Photoactivated ("caged") fluorescent dyes are modern tools for structure and function studies of cell membranes and subcellular organelles. Recently synthesized precursors of rhodamine fluorescent dyes (abbreviations PFD813 and PFD814) important for microscopic probing of biological objects have been studied in solution. In order to characterize the behavior at interfaces, monolayers of PFD813 and PFD814 on water have been formed and investigated. The interactions of these precursors with the biomembrane component dimyristoylphosphatidylethanolamine in monolayers at the air-water interface and after transfer to glass plates have been studied by measuring monolayer parameters and spectroscopic properties before and after photo-chemical formation of the fluorescent rhodamine dyes Rho813 and Rho814, respectively.

Photo-activated or "Caged" rhodamine dyes are the most useful for microscopic investigation of biological tissue by various fluorescent techniques. Novel precursor of the fluorescent dye (PFD813) has been studied for photosensitive staining of numerous animal cells. The functional rhodamine dye (Rho813) with intensive fluorescence has been obtained after photoactivation of its precursor PFD813 inside cells. The dye Rho813 has been successfully used for the optical detection of particular features in biological objects (HaCaT cells, HBL-100, MDCK, lymphocytes). Moreover, the chitosan conjugate with PFD molecules ("Chitosan-PFD813″) has been obtained and studied for the first time. The developed procedures and obtained data are important for further applications of novel precursors of fluorescent dyes ("caged" dyes) for microscopic probing of biological objects. As example, the synthesized "Chitosan-PFD813″ has been successfully applied in this study for intracellular transport visualization by fluorescent microscopy.

Conjugates of the photoactivated rhodamine dyes with biopolymers (proteins, polysaccharides, and nucleic acids) are important tools for microscopic investigation of biological tissue. In this study, a precursor of the photoactivated fluorescent dye (PFD) has been successfully used for staining of numerous mammalian cells lines and for conjugate formation with chitosan (“Chitosan-PFD”) and histone H1 (“Histone H1.3-PFD”). The intensive fluorescence has been observed after photoactivation of these conjugates inside cells (A431, HaCaT, HEK239, HBL-100, and MDCK). Developed procedures and obtained data are important for further application of novel precursors of fluorescent dyes (“caged” dyes) for microscopic probing of biological objects. Thus, the synthesized “Chitosan-PFD” and “Histone H1-PFD” have been successfully applied in this study for intracellular transport visualization by fluorescent microscopy.