Electrochemical sensors for environmental and clinical analyses

Nowadays, the concepts of smart cities, smart houses and Homo Deus (potential next stage in human evolution) are taking more and more attention. Sensors have a key role in this context: recording different parameters it will be possible to design cities able to manage efficiently all the resources or to warn people if a particular kind of disease, such as cancer or diabetes, is taking place. Current way of detecting these parameters or molecules are often laborious and expensive and cannot be used as in situ and real time. Electrochemical sensors, especially nano-sized sensors, are perfect candidates to address these challenges. Indeed, these sensors do not require special instrumentations to work but just an usual battery, so that this technology is cheap and suitable for in situ action. Furthermore, the electrical signal can be recorded over time and can be acquired and managed in remote. The main challenge of this technology is to achieve a Limit Of Detection (LOD) low enough to make the use of these sensors competitive with other analytical techniques, such as Inductively Coupled Plasma Mass Spectrometry (ICP-MS) or Enzyme Linked ImmunoSorbent Assay (ELISA). These goals can be achieved by nano-sized materials because they enhance mass transport and electron transfer rate. In addition, to once found the right sensing material, it is possible to select the electrochemical detection technique giving the best performances in dependence on the analyte that has to be detected. During my Ph.D I studied different electrodes to detect, electrochemically, 3 analytes: i) heavy metals, ii) proteins, and iii) H2O2. Heavy metals are the main source of water pollution. They have been extensively used in various applications due to their specific properties. The main problem using these chemicals is that they are non-biodegradable and thus they can accumulate in the human body through the food chain. Among heavy metals, one of the most dangerous is mercury because just the exposure to some ppb (µg/l) can cause several problems to human body. Lead, cadmium, zinc, arsenic and copper are considered toxic and dangerous as well, therefore, their monitoring is really important. H2O2 is a widely used chemical, employed as bleaching agent in textile and paper industry, for medical and pharmaceutical applications and to remove organic compounds from waste water and contaminated soil. Furthermore, H2O2 has a key role in the human body as well. For instance, its detection can be useful because can give indications about the glucose concentration and so it could be useful for diabetic patients. Furthermore, it is a biomarker of oxidative stress that is a pathological condition due to breakdown of the antioxidant defense system.. Detection of proteins was also investigated during my Ph.D. In order to detect these bio-compounds it is mandatory to use some bio recognition elements (such as antibodies, DNA or aptamers) so that the sensors are usually named biosensors. During my studies, I developed a biosensors towards Human ImmunoGlobulin G (H-IgG) and ParaThyroid Hormone Like Hormone (PTHLH). H-IgG is a protein always present in the human fluids (blood, urine, sweat) and its detection has not any particular relevance. It can be used as a model because is a cheap protein that has the bio-chemical properties of many other proteins. Instead, PTHLH is overproduced owing to different kind of cancer, consequently it can be used as a biomarker. This kind of application is really of great value because PTHLH starts to be produced at the beginning of the disease, so that its detection is useful for early diagnosis. Summarizing, the main goals of this Ph.D work are: 1. The development of new and innovative ways to fabricate electrodes with high surface area; 2. To find new, cheap, robust electrochemical sensors for detecting H2O2, heavy metals, and proteins; 3. Validate these sensors using real sample