The development of fluorescence-based methods for bioassays and medical diagnostics requires the design and synthesis of specific markers to target biological microobjects. However, biomolecular recognition in real cellular systems is not always as selective as desired. A new concept for creating fluorescent biomolecular probes, utilizing a fluorogenic dye and biodegradable, biocompatible nanomaterials, is demonstrated. The synthesis of a new dicationic asymmetric monomethine cyanine dye with benzo[d]thiazolium-N-propionamide and chloroquinoline end groups is presented. The photophysical properties of the newly synthesized dye were examined through the combined application of spectroscopic and theoretical methods. The applicability of the dye as a fluorogenic nucleic acid probe was proven by UV-VIS spectroscopy and fluorescence titration. The dye–nucleic acid interaction mode was investigated by UV-Vis and CD spectroscopy. The newly synthesized dicationic dye, like other similar fluorogenic structures, limited permeability, which restricts its use as a probe for RNA and DNA. To enhance cellular delivery, we utilized a patented technology that employs solid, insoluble lipid nanoparticles. This method ensures the complete introduction of the dye into cells while minimizing activity outside the cells. In our study involving two human cell lines, we observed improved penetration through the cell membrane and distinctive selectivity in visualizing nucleic acids within the cytoplasm and nucleus.

Precise mapping of structural heterogeneity at the sub-10 nm scale is pivotal for rational nanoparticle design, yet convention-al analytical workflows remain inadequate. Here we integrate dilution-controlled asymmetric flow field-flow fractionation (AF4) with small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS) to interrogate ellipsoidal solid–liquid lipid nanoparticles (LNPs). The dilution-controlled AF4 mode amplifies scattering contrast, enabling robust, shape-resolved analysis across entire elution profiles. Coupling AF4 to SANS in D₂O further sharpens resolution for the smallest fractions by reducing particle diffusion through increased solvent viscosity. Comparative sizing shows that SAXS/SANS accurately capture primary particles down to ~5 nm, whereas multi-angle light scattering chiefly detects loosely associated aggregates. Morphology profiling reveals that surfactant identity governs particle shape, polydispersity, and overall architec-ture. Joint SAXS/SANS modelling uncovers a 2–3 nm polar shell enveloping the hydrophobic lipid core. Together, these insights refine our understanding of LNP size and morphology and establish dilution-controlled AF4-SAXS/SANS as a high-resolution platform for dissecting complex nanoparticle systems relevant to biomedical applications.