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In this study, ultraviolet-visible (UV-Vis) spectrophotometry method was applied to determine benzotriazole (BTA) in aqueous solutions based on surface plasmon resonance (SPR) property of gold nanoparticles (AuNPs). The experimental variables such as pH, time, the volume of various buffers, the concentration of different electrolytes, and concentrations of AuNPs were investigated. Under optimum conditions, the proposed method represented a linear range between 10 to 150 μg L À 1 (R 2 = 0.9941) with a detection limit (LOD) of 5 μg L À 1 . This method was successfully used to measure trace amounts of BTA in Ahwaz drinking water and Ramin power plant cooling water samples. The proposed spectrophotometry assay is accurate, low-cost, simple, and does not need any separation steps compared to the other methods. In the next step, an artificial neural network (ANN) using Levenberg-Marquardt (LM) and Resilient Back propagation (RP) algorithms, was used to predict the absorbance of the mentioned factors. For each algorithm, 2 layers and for each layer 2,4,6,8, and 10 neurons were studied. According to mean square error (MSE) and coefficient of determination (R 2 ), the LM algorithm was better than the RP algorithm for the prediction of absorbance.[a] Dr.

For stem cell therapy of degenerative diseases, it is necessary to differentiate stem cells into the specific lineage. There are several growth factors which have been used for differentiation of stem cells. Some growth factors can dose-dependently induce differentiation of stem cells so that the increase of growth factor concentration results in production of the higher level of differentiated cells. However, due to the toxicity of some differentiation factors (e.g. retinoic acid), the lower dose of growth factors for the specific lineage differentiation of stem cells is desirable. This paper suggests a new approach in the field of controlled growth factor delivery system using semiconductor nanocrystals; known as quantum dots (QDs). This system contains polymeric microencapsulated growth factor which is conjugated to near infrared (NIR) absorbing QDs. The control release of growth factors from microcapsules in the culture plates can be achieved by irradiation. To modulate growth factor release in response to stem cells needs for differentiation, the intensity and period of irradiation will be controlled. Our hypothesis is based on the fact that QDs can absorb NIR energy and by excitation of electrons and then vibrational relaxation of them become heated when they were irradiated and then release growth factors. We believe that controlled growth factors delivery through the suggested system is an effective method to reduce the amount of growth factors required for differentiation of stem cells.

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