CHEMICAL FUNCTIONALIZATION OF CARBON NANOMATERIALS FOR PROSTATE CANCER DETECTION

In the last decades, nanomaterials have arisen a great interest for the scientific community because of their special properties derived from their small size. In particular, carbon nanomaterials (CNMs) present a unique set of intrinsic electronic, magnetic and optical properties. In addition, CNMs present high chemical versatility and biocompatibility, which makes them great candidates in a wide range of different applications. Carbon nanotubes (CNTs) and graphene are the most promising CNMs for several applications. However, the functionalization (i.e. the chemical modification) of their surface is an important requirement for some of these applications. The aim of this work is to manufacture a biosensor based on difunctionalized CNTs and graphene, for the detection of prostate cancer. In the present thesis work, the covalent difunctionalization of CNTs and subsequent modification of the introduced functional groups is presented in Chapter 2. Double-walled CNTs (DWCNTs) were difunctionalized through aryldiazonium addition, incorporating to their outer wall two molecular moieties which only differ on the protecting group of an amino function. Two different approaches were followed: the sequential addition of each aniline containing a kind of protected amino group in two steps or the addition of both in one reaction step (one-pot difunctionalization). The difunctionalization of oxidized multi-walled CNTs (ox-MWCNTs) by combination of the aryldiazionium addition and the amidation of carboxylic groups was also exploited. In Chapter 3, the functionalization of different graphene derivatives is described. Several approaches were studied with varying results. In a first study, reduced graphene oxide (rGO) was modified in only one functionalization step; introducing the desired difunctionality in the subsequent modification of the introduced functional group. Negative results were obtained at the one-pot difunctionalization of rGO, mimicking the procedure which was used for DWCNTs. However, we succeeded in the addition of sulfur radicals to graphene oxide (GO), with consequent reduction of GO, followed by the amidation of residual carboxylic groups present in rGO. Finally, the non-covalent modification of graphene obtained by chemical vapor deposition (CVDG) was exploited. Finally, the manufacturing of an immunosensor for the detection of prostate cancer biomarker prostate-specific membrane antigen (PSMA) using difunctionalized CNTs is presented in Chapter 4. Electrochemiluminescence (ECL) was used as signal for the detection. Different immunosensors were developed composed by difunctionalized ox-MWCNTs or DWCNTs as components, obtaining different results depending on the employed CNT. The different manufactured immunosensors were characterized in terms of limit of detection (LOD) and limit of quantification (LOQ). In addition, the ECL enhancement due to the presence of the CNTs could be demonstrated by comparison with a similar ECL immunosensor without the CNTs.