Study On Protein Determination With The Resonance Light Scattering Probes Of Nanoparticles

The detection of protein becomes increasingly important to many areas of life sciences because proteins are the substantial elements of vital phenomena. As the proteomics project has put forward in recent years, the routine methods are not possible to meet the protein detection in the studies due to their low sensitivities, complicated procedure, expensive instrument or other shortcomings. So it is very urgent to study the protein determination method of high sensitivity, simple operation and universal applicability.By using a resonance light scattering (RLS) technique, the resonance light scattering probes of nanoparticles are studied, and a highly sensitive method for protein determination based on the aggregation of nanoparticles on protein template is described. The nanoparticles can interact with proteins by electrostatic forces and thus aggregate on the protein surface. The big aggregation or the electric dipole-dipole interaction and coupling between the plasmons of neighboring particles will result in strong and stable RLS, the enhanced RLS intensity is well proportional to the concentration of protein.This study shows that the Au nanoparticles and ferric nanoparticles exhibit different RLS spectra, but the light intensities are greatly enhanced when a small amount of proteins is added to the solution. The light scattering peaks are located at 531nm and 451 nm respectively, and the light intensities in two peaks are well proportional to theconcentration of protein. The Au nanoparticles with different diameter are prepared according to the Fens. For the Au nanoparticles of 15nm, at the optimum condition of 0.01mol/L pH4.56 NaAc-HAc buffer solution, the detection limit of bovine serum albumin (BSA) is 4.6ng/mL and the linear range locate in 0.01-0.30ug/mL, but the Au nanoparticles of larger than 15nm takes on relatively poor linear relationship and even the 100nm diameter Au nanoparticles is not observed the enhanced RLS. For ferric nanoparticles, at the optimum condition of pH7.4 sodium cacodylate buffer solution, the detection limit of bovine serum albumin (BSA) is 6.6ng/mL and the linear range locate in 0.02-0.70ug/mL. The experimental results indicate that the ionic intensity have negativeeffect on the method, the permitted concentration of NaCl are 0.02mmol/L and 0.10mmol/L respectively. The various metal ions of 1.0 X 10~7mol/L and amino acids below 2.0ug/mL do not interfere the protein determination with this assay. The proposed RLS assay exhibits lower variation in response signal for the same weight of different proteins, such as HSA, BSA, Y -G, and Gelation. The proposed RLS method has been used for determination of proteins in human serum, and the results were in good agreement with those obtained by Bradford assay.The nanoparticles interact with protein by electrostatic force, so their aggregation belongs to physical process, which do not change the chemical character of proteins and is in favor of the further analysis of proteins. Moreover, the probes of nanoparticles are innoxious and prepared easily. Because of the good detection performance and practicability, this proposed method could probably become an efficient detection tool for nanogram level proteins and provide the technical fundamental for the study of immunoassay and protein chip.