5: Subnanolitre sensing and high integration.


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The authors thank M. Clément at ‘Clinique Vétérinaire du Clair Matin’ for performing the ionogram for [Mg2+], S. Frickey for discussions on the use of ionograms in the medical environment, Y. Coffinier for providing FBS and for discussions, and P. Joseph for advice on microfluidic chips. The authors also thank B. Coasne for assistance regarding MD and for discussions, and A. Shuchukarev, F. Alibart, A. Charrier, P. Temple-Boyer, A.M. Gué, C. Bergaud, L. Nicu, A. Bancaud, G. Larrieu, D. Vuillaume, D. Guérin, S. Lenfant and I. Mahboob for their feedback on the manuscript. This study was funded by Singlemol and BQR projects from the Nord-Pas de Calais Council, Lille University and NTT.

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R.S. fabricated the lab-on-a-chip, prepared solutions, performed electrical measurements and analysed the data. R.H., B.S. and J.-F.D. performed MD simulations. R.H. addressed overscreening and mixed electrolyte issues by MD and provided careful feedback on the manuscript. J.-F.D. derived equations (6) and (7) and wrote the related program. K.N. fabricated the silicon nanotransistors. A.F. continuously gave input on the study process and the manuscript. All authors discussed the results. N.C supervised the study, analysed the data, proposed the models for large slopes and additive effects, and wrote the paper.

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Correspondence to N. Clément.

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Sivakumarasamy, R., Hartkamp, R., Siboulet, B. et al. Selective layer-free blood serum ionogram based on ion-specific interactions with a nanotransistor. Nature Mater 17, 464–470 (2018).

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