An aptamer-based biosensor for sensitive thrombin detection with phthalocyanine@SiO2 mesoporous nanoparticles

Silica nanoparticles, with entrapped hydrophobic photosensitizer tetra-alpha-(2, 4-di-tert-butylphenoxy)-phthalocyaninato zinc (ZnPc(OAr)(4)), were synthesized by hydrolyzing triethoxyvinylsilane (TEVS) and 3-amino propyl triethoxysilane (APTES). The as-prepared nanoparticles, which were highly monodispersed spheres (about 100 nm), exhibited strong Q-band absorption of ZnPc(OAr)(4) centered at 701 nm. The aqueous solubility of ZnPc(OAr)(4) encapsulated in silica nanoparticles was obviously improved. The nanoparticles efficiently generated singlet oxygen (O-1(2)) both in organic and aqueous solutions after being irradiated at suitable wavelength. The resulting O-1(2) then initiated chemiluminescence (CL) by reacting with a methyl cypridina luciferin analog (MCLA). Based on the photoinduced CL, a sensitive aptamer-based sandwich-type sensor was presented to detect human thrombin. Thrombin was first attached to Pc@SiO2 via secondary aptamer, and then they were collected, for CL determination, by beads with primary aptamer. The proposed approach, which was highly selective with a low detection limit of 80 pmol/L, minimized the nonspecific adsorption. Such an aptamer-based biosensor is feasible in screening biomarkers in complex matrices at ultratrace levels. (C) 2013 Elsevier B.V. All rights reserved.