Fluorescence imaging of nanobiomaterials: Thioflavin T in electrospun poly(vinyl alcohol) fibres

Nanoindentation has been widely used to characterise the mechanical properties of various materials. As an alternative, we recently explored a new technique with which the Young's modulus of soft materials can be obtained using environment-sensitive fluorescent dyes. The fluorescence technique has an advantage over nanoindentation in that it can nondestructively measure the physical property of specific positions of nanomaterials. In this work, we have employed fluorescence lifetime imaging microscopy (FLIM) that utilises time-correlated single photon counting and confocal microscopy to investigate the rigidity image of nanostructured materials. ThT-embedded poly(vinyl alcohol) (PVA) polymer films and nanofibres were prepared by spin coating and electrospinning, respectively, and the fluorescence lifetime distribution was obtained by FLIM. It appears that the Thioflavin T (ThT) dye, which was originally used to detect amyloid fibrils, is an excellent probe for our purpose because the excited dynamics of ThT depends on the mechanical properties of surrounding matrices. That is, the time scale of the internal twisting motion of electronically excited ThT was well correlated to the mechanical properties of polymer nanostructures. Our approach opens a new way with which the mechanical properties of advanced nanobiomaterials can be obtained using the modulus-probing dye.