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Abstract: In this work, we have prepared three types of aptamer-conjugated Rubpy-doped silica nanoparticles for Human breast carcinoma MCF-7 cells labeling. Probe A is prepared through covalent conjugation between amine-labeled MUC-1 aptamer and carboxyl-modified Rubpy-doped NPs (NPs-aptamer). Probe B is prepared based on the interaction between biotin-labeled MUC-1 aptamer and avidin-conjugated Rubpy-doped NPs (NPs-avidin-biotin-aptamer). For Probe C, there is a PEG with flexible long chain as the bridge between avidin and the NPs (NPs-PEG-avidin-biotin-aptamer). In addition, we further investigate the practical number of MUC-1 aptamers on an NP of each probe using hoechst33258 dye. The binding efficiency of MUC-1 aptamer on the three types of probes as follows: Probe A < Probe B < Probe C. In addition, microscopic fluorescence imaging shows that Probe C containing the PEG molecules can be effectively applied for the recognition of MUC-1 protein in human breast carcinoma MCF-7 cells thus demonstrates that the PEG with flexible long chain as the bridge between the aptamer and NP can greatly enhances the freedom of MUC-1 aptamer. Compared with common organic dyes, the dye-doped silica nanoparticles serve as a stable bioprobe because of their facile conjugation with the desirable biomolecules, and have exhibited great potential in bioanalysis. [Copyright &y& Elsevier]

Abstract: In this work, we have developed a simple and sensitive method for ATP detection using silica nanoparticles (NPs) as the platform and hoechst33258 as the signal reporter. The ATP-binding aptamers hybridize with the probe DNA (DNAp) immobilized NPs to form the aptamer/DNAp duplex on the NPs surface. The conformational change of the aptamer leads to the decrease of the aptamer/DNAp duplex on the NPs due to the ATP-binding aptamer switches its structure from the aptamer/DNAp duplex to the aptamer/target complex in the presence of ATP. ATP detection can be easily realized by separating the silica nanoparticles and adding the hoechst33258 of intercalating to aptamer/DNAp (dsDNA). Good selectivity between ATP and CTP, GTP or UTP has been demonstrated, which is due to the specific recognition between ATP aptamer and ATP. The K d was estimated to be ∼1mM from 0 to 4mM and a liner response was observed from 0 to 0.2mM with a detection limit of ∼20μM. Compared with other methods, the carboxyl-modified silica nanoparticles (∼60nm) prepared by the reverse microemulsion method can serve as a stable and sensitive sensor platform because of their smaller size and facile conjugation with amine-containing molecules. In addition, the high sensitivity and selectivity of hoechst33258 was employed for the ssDNA and dsDNA determination, which takes advantage of the label-free aptamer and lower cost. [Copyright &y& Elsevier]