Changes in the electrical conductance of graphene field-effect transistors (GFETs) are used to perform quantitative analyses of biologically-relevant molecules such as DNA, proteins, ions and small molecules.

Chemical manipulation of estrogen receptor alpha ligand binding domain structural mobility tunes receptor lifetime and influences breast cancer therapeutic activities. Selective estrogen receptor modulators (SERMs) extend ERα cellular lifetime, accumulation, and are antagonists in the breast and agonists in the uterine epithelium and/or in bone. Selective estrogen receptor degraders (SERDs) reduce ERα cellular lifetime/accumulation and are pure antagonists. Activating somatic ESR1 mutations Y537S and D538G enable resistance to first-line endocrine therapies. SERDs have shown significant activities in ESR1 mutant setting while few SERMs have been studied. To understand whether chemical manipulation of ERα cellular lifetime and accumulation influences antagonistic activity, we synthesized a series of methylpyrollidine lasofoxifene derivatives that maintained the drug’s antagonistic activities while uniquely tuning ERα cellular accumulation. These molecules were examined alongside a panel of antiestrogens in live cell assays of ERα cellular accumulation, lifetime, SUMOylation, and transcriptional antagonism. High-resolution x-ray crystal structures of WT and Y537S ERα ligand binding domain in complex with the methylated lasofoxifene derivatives, SERMs, and SERDs show that molecules that favor a highly buried helix 12 conformation achieve the greatest transcriptional suppression activities. Together these results show that chemical reduction of ERα cellular lifetime does not necessarily correlate with transcriptional antagonism in ESR1 mutated breast cancer cells. Importantly, our approach shows how minor chemical additions modulate receptor cellular lifetime while maintaining other activities to achieve desired SERM or SERD profiles.

Graphene field-effect transistors (GFETs) present beneficial features for their application as biomolecular or chemical sensors. Due to their atomically-thin 2D dimensionality, their high electrical conductance is particularly sensitive to small changes in the distribution of charged species near the graphene surface. Taking advantage of this property, GFET sensors have been designed to report the detection or quantitation of various types of biologically-relevant molecular analytes such as nucleic acids, proteins, ions or small molecules. By analyzing data from published literature on GFET bioanalytical sensors, we have recently shown that the detection metrics of such sensors vary enormously between studies, and argued that this variance is mainly driven by disparities in the bio-recognition interface [1]. Indeed, the selectivity of GFET sensors must be engineered, typically by covering the graphene surface with biological molecules having a specific affinity for the chosen analyte (e.g. antibodies to capture the corresponding antigen, ssDNA to capture its complementary sequence). Yet, the coverage, orientation, stability and interactions between immobilized probes, blocking species and captured analytes are often not well known or controlled. In this presentation, I will discuss our efforts to understand and regulate the surface functionalization of graphene field-effect transistors. Using electrical conductance measurements and Raman spectroscopy, I will characterize the response of devices to both covalent chemistry, using aryldiazonium reagents, and non-covalent chemistry, using pyrene derivatives. I will describe our recent developments in controlling these functionalization routes, and compare their use for further bioconjugation with molecular probes for bioanalytical purposes. [1] A. Béraud, M. Sauvage, C. M. Bazán, M. Tie, A. Bencherif and D. Bouilly. Graphene Field-Effect Transistors as Bioanalytical Sensors: Design, Operation and Performance. Analyst 146, 403-428 (2021) https://doi.org/10.1039/D0AN01661F

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