ندا شهبازي

Metformin is one of common drugs to control diabetes mellitus type 2. Prescribed as a first-line treatment, various analytical methods have been reported for its measurement. However, accurate determination of its concentration by simple and inexpensive methods is still challenging. In this thesis, an optical sensor based on gold nanoparticles has been introduced to identify and measure Metformin. Gold nanoparticles with a citrate capping group synthesized by a one-step hydrothermal method are diagnostic components of the sensor. Adding Metformin to the sensing solution, the interaction between Metformin and gold nanoparticles decreased the intensity of the absorption peak of gold nanoparticles at the maximum wavelength of 525 nm and also a new peak appeared in the region of 645 nm. Also, the addition of Metformin to the sensing solution makes the gold nanoparticles to come closer to each other and the color change occurred in the sensing solution. Three factors affecting the response of optical sensor to Metformin including pH, nanoparticle concentration ratio and time were optimized using the experiment design method and with the help of the central composite design and the one-at-a time methods. Based on ANOVA table the optimal pH and ratio are 6.1 and 0.3, respectively.The optimal time is 10 second. In optimal conditions, the response of the noted sensor to Metformin was linear in the concentration range of 6.25 to 133.3 ppm, and the detection limit of the method was calculated as 1.79 ppm. The relative standard deviation of the method according to the formula was 2.53%. The selectivity of the sensor performance was also investigated in the presence of ions and medicinal compounds of the same family as Metformin. Finally the applicability of sensor was studied in human serum sample. The relative standard deviation of the method in human serum was 2.87% and the recovery was between 96.36 to 99.61 %. Trastuzumab (HER) is a monoclonal antibody used in the treatment of breast cancer. Determining low concentrations of this drug is particularly important. In this thesis, a ratiometric sensor based on gold and silver nanoparticles was designed and synthesized to measure and identify HER. The absorption peak of gold nanoparticles increased in the presence of HER and shifted to higher wavelengths while no effective interaction between HER and silver nanoparticles occurred. The mechanism of the sensing process was revealed by examining the absorption peaks of both nanoparticles and transmission electron microscope images. Effective parameters such as pH, temperature and ratio were optimized via experimental design under central composite design. Sixteen tratments in 2 blocks were done. The optimal pH, temperature and ratio were 7.6, 0.59 and 41, respectively.The linear range for HER measurement was obtained according to the experiments performed under optimal conditions in the range of 5 to 400 µM and the detection limit was 3.7 nM. The effect of interfering species was studied by examining ionic and medical compounds with functional groups similar to HER. The reproducibility of the sensor response has been compared in seven working days and acceptable results were obtained with relative standard deviation of less than 5%. Finally, the effectiveness of the method was eva‎luated in a human serum and feta bovine serum (FBS). The linear range in human serum was between 68 to 1700 nM and in FBS was between 85 to 850 nM. The relative standard deviation was less than 5 %. It is worth mentioning that the amount of serum sample required for the sensing process is about 37.5 µL.

نانو¬ذرات طلا، نانو¬ذرات نقره، متفورمين، HER، حسگر نوري، نمونه سرم انساني، نسبت¬¬سنجي، طراحي آزمايش، نانوذرات پلاسموني

Gold nanoparticles, Silver nanoparticles, Metformin, HER, Optical sensors, Experimental design, Human serum, Ratiometric

Neda Shahbazi

Dr. Rouholah Zare-Dorabei