Novel Fluorescent Nanosensors For The Detection Of Total Protein And Renin Concentration

In recent years,nanomaterials are widely used in various fields due to their special nature,the biosensor which base on the nanomaterials has been widely used in biochemical research.In this paper,we use quantum dots(QDs)and gold nanoparticles(AuNPs)to construct fluorescence sensors for detecting total protein and renin concentration,respectively,the details as follows:In this paper,a novel dual-emission fluorescent probes is designed for the detection of total protein content.Firstly,green fluorescence CdTe QDs are assembled on the surface of red fluorescent microspheres by layer-by-layer electrostatic self-assembly technique,the microspheres are made of polystyrene with blending inset organic dyes,then a novel dual-emission ratio fluorescent probes is finished.Under the UV lamp excitation,the probes have two distinct emission peaks.Because the outer green fluorescence intensity is significantly greater than the inner red fluorescence intensity,the probes show green fluorescence.Cu2+ can selectively quench the fluorescence of the outer CdTe QDs of the probes,which has little effect on the fluorescence of the inner microspheres of the probes.Therefore,when Cu2+ is present,the probes show the red fluorescence.Under alkaline conditions,the protein has the property of reducing Cu2+ to Cu+.Therefore,when the protein is present,Cu2+ is reduced to Cu+ and the outer of probes is no longer quenched,and the probes return to green fluorescence.The contentration of the protein is directly related to the fluorescence spectrum and the fluorescence color of the probes.The results show that the intensity ratio of the two emission bands of the probes are linearly proportional to the concentration of proteins in the range of 0.05 mg/mL to 4.0 mg/mL.And the fluorescence color of the probes gradually changes from red to yellow until green with the increase of the protein concentration.Using this method to detect the total protein content of the skim milk,the data obtained by our method is consistent with the classical BCA method.Hence,this method can quantify the total protein content by using the fluorescence spectroscopy,it canalso be semi-quantified by the change of the fluorescence color of the probes.Therefore,the colourmetric card can be further popularized to achieve the purpose of more convenient detection of total protein.In addition,the method of the detection of renin concentration was established by using AuNPs and fluorescein-labeled renin substrates as the fluorescence resonance energy transfer sensor.A special peptide is designed and can be specifically hydrolyze by renin.The peptide is modified with 5(6)-fluorescein isothiocyanate(FITC)at the C-terminus,and it is labeled with biotin at the N-terminal.The AuNPs is labeled with streptavidin(STV).Therefore,the structure of AuNP/peptide/FITC is obtained by specifically binding between STV and biotin.At the same time,due to the close distance between FITC and AuNPs,energy resonance transfer occurred,the fluorescence of FITC is quenched by AuNPs.When the renin is present,the peptide is specifically hydrolyzed by renin,and the peptide residue with FITC is away from the surface of AuNPs.Then,the energy resonance transfer between AuNPs and FITC disappears,and the fluorescence of FITC is recovered.The fluorescence intensity of FITC in the system is related to the concentration of renin,and when the renin concentration is in the range of 0.01 ? g/mL to 0.2 ? g/m L,it is proportional to the fluorescence intensity of the system.In addition,the method can also be used for the screening of renin inhibitors,it is promising for the clinical diagnosis and drug screening.