Later on, Roche Diagnostics happened to be pondering the question ‘Wouldn’t it be useful to have a non-electrical version of the ion selective electrode?’ especially for use in critical care wards where the patients are monitored by a bank of electrical monitors. A device with a non-electrical front end is less likely to suffer cross-talk. Again, fluorescent PET sensors turned out to be a satisfactory answer since they have an optical front end \cite{optimedicalcom}. Now these fluorescent PET sensors are seeing use in ambulances so that blood sodium levels can be determined in seconds at the scene of an injury. What is good for a human is also good for other animals. So it is no surprise that fluorescent PET sensors are also seeing use in veterinary situations \cite{idexxcom}.
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Figure 2 . The world of molecular logic-based computation.
Since fluorescent PET sensors are based on rather small (ca. 1 nm) molecules, they can enter living cells and remain undetected by the cell machinery for reasonable periods of time. During their residence, these molecules act as little James Bonds and gives us a window into the private lives of protons, for instance \cite{probescom}.
Fluorescent PET sensors switch their emission signal rather sharply upon encountering the target species, e.g. from ‘off’ to ‘on’. Such switching of signals is similar to those seen inside computers and we made recognized this connection between disciplines in 1993 \cite{de_Silva_1993}. The field of molecular logic-based computation arose as a result \cite{2012,Daly_2017}. Over 610 laboratories have joined this field (Figure 2). Many logic gate arrays of varying degrees of small-scale integration have now been constructed. Some of these have been operated within small spaces, some of which are alive. Since these small spaces are not usually accessible by semiconductor logic devices, they are virgin territory for exploration by intelligent molecular devices.9 Even certain aspects of human behaviour can be emulated by molecular logic-based computation already . More progress along these lines can be expected.
1. B. Daly, J. Ling and A. P. de Silva, Chem. Soc. Rev. 2015, 44 , 4203.
2. A. P. de Silva, H. Q. N. Gunaratne, T. Gunnlaugsson, A. J. M. Huxley, C. P. McCoy, J. T. Rademacher and T.E. Rice, Chem. Rev. 1997, 97 , 1515.
3. R. A. Bissell, A. P. de Silva, H. Q. N. Gunaratne, P. L. M. Lynch, G. E. M. Maguire and K. R. A. S. Sandanayake, Chem. Soc. Rev. 1992, 21 , 187.
4. See OPTI products at optimedical.com.
5. See VETSTAT products at idexx.com.
6. See Lysosensor Blue and Lysosensor Green products at probes.com.
7. A. P. de Silva, H. Q. N. Gunaratne, C. P. McCoy, Nature 1993, 364, 42.
8. A. P. de Silva, Molecular Logic-based Computation , Royal Society of Chemistry, Cambridge, 2013.
9. B. Daly, J. Ling, V. A. D. Silverson and A. P. de Silva, Chem. Commun. 2015, 51 , 8403.
10. J. Ling, G. W. Naren, J. Kelly, T. S. Moody, A. P. de Silva, J. Am. Chem. Soc. 2015 , 137 , 3763.
11. J. Ling, G. W. Naren, J. Kelly, D. B. Fox, A. P. de Silva, Chem. Sci. 2015 , 6 , 4472.
12. J. Ling, G. W. Naren, J. Kelly, A. Qureshi, A. P. de Silva, Faraday Disc. 2015 , 185 , 337.