TGA/Chemometrics addressing innovative preparation strategies for functionalized carbon nanotubes

In this work, functionalized carbon nanotubes (CNTs) using two polyamine polymers, polyethyleneimine (PEI) and polyamidoamine dendrimer (PAMAM), were investigated by thermal analysis in order to address preparation strategies to obtain low cytotoxic compounds with the ability to conjugate microRNAs and, at the same time, to transfect efficiently endothelial cells. Thermogravimetric analysis (TGA) was coupled to chemometrics as a novel analytical strategy to characterize functionalized CNTs from different preparation conditions. In particular, two starting materials were considered: very small CNTs and carboxylated CNTs (CNT-COOH) in order to examine the affinity with polymers. Chemometrics permitted to compare results from TGA and to investigate the effect of a number of factors affecting the synthesis of coated nanotubes including a different amount of involved polymer and the time required for the suspension for a satisfactory and reproducible preparation procedure. The results demonstrated the effectiveness of TGA as a tool able to address synthesis of coated CNTs to be employed as efficient drug delivery vectors in biomedical applications.     

紫萍与青萍中黄酮类成分的测定及多变量统计分析

目的：建立紫萍与青萍中黄酮类成分测定的方法,对其含量测定结果进行多变量统计分析。方法：采用高效液相色谱四级杆飞行时间串联质谱（HPLC-QTOF-MS）法,色谱柱：Agilent ZORBAX Extend-C18 RRHT（2.1 mm × 50 mm,1.8 μm）;以甲醇为流动相A,以0.1%甲酸溶液为流动相B,梯度洗脱;流速为0.3 mL·min-1;柱温为30 ℃;进样量为1 μL;测定52批浮萍样品中荭草苷、异荭草苷、牡荆苷、木犀草苷、木犀草素、芹菜素6种黄酮类成分含量,并采用主成分分析（PCA）和正交偏最小二乘法-判别分析（OPLS-DA）进行多变量统计分析。结果：6种黄酮类化合物的精密度、重复性和稳定性良好（RSD≤4.0%）,平均加样回收率在95.41%~105.82%,RSD为2.03%~4.16%（n=6）。HPLC-QTOF-MS法结合主成分聚类分析宜用于比较不同品种浮萍中黄酮类成分含量差异。结论：采用PCA与OPLS-DA进行多维变量统计分析与测定结果相符,HPLC-QTOF-MS结合化学计量学方法能够评价不同浮萍中的6种黄酮类化合物。     

小波变换在NIR定量模型中的应用

本文基于小波变换在近红外（NIR）定量模型中的作用：降噪、消除背景干扰,数据压缩和变量筛选,结合化学计量学在近红外建模中的应用,综述了近10年来小波变换在近红外定量模型中的应用概况。随着近红外分析技术的不断发展和完善,小波变换将会发挥它的优势,为NIR定量模型建立与应用提供支撑。     

中药四性和微量元素含量关系的初步研究

本文尝试利用化学计量学技术从整体上探讨无机元素含量水平与中药四性的关系,对115味中草药的32种元素的三电极直流等离子体原子发射光谱数据应用模式识别方法进行了系统的多变量统计分析。以中药四性理论为依据的三类药物(温热药、平性药、寒凉药)中,有监督模式识别方法之一——线性判别法(LDA)的正确判断能力高达70.43%,显示了这115味中草药的数值分类结果和以中药四性理论为依据自然分类的良好的一致性;2个无机元素含量均值中,寒凉药类有84.37%高于整体,而温热药类和平性药类分别有90.62%和84.37%低于整体,进一步证明了中药无机元素含量水平是决定中药四性的物质基础之一,揭示了微量元素含量和中药疗效之间存在的相关性。     

Quantifying low levels of polymorphic impurity in clopidogrel bisulphate by vibrational spectroscopy and chemometrics

Vibrational spectroscopic methods were developed for quantitative analysis of Form II of clopidogrel bisulphate in Form I and Form II polymorphic mixtures. Results show that both IR and Raman spectroscopy combined with chemometrics are suitable to quantify low levels of Form II in Form I, down to 2 and 3%, respectively, with less than 1% limit of detection. Different preprocessing and multivariate methods were applied for spectral processing and were compared to find the best chemometric model. Common problems of quantitative vibrational spectroscopy in the solid phase are discussed; and procedures appropriate to eliminate them are proposed.     

Cancer diagnosis by discrimination between normal and malignant human blood samples using attenuated total reflectance-Fourier transform infrared spectroscopy

FTIR spectroscopy is a common technique for cancer diagnosis. Applied tissue samples are heterogeneous and may be damaged in preparation procedures. Easier sampling, more available samples and also easier process with assured results would be interesting. Whole blood samples include all of these qualifications and our hypothesis was the bio-molecular changes in blood which manifest themselves in different optical signatures, detectable by FTIR spectroscopy. Noncancerous blood samples were differentiated from cancerous ones using ATR-FTIR spectroscopy and LDA classification method. Procedure was 100 percent and 90 percent accurate in prediction of cancerous or noncancerous situation for 33 known and 10 unknown samples, respectively.     

Raman spectroscopy of coated pharmaceutical tablets and physical models for multivariate calibration to tablet coating thickness

Raman spectra of a set of coated pharmaceutical tablets were analyzed for the purpose of calibrating the spectra to tablet coating thickness. Acetaminophen tablets were coated with a hydroxypropylmethylcellulose/polyethylene glycol film coating whose thickness was varied from 0 to 6% weight gain. Coatings were also prepared with two concentrations of TiO2 at several film thicknesses. The resulting spectral data set was analyzed using several different multivariate calibration procedures. The procedures examined in this study included spectral correction followed by target factor analysis, spectral correction with baseline subtraction followed by principal component regression, and first derivative computation followed by principal component regression. The results demonstrate that target factor analysis is a viable method for calibration of Raman spectra to tablet coating thickness. Calibration based on derivative spectra resulted in linear correlation that was equal to that of the results of target factor analysis for coatings without TiO2. However, target factor analysis was found to be superior to other methods when TiO2 was present in the tablet coatings. The effect of sample fluorescence on each of these chemometric methods was also examined. It was found that when photobleaching of fluorescent impurities due to exposure to the Raman excitation source was controlled, the tablet coating thickness could be calibrated to the intensity of the fluorescence signal. The results also demonstrate that for the samples examined here, calibration by target factor analysis is insensitive to variation in fluorescent intensity when the tablet coating emission spectrum is included in the matrix of target vectors.     

Synthesis and evaluation of sesquiterpene lactone inhibitors of phospholipase A2 from Bothrops jararacussu

Several sesquiterpene lactone were synthesized and their inhibitive activities on phospholipase A₂ (PLA₂) from Bothrops jararacussu venom were evaluated. Compounds Lac01 and Lac02 were efficient against PLA₂ edema-inducing, enzymatic and myotoxic activities and it reduces around 85% of myotoxicity and around 70% of edema-inducing activity. Lac05-Lac08 presented lower efficiency in inhibiting the biological activities studied and reduce the myotoxic and edema-inducing activities around only 15%. The enzymatic activity was significantly reduced. The values of inhibition constants (K_I) for Lac01 and Lac02 were approximately 740 μM, and for compounds Lac05-Lac08 the inhibition constants were approximately 7.622-9.240 μM. The enzymatic kinetic studies show that the sesquiterpene lactones inhibit PLA₂ in a non-competitive manner. Some aspects of the structure-activity relationships (topologic, molecular and electronic parameters) were obtained using ab initio quantum calculations and analyzed by chemometric methods (HCA and PCA). The quantum chemistry calculations show that compounds with a higher capacity of inhibiting PLA₂ (Lac01-Lac04) present lower values of highest occupied molecular orbital (HOMO) energy and molecular volume (VOL) and bigger values of hydrophobicity (LogP). These results indicate some topologic aspects of the binding site of sesquiterpene lactone derivatives and PLA₂.     

基于化学计量学的左金丸及其类方组分溶出规律的模式识别研究

目的:建立左金丸及其类方的HPLC相对溶出率图谱,对其溶出规律进行化学模式识别和验证。方法:以左金丸及其类方HPLC图谱中各组分的相对溶出率为指标,建立左金丸及其类方HPLC相对溶出率图谱,并使用主成分分析、系统聚类分析和Fisher判别分析对其溶出规律进行模式识别研究。结果:主成分分析划分的3个主成分可全面概括左金丸及其类方HPLC相对溶出率图谱的20项指标;在主成分分析的基础上,采用聚类分析将左金丸及其类方各组分溶出规律划为6类,并建立了相应的Fisher判别函数,回判准确率100%。结论:初步建立了左金丸及其类方各组分溶出规律的化学模式识别的评价方法,可对左金丸及其类方的溶出规律进行准确、可靠、客观的识别和验证。     

同时定性定量测定混合物的光谱多元分析法

本文采用逐步回归方法,并结合光谱多组分分析的品质因数理论,对已知可能存在物种的范围,而实际的物种及其含量需待分析确定的混合物体系,可进行光谱数据解析,同时解决定性定量测定问题。与目标转换因子分析方法不同,本法毋需获取组分浓渡不尽相同的一组混合物光谱,仅用一个试样的光谱矢量数据即能同时完成定性定量分析,用药物试样对本法进行校验,获得满意结果。