Abstract
AbstractDue to their large contact and loading surfaces as well as high sensitivities to chemical changes, graphene‐based materials (GBMs) are increasingly being employed into novel nanomedicine technologies. Here biomolecule—monolayer graphene—kidney tissue hybrid structures are studied using mapping micro‐Raman and fluorescence spectroscopies. Because in this configuration graphene interacts with molecules on both sides, a double‐sided graphene‐enhanced Raman scattering (GERS) effect up to ≈10.1 is found for biomolecules adsorbed on graphene and amino acids in the kidney tissue below graphene. Moreover, graphene causes an efficient autofluorescence quenching (FLQ) up to ≈20% emitted by the kidney tissue. Despite the complexity of such layered materials, the intriguing simultaneous occurrence of double‐sided GERS (a new development of GERS) and FLQ phenomena can be well explained by suitable molecular structure and energy level alignment between molecules and graphene. These result in effective charge transfer mediated by non‐covalent interactions as indicated by correlative strain, doping, and defect analyses in graphene based on the Raman data and energy level calculations. Last, the advantages of using graphene over standard photobleaching are demonstrated. This work can be extended to other macromolecular entities toward integrating GBMs in versatile drug delivery, imaging, and sensing devices.
Highlights
Due to their large contact and loading surfaces as well as high non-covalent interaction with various types sensitivities to chemical changes, graphene-based materials (GBMs) are increasingly being employed into novel nanomedicine technologies
The supporting Si wafer was covered by a 100 nm thick Ni film, which suppresses the Si Raman background, exhibits a flat spectrum, and acts as a metallic mirror coating increasing the Raman intensity of the kidney tissue, graphene, and molecules both in excitation and detection (Figures S1 and S2, Supporting Information).[25,26]
The molecular structural variability of amino acids enables different binding affinities to GBMs through non-covalent van der Waals, π–π stacking, and hydrophobic interactions, and distinct electronic structures.[41]. The latter leads to specific HOMO and LUMO energy levels for amino acids that can be used as orientation values to tune the enhancement factors (EFs) position of graphene through external p- or n-type doping for efficient charge transfer in prospective studies.[29,51]
Summary
Large-area, high quality predominantly singlelayer graphene films overlaid with biocompatible nitrocellulose molecules were transferred onto the Ni film and kidney tissue, denoted Mo/Gr/Ni and Mo/Gr/Ki/Ni, respectively. The biocompatibility of nitrocellulose is demonstrated by its extensive use in biomedicine as membrane for protein blotting.[27,28] These probe biomolecules are the remains from a newly developed collodion-mediated transfer method that works at room temperature, in contrast to the well-established, temperature-intensive PMMA-assisted transfer process, so that heat-induced changes of the kidney tissue, graphene, and molecules can be excluded in our case (Experimental Section).[29] our hybrid structures can be regarded as a model system for drug delivery, imaging, and sensing applications down to organs (here kidney).
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