Preparation Of Gold Nanoparticles And Its Application In Fiber Optic Biosensor

Micro RNA(miRNA)is a kind of endogenous,noncoding single stranded RNA that plays an important role in regulating m RNA translation and expression.The abnormal expression of miRNA is closely related to the occurrence and development of various diseases.At the same time,it exists in the body fluids including blood,saliva and urine in a stable form.Therefore,miRNA have been proposed as biomarkers for early detection,classification and predictive diagnosis of diseases(especially cancer).It is necessary to find a reliable test method to accurately measure the expression level of miRNA.Gold nanoparticles(AuNPs)have been widely used in the field of biological detection due to their unique optical properties of local surface plasmon resonance(LSPR),large specific surface area,good biocompatibility and so on.Moreover,the fiber optic sensor plays an increasingly important role in medical diagnosis system owing to its'characteristics of miniaturization,anti-electromagnetic interference and real-time online detection.In this paper,a colorimetric sensor and a fiber optic biosensor for miRNA-148a were fabricated by combining the LSPR property of AuNPs with optical fiber sensing technology.The main research works and conclusions are as following:(1)A series of AuNPs with different sizes were prepared by trisodium citrate reduction method.The AuNPs-RNA_P conjugate probes were obtained by the conjugation of AuNPs with RNA probe(RNA_P)vis Au-S bond.Subsequently,the UV-Vis,TEM,SEM and FTIR were used to characterize their features.(2)The colorimetric sensor for miRNA-148a was fabricated by the optical property of AuNPs that the LSPR effect is changed owing to the hybridization reaction between the AuNPs-RNA_P conjugates and the target RNA.The influence of different experimental conditions on the performance of the colorimetric sensor was investigated.The results showed that when the RNAP:AuNPs molar ratio was 600:1;and the probes align in a tail-to-tail fashion onto the target RNA,there was a good linear relationship between the intensity of LSPR peak with the miRNA-148a concentration in the range of 1 n M?10³ n M,and the limit of detection(LOD)of this senor is about 1.9 n M.In addition,the specificity test result showed that the sensor has good specificity for the detection of mirna-148a.(3)The AuNPs were immobilized on the surface of optical fiber to use Poly(allylamine hydrochloride)as cross-linker by electrostatic self-assembly monolayer technology,and then the RNA_P was modified on the surface of AuNPs by covalent interaction to render the optical fiber probe a biological function.A series of optimization experiments were carried out to investigate the influence factors on the performance of the fiber LSPR sensor.The results showed that the optimal particle size of the AuNPs was about 40 nm;the optimal time for HF corrosion was 3 h;and the optimal incubation time for AuNPs was 6 h.The miRNA-148a was quantitatively measured by reflective optical fiber LSPR sensing system.The results showed that there was a good linear relationship between the intensity of the resonance peak with the concentration of miRNA-148a in the range of 10^-1?10³n M.The LOD of the fiber LSPR biosensor is about 0.1 n M,and this sensor has good specificity.