Maryam Shojaei

Experimental design and multi-objective optimization of molecularly imprinted polymers for monosaccharides

The Taguchi method was used as an experimental design and optimization tool for the preparation of monosaccharide molecularly imprinted polymers (MIPs). Three factors, namely type of functional monomer, molar percentage of functional monomer, and functional monomer to template molar ratio, were included in the experimental design and based on the L16 (43) array, four levels of each factor were chosen. Imprinting factor, selectivity, and equilibration time were considered as quality characteristics of MIPs. For quantitative assessment of the quality of the prepared MIPs, the adsorption of template and competing substance on the prepared MIPs and non-imprinted polymers was monitored by the quartz crystal nanobalance (QCN) technique. The results revealed that regarding each quality characteristic, there are different optimal levels of the factors. The principal component analysis (PCA) technique was used to combine the quality characteristics in order to obtain a single characteristic for overall optimization of monosaccharide MIPs performance. So, PCA coupled with the Taguchi method was developed as an efficient procedure to optimize monosaccharide MIPs. The optimum values of molar percentage of functional monomer and the functional monomer to template molar ratio were found to be 30 and 4, respectively. We also found that acrylic acid (AAc) is a favourable functional monomer for preparing monosaccharide MIPs.

Design and evaluation of mixed self-assembled monolayers for a potential use in everolimus eluting coronary stents

Coronary artery disease (CAD) is still the leading cause of death throughout the world. Metal stents are used to widen narrowed arteries. In addition, drug-eluting stents (DES) are widely implanted to decrease the risk of in-stent restenosis. Commercially available polymer-based DES suffer from some limitations. To avoid these drawbacks, the use of self-assembled monolayers (SAMs) in DES has recently been investigated. In this study, methyl- and carboxyl-terminated mixed SAMs on gold (Au) surfaces were successfully prepared. The samples were characterized using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), and contact angle goniometry (CA). The mixed SAM-coated surfaces were evaluated for everolimus delivery. The drug release in PBS was studied using high performance liquid chromatography (HPLC) and quartz crystal nanobalance (QCN). The results were compared with those related to homogenous SAM-coated surfaces. Significant differences (p<0.05) were found in the amount of drug eluted between the mixed SAM and the homogenous one. The findings are promising for the application of mixed SAMs in DES.

Application of quartz crystal nanobalance and principal component analysis for detection and determination of nickel in solution

Quartz crystal nanobalance (QCN) sensors are considered as powerful mass sensitive sensors to determine materials in the sub-nanogram level. In the first part of this study, a single piezoelectric QCN modified with polypyrrole (PPy) has been tested for detection and determination of nickel ions in the solution at room temperature. The developed method was successfully applied for detection of total nickel in samples taken from several hot springs located at the Northwest of Iran. The frequency shifts were linear with respect to the concentration of nickel in solution. Using this method, nickel can be measured in the range of 3–20 mg L− 1. A lower limit of detection of 0.79 mg L− 1 and a sensivity factor of 4.429 Hz/mg L− 1 were obtained. Some possible interference such as heavy metal ions (lead, mercury, and cadmium) was checked. No major interference was observed with the performance of the sensor except for mercury. To evaluate the ability of the PPy-modified QCN in discriminating between nickel ions and interfering mercury ions, a principal component analysis (PCA) was carried out. PCA was utilized to process the frequency response data of the single piezoelectric crystal at different times, considering different adsorption-desorption dynamics of nickel and interfering mercury ions on electrode. Using PCA, it was found that about 97.90% of the data variance could still be explained by two principal components (PC1 and PC2). The score plot of the data for the first two PCs showed that the PPy-modified QCN yields favorable identification and quantification performances for nickel ions. The accuracy of method for hot spring samples was evaluated and RSD of 4.10% was obtained.

Application of Molecularly Imprinted Polymer for Determination of Glucose by Quartz Crystal Nanobalance Technique

Accurate determination of glucose is of great importance in various biotechnological processes, food industries, and diagnosing several metabolic disorders. To this point, many methods have been developed to meet this goal. Most of these methods are based on the enzymatic oxidation of glucose. However, the enzymes may be deactivated in different possible condition during storage and use. In this paper, a quartz crystal nanobalance (QCN) modified with a molecularly imprinted polymer (MIP) was developed for online monitoring of glucose in aqueous media without the use of enzymes. The MIP was synthesized by free radical polymerization using different functional monomers, including acrylamide, acrylic acid, allyl alcohol, and acrylonitrile. The findings indicate that acrylic acid has significantly better performance in terms of sensitivity and response time as compared with the other functional monomers. All measurements were performed in a flow cell. The frequency shifts due to the adsorption of glucose were found to be linear versus the concentration of glucose within the concentration range of 10-200 mg L-1 with a correlation coefficient of R2 = 0.9996. The sensitivity and lower limit of detection of the sensor were found to be 1.20 Hz/mg L-1 and 4.4 mg L-1, respectively. The results also indicate that organic compounds do not cause any significant interference with glucose determination by the MIPmodified QCN sensor, and using ion exchange resins can eliminate interference of ionic compounds.

Interactions of anti-proliferative and anti-platelet drugs with self-assembled monolayers: a future strategy in stent development

The current study is part of an overall goal to develop new drug-eluting stents (DES). In this paper, for the first time, simultaneous elution of anti-proliferative and anti-platelet drugs from self-assembled monolayers was investigated. Methyl- and carboxyl-terminated mixed self-assembled monolayers were prepared on gold (Au) surfaces. The samples were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), contact angle goniometry (CA), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). To demonstrate that the resulting structures can be used for simultaneous delivery of paclitaxel and dipyridamole, the drug release in phosphate-buffered saline (PBS) was studied using high performance liquid chromatography (HPLC). Obtained results confirmed successful transfer of drugs to PBS. Released dipyridamole levels were significantly higher (p < 0.05) than the delivered paclitaxel after 1, 2, 3, 7, 14 and 28 days. These findings indicate that the proposed method might be suitable for development of an advanced generation of drug-eluting stents.

A Rapid and Cost Effective Method for Measurement of Cyclosporine

Cyclosporine, a powerful immunosuppressive agent, is used to prevent allograft rejection. This paper describes a simple, rapid, and cost effective method based on a quartz crystal nanobalance for the detection of cyclosporine. Measurement is based on the frequency shifts of a methyl phenyl silicon, 75% phenyl (OV25)-coated quartz crystal because of the adsorption of analytes. The frequency shift of sensor is linear related to the concentration of cyclosporine in solution. Linear calibration curve is obtained in the range of 2-8 mg L-1. The correlation coefficient and the lower limit detection are 0.993 and 0.94 ppm, respectively.