Volume 32, Issue 2

Since the electrogenerated chemiluminescence (ECL) of silicon quantum dots (QDs) was reported in 2002, a series of QDs with different sizes, components, and shapes has been extensively studied as ECL emitters for biosensors. Lately, near-infrared (NIR) ECL analysis has emerged as an alternative to traditional visible-range ECL bioassays, especially in some complex biological systems. This is because the NIR spectral region could provide a “clear window” to effectively fulfill the requirement of interference-free sensing. Among the present reported ECL emitters, QDs hold great promise as NIR ECL emitters owing to their size or surface-dependent luminescence and photochemical stability. This review presents a general picture of the latest advances and developments related to QDs for NIR ECL emitters. It briefly covers the synthetic strategies of NIR QDs and the advances in QD-based NIR ECL and related biosensing methodologies. Finally, we conclude with a look at the future challenges and prospects in the development of QD-based NIR ECL.

The continuous flow assay is a capillary electrophoresis-based methodology for the simultaneous measurement of the catalytic rate and electrophoretic mobility of individual molecules of the enzyme β-galactosidase. The method also provides time resolution. This method was used to measure the distribution of single-molecule activities and mobilities of a population of the wild-type Escherichia coli β-galactosidase. The catalytic rate was found to vary over time at an elevated temperature, suggesting a switching between different conformations. The successive incubation of individual molecules at 27°C, 45°C, and again at 27°C was found to convert molecules from one form with a stable catalytic rate to a different form with a different stable catalytic rate. Incubation at higher temperatures was found to cause a sudden and catastrophic loss in activity, which was consistent with denaturation. Increasing the incubation temperature over time was used to generate an Arrhenius plot for a single enzyme molecule. Finally, assaying the enzyme as the slow-release inhibitor d -galactal dissociated allowed for the measurement of the activity of individual subunits within a single molecule.

Owing to the high measuring speed and requirement of less or even no sample preparation, spectroscopic technologies have been increasingly applied in areas of food technology, agriculture, and pharmaceutics where heterogeneous samples are more frequently encountered than homogeneous ones. For heterogeneous samples, the potential uncontrolled variations in optical path length due to the physical variations such as particle size and distribution, shape and sample packing may cause dominant multiplicative light scattering perturbations which will mask the spectral variations related to the content differences of chemical compounds in samples and hence deteriorate the accuracy and reliability of quantitative spectroscopic analysis. Consequently, with a view to improve the accuracy and reliability of spectroscopic analysis for heterogeneous samples, a number of chemometric techniques have been developed to correct for the effects of multiplicative light scattering. This paper reviews currently available correction techniques for absorption spectroscopy with emphasis on their theories, limitations, and suitability for practical applications.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) is a new tool for rapid identification of bacterial microorganisms. With the development of matrix-assisted laser desorption/ionization time-of-flight-time-of-flight (MALDI-TOF-TOF) instruments, new capabilities for characterizing bacteria and their protein biomarkers and toxins by top-down proteomic identification is now possible. A number of researchers have demonstrated top-down proteomic identification of nondigested proteins using MALDI-TOF-TOF platforms. The current review briefly discusses the use of MS instrumentation for bacterial identification and characterization as well as recent developments in the use of MALDI-TOF-TOF for top-down proteomic identification of protein biomarkers and toxins from unfractionated bacterial cell lysates. This approach provides great promise as a rapid method for identification and characterization of pathogenic microorganisms and their virulence factors.

Microcantilever (MC) sensors have become a more attractive technique for gas phase sensing during recent years. The purpose of this review is to critically summarize the recent advances in terms of theory, detection and sensing scheme, sensor design, and applications of MC-based gas sensors, with most of the related work reported since 2005.

The electrochemical properties of lanthanides (Ln) and actinides (An) are reviewed. This review summarizes papers from 1986 to 2011 with a primary focus on the electrochemical and redox properties of Ln/An elements in aqueous solution and their responses to a variety of electrode materials including Hg, Hg films, solid electrodes, modified carbon paste, and microelectrodes. A section is also devoted to the electrochemical properties and responses of Ln and An in nonaqueous and mixed solvent systems.