Saeed Khan

Physico-mechanical and Stability Evaluation of Carbamazepine Cocrystal with Nicotinamide

The focus of this investigation was to prepare the cocrystal of carbamazepine (CBZ) using nicotinamide as a coformer and to compare its preformulation properties and stability profile with CBZ. The cocrystal was prepared by solution cooling crystallization, solvent evaporation, and melting and cryomilling methods. They were characterized for solubility, intrinsic dissolution rate, chemical identification by Fourier transform infrared spectroscopy, crystallinity by differential scanning calorimetry, powder X-ray diffraction, and morphology by scanning electron microscopy. Additionally, mechanical properties were evaluated by tensile strength and Heckel analysis of compacts. The cocrystal and CBZ were stored at 40°C/94% RH, 40°C/75% RH, 25°C/60% RH, and 60°C to determine their stability behavior. The cocrystals were fluffy, with a needle-shaped crystal, and were less dense than CBZ. The solubility profiles of the cocrystals were similar to CBZ, but its intrinsic dissolution rate was lower due to the high tensile strength of its compacts. Unlike CBZ, the cocrystals were resistant to hydrate transformation, as revealed by the stability studies. Plastic deformation started at a higher compression pressure in the cocrystals than CBZ, as indicated by the high yield pressure. In conclusion, the preformulation profile of the cocrystals was similar to CBZ, except that it had an advantageous resistance to hydrate transformation.

A Polymeric Nanoparticle Encapsulated Small Molecule Inhibitor of Hedgehog Signaling (NanoHHI) Bypasses Secondary Mutational Resistance to Smoothened Antagonists

Aberrant activation of the hedgehog (Hh) signaling pathway is one of the most prevalent abnormalities in human cancer. Tumors with cell autonomous Hh activation (e.g., medulloblastomas) can acquire secondary mutations at the Smoothened (Smo) antagonist binding pocket, which render them refractory to conventional Hh inhibitors. A class of Hh pathway inhibitors (HPI) has been identified that block signaling downstream of Smo; one of these compounds, HPI-1, is a potent antagonist of the Hh transcription factor Gli1 and functions independent of upstream components in the pathway. Systemic administration of HPI-1 is challenging due to its minimal aqueous solubility and poor bioavailability. We engineered a polymeric nanoparticle from [poly(lactic-co-glycolic acid); (PLGA)] conjugated with polyethylene glycol (PEG), encapsulating HPI-1 (NanoHHI). NanoHHI particles have an average diameter of approximately 60 nm, forms uniform aqueous suspension, and improved systemic bioavailability compared with the parent compound. In contrast to the prototype targeted Smo antagonist, HhAntag (Genentech), NanoHHI markedly inhibits the growth of allografts derived from Ptch−/+; Trp53−/− mouse medulloblastomas that harbor a SmoD477G binding site mutation (P < 0.001), which is accompanied by significant downregulation of mGli1 as well as bona fide Hh target genes (Akna, Cltb, and Olig2). Notably, NanoHHI combined with gemcitabine also significantly impedes the growth of orthotopic Pa03C pancreatic cancer xenografts that have a ligand-dependent, paracrine mechanism of Hh activation when compared with gemcitabine alone. No demonstrable hematologic or biochemical abnormalities were observed with NanoHHI administration. NanoHHI should be amenable to clinical translation in settings where tumors acquire mutational resistance to current Smo antagonists. Mol Cancer Ther; 11(1); 165–73. ©2011 AACR.

Biological evaluation of paclitaxel-peptide conjugates as a model for MMP2-targeted drug delivery

Paclitaxel (PTX) is a highly effective and cytotoxic agent widely used for the treatment of several solid tumors. However, PTX shows dose-limiting cytotoxicity and in most of the cases induces drug resistance followed by failure in treatments. To enhance the therapeutic index of a given drug, various drug delivery methods are being explored to systemically deliver sufficient amount of the drug to the desired site. In the present study, we designed and synthesized two PTX prodrugs by conjugating PTX at different sites with an octapeptide (AcGPLGIAGQ) that can be cleaved by MMP-2 at tumor sites. As a result, PTX is expected to be released in the tumor sites, absorbed by the tumor cells, and thereby inhibit the tumor growth. We evaluated the in vitro activities of the two drugs in a panel of drug-sensitive and -resistant cancer cell lines and their in vivo efficacy in a HT1080 fibrosarcoma mouse xenograft model that highly overexpress MMP2. Our in vitro results showed that the PTX-AcGPLGIAGQ conjugates inhibited cancer cell proliferation with higher activity compared with that observed for free PTX, both of which were mediated by an arrest of G2/M-phase of the cell cycle. Consistent with the in vitro results, treatment with PTX-octapeptide conjugate resulted in extensive areas of necrosis and a lower percentage of proliferating cells in xenograft tumor sections. Together, our results indicate the potential of the tumor-targeted delivery of PTX exploiting the specific recognition of MMP2 to reduce toxicity and selective killing of tumor cells.

Molecular characterization of tetracycline-resistant genes and integrons from avirulent strains of Escherichia coli isolated from catfish.

A study was undertaken to investigate the occurrence of tetracycline-resistant genes and to characterize the integrons present in Escherichia coli isolated from catfish. Sixty-three tetracycline-resistant E. coli strains were isolated from the intestinal contents of 407 farm-raised catfish. All strains were resistant to multiple antibiotics. A polymerase chain reaction (PCR) assay detected tetA in the DNA of 15 of 63 (25.0%) isolates by amplifying a PCR amplicon measuring 957 bp. Oligonucleotide primers targeting a 436-bp region of tetB successfully amplified a PCR amplicon from 47 of 63 (77.0%) isolates, indicating that tetB was predominant. Oligonucleotide primers specific for tetC amplified a 589-bp PCR amplicon from 3 of 63 (5%) isolates. Eleven (17.0%) of the isolates contained both tetA and tetB genes. Class I integrons amplified from the genomic DNA of 14 of 63 (22.0%) isolates measured 1.6 and 1.8 kb. Sequence analysis of the 1.6 kb integrons indicated the presence of three different gene cassettes: a dfrA12, conferring resistance to trimethoprim; an open reading frame, orfF, a hypothetical protein of unknown function; and aadA2, conferring resistance to aminoglycosides. Sequence analysis of the 1.8-kb integron indicated the presence of dfrA17 and aadA5. PCR assays for the detection of the six predominant virulence genes failed to amplify any genes from the genomic DNA. Pulsed-field gel electrophoresis using XbaI identified 16 distinct macro restriction patterns among the 63 isolates. The dendrogram analysis indicated that the DNA from 4 of 16 isolates had a similarity index of 90.0%. Our results indicate that the use of oxytetracycline and Romet 30 (sulfadimethoxine and ormetoprim) in farm-raised catfish may select for multiple antibiotic-resistant E. coli that could serve as a reservoir of tetracycline, trimethoprim, and aminoglycoside resistance genes.

Cholorpheniramine tannate complexes: Physicochemical, chemometric, and taste masking evaluation

The focus of present investigation was to evaluate the tannic acid (TA) complexes of cholorpheniramine maleate (CPM) and characterize it by a variety of physicochemical, dissolution, and electronic tongue methods. The complexes were prepared in various molar ratios by solvent evaporation method. They were characterized by spectroscopic, thermal, powder X-ray, electronic tongue, solubility and dissolution methods. FTIR (infrared red) spectra showed complex formation between the TA and CPM. Complex formation has significantly lowered the drug solubility and sustained its release for more than 24 h in phosphate buffer pH 6.8. On the contrary, the release was much faster in the presence of Avicel PH 113 in the same molar ratio complex. The complex formulation has suppressed the bitter taste of CPM as indicated by Euclidean distance in electronic tongue evaluation. NIR-CI (near infrared chemical imaging) showed lower skew value that indicated the homogenous distribution of formulation components. The chemometric models were also developed using the NIR data. The model based on second derivative data was better in predicting the TA and CPM loading as indicated by higher values of R, R(2) and lower values of root mean square error and standard errors. Furthermore, it has a better accuracy and less biased in comparison to other models. In conclusion, the CPM tannate has a sustained release behavior and excipients play a major role in modifying its release. Additionally, the complexes with varying molar ratio of tannate to CPM have differential taste masking abilities than that of the pure drug.

Molecular Characterization of Fluoroquinolone-Resistant Aeromonas spp. Isolated from Imported Shrimp

ABSTRACT Sixty-three nalidixic acid-resistant Aeromonas sp. isolates were obtained from imported shrimp. Phylogenetic analysis of gyrB sequences indicated that 18 were A. enteropelogenes, 26 were A. caviae, and 19 were A. sobria. Double missense mutations in the quinolone resistance-determining region (QRDR) of gyrA at codon 83 (Ser→Val/Ile) and codon 92 (Leu→Met) coupled with a point mutation of parC at codon 80 (Ser→Ile/Phe) conferred high levels of quinolone resistance in the isolates. A majority of A. enteropelogenes and A. caviae strains harbored toxin genes, whereas only a few A. sobria strains harbored these genes. The fluoroquinolone-resistant Aeromonas spp. exhibited higher cytotoxicity than fluoroquinolone-sensitive, virulent Aeromonas spp. to rat epithelial cells.

Development and application of a validated stability-indicating Ultra-Performance Liquid Chromatography (UPLC) method for the determination of dantrolene and its related impurities

A rapid, sensitive, and specific ultra-performance liquid chromatographic (UPLC) method was developed for the simultaneous determination of dantrolene and its potential degradation impurities. Chromatographic separation was achieved on a Waters Acquity UPLC system using a Waters BEH C18 (2.1 × 100 mm, 1.7 µM) analytical column and Waters BEH C18 (2.1 × 5 mm, 1.7 µM) guard column. The compounds were eluted with a linear acetonitrile gradient (25–75%) over 3 min with a buffer composition of sodium acetate for method development, quantitation, and forced degradation studies. The flow rate was maintained at 0.5 mL/min. Column temperature was maintained at 35°C. Injection volume was 4 µL, and analysis was detected by a photodiode array detector at 375 nm. The method was validated according to USP Category I requirements for dantrolene. Forced degradation of dantrolene was conducted under the conditions of hydrolysis, oxidation, photolysis, and stability-indicating UPLC method was developed and validated. Two degradation products (related compound B and C) were formed in 0.1 N NaOH and 0.1 N HCl, respectively. The dantrolene was stable to oxidative decomposition. The degradation behavior under UV light was similar to 0.1 N HCl conditions. The method was used successfully for the quality assessment of dantrolene and its three impurities.

Draft Genome Sequence of Methicillin-Resistant Clinical Staphylococcus aureus Isolate 51S (Sequence Type 291)

ABSTRACT We report the draft genome sequence of a methicillin-resistant clinical Staphylococcus aureus isolate with a novel spa type and sequence type (ST291), isolated from a renal failure patient in Rawalpindi, Pakistan.

Draft Genome Sequence of Multidrug-Resistant Enterococcus faecium Clinical Isolate VRE3, with a Sequence Type 16 Pattern and Novel Structural Arrangement of Tn1546

ABSTRACT Multidrug-resistant Enterococcus faecium has emerged as a nosocomial pathogen that may infect the body at various sites, including the gastrointestinal tract, and has serious implications in human health and disease. Here, we present the draft genome sequence of clinical strain VRE3, which exhibited a sequence type 16 (ST16) pattern and carried truncated Tn1546, a mobile genetic element encoding a high level of vancomycin resistance.

Draft Genome Sequence of a Methicillin-Resistant Staphylococcus aureus ST1413 Strain for Studying Genetic Mechanisms of Antibiotic Resistance.

ABSTRACT Here we report the whole draft genome sequence of a methicillin-resistant Staphylococcus aureus ST1413 strain. Determining the distribution and arrangement of various genes associated with drug resistance, toxicity, and diseases will enhance our understanding about its adaptability to thrive in different ecological niches and help in the development of effective treatments for enterotoxigenic staphylococcal infections.