Preparation And Applications Of Silver Nanoparticle Immunoprobe

Nano-materials show unique physical and chemical properties, such as high molar extinction coefficient, surface enhanced Raman effect and good catalytic properties, which have been widely used in the field of bio-technology and immunoassay. Gold nanoparticles (AuNPs) are commercially available for a variety of immunoassay test strip. Silver nanoparticles (AgNPs) attract less attention due to their instability and difficulty of modification. Compared with AuNPs, however, AgNPs have stronger enhanced fluorescence effect, better catalytic ability, and cheaper production costs. Therefore, we focuse on synthesis and functionalization of AgNPs.In this work, antibody modified AgNPs(anti-AgNPs) are successfully prepared. Based on such novel probes, a colorimetric method was developed to detect IgG by using anti-AgNPs and catalytic reaction. This method was proved by detecting trace amounts of protein. The method presented a good linear relationship when the IgG concentration was from 3.9 μg/mL to 500 μg/mL, and the detection limit was as lower as 1.95 μg/mL. Compared with the commercial anti-AuNPs, the method showed several advantages such as wider detection range and short analytical time as well as lower cost.We prepared Au@Ag nanoparticles with strong metal enhanced fluorescence. Compared with fluorescent molecule modified AuNPs, the fluorescence intensity increased 18-fold when Au@Ag was used for binding fluorescent molecule. Based on the performance of Au@Ag, we tried to establish a fluorescence resonance energy transfer (FRET) sensor. Based on the interaction between streptavidin and biotin biotin and fluorescent molecule modified Au@Ag was fixed on aldehyde-modified slides. After addition of a quencher ATP-BHQ, the fluorescence signal was partley quenched due to the FRET between the fluorescent molecule and the quencher.Upon the addition of ATP, the quencher was displaced and the fluoresence was recovered. Unfortunately, we optimized parameters of the sensor and the quenching efficiency was 77%. But the fluorescence was changed little when the ATP was added. So we took the advantage of Au@Ag which can resulted in metal enhanced fluoresence and amplify the fluoresence signal. The results showed that a good linear response was obtained when the concentration was in the range of 15.6 ng/mL-500 ng/mL with the correlation coefficient:R2=0.984. In addition, the probe could simultaneously detect human IgE and PDGF-BB with good specificity.