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author:("Patel, deal")
1.  Physicochemical Characterization of 9-Aminocamptothecin in Aqueous Solutions 
AAPS PharmSciTech  2013;15(1):223-229.
The present manuscript provides a detailed physicochemical and thermodynamic characterization of 9-aminocamptothecin (9AC) which can be used as a tool to develop novel formulation strategies for optimum pharmacological activity. The pKa of 9AC was determined to be 2.43 at 37°C, while the basicity of quinoline nitrogen of 9AC was found to decrease with increasing temperature due to a positive enthalpy of deprotonation of 10.36 kJ mol−1. The equilibrium solubility as well as the intrinsic solubility of the drug was found to increase with increasing temperature and decreasing pH. The enthalpies of solution of unionized and ionized forms of 9AC obtained from isothermal and iso-pH equilibrium solubility measurements were found to be 36.01 and 24.72 kJ mol−1, respectively. Equilibrium hydrolysis studies revealed the hydrolytic susceptibility of 9AC with only 14% of active lactone species remaining at physiological pH 7.4. The intrinsic partition coefficient log P of the free base, 9AC–lactone, was estimated to be 1.28 (a characteristic of molecules suitable for oral absorption). The estimated pKa and log P values of 9AC, combined with its increased solubility at lower pH, are features that can be utilized to develop novel drug delivery systems to optimize the antitumor activity of 9AC.
PMCID: PMC3909166  PMID: 24297599
9-aminocamptothecin; hydrolysis; partition coefficient; physicochemical characterization; solubility
2.  Application of Novel CO2 Laser-Suction Device 
Background Development of the flexible CO2 fiber has presented new opportunities for the use of precision laser cutting in cranial procedures. The efficacy of the CO2 scalpel is further enhanced by combining it with a fluid removal suction capability.
Objectives We report our experience with a novel CO2 laser-suction device.
Methods The novel laser-suction device was designed in conjunction with OmniGuide Inc. (Cambridge, Massachusetts, USA). We performed a case review of its use in firm tumors that were resistant to resection by bipolar, suction, and ultrasonic aspirator.
Results The laser-suction device was applied in three tumors where resection with ultrasonic aspiration failed. Tumor resection using the laser-suction device was successful in all three cases. There were no complications related to the laser-suction device. There were no instances of intraoperative device malfunction.
Discussion The CO2 laser combined with suction is a useful instrument for resection of firm tumors that prove to be resistant to ultrasonic aspiration. We also find it to be useful in settings where precise tissue incisions are desired with minimal manipulation. In our experience, the surgical efficiency of the CO2 laser is improved by the laser-suction device. This device allows the surgeon to utilize a suction device and laser in a single hand and enables concurrent use of bipolar electrocautery without repeated instrument changes.
PMCID: PMC3866789  PMID: 24436938
laser surgery; carbon dioxide laser; neurosurgical procedure; omniguide; microsurgery; laser suction
3.  Somatic hybrid plants of Nicotiana × sanderae (+) N. debneyi with fungal resistance to Peronospora tabacina 
Annals of Botany  2011;108(5):809-819.
Background and Aims
The genus Nicotiana includes diploid and tetraploid species, with complementary ecological, agronomic and commercial characteristics. The species are of economic value for tobacco, as ornamentals, and for secondary plant-product biosynthesis. They show substantial differences in disease resistance because of their range of secondary products. In the last decade, sexual hybridization and transgenic technologies have tended to eclipse protoplast fusion for gene transfer. Somatic hybridization was exploited in the present investigation to generate a new hybrid combination involving two sexually incompatible tetraploid species. The somatic hybrid plants were characterized using molecular, molecular cytogenetic and phenotypic approaches.
Mesophyll protoplasts of the wild fungus-resistant species N. debneyi (2n = 4x = 48) were electrofused with those of the ornamental interspecific sexual hybrid N. × sanderae (2n = 2x = 18). From 1570 protoplast-derived cell colonies selected manually in five experiments, 580 tissues were sub-cultured to shoot regeneration medium. Regenerated plants were transferred to the glasshouse and screened for their morphology, chromosomal composition and disease resistance.
Key Results
Eighty-nine regenerated plants flowered; five were confirmed as somatic hybrids by their intermediate morphology compared with parental plants, cytological constitution and DNA-marker analysis. Somatic hybrid plants had chromosome complements of 60 or 62. Chromosomes were identified to parental genomes by genomic in situ hybridization and included all 18 chromosomes from N. × sanderae, and 42 or 44 chromosomes from N. debneyi. Four or six chromosomes of one ancestral genome of N. debneyi were eliminated during culture of electrofusion-treated protoplasts and plant regeneration. Both chloroplasts and mitochondria of the somatic hybrid plants were probably derived from N. debneyi. All somatic hybrid plants were fertile. In contrast to parental plants of N. × sanderae, the seed progeny of somatic hybrid plants were resistant to infection by Peronospora tabacina, a trait introgressed from the wild parent, N. debneyi.
Sexual incompatibility between N. × sanderae and N. debneyi was circumvented by somatic hybridization involving protoplast fusion. Asymmetrical nuclear hybridity was seen in the hybrids with loss of chromosomes, although importantly, somatic hybrids were fertile and stable. Expression of fungal resistance makes these somatic hybrids extremely valuable germplasm in future breeding programmes in ornamental tobacco.
PMCID: PMC3177675  PMID: 21880657
Chloroplast DNA (cpDNA); protoplasts; electrofusion; fungal resistance; genomic in situ hybridization (GISH); mitochondrial DNA (mtDNA); Nicotiana debneyi; N. × sanderae; Peronospora tabacina; random amplified polymorphic DNA (RAPD); somatic hybridization
4.  Simultaneous Estimation of Amlodipine Besylate and Indapamide in a Pharmaceutical Formulation by a High Performance Liquid Chromatographic (RP-HPLC) Method 
Scientia Pharmaceutica  2012;80(3):581-590.
An isocratic reversed-phase liquid chromatograpic assay method was developed for the quantitative determination of amlodipine besylate (AML) and indapamide (IND) in combined dosage form. A Brownlee C-18, 5 μm column with a mobile phase containing 0.02 M potassium dihydrogen phosphate–methanol (30+70, v/v) total pH-adjusted to 3 using o-phosphoric acid was used. The flow rate was 1.0 mL min−1 and effluents were monitored at 242 nm. The retention times of amlodipine besylate and indapamide were 5.9 min and 3.6 min, respectively. The proposed method was validated with respect to linearity, accuracy, precision, and robustness. The method was successfully applied to the estimation of amlodipine besylate and indapamide in combined tablet dosage forms.
PMCID: PMC3447622  PMID: 23008807
RP-HPLC; Amlodipine; Indapamide; Tablet; Validation

Results 1-4 (4)