Analytica Chimica Acta (v.847, #C)

Paper-based electrochemical cyto-device for sensitive detection of cancer cells and in situ anticancer drug screening by Min Su; Lei Ge; Shenguang Ge; Nianqiang Li; Jinghua Yu; Mei Yan; Jiadong Huang (1-9).
In this work, a novel versatile microfluidic paper-based electrochemical cyto-device was fabricated for sensitive cancer cell detection and in situ screening of anticancer drugs in a multiplex manner based on in-electrode three-dimensional cell culture.Display OmittedIn this work, using human acute promyelocytic leukemia cells (HL-60) as a model, a novel microfluidic paper-based electrochemical cyto-device (μ-PECD) was fabricated to demonstrate a facile, portable, and disposable approach for cancer cell detection and in situ screening of anticancer drugs in a high-throughput manner. In this μ-PECD, aptamers modified three-dimensional macroporous Au-paper electrode (Au-PE) was fabricated and employed as the working electrode for specific and efficient cancer cell capture as well as for sequential in-electrode 3D cell culture. This Au-PE showed enhanced capture capacity for cancer cells and good biocompatibility for preserving the activity of captured living cells. Sensitive cancer cell detection was achieved in this μ-PECD, which could respond down to four HL-60 cells in 10 μL volume with a wide linear calibration range from 5.0 × 102 to 7.5 × 107 cells mL−1 and exhibited good stability and reproducibility. Then, in situ anticancer drug screening was successfully implemented in this μ-PECD through monitoring of the apoptotic cancer cells after the in-electrode 3D cell culture with drug-containing culture medium, demonstrating its wide range of potential applications to facilitate effective clinical cancer diagnosis and treatment.
Keywords: Lab-on-paper; Electrochemistry; Cytosensor; Cancer cell; Drug screening;

Display OmittedCeO2-deposited mesoporous silica nanoparticles were synthesized as a probe to determine carcinoembryonic antigen (CEA) in serum by inductively coupled plasma-mass spectrometry (ICP-MS). The prepared mesoporous nanoparticles were modified and tagged to the target for sandwich-type immunoassay. Fe3O4 magnetic nanoparticles (MNPs) were also synthesized and immobilized with antibody to extract the target biomarker. The calibration curve of the synthesized CeO2-deposited silica nanoparticles, which was plotted by the signal ratio of 140Ce/57Fe measured by ICP-MS vs. the concentration of CEA, showed excellent linearity and sensitivity owing to the signal amplification and low spectral interference. Under optimal conditions, the sandwich-type analytical method was applied to determine CEA in serum spiked in the range of 0.001–5 ng mL−1 and showed a limit of detection of 0.36 ng mL−1. Since the deposited CeO2 in the mesoporous silica layer can be substituted by other metal compounds, various kinds of metal-deposited nanoparticles can be prepared as probe materials for multiplex detection in bioanalysis.

Display OmittedA method is described for the characterization of measurement errors with non-uniform variance (heteroscedastic noise) in contiguous signal vectors (e.g., spectra, chromatograms) that does not require the use of replicated measurements. High-pass digital filters based on inverted Blackman windowed sinc smoothing coefficients are employed to provide point estimates of noise from measurement vectors. Filter parameters (number of points, cutoff frequency) are selected based on the amplitude spectrum of the signal in the Fourier domain. Following this, noise estimates from multiple signals are partitioned into bins based on a variable that correlates with the noise amplitude, such as measurement channel or signal intensity. The noise estimates in each bin are combined to estimate the standard deviation and, where appropriate, a functional model of the noise can be obtained to characterize instrumental errors (e.g., shot noise, proportional noise). The proposed method is demonstrated and evaluated with both simulated and experimental data sets, and results are compared with replicated measurements. Experimental data includes fluorescence spectra, ion chromatograms from liquid chromatography/mass spectrometry, and UV–vis absorbance spectra. The limitations and advantages of the new method compared to replicate analysis are presented.
Keywords: Measurement errors; Heteroscedastic noise; Digital filters; Error models; Variance estimation; Limit of detection;

A label-free amperometric immunosensor for detection of zearalenone based on trimetallic Au-core/AgPt-shell nanorattles and mesoporous carbon by Lei Liu; Yingjun Chao; Wei Cao; Yulan Wang; Chuannan Luo; Xuehui Pang; Dawei Fan; Qin Wei (29-36).
Display OmittedA novel label-free amperometric immunosensor is proposed for the ultrasensitive detection of zearalenone (ZEN) based on mesoporous carbon (MC) and trimetallic nanorattles (core/shell particles with movable cores encapsulated in the shells). The nanorattles are composed of special Au-core and imperfect AgPt-shell structure (Au@AgPt). The Au@AgPt nanorattles are loaded onto the MC by physical adsorption. The structure of the Au@AgPt nanorattles was characterized by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Energy dispersive X-ray spectroscopy (EDS) confirmed the composition of the synthesized nanorattles. Compared with monometallic and bimetallic nanoparticles (NPs), Au@AgPt nanorattles show a higher electron transfer rate due to the synergistic effect of the Au, Ag and Pt NPs. MC further improves the sensitivity of the immunosensor because of its extraordinarily large specific surface area, suitable pore arrangement and outstanding conductivity. The large specific surface area of MC and MC@Au@AgPt were characterized by the BET method. ZEN antibodies are immobilized onto the nanorattles via Ag–NH2 bonds and Pt–NH2 bonds. Cyclic voltammetry and square wave voltammetry were used to characterize the recognizability of ZEN. Under optimum experimental conditions, the proposed immunosensor exhibited a low detection limit (1.7 pg mL−1), a wide linear range (from 0.005 to 15 ng mL−1) as well as good stability, reproducibility and selectivity. The sensor can be used in clinical analysis.
Keywords: Zearalenone; Label-free; Amperometric immunosensor; Trimetallic Au@AgPt nanorattles; Mesoporous carbon;

Display OmittedAn ultrasensitive multiplexed immunoassay method was developed by using streptavidin/nanogold/carbon nanohorn (SA/Au/CNH) as a novel signal tag to induce silver enhancement for signal amplification. The Au/CNH was prepared by in situ growth of nanogold on carboxylated CNH and functionalized with streptavidin. The SA/Au/CNH showed well dispersibility in physiological buffer and could sever as a common tracing tag to recognize biotinylated signal antibody. The immunosensor array was prepared on disposable screen-printed electrodes. Through sandwich-type immunoreaction and biotin-streptavidin affinity reaction, the SA/Au/CNH tag was captured on the immunoconjugates to induce silver deposition and amplify the electrochemical stripping signals. Using α-fetoprotein and carcinoembryonic antigen as model analytes, the proposed method showed wide linear ranges with the detection limits down to 0.024 pg mL−1 and 0.032 pg mL−1, respectively, and eliminated completely signal cross-talk between adjacent immunosensors. It provided a convenient, high-efficient and ultrasensitive electrochemical detection route for biological analytes, showing great potential in clinical application.
Keywords: Electrochemical sensor; Immunosensor; Multiplexed immunoassay; Signal amplification; Silver enhancement; Carbon nanohorn;

Display OmittedThe stability of antimonite in iron rich water samples is rather poor. The aim of the study was to find a simple procedure by using preservation agents to keep the speciation information from sampling till analysis. Species analysis of antimony traces (lower μg L−1 range) was done by HPLC–ICP-MS. Phosphoric acid, tartrate, and EDTA were tested as preservation agents in comparison to no addition. The use of EDTA as the preservation agent provided the best results. The suggested procedure is to add 20 mM EDTA as final concentration immediately during sampling and store them at dark and cool (6 °C) as usual. Using this procedure, the stability of Sb(III) as well as of Sb(V) was proven for at least 7 days, even for high iron concentrations.
Keywords: Antimony speciation; Inductively coupled plasma-mass-spectrometry; Preservation procedure; Sample storage;

One-step synthesis and applications of fluorescent Cu nanoclusters stabilized by l-cysteine in aqueous solution by Xiaoming Yang; Yuanjiao Feng; Shanshan Zhu; Yawen Luo; Yan Zhuo; Yao Dou (49-54).
An innovative and simple strategy for synthesizing high-fluorescent Cu nanoclusters stabilized with l-cysteine has been successfully established in aqueous solution. Significantly, the Cu nanoclusters were employed for sensitive and selective detections of Hg2+, coding and fluorescent staining, suggesting their potential toward various applications.Display OmittedHerein, an innovative and simple strategy for synthesizing high fluorescent Cu nanoclusters was successfully established while l-cysteine played a role as the stabilizer. Meaningfully, the current Cu nanoclusters together with a quantum yield of 14.3% were prepared in aqueous solution, indicating their extensive applications. Subsequently, the possible fluorescence mechanism was elucidated by fluorescence, UV–vis, HR-TEM, FTIR, XPS, and MS. Additionally, the CuNCs were employed for assaying Hg2+ on the basis of the interactions between Hg2+ and l-cysteine; thus facilitating the quenching of their fluorescence. The proposed analytical strategy permitted detections of Hg2+ in a linear range of 1.0 × 10−7  mol L−1  × 10−3  mol L−1, with a detection limit of 2.4 × 10−8  mol L−1 at a signal-to-noise ratio of 3. Significantly, this CuNCs described here were further applied for coding and fluorescent staining, suggesting may broaden avenues toward diverse applications.
Keywords: Cu nanoclusters; l-cysteine; One-step synthesis; Applications;

Display OmittedA sensitive fluorescence turn-on method for trace amounts of uranyl ion (UO2 2+) in solution has been developed in this study, based on aggregation induced emission enhancement (AIEE) characteristics of 4-pethoxycarboxyl salicylaldehyde azine (PCSA) induced by complex interaction between UO2 2+ and PCSA. Under optimized conditions, a fluorescence enhancement at 540 nm could be observed, which was linearly related to the concentration of UO2 2+ in the range of 1–25 ppb (part per billion). Analytical data showed that a detection limit of 0.2 ppb was achieved with the relative standard deviation (R.S.D.) 1.3% (n  = 5). The proposed method was successfully utilized in quantifying UO2 2+ in fuel processing wastewaters.
Keywords: Uranyl ion detection; Schiff base; Aggregation induced emission enhancement; Fluorescence turn-on detection;

Investigating sub-2 μm particle stationary phase supercritical fluid chromatography coupled to mass spectrometry for chemical profiling of chamomile extracts by Michael D. Jones; Bharathi Avula; Yan-Hong Wang; Lu Lu; Jianping Zhao; Cristina Avonto; Giorgis Isaac; Larry Meeker; Kate Yu; Cristina Legido-Quigley; Norman Smith; Ikhlas A. Khan (61-72).
PCA analysis of the commercial tea sample extracts combined with the dataset of the authenticated chamomile extracts was examined. The phytochemical profile of the tea samples analyzed showed a similar profile compared to German chamomile.Display OmittedRoman and German chamomile are widely used throughout the world. Chamomiles contain a wide variety of active constituents including sesquiterpene lactones. Various extraction techniques were performed on these two types of chamomile. A packed-column supercritical fluid chromatography–mass spectrometry method was designed for the identification of sesquiterpenes and other constituents from chamomile extracts with no derivatization step prior to analysis. Mass spectrometry detection was achieved by using electrospray ionization. All of the compounds of interest were separated within 15 min. The chamomile extracts were analyzed and compared for similarities and distinct differences. Multivariate statistical analysis including principal component analysis and orthogonal partial least squares-discriminant analysis (OPLS-DA) were used to differentiate between the chamomile samples. German chamomile samples confirmed the presence of cis- and trans-tonghaosu, chrysosplenols, apigenin diglucoside whereas Roman chamomile samples confirmed the presence of apigenin, nobilin, 1,10-epioxynobilin, and hydroxyisonobilin.
Keywords: Convergence chromatography; Supercritical fluid chromatography; Mass spectrometry; Chamomile; Chemical profiling; Multivariate analysis;

Display OmittedRNA integrity is important in RNA studies because poor RNA quality may impact downstream methodologies. This study proposes a rapid and cost-effective method for the determination of RNA integrity based on CE-LIF in the presence of electroosmotic flow. The proposed method uses poly(ethylene) oxide (M avg  = 4,000,000 Da) as a sieving matrix for total RNA separation. Ethidium bromide (μg mL−1) was dissolved in a polymer solution as an interchelating dye for on-column fluorescent labeling. The 28S rRNA, 18S rRNA, 5.8S rRNA, 5S rRNA and tRNA from the total human RNA extracted from the cells were fully separated using the proposed method. The lowest detectable concentration of total RNA achieved was 100 pg μL−1 with a 6 min sample injection followed by on-column concentration. In addition, the temperature-induced degradation of total RNA was observed by CE-LIF. The electropherograms revealed more fragmentation of 28S and 18S rRNAs by temperature-induced hydrolysis compared with the 5.8S rRNA, 5S rRNA and tRNA. Therefore, the results indicated that RNA degradation should be considered for long-term, high-temperature incubations in RNA-related experiments involving RNA hybridization. The proposed method is furthermore, applied to the determination of 5S rRNA overexpressed in ovarian cancer cells as compared to the cervical cancer cells. Overall, CE-LIF is highly promising for rapid screening of ovarian cancers without tedious pre-amplification steps.
Keywords: Ethidium bromide; Capillary electrophoresis; Laser-induced fluorescence; Poly(ethylene oxide); On-column concentration; Ovarian cancer; Ribonucleic acid;

Variation of mobility with pH, temperature, and bulk salt concentration.Display OmittedThe influence of temperature on the electrophoresis of a spherical, pH-regulated polyelectrolyte (PE) particle having both acidic and basic functional groups in an aqueous salt solution containing multiple ionic species is investigated theoretically. The type of particle considered simulates entities including proteins, biomolecules, and synthetic polymers. The applicability of the model proposed is verified by the experimental data of succinoglycan nanoparticles reported in the literature. Taking a glycin PE as an example, the variations of its mobility with the temperature, bulk salt concentration, and pH are examined through numerical simulation. Empirical relationships that correlate the mobility with these factors are obtained for temperature, bulk salt concentration, and pH ranging from 293 to 308 K, 10−4 to 10−2  M, and 2-10.5, respectively. Several interesting and important results for the PE mobility are observed. These results provide not only valuable information for interpreting experimental data but also for designing electrophoresis devices where temperature can play a role.
Keywords: Electrophoresis; pH-regulated polyelectrolyte; Temperature effect;