الفهرس 
General introductionOnly 14 pages are availabe for public view
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Abstract
Abstract
The aim of this work is to prepare and characterize biosensors to detect and quantify of some basic molecules and Portions in biological fluids.
Chapter one
The basic principles, historical background, classifications, selectivity, applicability, some strategies used in fabrication and application of potentiometric sensors.
Chapter two
It presents for the first time a novel potentiometric sensor based on the stimulus-responsive molecularly imprinted polymer (MIP) as a selective receptor for neutral dopamine determination. This smart receptor can change its capabilities to recognize according to external environmental stimuli. Therefore, MIP-binding sites can be regenerated in the polymeric membrane by stimulating with stimulus after each measurement. Based on this effect, reversible detection of the analyte via potentiometric transduction can be achieved. MIPs based on 4-vinylphenylboronic acid as the functional monomer were prepared as the selective receptor. This monomer can successfully bind to dopamine via covalent binding and forming a five- or six-membered cyclic ester in a weakly alkaline aqueous solution. In acidic medium, the produced ester dissociates and regenerates new binding sites in the polymeric membrane. The proposed smart sensor exhibited fast response and good sensitivity towards dopamine with a limit of detection 0.15 µM over the linear range 0.2–10 µM. The selectivity pattern of the proposed ISEs was also evaluated and revealed an enhanced selectivity towards dopamine over several phenolic compounds. Constant-current chronopoten-tiometry is used for evaluating the short-term potential stability of the proposed ISEs. The obtained results confirm that the stimulus-responsive MIPs provide an attractive way towards reversible MIP-based electrochemical sensors designation.
Chapter three
It presents a simple, rapid and easy method is proposed for the detection of a cytostatic therapeutic drug, cytarabine, in real samples. The method is based on potentiometric transduction using prepared and characterized new ion-selective electrodes for cytarabine. The electrodes were integrated with novel man-tailored imprinted polymers and used as a sensory element for recognition. The electrodes revealed a remarkable potentiometric response for cytarabine over the linearity range 1.0 × 10−6–1.0 × 10−3 M at pH 2.8–4 with a detection limit of 5.5 × 10−7 M. The potentiometric response was near-Nernstian, with average slopes of 52.3 ± 1.2 mV/decade. The effect of lipophilic salts and plasticizer types on the potentiometric response was also examined. The electrodes exhibited an enhanced selectivity towards cytarabine over various foreign common ions. Validation and verification of the presented assay method are demonstrated by evaluating the method ruggedness and calculating the detection limit, range of linearity, accuracy (trueness), precision, repeatability (within-day) and reproducibility (between-days). The proposed ion-selective electrodes revealed good performance characteristics and possible application of these electrodes for cytarabine monitoring in different matrices. The electrodes are successfully applied to cytarabine determination in spiked biological fluid samples and in pharmaceutical formulations.
Chapter four:
Herein, novel electrochemical methods based on potentiometric and impedimetric transduction were presented for targeting albumin protein. The presented methods employed screen-printed ceramic electrodes with conductive ink as a background support, achieving the goal to make easy and cost-effective electrodes with good detection merits. The bio-sensors were fabricated using either tridodecyl methyl-ammonium chloride (TDMAC) or aliquate 336S in plasticized carboxylated poly vinyl chloride (PVC-COOH) as polymeric matrix. The analytical performances of the resulting biosensors were evaluated using two different electrochemical techniques, including potentiometry and electrochemical impedance spectroscopy (EIS). For potentiometric assay, the biosensors exhibited a potentiometric response towards albumin with a slope of -81.7±1.7 (r2=0.9986) and -146.2±2.3 (r2=0.9991) mV/decade over a linearity range starts from 1.5 µM to 1.5 mM with detection limits of 0.8 and 1.0 µM for sensors based on TDMAC and aliquate, respectively. The interference of co-existing species was tested and good selectivity was observed. For EIS assay, the impedance measurements were carried out in 10 mM PBS (pH 7.5) containing 0.02 M 〖[Fe(CN)6]〗^((-3)⁄(-4)) as a redox-active electrolyte. The biosensors showed detection limits of 4.3x10-8 and 1.8x10-7 M over the linear range 5.2x10-8-1.0x10-4 M and 1.45x10-6-1.45x10-3 M with slope sensitivity of 0.09±0.004 and 0.168±0.009 log Ω/decade for sensors based on TDMAC and aliquate, respectively. The presented biosensors were successfully applied to albumin assessment in biological fluids. The bio-sensors described in this work can be considered as a potential tool for screening albumin in point-of-care. This is attributed to their ease of fabrication, disposability, short-time response, cost-effectiveness, good sensitivity and high selectivity.
Chapter five
A biomimetic sensor for Acetylcholine (ACh) based on host-guest interactions and potentiometric transduction is designed, characterized and presented. The artificial man-tailored host was synthesized using methacrylic acid (MAA) as a functional monomer, ethylene glycol di methacrylate (EGDMA) as a cross linker in the presence of benzoyl peroxide (BPO) as an initiator. The imprinted beads were dispersed in 2-nitrophenyloctyl ether and entrapped in a poly (vinyl chloride) matrix. Slopes and detection limits ranged 55.2-59.6 mV decade-1 and 0.65-1.31 μg mL-1, respectively. Significantly, improved accuracy, precision, good reproducibility, long-term stability, selectivity and sensitivity were offered by these simple and cost-effective potentiometric biosensors. The sensors were used to follow up the decrease of a fixed concentration of ACh+ substrate as a function of acetyl cholinesterase (AChE) activity under optimized conditions of pH and temperature. A linear relationship between the initial rate of ACh+ substrate hydrolysis and enzyme activity hold 0.01- 5.0 IU L-1 of AChE enzyme