In this study, novel water dispersible conjugated polymer nanoparticles having various potential applications in the areas including biomedicine and photonics have been synthesized from blue, green and yellow light emitting conjugated polymers. Their sizes, morphology, surface charges and optical properties have been determined using various techniques. Cell viability of nanoparticles was tested in mesenchymal stem cells. For the synthesis of nanoparticles, first the following polymers carrying a number of different functional groups and based on derivatives of fluorene and benzothiodiazole monomers are designed and synthesized using the Suzuki coupling reactions: Poly[(9,9-bis{propeny}fluorenyl-2,7-diyl)-co-(9,9-dihexyl-9H-fluorene)] (P1), poly[(9,9-bis{carboxymethylsulfonyl-propyl}fluorenyl-2,7-diyl)-co-(9,9-dihexyl-9Hfluorene) (P2), poly[(9,9- bis{propeny}fluorenyl-2,7-diyl))-co-(1,4-benzo-{2,1,3}- thiodiazole)] (P3), poly[(9,9- bis{carboxymethylsulfonyl-propyl}fluorenyl-2,7-diyl)- co(1,4-benzo-{2,1,3}-thiodiazole)] (P4), poly[(9,9-bis{3-bromopropyl}fluorenyl- 2,7-diyl)-co-(1,4-benzo-{2,1,3}-thiodiazole)] (P5), poly[(9,9-bis{3- azidopropyl}fluorenyl-2,7-diyl)-co-(benzothiadiazole)] (P6). Polymers were characterized by using spectroscopic techniques such as 1H-NMR, FT-IR, UV-Vis, Fluorescence spectrophotometer and Gel Permeation Chromatography (GPC). Conjugated polymers carry functional groups on their side chains, such as azide and allyl groups that can be cross-linkable using UV light to form shape-persistent, stable nanoparticles. Nanoparticles were characterized by various techniques before and after UV-treatment. Their sizes and morphologies were determined by using dynamic light scattering measurements (DLS) and imaging techniques such as scanning electron microscopy (SEM) and atomic force microscopy (AFM). For optical characterization UV-vis, fluorescent spectroscopies and FT-IR were used. CNPs affect on cells shows their nontoxic and biocompatible properties which give opportunity to use them in cell imaging.