Diamond biosensors

International audienceDiamond is wide band gap semiconductor presenting many extreme properties. It is notably known as the most stable material with the highest chemical inertness, the highest mechanical hardness and the highest thermal conductivity. Since the mid 1970s it has been possible to grow synthetic diamond by several methods. High Pressure High Temperature techniques that mimic the diamond formation in the earth's crust were first developed. Then Chemical Vapour Deposition (CVD) methods enable diamond growth at laboratory scale as well as the control the P-type and N-type doping of diamond. Besides, it is possible to tune the diamond electrical properties form very resistive to metallic thanks to the P-type doping with boron. Current achievements have enabled the development of diamond sensors that can operate in extreme conditions. After being used for its mechanical and thermal properties, diamond was considered for chemical sensing. In fact the chemical stability and the close-to-metallic conductivity of diamond make it a powerful tool for electrochemical detection in various environment. Furthermore, the diamond is an ideal substrate for surface functionalization thanks to the wide and very known carbon based chemistry. Such a feature combined to the outstanding electrochemical properties of the diamond electrodes have enable the production of very efficient biosensors and biochips. Diamond is also an interesting sensor for medical imaging. Its carbon nature, well tolerated by living tissues, are actually very useful for its use as a biosensor capable of working in contact with bio-environments as well as real neuronal interfaces. Both those topics will be discussed in details in the following pages. In a first part an overview on electrochemical based biosensors and their performance is described. Then in a second half of the chapter, novel applications where diamond is directly used as an electrode for neural tissue interfacing is presented in details

Algorithms for survival: a comparative perspective on emotions

The nature and neural implementation of emotions is the subject of vigorous debate. Here, we use Bayesian decision theory to address key complexities in this field and conceptualize emotions in terms of their relationship to survival-relevant behavioural choices. Decision theory indicates which behaviours are optimal in a given situation; however, the calculations required are radically intractable. We therefore conjecture that the brain uses a range of pre-programmed algorithms that provide approximate solutions. These solutions seem to produce specific behavioural manifestations of emotions and can also be associated with core affective dimensions. We identify principles according to which these algorithms are implemented in the brain and illustrate our approach by considering decision making in the face of proximal threat