Abstract: The invention relates to fluorescent dyes that are substituted or unsubstituted derivatives of 1-(isoindolyl)methylene-isoindole that are bound through both isoindole nitrogens to a boron difluoride moiety, forming a fluorescent dibenzopyrrometheneboron difluoride compound ##STR1## that is further substituted by bathochromic substituents that are aryl or heteroaryl moieties further substituted by an additional aryl or heteroaryl, that is itself optionally further substituted by an additional aryl or heteroaryl. These aryl and heteroaryl groups are separated by a covalent bond, or by an ethenyl, butadienyl or hexatrienyl linkage. The dyes of the invention are particularly useful as labels for carriers, particularly polymeric microparticles. The resulting microparticles have a long-wavelength fluorescence emission, and possess utility for tracing flow in biological systems, particularly in tracing blood flow.

Abstract: The invention describes useful conjugates of sulforhodamine, wherein the conjugated substance and the fluorophore are separated by an alkanoic acid spacer that is attached to the fluorophore via a sulfonamide bond. The increased length of the covalent linkage due to the spacer results in dye-conjugates having a number of surprisingly advantageous properties relative to previous sulforhodamine-labeled conjugates, including increased fluorescence.

Abstract: The invention is a novel fluorescently labeled microparticle, where the microparticle internally incorporates at least one dipyrrometheneboron difluoride dye. Appropriate selection of substituents results in dipyrrometheneboron difluoride derivatives that, when incorporated into polymer microparticles, give the desired excitation and emission wavelengths. The spectral characteristics of the labeling dyes in liquid are not greatly changed when the dye is incorporated into the particles, and the spectral excitation and emission wavelengths are compatible with commonly used filter sets. Other embodiments of the fluorescent microparticles include additional dyes and/or bioreactive substances.