Thiolated DAB dendrimer/ZnSe nanoparticles for C-reactive protein recognition in human serum

A nanocomposite obtained by a thiol DAB-dendrimer (generation 5), coated with fluorescent ZnSe quantum dots, was successfully synthesized for the selective recognition of C-reactive protein. The procedure presented was carried out by a novel, cheap and non-toxic bottom up synthesis. The nanocomposite showed an excitation at 180 nm, with two emission bands at 411 and 465 nm, with a full-width at half-maximum of 336 nm. The Stokes shift was influenced by the presence of coating molecules and the intensity was dependent on pH due to the presence of a charge transfer process. The transmission electron microscopy images demonstrated that the spherical nanoparticles obtained displayed a regular shape of 30 nm size. The fluorescence intensity was markedly quenched by the presence of C-reactive protein, with a dynamic Stern-Volmer constant of 0.036 M(-1). The quenching profile shows that about 51% of the ZnSe QDs are located in the external layer of the thiol dendrimer accessible to the quencher. The precision of the method obtained as relative standard deviation was 3.76% (4 mg L(-1), n=3). This water soluble fluorescent nanocomposite showed a set of favorable properties to be used as a sensor for the C-reactive protein in serum samples, at concentrations of risk levels.