Huma Shaikh

Molecularly imprinted surface plasmon resonance (SPR) based sensing of bisphenol A for its selective detection in aqueous systems

Bisphenol A (BPA) imprinted poly(ethylene glycol dimethacrylate-N-methacryloyl-L-phenylalanine-vinyl imidazole) [poly(EGDMA-MAPA-VI)] film deposition on a SPR sensor with improved efficiency is described in this paper. The molecularly imprinted SPR sensor was characterized by FTIR-ATR, atomic force microscopy and ellipsometry. A water-compatible molecularly imprinted film has been developed for rapid, sensitive, and label-free detection of BPA in aqueous solutions prepared in Milli Q water, tap water and synthetic wastewater. The real-time response allows the detection of BPA with concentrations ranging from 0.08 to 10 μg L−1 with LOD and LOQ values of 0.02 and 0.08 μg L−1 in Milli Q water, 0.06 and 0.2 μg L−1 in tap water and 0.08 and 0.3 μg L−1 in synthetic wastewater, respectively. A significant increase in sensitivity was therefore expected due to the use of the imprinted poly(EGDMA-MAPA-VI) thin film. The method showed good recoveries and precision for the samples spiked with BPA. The results suggest that the imprinted SPR sensing method can be used as a promising alternative for the detection of BPA. The sensor data fitted well with the Langmuir adsorption model. The selectivity studies showed that the imprinted cavities formed in the polymeric nanofilm recognize BPA preferentially rather than 4-nitrophenol, hydroquinone, phenol and 8-hydroxy quinoline with a relative selectivity coefficient of 2.5, 2.6, 2.7 and 2.5, respectively. The prepared BPA imprinted SPR sensor enables high sensitivity, label-free detection, real-time monitoring, low volume sample consumption, quantitative evaluation, and determination of kinetic rate constants very well. In addition, the SPR based BPA sensor is easy to use and can be a cost effective solution due to the reusability of the prepared sensor. Furthermore, the storage stability will be higher than antibody-based detection methods.

Molecular imprinted magnetic nanoparticles for controlled delivery of mitomycin C

Abstract Controlled drug delivery system is a technique which has considerable recent potential in the fields of pharmacy and medicine. Mitomycin C is commonly used drug in the treatment of superficial bladder and breast cancers. In the present study, mitomycin C-imprinted magnetic poly(hydroxyethyl methacrylate)-based nanoparticles (MIMNs) were prepared using surfactant free emulsion polymerization for controlled delivery of mitomycin C. The MIMNs were characterized by fourier transform infrared spectroscopy, scanning electron microscopy, atomic force microscopy, electron spin resonance, and elemental analysis. The average particle diameter of MIMNs was about 200 nm.

Selectivity of Brij-35 in Micellar Liquid Chromatographic Separation of Positional Isomers

Implementation of Brij-35, a nonionic surfactant, as a mobile phase for separation of positional isomers is investigated. Chromolith C-18 SpeedROD is used as a stationary phase. The effect of surfactant and organic modifier (propanol) concentration on the separation of some selected isomers is studied and evaluated in terms of linear solvation energy relationship (LSER). Shape selectivity is assessed by α value of sorbic and benzoic acid, which is found to be 1.339 by using mobile phase composed of 0.5% aqueous solutions of Brij-35 and propanol in 9 : 1. Isomers of parabens, nitroanilines, nitrophenols, and quinolinols are successfully separated using mobile phases composed of various percentages of surfactant and propanol. System constants for nonionic MLC using LSER analysis show that hydrogen bond basicity and dipolarity may be major contributors to selectivity, while excess molar refraction helps fine-tuning the separation which also imparts unique selectivity to nonionic surfactants as compared to ionic ones.

Synthesis and characterization of molecularly imprinted polymer embedded composite cryogel discs: application for the selective extraction of cypermethrins from aqueous samples prior to GC-MS analysis

Molecularly imprinted particles embedded composite cryogel discs specific for α-cypermethrin and β-cypermethrin were prepared. Two different types of imprinted particles were embedded into cryogel to prepare composite cryogels specific for two isomers of cypermethrin simultaneously. Adsorption studies revealed that MIP is extremely selective for α-cypermethrin and β-cypermethrin with outstanding adsorption capacity. A sensitive analytical method comprising MISPE coupled with GC-MS has been developed to quantify trace levels of α-cypermethrin and β-cypermethrin in real water matrices. The polymer showed fast kinetics and follows a pseudo-second-order kinetic model very well (R2 = 0.9999). It shows excellent capacity towards α-cypermethrin and β-cypermethrin with a higher total number of binding sites (Nt = 96 μmol g−1 for α-cypermethrin and 95 μmol g−1 for β-cypermethrin). The MIP showed selectivity over the homologues of α-cypermethrin and β-cypermethrin with imprinting factor (IF) 11.2, 10.0, 1.04 and 1.20 for α-cypermethrin, β-cypermethrin, deltamethrin and permethrin, respectively. The developed MISPE method followed by GC-MS enhanced the sensitivity and selectivity of the assay. This method was successfully applied to samples of lake water for the determination of α-cypermethrin and β-cypermethrin simultaneously. Moreover, the synthesized MIP can be easily regenerated and repeatedly used without loss of efficiency.

Megaporous poly(hydroxy ethylmethacrylate) based poly(glycidylmethacrylate-N-methacryloly-(l)-tryptophan) embedded composite cryogel

One-step activation, purification, and stabilization of lipase enzyme were performed by using composite hydrophobic support at low ionic strength with increased surface area during embedding process. A novel hydrophobic poly(hydroxyethylmethacrylate) [PHEMA] based, poly(glycidyl methacrylate-N-methacryloly-(L)-tryptophan) [PGMATrp] bead embedded composite cryogel membrane having specific surface area of 195m(2)/g was used as hydrophobic matrix for adsorption of commercial Candida Rugosa lipase in a continuous system. PGMATrp embedded PHEMA cryogel membrane with 60-100 μm pore size was obtained by dispersion polymerization of GMA and MATrp to form PGMATrp beads followed by embedding of PGMATrp to HEMA via APS and TEMED redox pair. The introduction of hydrophobic MATrp monomer into bead structure aiming to increase interaction between lipase and composite membrane was estimated using nitrogen stoichiometry of elemental analysis and found to be 239 μmol/g of polymer. Hydophobicity increment due to embedding process was confirmed by measuring contact angle, it was found 42° and 48.4° for the PHEMA and PHEMA/PGMATrp composite cryogel respectively. Some parameters i.e. pH, flow-rate, protein concentration, temperature, salt type and ionic intensity were evaluated on the adsorption capacity in a continuous system. Fast protein liquid chromatography (FPLC) studies were performed for specific adsorption of lipase onto the PHEMA/PGMATrp embedded composite cryogel membrane.

Recent Applications of Molecularly Imprinted Polymers in Analytical Chemistry

The increased complexity of sample matrices resulted in the requirement of specific and sensitive molecular recognition systems. Although molecular imprinting is an old idea, its potential as molecular recognition tool in analytical chemistry has been revived in recent times. This review intended to comprehensively discuss and evaluate the recent progress in the applications of molecularly imprinted polymers (MIPs) in analytical chemistry. A concise introduction for new readers in the field is followed by the comprehensive critical review of these developments in MIP technology and their applications in analytical chemistry. This review is divided into three sections namely, extraction, sensors and chromatography. The three sections are further separated into several sub-sections. The applications related to compound extraction are subdivided into extraction of toxins and bioactive compound extraction. MIPs as sensors are subdivided into luminescence probes, surface plasmon resonance (SPR) sensors, quartz crystal microbalance (QCM) and electrochemical sensors. Finally, the MIP applications as stationary phase for chromatography are elaborated. This section is subdivided into HPLC and capillary electrochromatography (CEC). The significant aspects of applications of the molecular imprinting polymers in analytical chemistry are evaluated focusing majorly on literature appeared in last five years.

2,3-Pyridine dicarboxylic acid functionalized gold nanoparticles: Insight into experimental conditions for Cr(3+) sensing.

Selectivity of gold nanoparticles (AuNPs) depends upon surface functionality; small changes in structure or concentration bring significant changes in the behavior of AuNPs. In this study, citrate-capped AuNPs were functionalized with ortho-dicarboxylate substituted pyridine (2,3-PDCA) and detailed studies on experimental conditions were carried out to check the stability of AuNPs and response for Cr3+. Stability of PDCA-AuNPs was found sensitive to the pH, ionic strength of buffer and its type. Capping behavior of PDCA on C-AuNPs was examined by FTIR spectroscopy. Surface morphology and size of synthesized AuNPs were confirmed by AFM, XRD, and DLS techniques where particles were found 11nm in size, monodisperse and spherical in shape. Interaction of stabilized AuNPs was tested with various metal ions; where Cr3+ induced the changes in localized surface plasmon band (LSPR) of PDCA-AuNPs which leads to a color change from wine red to violet blue. The phenomenon is explained as cooperative effect of citrate and pyridine nitrogen on surface of AuNPs in contrary to meta-dicarboxylate substituted pyridine derivatives. Further, under optimized and controlled conditions Cr3+ shows linear response with decrease in absorbance at LSPR intensity of AuNPs (518nm). Moreover, to demonstrate the applicability of method, Cr3+ was determined in the presence of Cr (VI) which shows 96% recovery.