Kiran Kumar Tadi

Voltammetric techniques at chemically modified electrodes

Voltammetric and amperometric techniques are powerful analytical tools that are widely used in chemical analysis. This article reviews a summary of some important types of modifying agents and their application in voltammetric and amperometric sensors for clinically and biologically important target species reported from the period 2003 to 2013. In this review, different modifiers such as molecularly imprinted polymers (MIPs), polymers, metal complexes, nanomaterials and composite films are discussed. Under the heading of each modifier, method of fabrication, properties, and applications of chemically modified electrodes (CMEs) are given. Tables that give analyte, modified electrode, measurement technique, measuring medium, linear detection range (LDR) and limit of detection (LOD) referenced from original work are also provided.

Rational synthesis of pindolol imprinted polymer by non-covalent protocol based on computational approach

Pindolol (PDL) is a potent and specific adrenoreceptor blocking agent. It is widely used in the treatment of hypertension, cardiac arrhythmia and angina pectoris. Molecularly imprinted polymers (MIPs) are synthetic receptors having potential applications in drug delivery systems and devices such as diagnostic sensors. In the present work, ab initio quantum mechanical simulations and computational screening were used to identify functional monomer having best interactions with PDL. A virtual library of 16 functional monomers was built and the possible minimum energy conformation of the monomers and PDL were calculated using Hartree-Fock (HF) method for the synthesis of PDL imprinted polymer. The interaction energy between functional monomer and the template were corrected by means of basis set superposition error (BSSE) in all pre-polymerization complexes. The hydrogen bonding between PDL and functional monomer was evaluated by changes in bond lengths before and after complex formation. The virtual template-monomer complex with highest interaction energy is more stable during the polymerization and leads to high selectivity and specificity toward the template. The interaction energy of PDL was found to be the highest with itaconic acid followed by 4-vinyl pyridine and least with acrylonitrile. Taking a spectroscopic viewpoint, results obtained from analysis of the harmonic infrared spectrum were examined. Red and blue shifts related to the stretching frequencies of either donors or acceptors of protons were identified and compared experimentally. Stoichiometric mole ratio of template to functional monomer was optimized and confirmed by UV visible spectra titrations. The theoretical results were correlated by evaluation of binding parameters of MIPs. The experimental binding results were in good agreement with theoretical computations.

Electrochemical detection of epinephrine using a biomimic made up of hemin modified molecularly imprinted microspheres

In this study, a highly sensitive and selective molecularly imprinted polymer (MIP) was synthesized using a functional monomer, 2,4,6-trisacrylamido-1,3,5-triazine, and its application for electrochemical detection of epinephrine (EP) was demonstrated. This particular monomer was selected based on the interaction energies computed for the formation of a pre-polymer complex using computational studies. Furthermore, EP imprinted microspheres were prepared by precipitation polymerization using hemin as the catalytic centre in order to mimic the active site of an enzyme namely peroxidase. Molecularly imprinted and non-imprinted microspheres were characterized using Fourier transform infrared spectroscopy (FTIR) and field emission scanning electron microscopy (FESEM). An electrochemical sensor for EP detection was fabricated by modifying a gold disc electrode with molecular imprinted microspheres stabilized by a chitosan/Nafion mixture. A linear concentration range from 5 × 10−8 M to 40 × 10−6 M with a very low detection limit of 1.2 × 10−8 M (S/N = 3) is determined for the proposed sensor. Our results clearly demonstrate an efficient sensing capability of imprinted polymer with good reproducibility, stability and higher selectivity for EP detection over its other structural analogues and potential interferents. Essentially, the proposed electrochemical sensor follows a cascade reaction mechanism since it consists of two catalytic sites that aid in EP detection. The analytical applicability of this sensor towards the determination of EP is demonstrated using human blood serum and injection samples.

Computational and experimental studies on oxalic acid imprinted polymer

AbstractComputational approach plays an important role to pre-evaluate the interactions between template and functional monomer, so that to choose functional monomer having stronger interactions with template during synthesis of molecularly imprinted polymers (MIPs). Hence template-monomer interactions in pre-polymerization were mainly focused. In this paper, computational chemistry was applied to screen the number of mol of functional monomer that interacts with one mol of template. Intermolecular interactions between oxalic acid and acrylamide have been investigated. The binding energies ΔEbind were calculated by DFT (B3LYP) level of theory with the 6−31+G(d,p) basis set. It was found that four mol of acrylamide were sufficient to interact with one mol of oxalic acid in the pre-polymerization mixture. Four possible conformations and frequency calculations were performed to locate minima. Oxalic acid specific bulk polymer was obtained by the thermal initiated free radical co-polymerization of acrylamide and ethylene glycol dimethacrylate with oxalic acid as template and acetonitrile as porogen. The synthesized MIP efficiently adsorbed oxalic acid from aqueous solutions. The binding parameters of MIP and non-imprinted polymer (NIP) were compared by Freundlich and Langmuir adsorption isotherms. Graphical AbstractDensity functional theory was applied to screen the number of acrylamide moles that interacts with one mole of oxalic acid and based on the optimized ratio, oxalic acid imprinted polymer was synthesized. The imprinted and nonimprinted polymers were characterized by rebinding studies.

Molecular Imprinted Polymer based Impedimetric Sensor for Trace Level Determination of Digoxin in Biological and Pharmaceutical Samples

DOI: 10.2174/1573411013666171117163609 Abstract: Background: Molecularly imprinted polymers (MIPs) are used as artificial receptors in biosensors for the detection of a wide range of analytes from small drug molecules to large molecular weight biomolecules. Quantification of Digoxin (DIG) in human serum and pharmaceutical samples has very high importance due to its low margin of safety. In this report, a highly sensitive molecularly imprinted polymer for DIG is prepared and the detection of analyte was conducted using electrochemical impedance spectroscopy.

Synthesis and Characterization of Pindolol Imprinted Polymer

Molecularly imprinted polymers (MIPs) are capable of recognizing a particular molecule in presence of others due to the selective cavities on it and thus are known as plastic antibodies. Pindolol (PDL) is a synthetic beta-adrenergic receptor blocking agent and widely used for the treatment of hypertension, cardiac arrhythmia and angina pectoris. Using a combinatorial method PDL imprinted polymers were prepared with three functional monomers viz., itaconic acid, 4-vinylpyridine and methacrylic acid by thermal initiated bulk polymerization technique using ethylene glycol dimethacrylate, 2, 2′-azobisisobutyronitrile and acetonitrile as crosslinker, initiator and solvent respectively. Among the three, PDL-itaconic acid MIP shows the best binding capacity. The PDL imprinted polymer was characterized by FTIR spectra and morphology was studied by SEM images. The binding parameters of MIP and non-imprinted polymer (NIP) were compared by the Freundlich and Langmuir adsorption isotherms.

Synthesis and Evaluation of Molecularly Imprinted Polymer for Oxalic Acid

Molecular imprinting technology is a convenient approach for preparing synthetic receptors that possesses user defined recognition properties. Oxalic acid imprinted bulk polymer was synthesized by thermal initiated free radical co-polymerization of oxalic acid (template) with two different functional monomers (acrylamide and methacrylic acid) and ethylene glycol dimethacrylate as crosslinker, using acetonitrile (porogen) as solvent. Scanning electron microscopy and FT-IR spectra confirmed the formation of molecularly imprinted polymer (MIP) with acrylamide. The synthesized MIP(ACR) efficiently adsorbed oxalic acid from aqueous solutions. The binding parameters of molecularly imprinted polymer and non-imprinted polymer were compared by Langmuir-Freundlich adsorption (LF) isotherm.