Catherine F. Yang

An electrochemical immunosensor for carcinoembryonic antigen enhanced by self-assembled nanogold coatings on magnetic particles

A quick and reproducible electrochemical-based immunosensor technique, using magnetic core/shell particles that are coated with self-assembled multilayer of nanogold, has been developed. Magnetic particles that are structured from Au/Fe(3)O(4) core-shells were prepared and aminated after a reaction between gold and thiourea, and additional multilayered coatings of gold nanoparticles were assembled on the surface of the core/shell particles. The carcinoembryonic antibody (anti-CEA) was immobilized on the modified magnetic particles, which were then attached on the surface of solid paraffin carbon paste electrode (SPCE) by an external magnetic field. This is an assembly of a novel immuno biosensor for carcinoembryonic antigen (CEA). The sensitivity and response features of this immunoassay are significantly affected by the surface area and the biological compatibility of the multilayered nanogold. The linear range for the detection of CEA was from 0.005 to 50 ng mL(-1) and the limit of detection (LOD) was 0.001 ng mL(-1). The LOD is approximately 500 times more sensitive than that of the traditional enzyme-linked immunosorbent assay for CEA detection.

Electrochemical determination of interaction parameters for DNA and mitoxantrone in an irreversible redox process

Mitoxantrone (MXT), an anti-tumor antibiotic, shows irreversible electrochemical behavior at a waxed graphite electrode in a 0.05 M Tris-HCl buffer (pH 7.4) solution. The interaction between MXT and calf thymus DNA (ctDNA) in solution has been studied using cyclic voltammetry. An electrochemical equation suitable for examining the binding of irreversibly electroactive molecules to DNA is established. Determination of diffusion coefficients of both free and binding MXT (D(f), D(b)), the binding constant (K) and binding site size (s base pairs per molecule, bp) of MXT with DNA was performed on the basis of the equation. A nonlinear fit analysis of the experimental data yielded: D(f)=3.76 x 10(-5) cm(2)s(-1), D(b)=2.73 x 10(-7) cm(2)s(-1), K=8.7 x 10(9) cm(3)mol(-1), s=2.8 bp. The results demonstrate that MXT binds tightly to ctDNA and covers three base pairs. The anthraquinone of MXT, which is a planar heterocyclic ring, intercalates between the DNAs base pairs. The two aminoethylamino side-chains of the drug fit to the major groove reinforce the combination of MXT and DNA. The results show that MXT is a DNA intercalator with a high binding constant compared to those of other anthraquinones.

Investigation on the interaction of DNA and electroactive ligands using a rapid electrochemical method

A rapid method for investigation of the interaction of DNA and electroactive ligands based on an electrochemical equation for irreversible processes is presented. The binding constant (K) and the size of binding site (s) are simultaneously obtained from the dependence of the current on the amount of added DNA in voltammetry. A non-intercalative binder (Hoechst 33258) and two DNA-intercalators (mitoxantrone (MXT) and actinomycin D (AMD)) were examined in experiments. It was found that the binding constant of Hoechst 33258, mitoxantrone and actinomycin D, were 2.1 x 10(8), 8.9 x 10(9) and 9.1 x 10(9) cm(3) mol(-1); and the size of their binding sites were 4, 3 and 8, respectively. The study provides a convenient and sensitive approach for estimating affinity parameters and outlining the interaction between DNA and electroactive targeting compounds.

Investigation of the interaction of DNA and actinomycin D by cyclic voltammetry

Abstract An electrochemical method was used to probe the interaction of actinomycin D (AMD) and calf thymus DNA (ctDNA) in phosphate buffer solution (pH 7.0) at an oxidized waxed graphite electrode. AMD showed a pair of nonsymmetric peaks at −0.51 and 0.19 V in cyclic voltammetry. As a result of reaction with ctDNA, the voltammetric peaks of AMD disappeared. The diffusion coefficient of free AMD ( D f =1.9×10 −5 cm 2 s −1 ), binding constant ( K =7.54×10 9 cm 3 mol −1 ) and binding site size ( s =8.1) of the AMD–DNA complex were obtained simultaneously by nonlinear fit analysis of voltammetric data based on an electrochemical equation, which was derived to examine the interaction of DNA and irreversibly electroactive compounds. The results demonstrate that AMD binds tightly to ctDNA. The AMD phenoxazone ring intercalates between the DNA base pairs. The two side chains of the depsipeptide extend along the minor groove of DNA and cover eight base pairs. The study provides a convenient and sensitive approach to estimate affinity parameters of the interaction between DNA and targeting compounds.

Effects of acidity on the size of polyaniline-poly(sodium 4-styrenesulfonate) composite particles and the stability of corresponding colloids in water

The practical application of polyaniline-poly(sodium 4-styrenesulfonate) (PANI-PSS) composite particles has been held back by the low stability of their dispersed state in water. In this work, we present a general oxidation approach to prepare PANI-PSS composite nanoparticles that can form highly stable colloids in water or buffer over a wide range of pH from 1 to 11. We demonstrate that the size of the PANI-PSS composite particles can be controlled by the acidity of precursor solutions. It is hypothesized that the number of negatively charged sites on PSS, which can be affected by the acidity of the precursor solutions, plays an important role in determining the size of the PANI-PSS composite particles and the stability of corresponding colloids in water.

Binding specificity of post-activated neocarzinostatin chromophore drug-bulged DNA complex studied using electrospray ionization mass spectrometry

Electrospray ionization mass spectrometry (ESI-MS) was employed to characterize the binding specificity of a bulged 22-mer DNA hairpin with a post-activated neocarzinostatin chromophore (NCS-Chrom) having two similar forms, where 2a has an H in a location for which 2b has it replaced by a CH2OH group. Specific binding of 2a to the bulged 22-mer DNA was observed whereas little binding was detected for 2a to non-bulged DNA 19-mer and 12-mer duplexes. The stoichiometry of the 22-mer DNA complex with 2a was determined to be predominantly 1:1. Substitution of hydrogen in 2a for the hydroxymethylene group in 2b dramatically reduced the binding strength to the 22-mer DNA. Little complex formation was observed for 2b and 22-mer DNA based upon the ESI-MS data, consistent with earlier fluorescence studies. The results indicate that ESI-MS can be a sensitive technique for probing conformational specificity in studies of biomolecular binding.

Electrochemical Behavior and In Vivo Determination of the Neurotransmitter Dopamine Using Sodium Montmorillonite Modified Electrodes

A modified glassy carbon electrode is used to examine the mass transport characteristics of the neurotransmitter dopamine (DA) in sodium montmorillonite films. The apparent diffusion coefficient (Dapp) of DA in the film is measured by chronocoulometry and cyclic voltammetry to be 2.3×10–9and 5.1×10–9 cm2/s. According to the Nicholson theory, the standard rate constant (ks) of heterogeneous electron transfer reaction for DA is estimated to be 2.7×10–6 cm/s by cyclic voltammetry. Montmorillonite has been modified on carbon fiber electrodes, and voltammetric response of some neurotransmitters and their metabolites has been examined. The variation of DA concentration in a rat brain with decreasing blood supply has been detected when the modified microelectrode is used in in vivo experiments.

Recent advances in micro/nano-particles for clinical detection of cancer biomarkers

Cancer is a major threat to public health and is still one of the leading causes of death worldwide. Cancer biomarkers are extremely important in the process of early detection of cancer, diagnosis, judgment of the curative effect and the prognosis. They also play an important role in mechanistic research into carcinogenesis. Detection methods based on cancer biomarkers for the determination of cancer can directly affect the diagnosis and treatment. Therefore, the development of highly sensitive and selective approaches for the detection of cancer biomarkers is critical. Micro- and nanoparticles play an important role in the clinical detection of cancer biomarkers. In this review, we provide an overview of the commonly used clinical detection methods for cancer biomarkers, such as enzyme-linked immunosorbent assay, chemiluminescence, electrochemiluminescence, as well as their technical characteristics. Additionally, various applications of recent advances in microparticles and nanoparticles in the clinical detection of cancer biomarkers are also reviewed.

Gold Nanoparticle Determination by Inductively Coupled Plasma-Mass Spectrometry, Anodic Stripping Voltammetry, and Flame Atomic Absorption Spectrophotometry

Gold Nanoparticles (AuNP) were measured by Inductively Coupled Plasma–Mass Spectrometry (ICP-MS), Anodic Stripping Voltammetry (SV), and flame Atomic Absorption Spectrophotometry (AAS). Experiments investigated the relationships between counts per second (ICP-MS), absorbance (AAS), or μA (SV) and Au concentrations in solutions bearing AuNP with sizes of 5, 15, and 50 nm. Similarly the impact of the solution matrix was assessed using deionized water, 1.0 M HNO3, 1.0 M HCl (ICP-MS and AAS), and water containing the bacterium E. coli (∼106 organisms/mL) by all three types of instrumentation. Each instrument yielded linear calibration curves with a signal proportional to Au concentration over the concentration range 0.02 ppm to 1 ppm.The methods were all reliable when biomacromolecules or when organisms such as E.coli existed in the matrix. Comparing the limits of detection for the three methods, ICP-MS and SV were lower than AAS. Comparing cost, SV and AAS were less expensive than ICP-MS. Comparing time required for each measurement, AAS was shorter than ICP-MS and SV. In comparison of the interfering effects of E-coli, ICP-MS and AAS were less-affected, while SV was more affected. An intact E.coli or organism may be very absorptive on the electrode surface,which reduced the measured anodic currents in SV and also increased the standard deviations.

Components in aqueous Hibiscus rosa-sinensis flower extract inhibit in vitro melanoma cell growth

Skin cancer is extremely common, and melanoma causes about 80% of skin cancer deaths. In fact, melanoma kills over 50 thousand people around the world each year, and these numbers are rising. Clearly, standard treatments are not effectively treating melanoma, and alternative therapies are needed to address this problem. Hibiscus tea has been noted to have medicinal properties, including anticancer effects. Extracts from Hibiscus have been shown to inhibit the growth of a variety of cancer cells. In particular, recent studies found that polyphenols extracted from Hibiscus sabdariffa by organic solvents can inhibit melanoma cell growth. However, effects of aqueous extracts from Hibiscus rosa-sinesis flowers, which are commonly used to make traditional medicinal beverages, have not been examined on melanoma cells. Here, we report that aqueous H. rosa-sinesis flower extract contains compounds that inhibit melanoma cell growth in a dose dependent manner at concentrations that did not affect the growth of nontransformed cells. In addition, these extracts contain low molecular weight growth inhibitory compounds below 3 kD in size that combine with larger compounds to more effectively inhibit melanoma cell growth. Future work should identify these compounds, and evaluate their potential to prevent and treat melanoma and other cancers.