The Applications Of Gold Nanorods In Detection And Differentiation Of Small Biomolecules

Small biomolecules,such as polyamines,biothiols and nucleotides in biological fluids,play important roles in maintain metabolism,tissue repair,providing energy and information transfer,thus their content is closely related to the human health.These small biomolecules are often used as biomarkers to diagnose the diseases and monitor the life activities in living organisms.Simultaneously,because they are associated with different diseases,the selective detection and accurate differentiation of them are particularly significant.Owing to the similar structures of small biomolecules,in which faces with a great challenge about highly selectively sensing and accurately discriminating with them.To address the above problems,this thesis has carried out the following three researches on the selective detection and accurate differentiation of small biomolecules in biological fluids.1.Highly selective sensing of spermine in human urine via the nanometal surface energy transfer?NSET?between gold nanorods?AuNRs?and tetrakis?4-sulfonatophenyl?porphyrin?TPPS₄?.As a one-dimensional nanomaterial with unique properties,AuNRs have been widely used in the fields of chemistry and medicine.The surface plasmon resonance absorption wavelength of AuNRs can be continuously adjusted from visible to near-infrared region by increasing the aspect ratios.Especially,AuNRs display abundant colors depending on their sizes.In the work,a NSET strategy via the positively charged AuNRs and the negatively charged TPPS₄ was developed to detect spermine in human urine samples.Under acidic condition,spermine showed multi-cationic property and a strong affinity towards the anionic phosphate backbone of calf thymus DNA?ctDNA?by electrostatic attraction and as well as the groove binding,which enabled the NSET between AuNRs and TPPS₄ based on electrostatic interaction,leading to the fluorescence quenching of TPPS₄.Moreover,the quenched fluorescence was proportional to the concentration of spermine,which was applicable to monitor the level of spermine in human urine in the concentration range of 0.5-7.5?M.The NSET system was simple,sensitive and timesaving,which had great significance in early cancer diagnosis.2.Based on the etching of AuNRs and principal component analysis?PCA?to distinguish ribonucleotide in urine.As a multivariate statistical analysis method,PCA can reduce the dimensionality of multivariate data,which can be linearly converted into important component and reduce the difficulty of the problem.In this work,four kinds of AuNRs were introduced as sensor arrays.The purpose of distinguishing twelve ribonucleotides was achieved.During the etching process,AuNRs were preferentially shortened and eventually turned into Au?III?state by Fenton reaction.The morphological change of AuNRs led to the significant color change and blue shift in the corresponding extinction spectrum.Herein,Fe²⁺played an important role in the Fenton reaction.When Fe²⁺coordinated with ribonucleotide,the Fenton reaction was prevented and the ability of etching AuNRs was weakened or disappeared.Due to the different structures of ribonucleotides,the ability of each molecule binding with Fe²⁺was distinct,which resulted in a certain difference in the etching of AuNRs.At the same time,the method also can distinguish ribonucleotide in complex biological samples?human urine samples?.3.Based on the etching of AuNRs and PCA to detect and distinguish biothiols in urine.In this work,a colorimetric nanosensing array for detecting and distinguishing biothiols was established,which was composed of AuNRs and four kinds of metal ions(Hg²⁺,Pb²⁺,Cu²⁺,Ag⁺).The morphological change of AuNRs led to the significant color change due to the Fenton reaction.However,the presence of biothiols can inhibit the etching process by covalently binding with AuNRs through Au-S bond.As a result,the solution color obviously changed in the presence of various concentrations of biothiols during the etching process.Interestingly,this process can be further tuned by different metal ions,which owned high affinity with biothiols,and thus hinder the binding of biothiols with AuNRs,resulting in the etching of AuNRs.The variance in affinity between biothiols and metal ions made the sensor array exhibit similarity to the fingerprint feature,and thus can distinguish different biothiols.This strategy combined PCA and sensor array to achieve rapid and accurate discrimination and detection of biothiols.In addition,the method showed the great potential in analysis of biothiols in human urine samples.In summary,based on the surface energy transfer and etching of AuNRs,this thesis used AuNRs as optical probes to established simple and rapid analysis methods,which achieved the purpose of selective detection and distinguishing different small molecules in urine.