Sara Khalid

Development of a molecularly imprinted polymer for selective extraction followed by liquid chromatographic determination of sitagliptin in rat plasma and urine

A novel water-compatible molecularly imprinted solid-phase extraction (MISPE) combined with zwitterionic hydrophilic interaction liquid chromatography (ZIC-HILIC) method for selective extraction and determination of sitagliptin in rat serum and urine was developed and validated. The effects of progenic solvents, pH, cross linker and amount of monomer were studied to optimize the efficiency and selectivity. The adsorption kinetics and isotherms were measured. The molecularly imprinted polymer (MIP) showed good specific adsorption capacity with an optimum of 180 mg/g at pH 7.5 and selective extraction of sitagliptin from rat plasma and urine. The recovery of sitagliptin from rat urine and plasma was >98%. The limits of detection (LOD) and quantification (LOQ) were 0.03 and 0.10 μg/L respectively. The proposed method overcomes the matrix effects of phospholipids generally encountered while preparation of plasma samples by precipitation of proteins.

Gas chromatographic-mass spectrometric separation and identification of combustion products of organo-phosphorus and chlorine pesticides and evaluation of their impact on the environment.

A simple and rapid GC-MS method for separation, identification and quantitative determination of combustion products of organophosphorus and chlorine pesticides viz; monocrotophos, chloropyriphos, butachlor and benzenehexachloride has been developed. The method provides a positive means of identifying organic combustion products and enables to assess not only their toxicity to human beings but also their impact on the environment. The data is useful for emergency preparations in case of fire in chemical plants and warehouses that store pesticides in large quantities.

Precolumn derivatization followed by liquid chromatographic separation and determination of tramiprosate in rat plasma by fluorescence detector: Application to pharmacokinetics

Alzheimer disease (AD) is characterized pathologically by extracellular amyloid deposits composed of amyloid β (Aβ) protein. A simple and rapid method using HPLC with fluorescence detector was developed and validated for determination of tramiprosate in rat plasma. Pre-column derivatization of the deproteinized rat plasma was carried out using o-phthaldialdehyde (OPA) as a fluorescent reagent in presence of 3-mercaptopropionic acid. The liquid chromatographic separation was achieved on a Kromasil C18 column using methanol:acetonitrile: 20 mM phosphate buffer pH 7.5 (8.0:17.5:74.5 v/v/v) as a mobile phase in an isocratic elution mode. The eluents were monitored by a fluorescence detector set at 330 and 450 nm of excitation and emission wavelength respectively. Vigabatrin was used as an internal standard. The method was linear within the range 30.0-1000.0 ng/mL. Design of experiments (DOE) was used to evaluate the robustness of the method. The developed method was applied to study the pharmacokinetics of tramiprosate in rats.

LC-MS/MS structural characterization of stress degradation products including the development of a stability indicating assay of Darunavir: An anti-HIV drug.

Darunavir, an anti-HIV drug was subjected to forced degradation under acid, base, thermal and neutral hydrolysis, oxidation and photolysis as prescribed by ICH guidelines. Four major degradation products were formed under acid and base hydrolysis, while stable under neutral and thermal hydrolysis, oxidative and photolysis. The drug and its degradation products were separated on Hiber, LiChrospher® 60, RP-select B, C8 column (250mm×4.6mm i.d., 5μm) using 10mM ammonium acetate: acetonitrile (52:48, v/v) as mobile phase in an isocratic elution mode by LC. The degradation products were characterized by LC-MS/MS and fragmentation pathways were proposed. The proposed structures of degradation products were confirmed by HRMS and the LC method was validated with respect to specificity, linearity, accuracy, recovery, LOD and LOQ.

Application of normal- and reversed-phase high-performance liquid chromatography for monitoring the progress of reactions of anthraquinone manufacturing processes

Abstract Two different methods for the separation and determination of the reactants intermediates and products of anthraquinone manufacturing processes using normal- and reversed-phase high-performance liquid chromatography were developed. The separations were achieved on Spherisorb silica and reversed phase C 18 columns using n -heptane—ethanol—chloroform—acetic acid (89:5:5:1, v/v) and acetonitrile—water (65:35, v/v) as the eluents, respectively. These methods were used not only for monitoring the reaction conditions but also the yields of anthraquinone.

Au-CGKRK Nanoconjugates for Combating Cancer through T-Cell-Driven Therapeutic RNA Interference

Numerous prior studies on fighting cancer have been based on using inhibitors of JAK-STAT pathway (signal transducer and activator of transcription 3 (STAT3) inhibitor in particular), a signaling pathway responsible for progression of many types of cancer cells. However, recent studies have shown that STAT3 activation leads to upregulation of program death receptor-ligand 1 (PD-L1, an immune checkpoint protein that plays a major role behind evasion of immune systems by growing tumors) expression levels in tumor cells, leading to enhanced immune suppression. This is why global efforts are being witnessed in combating cancer through use of immune checkpoint inhibitors. Herein, we report on the design, synthesis, physicochemical characterizations, and bioactivity evaluation of novel tumor- and tumor-vasculature-targeting noncytotoxic Au-CGKRK nanoconjugates (17–80 nm) for combating tumor. Using a syngeneic mouse tumor model, we show that intraperitoneal (i.p.) administration of the Au-CGKRK nanoparticles (NPs) complexed with both PD-L1siRNA (the immune checkpoint inhibitor) and STAT3siRNA (the JAK-STAT pathway inhibitor) results in significant (>70%) enhancement in overall survivability (OS) in melanoma-bearing mice (n = 5) when compared to the OS in the untreated mice group. The expression levels of CD8 and CD4 proteins in the tumor lysates of differently treated mice groups (by Western blotting) are consistent with the observed OS enhancement being a T-cell-driven process. Biodistribution study using near-infrared dye-loaded Au-CGKRK nanoconjugates revealed selective accumulation of the dye in mouse tumor. Notably, the overall survival benefits were significantly less (∼35%) when melanoma-bearing mice were treated (i.p.) with Au-CGKRK NPs complexed with only PD-L1siRNA or with STAT3siRNA alone. The presently described Au-CGKRK nanoconjugates are expected to find future use in therapeutic RNA-interference-based cancer immunotherapy.

Liquid chromatography-mass spectrometry determination of iloperidone on rat dried blood spots: application to pharmacokinetics

A simple, rapid and highly sensitive liquid chromatography-mass spectrometry method was developed and validated for analysis of iloperidone on rat dried blood spots. The chromatographic separation was achieved on an Agilent RP-18 column (250 × 4.6 mm; 5 μm), using 20 mM ammonium acetate (adjusted to pH 5 with TFA) and acetonitrile (60 : 40 v/v) as a mobile phase at a flow rate of 1.0 mL min−1 in an isocratic mode. The analytes were detected in positive electrospray ionization mode and monitored selectively at m/z 427 [M + H]+ for iloperidone and paliperidone used as an internal standard. The mean recovery of iloperidone from dried blood spots was 95.7% with an intra- and inter-day precision of 9.6%. The assay was linear over a range of 1–300 ng mL−1. The limits of detection and quantification were found to be 0.09 ng mL−1 and 0.3 ng mL−1 respectively. Stability studies showed that iloperidone was stable on dried blood spots for 1 month at −20 °C. The effect of hematocrit to assess the accuracy of extraction of iloperidone from dried blood spots was evaluated and found to be more than 94%. The developed method was applied to study the pharmacokinetics of iloperidone by an oral administration of 5 mg kg−1 in healthy rats.