Structure- and Reactivity-Guided Molecular Designs for New Opportunities in Biosensing and Bioimaging
Presented by: Prof. Enver Cagri Izgu
Abstract:
Our interdisciplinary research program aims to investigate physiologically important targets and develop well-performing methodologies for biotechnology applications. A few examples are summarized here and more will be presented during the seminar.
High-fidelity detection of upregulated microRNAs (miRNAs) can be critical for cancer diagnosis and prognosis. We reported a systematic approach to cost-effectively and quickly produce split aptasensors for miRNA detection. These sensors are assembled from unmodified DNAs, can achieve single-nt RNA specificity, and perform within biological media. It is our broader interest and ongoing effort to implement unnatural polymer backbones to enhance aptasensor biostability: one potential candidate is N3’→P5’ phosphoramidate DNA (conveniently named as NP-DNA).
Inorganics are also important biological targets, some involved in immune response and signaling. However, majority of biologically relevant inorganics are intrinsically non-fluorescent or have no affinity for aptamers. Furthermore, the aptamer-ligand binding is an equilibrium process that relies on the local availability of free ligand. As a result, it would be challenging, if not impossible, to come up with an aptamer that can bind [inorganic] targets with limited lifetime. We recently developed a small-molecule approach to address these fundamental challenges. With this approach in vitro selection (or SELEX) of a new aptamer is no longer required. Synthetically engineered pre-ligands enable a known aptamer, which binds organic fluorogens, to detect structurally unique, non-fluorogenic, and reactive inorganics (hydrogen sulfide and hydrogen peroxide). Additionally, this method can easily be adapted to live E. coli to construct whole-cell biosensors for these inorganic species.
Finally, our biosensing applications also focus on lipid membranes, at the levels of model protocells and live mammalian cells and tissues. Certain redox conditions have been associated with signaling and pathophysiology. Just as an example, nitrative stress, which generates high concentrations of peroxynitrite, can damage lipid membranes and cause pro-inflammatory pathways associated with pulmonary complications. We developed a DPPC-derived probe to detect peroxynitrite in lipid-rich cell compartments (primarily the ER) and within the lung lining. In murine models of acute lung injury, this probe allowed for the observation of iNOS-dependent nitrative stress around bronchioles in lung tissues exposed to xenobiotics and in pulmonary macrophages upon intratracheal bleomycin challenge.
