A method for synthesizing ultrabright fluorescent silica particles with hydrophilic functional groups, comprising the steps of: (i) forming a first mixture comprising a plurality of nano-sized silica particles and a gelation agent; (ii) forming a second mixture by combining the first mixture with a surfactant, a plurality of fluorescent dye molecules, and water, wherein fluorescent dye molecules are encapsulated within a plurality of pores of the nano-sized silica particles; (iii) forming a third mixture by adding a co-source of silica to the second mixture, wherein the co-source of silica prevents leakage of the encapsulated fluorescent dye molecules from the pores of the nano-sized silica particles and provides hydrophilic functional groups to the silica particles while preserving the fluorescence of the silica particles; (iv) optional further functionalization of the obtained nanoparticles with functional molecules, exemplified by carboxylic groups and folic acid, and (v) removing excess fluorescent dye from the third mixture.