Showing papers in "Analyst in 2010"
TL;DR: The increasing interest in Support Vector Machines (SVMs) over the past 15 years is described, including its application to multivariate calibration, and why it is useful when there are outliers and non-linearities.
Abstract: The increasing interest in Support Vector Machines (SVMs) over the past 15 years is described. Methods are illustrated using simulated case studies, and 4 experimental case studies, namely mass spectrometry for studying pollution, near infrared analysis of food, thermal analysis of polymers and UV/visible spectroscopy of polyaromatic hydrocarbons. The basis of SVMs as two-class classifiers is shown with extensive visualisation, including learning machines, kernels and penalty functions. The influence of the penalty error and radial basis function radius on the model is illustrated. Multiclass implementations including one vs. all, one vs. one, fuzzy rules and Directed Acyclic Graph (DAG) trees are described. One-class Support Vector Domain Description (SVDD) is described and contrasted to conventional two- or multi-class classifiers. The use of Support Vector Regression (SVR) is illustrated including its application to multivariate calibration, and why it is useful when there are outliers and non-linearities.
1,899 citations
TL;DR: Recent developments in optical biolabeling and bio-imaging involving upconversion nanoparticles are reviewed, simultaneously bringing to the forefront the desirable characteristics, strengths and weaknesses of these luminescent nanomaterials.
Abstract: Upconversion refers to non-linear optical processes that convert two or more low-energy pump photons to a higher-energy output photon. After being recognized in the mid-1960s, upconversion has attracted significant research interest for its applications in optical devices such as infrared quantum counter detectors and compact solid-state lasers. Over the past decade, upconversion has become more prominent in biological sciences as the preparation of high-quality lanthanide-doped nanoparticles has become increasingly routine. Owing to their small physical dimensions and biocompatibility, upconversion nanoparticles can be easily coupled to proteins or other biological macromolecular systems and used in a variety of assay formats ranging from bio-detection to cancer therapy. In addition, intense visible emission from these nanoparticles under near-infrared excitation, which is less harmful to biological samples and has greater sample penetration depths than conventional ultraviolet excitation, enhances their prospects as luminescent stains in bio-imaging. In this article, we review recent developments in optical biolabeling and bio-imaging involving upconversion nanoparticles, simultaneously bringing to the forefront the desirable characteristics, strengths and weaknesses of these luminescent nanomaterials.
1,284 citations
TL;DR: A novel algorithm named adaptive iteratively reweighted Penalized Least Squares (airPLS) that does not require any user intervention and prior information, such as peak detection etc., is proposed in this work.
Abstract: Baseline drift always blurs or even swamps signals and deteriorates analytical results, particularly in multivariate analysis. It is necessary to correct baseline drift to perform further data analysis. Simple or modified polynomial fitting has been found to be effective to some extent. However, this method requires user intervention and is prone to variability especially in low signal-to-noise ratio environments. A novel algorithm named adaptive iteratively reweighted Penalized Least Squares (airPLS) that does not require any user intervention and prior information, such as peak detection etc., is proposed in this work. The method works by iteratively changing weights of sum squares errors (SSE) between the fitted baseline and original signals, and the weights of the SSE are obtained adaptively using the difference between the previously fitted baseline and the original signals. The baseline estimator is fast and flexible. Theory, implementation, and applications in simulated and real datasets are presented. The algorithm is implemented in R language and MATLAB™, which is available as open source software (http://code.google.com/p/airpls).
644 citations
TL;DR: This critical review evaluates progress toward viable point-of-care protein biomarker measurements for cancer detection and diagnostics using a number of ultrasensitive immunosensors and some arrays developed, many based on nanotechnology.
Abstract: This critical review evaluates progress toward viable point-of-care protein biomarker measurements for cancer detection and diagnostics. The ability to measure panels of specific, selective cancer biomarker proteins in physicians' surgeries and clinics has the potential to revolutionize cancer detection, monitoring, and therapy. The dream envisions reliable, cheap, automated, technically undemanding devices that can analyze a patient's serum or saliva in a clinical setting, allowing on-the-spot diagnosis. Existing commercial products for protein assays are reliable in laboratory settings, but have limitations for point-of-care applications. A number of ultrasensitive immunosensors and some arrays have been developed, many based on nanotechnology. Multilabel detection coupled with high capture molecule density in immunosensors and arrays seems to be capable of detecting a wide range of protein concentrations with sensitivity ranging into the sub pg mL−1 level. Multilabel arrays can be designed to detect both high and ultralow abundance proteins in the same sample. However, only a few of the newer ultrasensitive methods have been evaluated with real patient samples, which is key to establishing clinical sensitivity and selectivity.
492 citations
TL;DR: A review of the current literature concerning the electrochemical applications and advancements of graphene, starting with its use as a sensor substrate through to applications in energy production and storage, depicting the truly remarkable journey of a material that has just come of age.
Abstract: Graphene, a 2D nanomaterial that possesses spectacular physical, chemical and thermal properties, has caused immense excitement amongst scientists since its freestanding form was isolated in 2004. With research into graphene rife, it promises enhancements and vast applicability within many industrial aspects. Furthermore, graphene possesses a vast array of unique and highly desirable electrochemical properties, and it is this application that offers the most enthralling and spectacular journey. We present a review of the current literature concerning the electrochemical applications and advancements of graphene, starting with its use as a sensor substrate through to applications in energy production and storage, depicting the truly remarkable journey of a material that has just come of age.
470 citations
TL;DR: The lysozyme-stabilized gold fluorescent clusters (LsGFC) have an average size of 1 nm and emission approximately 657 nm and can be used as a sensor for sensitive and selective Hg(2+) detection with a detection limit of 10 nM.
Abstract: Highly fluorescent gold clusters have been synthesized in basic aqueous solution by using lysozyme as reducing and stabilizing agents. The lysozyme-stabilized gold fluorescent clusters (LsGFC) have an average size of 1 nm and emission ∼ 657 nm. The fluorescence could be specifically quenched by Hg2+, so the LsGFC can be used as a sensor for sensitive and selective Hg2+ detection with a detection limit of 10 nM.
405 citations
TL;DR: Nanospray desorption electrospray ionization (nano-DESI) mass spectrometry is presented as an ambient pressure liquid extraction-ionization technique for analysis of organic and biological molecules on substrates and its potential for imaging applications is discussed.
Abstract: Nanospray desorption electrospray ionization (nano-DESI) mass spectrometry is presented as an ambient pressure liquid extraction-ionization technique for analysis of organic and biological molecules on substrates. Analyte is desorbed into a solvent bridge formed between two capillaries and the analysis surface. One capillary supplies solvent to create and maintain the bridge, while the second capillary transports the dissolved analyte from the bridge to the mass spectrometer. A high voltage applied between the inlet of mass spectrometer and the primary capillary creates a self-aspirating nanospray. This approach enables the separation of desorption and ionization events, thus providing independent control of desorption, ionization, and transport of the analyte. We present analytical capabilities of the method and discuss its potential for imaging applications.
397 citations
TL;DR: This review of DESI and other ambient methods centers on the accompanying chemical processes, which can be used to optimize chemical analysis, including molecular imaging.
Abstract: Mass spectrometry allows rapid chemical analysis of untreated samples in the ambient environment. This is a result of recent rapid progress in ambient ionization techniques. The most widely studied of these new methods, desorption electrospray ionization (DESI), uses fast-moving solvent droplets to extract analytes from surfaces and propel the resulting secondary microdroplets towards the mass analyzer. This review of DESI and other ambient methods centers on the accompanying chemical processes. Manipulation of the chemistry accompanying ambient ionization can be used to optimize chemical analysis, including molecular imaging. Solvent effects, geometry effects, electrochemical processes and mechanisms are covered. Extensions of the methodology to solution-phase analysis, to stand-off detection and to therapeutic drug analysis using miniature mass spectrometers are also treated.
366 citations
TL;DR: In this paper a preliminary algorithm for correcting RMieS is presented and evaluated using simulated data and results show that the 'dispersion artefact' appears to be removed; however, the correction is not perfect.
Abstract: Infrared spectra of single biological cells often exhibit the ‘dispersion artefact’ observed as a sharp decrease in intensity on the high wavenumber side of absorption bands, in particular the Amide I band at ∼1655 cm−1, causing a downward shift of the true peak position. The presence of this effect makes any biochemical interpretation of the spectra unreliable. Recent theory has shed light on the origins of the ‘dispersion artefact’ which has been attributed to resonant Mie scattering (RMieS). In this paper a preliminary algorithm for correcting RMieS is presented and evaluated using simulated data. Results show that the ‘dispersion artefact’ appears to be removed; however, the correction is not perfect. An iterative approach was subsequently implemented whereby the reference spectrum is improved after each iteration, resulting in a more accurate correction. Consequently the corrected spectra become increasingly more representative of the pure absorbance spectra. Using this correction method reliable peak positions can be obtained.
349 citations
TL;DR: An overview of the field of ambient ionization MS is given, followed by broad classification to allow detailed discussion of theory and common mechanistic factors underpinning a number of key techniques, and consideration will be given to experimental design, ease of implementation and analytical performance.
Abstract: Ambient ionization mass spectrometry allows the rapid analysis of samples or objects in their native state in the open environment with no prior preparation. Over the past six years, the ability of these techniques to provide selective analyte desorption and ionization, in combination with mass spectrometry (MS), has provided a growing number of powerful analytical alternatives across broad application areas, both quantitative and qualitative in nature, including pharmaceutical analysis, process chemistry, biological imaging, in vivo analysis, proteomics, metabolomics, forensics, and explosives detection. With the emergence of new ambient ionization methods, and the complementary nature of existing desorption and/or ionization techniques, additional hyphenated methods have been devised, which pushes the total number of documented methods to almost thirty. To cover all current ambient ionization techniques in detail would be too complex and detract from the main objective of this review. Rather, an overview of the field of ambient ionization MS will be given, followed by broad classification to allow detailed discussion of theory and common mechanistic factors underpinning a number of key techniques. Consideration will be given to experimental design, ease of implementation and analytical performance, detailing subsequent impact on a number of application areas, both established and emerging.
344 citations
TL;DR: This minireview describes the main developments of electronic tongues (e-tongues) and taste sensors in recent years, with a summary of the principles of detection and materials used in the sensing units.
Abstract: This minireview describes the main developments of electronic tongues (e-tongues) and taste sensors in recent years, with a summary of the principles of detection and materials used in the sensing units. E-tongues are sensor arrays capable of distinguishing very similar liquids employing the concept of global selectivity, where the difference in the electrical response of different materials serves as a fingerprint for the analysed sample. They have been widely used for the analysis of wines, fruit juices, coffee, milk and beverages, in addition to the detection of trace amounts of impurities or pollutants in waters. Among the various principles of detection, electrochemical measurements and impedance spectroscopy are the most prominent. With regard to the materials for the sensing units, in most cases use is made of ultrathin films produced in a layer-by-layer fashion to yield higher sensitivity with the advantage of control of the film molecular architecture. The concept of e-tongues has been extended to biosensing by using sensing units capable of molecular recognition, as in films with immobilized antigens or enzymes with specific recognition for clinical diagnosis. Because the identification of samples is basically a classification task, there has been a trend to use artificial intelligence and information visualization methods to enhance the performance of e-tongues.
TL;DR: The ensemble showed highly sensitive and selective fluorescent and colorimetric response to pyrophosphate among the anions in 100% aqueous solutions and no interference of the potent biological competitors including ATP, ADP, and phosphate.
Abstract: We developed a simple dual signal (color and ‘Off-On’ fluorescent change) ensemble system based on the complex between a rhodamine derivative 1 and Al3+ for the detection of pyrophosphate (PPi) in 100% aqueous solutions. The complex between the rhodamine compound and Al3+ was utilized as a chemosensing ensemble for the first time. The ensemble showed highly sensitive and selective fluorescent and colorimetric response to pyrophosphate among the anions in 100% aqueous solutions and no interference of the potent biological competitors including ATP, ADP, and phosphate for the detection of PPi in 100% aqueous solutions at pH 7.4.
TL;DR: A simple, reliable and sensitive colourimetric visualization of melamine in milk products using citrate-stabilized gold nanoparticles (Au NPs) and the sensitivity is significantly improved when NaHSO(4) is added to promote the ligand exchange between citrate and melamine at the surface of Au NPs.
Abstract: In this paper, we report a simple, reliable and sensitive colourimetric visualization of melamine in milk products using citrate-stabilized gold nanoparticles (Au NPs). Upon exposure to ppb-level melamine, gold nanoparticle solution exhibits a highly sensitive colour change from red to blue and rapid aggregation kinetics within the initial 5 min, which can directly be seen with the naked eye and monitored by UV-vis absorbance spectra. As confirmed by the comparison with six other typical amino compounds, the melamine molecule itself contains multiple strong-binding sites to the surface of Au NPs and thus plays a role of molecular linker to efficiently crosslink Au NPs. Further evidence is that the sensitivity is significantly improved when NaHSO4 is added to promote the ligand exchange between citrate and melamine at the surface of Au NPs. The NaHSO4-optimized Au NPs system provides a rapid colourimetric assay for the rapid detection of melamine down to ∼25 ppb in real milk products.
TL;DR: This chapter introduces analytical methods those are frequently integrated into micromixing technologies, such as NMR, FT-IR, and Raman spectroscopies, and discovered that the Re number and mixing time depends on the specific application, and clustered micromixeders in various applications according to the Re numbers and mixing performance.
Abstract: This review presents an application of micromixer technologies, which have driven a number of critical research trends over the past few decades, particularly for chemical and biological fields. Micromixer technologies in this review are categorized according to their applications: (1) chemical applications, including chemical synthesis, polymerization, and extraction; (2) biological applications, including DNA analysis, biological screening enzyme assays, protein folding; and (3) detection/analysis of chemical or biochemical content combined with NMR, FTIR, or Raman spectroscopies. In the chemical application, crystallization, extraction, polymerization, and organic synthesis have been reported, not only for laboratory studies, but also for industrial applications. Microscale techniques are used in chemical synthesis to develop microreactors. In clinical medicine and biological studies, microfluidic systems have been widely applied to the identification of biochemical products, diagnosis, drug discovery, and investigation of disease symptoms. The biological and biochemical applications also include enzyme assays, biological screening assays, cell lysis, protein folding, and biological analytical assays. Nondestructive analytical/detection methods have yielded a number of benefits to chemical and biochemical processes. In this chapter, we introduce analytical methods those are frequently integrated into micromixing technologies, such as NMR, FT-IR, and Raman spectroscopies. From the study of micromixers, we discovered that the Re number and mixing time depends on the specific application, and we clustered micromixers in various applications according to the Re number and mixing performance (mixing time). We expect that this clustering will be helpful in designing of micromixers for specific applications.
TL;DR: N nanopore-based sensory techniques that have been created for the detection of myriad biomedical targets, from metal ions, drug compounds, and cellular second messengers to proteins and DNA are overviewed.
Abstract: Molecular-scale pore structures, called nanopores, can be assembled by protein ion channels through genetic engineering or be artificially fabricated on solid substrates using fashion nanotechnology. When target molecules interact with the functionalized lumen of a nanopore, they characteristically block the ion pathway. The resulting conductance changes allow for identification of single molecules and quantification of target species in the mixture. In this review, we first overview nanopore-based sensory techniques that have been created for the detection of myriad biomedical targets, from metal ions, drug compounds, and cellular second messengers to proteins and DNA. Then we introduce our recent discoveries in nanopore single molecule detection: (1) using the protein nanopore to study folding/unfolding of the G-quadruplex aptamer; (2) creating a portable and durable biochip that is integrated with a single-protein pore sensor (this chip is compared with recently developed protein pore sensors based on stabilized bilayers on glass nanopore membranes and droplet interface bilayer); and (3) creating a glass nanopore-terminated probe for single-molecule DNA detection, chiral enantiomer discrimination, and identification of the bioterrorist agent ricin with an aptamer-encoded nanopore.
TL;DR: A new homogeneous assay for rapid, highly selective and sensitive detection of Hg(2+) in aqueous solution based on the induced photoluminescence (PL) quenching of BSA-modified gold nanoclusters (BSA-Au NCs), which has excellent selectivity over metal ions and anions.
Abstract: In this paper, we report a new homogeneous assay for rapid, highly selective and sensitive detection of Hg2+ in aqueous solution based on the induced photoluminescence (PL) quenching of BSA-modified gold nanoclusters (BSA-Au NCs). There was a linear correlation between the expression (I0 − I)/I0 and the concentrations of Hg2+ over the ranges of 0.4–43.2 μM, and the corresponding limit of detection (LOD) was 80 nM. The relative standard deviation of 5 replicate measurements was 1.4% for 1.0 × 10−5 mol L−1 Hg2+. Moreover, this method has excellent selectivity over metal ions and anions. The feasibility of the BSA-Au NCs sensor for Hg2+ in different aqueous samples was demonstrated with satisfactory results. Moreover, the possible sensing Hg2+ mechanism was also discussed.
TL;DR: This review looks at several of the most relevant deposition and patterning methodologies that are emerging, either for their high production yield, their ability to reach micro- and nano-dimensions, or both, as well as lithographies such as scanning probe, photo- and e-beam lithographies and laser printing.
Abstract: Advanced printing and deposition methodologies are revolutionising the way biological molecules are deposited and leading to changes in the mass production of biosensors and biodevices. This revolution is being delivered principally through adaptations of printing technologies to device fabrication, increasing throughputs, decreasing feature sizes and driving production costs downwards. This review looks at several of the most relevant deposition and patterning methodologies that are emerging, either for their high production yield, their ability to reach micro- and nano-dimensions, or both. We look at inkjet, screen, microcontact, gravure and flexographic printing as well as lithographies such as scanning probe, photo- and e-beam lithographies and laser printing. We also take a look at the emerging technique of plasma modification and assess the usefulness of these for the deposition of biomolecules and other materials associated with biodevice fabrication.
TL;DR: An overview of some of the most interesting bio-detections carried out during the last 2-3 years with the microcantilever-based platforms, which highlight the continuous expansion of this kind of sensor in the medical diagnosis field, reaching limits of detection at the single molecule level.
Abstract: The fast and progressive growth of the biotechnology and pharmaceutical fields forces the development of new and powerful sensing techniques for process optimization and detection of biomolecules at very low concentrations. During the last years, the simplest MEMS structures, i.e. microcantilevers, have become an emerging and promising technology for biosensing applications, due to their small size, fast response, high sensitivity and their compatible integration into “lab-on-a-chip” devices. This article provides an overview of some of the most interesting bio-detections carried out during the last 2–3 years with the microcantilever-based platforms, which highlight the continuous expansion of this kind of sensor in the medical diagnosis field, reaching limits of detection at the single molecule level.
TL;DR: The resulting Raman spectral imaging methodology directly utilizes the spectral contrast provided by small (bio)chemical compositional changes over the spatial dimension of the sample to construct images that can rival fluorescence images in terms of spatial information, yet without the use of any external dye or label.
Abstract: Raman microspectroscopy-based, label-free imaging methods for human cells at sub-micrometre spatial resolution are presented. Since no dyes or labels are used in this imaging modality, the pixel-to-pixel spectral variations are small and multivariate methods of analysis need to be employed to convert the hyperspectral datasets to spectral images. Thus, the main emphasis of this paper is the introduction and comparison of a number of multivariate image reconstruction methods. The resulting Raman spectral imaging methodology directly utilizes the spectral contrast provided by small (bio)chemical compositional changes over the spatial dimension of the sample to construct images that can rival fluorescence images in terms of spatial information, yet without the use of any external dye or label.
TL;DR: Recent advances in fluorescent and colorimetric conjugated polymer-based biosensors are highlighted, which result in mainly three types of measurable signal generation: turn on or turn off fluorescence, or change in either visible color or fluorescence emission color of the conjugate polymer.
Abstract: Conjugated polymers recently have drawn much attention as an emerging sensory material due to their meritorious signal amplification, convenient optical detection, readily tunable properties, and easy fabrication. We review the molecular design principles of sensory conjugated polymer recognition events, which can trigger conformational change of the conjugated polymer, induce intermolecular aggregation, or change the distance between the conjugated polymer as an energy donor and the reporter dye molecule as an energy acceptor. These recognition/detection mechanisms result in mainly three types of measurable signal generation: turn on or turn off fluorescence, or change in either visible color or fluorescence emission color of the conjugated polymer. In this article, we highlight recent advances in fluorescent and colorimetric conjugated polymer-based biosensors.
TL;DR: Modern methods of graphene production and functionalization are surveyed with an emphasis on the development of chemical sensors and fuel cell electrodes with brief comparisons to state-of-the-art carbon nanotube-based systems.
Abstract: Graphene, an atomically thin layer of sp2 hybridized carbon, has emerged as a promising new nanomaterial for a variety of exciting applications including chemical sensors and catalyst supports. In this article, we survey modern methods of graphene production and functionalization with an emphasis on the development of chemical sensors and fuel cell electrodes with brief comparisons to state-of-the-art carbon nanotube-based systems.
TL;DR: The aberrations and artefacts that can arise in Raman microscopy can be avoided by adhering to a few basic principles that are well known to optical microscopists but which were largely ignored in the spectroscopic community for many years.
Abstract: Confocal Raman microscopy is a powerful tool for research and analysis in the chemical, materials and life sciences, particularly for non-destructive depth profiling of transparent systems. Unfortunately, many Raman microscopes are not optimally configured for this purpose, and so yield unnecessarily low signal-to-noise spectra with poor spatial resolution and grossly incorrect depth scales. This review discusses the aberrations and artefacts that can arise and describes how these can be avoided by adhering to a few basic principles that are well known to optical microscopists but which were largely ignored in the spectroscopic community for many years.
TL;DR: The results indicate the potential of textile-based screen-printed amperometric sensors for future healthcare, sport or military applications, which would benefit from tailoring the ink composition and printing conditions to meet the specific requirements of the textile substrate.
Abstract: The incorporation of amperometric sensors into clothing through direct screen-printing onto the textile substrate is described. Particular attention is given to electrochemical sensors printed directly on the elastic waist of underwear that offers tight direct contact with the skin. The textile-based printed carbon electrodes have a well-defined appearance with relatively smooth conductor edges and no apparent defects or cracks. Convenient voltammetric and chronoamperometric measurements of 0–3 mM ferrocyanide, 0–25 mM hydrogen peroxide, and 0–100 μM NADH have been documented. The favorable electrochemical behavior is maintained under folding or stretching stress, relevant to the deformation of clothing. The electrochemical performance and tolerance to mechanical stress are influenced by the physical characteristics of the textile substrate. The results indicate the potential of textile-based screen-printed amperometric sensors for future healthcare, sport or military applications. Such future applications would benefit from tailoring the ink composition and printing conditions to meet the specific requirements of the textile substrate.
TL;DR: This review focuses on the development and analytical applications of near-infrared (NIR) quantum dots, and the advantages and challenges in developing NIR QDs are summarized in this review from the viewpoint of analytical chemistry.
Abstract: As light-emitting nanocrystals, quantum dots (QDs) have been a major focus of research and development during the past decade. The impetus behind such endeavors can be attributed to their unique chemical and optical properties, with size-tunable light emission, high photostability, and multiple fluorescence colors. In recent years, near-infrared (NIR) quantum dots have emerged as a promising tool in analytical applications, especially for in vivo imaging and therapy. NIR QDs allow photon penetration through tissue and minimize the effects of tissue autofluorescence. This is important for detecting or identifying species in complex biological samples. This review focuses on the development and analytical applications of NIR QDs. Different types of NIR QDs have been synthesized and characterized from various designed strategies. In the functional process, QDs can be modified as sensitive probes with high affinity and specificity, such as being linked with proteins, peptides or other small molecules. Recent advances of NIR QDs applications are presented, including in vivo imaging, fluorescence enhancement/quenching, and fluorescence resonance energy transfer. We also discuss the limitation of NIR QDs in applications. The advantages and challenges in developing NIR QDs are summarized in this review from the viewpoint of analytical chemistry.
TL;DR: Serum samples from kidney cancer patients and healthy controls were analyzed by both direct infusion mass spectrometry (DIMS) and liquid chromatography-mass spectromaetry (LC-MS) with a high resolution ESI-Q-TOFMS to find biomarkers.
Abstract: Serum samples from kidney cancer patients and healthy controls were analyzed by both direct infusion mass spectrometry (DIMS) and liquid chromatography-mass spectrometry (LC-MS) with a high resolution ESI-Q-TOFMS. The classification and biomarker discovery capacities of the two methods were compared, and MS/MS experiments were carried out to identify potential biomarkers. DIMS had comparable classification and prediction capabilities to LC-MS but consumed only ~5% of the analysis time. With regard to biomarker discovery, twenty-three variables were found as potential biomarkers by DIMS, and 48 variables were obtained by LC-MS. DIMS is recommended to be a fast diagnostic method for kidney cancer, while LC-MS is necessary when comprehensive screening of biomarkers is required.
TL;DR: A highly specific ferrocene-based fluorescent probe, (9-anthryl)ethenylferrocene, has been designed, synthesized and characterized for fluorescence imaging of hypochlorous acid (HOCl) in live cells and its applicability has been successfully demonstrated for fluorescent imaging of HOCl in HeLa cells.
Abstract: A highly specific ferrocene-based fluorescent probe, (9-anthryl)ethenylferrocene, has been designed, synthesized and characterized for fluorescence imaging of hypochlorous acid (HOCl) in live cells. The design strategy for the probe is based on the strong quenching effect of electron-donor ferrocene on anthracene fluorescence via an intramolecular charge transfer process, and is accomplished through constructing the conjugated molecule by using a cleavable double bond as a linker. The double bond in the probe reacts selectively with HOCl rather than the other reactive oxygen species (e.g., ˙OH, ˙O2−, 1O2, and H2O2) in pH 7.4, accompanied by more than 100-fold fluorescence enhancement. Moreover, the probe is cell membrane permeable, and its applicability has been successfully demonstrated for fluorescence imaging of HOCl in HeLa cells.
TL;DR: Applications of these novel plAsmonic materials will be demonstrated as substrates for a localized surface plasmon resonance, Surface Plasmon Resonance (SPR), surface enhanced Raman spectroscopy (SERS), and in electrochemistry with nano-patterned electrodes.
Abstract: Since the last decade, nanohole arrays have emerged from an interesting optical phenomenon to the development of applications in photophysical studies, photovoltaics and as a sensing template for chemical and biological analyses. Numerous methodologies have been designed to manufacture nanohole arrays, including the use of focus ion beam milling, soft-imprint lithography, colloidal lithography and, more recently, modified nanosphere lithography (NSL). With NSL or colloidal lithography, the experimental conditions control the density of the nanosphere mask and, thus, the aspect of the nanohole arrays. Low surface coverage of the nanosphere mask produces disordered nanoholes. Ordered nanohole arrays are obtained with a densely packed nanosphere mask in combination with electrochemical deposition of the metal, glancing angle deposition (GLAD) or etching of the nanospheres prior to metal deposition. A review of these methodologies is presented here with an emphasis on the optical properties of nanoholes interesting in analytical chemistry. In particular, applications of these novel plasmonic materials will be demonstrated as substrates for a localized surface plasmon resonance (LSPR), Surface Plasmon Resonance (SPR), surface enhanced Raman spectroscopy (SERS), and in electrochemistry with nano-patterned electrodes.
TL;DR: A sensitive and low-cost colorimetric method for detection of melamine using simple circuitry, which was successfully utilized to a practical infant formula sample and showed sensitivity and selectivity towards melamine.
Abstract: The purpose of this paper is to develop a sensitive and low-cost colorimetric method for detection of melamine using simple circuitry. The stable p-nitroaniline-modified silver nanoparticles (Ag NPs) were synthesized by a zero-length covalent coupling chemistry, which showed sensitivity and selectivity towards melamine. The melamine induces the aggregation of nanoparticles due to electron donor-acceptor interaction between melamine and p-nitroaniline at the Ag NP interface, resulting in a shift in the surface plasmon band and a consequent color change of the Ag NPs from yellow to blue. The color change was monitored using UV-vis spectrophotometry. More importantly, this optical method was successfully utilized to a practical infant formula sample. As low as 0.1 ppm melamine in infant formula could be distinguished upon a color change of solution in two minutes.
TL;DR: Partial least squares regression model gives a semiquantitative mapping of the biochemical constituents in agreement with average composition found in the literature, and the combination of hierarchical and fuzzy cluster analysis succeeds in detecting variations between different regions of the extra-cellular matrix.
Abstract: Raman mapping in combination with uni- and multi-variate methods of data analysis is applied to articular cartilage samples. Main differences in biochemical composition and collagen fibers orientation between superficial, middle and deep zone of the tissue are readily observed in the samples. Collagen, non-collagenous proteins, proteoglycans and nucleic acids can be distinguished on the basis of their different spectral characteristics, and their relative abundance can be mapped in the label-free tissue samples, at so high a resolution as to permit the analysis at the level of single cells. Differences between territorial and inter-territorial matrix, as well as inhomogeneities in the inter-territorial matrix, are properly identified. Multivariate methods of data analysis prove to be complementary to the univariate approach. In particular, our partial least squares regression model gives a semiquantitative mapping of the biochemical constituents in agreement with average composition found in the literature. The combination of hierarchical and fuzzy cluster analysis succeeds in detecting variations between different regions of the extra-cellular matrix. Because of its characteristics as an imaging technique, Raman mapping could be a promising tool for studying biochemical changes in cartilage occurring during aging or osteoarthritis.
TL;DR: This review discusses recent technical advances in NMR spectroscopy based metabolite profiling methods, data processing and analysis over the last three years.
Abstract: Significant improvements in NMR technology and methods have propelled NMR studies to play an important role in a rapidly expanding number of applications involving the profiling of metabolites in biofluids. This review discusses recent technical advances in NMR spectroscopy based metabolite profiling methods, data processing and analysis over the last three years.