Quantum Dot Based Aptasensors for the Detection of Biomolecules with Related Raman/SERS Spectral Analysis

The first part of this work explores DNA aptamer based optical sensors suitable for biomedical applications. These are highly selective towards a wide variety of biomolecules. Such sensors (also called molecular beacons) operate on the principle of Fluorescent Resonance Energy Transfer. Sensors detecting Glycated Albumin, Tumor Necrosis Factor – alpha, C – Reactive Protein and calcium ions, respectively, have been designed and characterized. Ultra low detection capabilities in the picomolar concentration ranges have been observed in sensors detecting C – Reactive Protein and calcium ions. The second part of this work involves the modification of the structure of the molecular beacons. They have been conjugated with a cell penetrating peptide called DSS, which assisted the molecular beacons in crossing the biological cell membrane. This design has been used to characterize the response of the aptamer sensors in an intracellular environment. In another study, the molecular beacons have been anchored on to a graphene oxide substrate for the detection of C – Reactive Protein. The optical properties of these substrate conjugated nanoconstructs have been investigated in the presence of human serum based simulated samples. In both cases of structural modifications, the research opened up a new avenue in theranostics because the DSS peptide as well as the graphene oxide can be easily functionalized with drugs for future drug delivery applications. The third part of this work involves the analysis of the Raman / SERS signatures of several biomolecules. Raman spectra and peak assignments of biomarker proteins, associated to inflammatory diseases such as diabetes mellitus and sepsis, have been studied. Another aspect of this study employs a SERS substrate composed of silver nanorod arrays to obtain the Raman spectra of complex bio fluids like human serum. The main focus of this part of the work is to obtain information on the composition of the biomolecules as well the secondary structure of the biomarker proteins.