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Titanium dioxide nanoparticles (TiO2NPs) have been widely used in food, medical, and other fields; their reproductive toxicity has been reported in numerous studies. However, the relevant toxicity mechanism still requires further exploration. In this paper, the effect of oral exposure to 500 mg/kg TiO2NPs (anatase and rutile) in adult male SD rats was studied over 3 and 7 days. Results showed that the total sperm count and testosterone level of 7 days of exposure in serum decreased in the experimental group. Testicular tissue lesions, such as disappearance of Leydig cells, disorder of arrangement of spermatogenic cells in the lumen of convoluted seminiferous tubules, and disorder of arrangement of germ cells, were observed. Meanwhile, the expression of steroidogenic acute regulatory (StAR; the key factors of testosterone synthesis), MAPK (ERK1/2), and phosphorylated ERK1/2 in testes of SD rats after exposure to TiO2NPs for 7 days decreased, while the malondialdehyde content increased and superoxide dismutase activity decreased in serum. The present study showed that TiO2NPs could cause reproductive toxicity. Notably, anatase is more toxic than rutile. In addition, exposure to 500 mg/kg TiO2NPs for 7 days inhibited testosterone synthesis in male rat, which may be related to the reactive oxygen species (ROS)-MAPK (ERK1/2)-StAR signal pathway. Warning that the use of TiO2NPs should be regulated.

Studies regarding circulating tumor cells (CTCs) have great significance for cancer prognosis, treatment monitoring, and metastasis diagnosis. However, due to their extremely low concentration in peripheral blood, isolation and enrichment of CTCs are the key steps for early detection. To this end, targeting the folic acid receptors (FRs) on the CTC surface for capture with folic acid (FA) using bovine serum albumin (BSA)-tether for multibiotin enhancement in combination with streptavidin-coated magnetic nanoparticles (MNPs-SA) was developed for ovarian cancer CTC isolation. The streptavidin–biotin-system-mediated two-step binding strategy was shown to capture CTCs from whole blood efficiently without the need for a pretreatment process. The optimized parameters for this system exhibited an average capture efficiency of 80%, which was 25% higher than that of FA-decorated magnetic nanoparticles based on the one-step CTC separation method. Moreover, the isolated cells remained highly viable and were cultured directly without detachment from the MNPs-SA–biotin–CTC complex. Furthermore, when the system was applied for the isolation and detection of CTCs in ovarian cancer patients’ peripheral blood samples, it exhibited an 80% correlation with clinical diagnostic criteria. The results indicated that FA targeting, in combination with BSA-based multibiotin enhancement magnetic nanoparticle separation, is a promising tool for CTC enrichment and detection of early-stage ovarian cancer.

The article discusses how proper nutrition through consumption of healthy diet can boost immune health and protect the body against infections and diseases. Also cited are the organs, tissues, cells and molecules comprising the immune system, the roles played by macrophages, T lymphocytes, and leukocytes in developing innate immunity, and how nutraceuticals can be good alternatives to healthy diet.

Quantum dots (QDs) have recently attracted considerable attention in the biomedical fields because of their unique and excellent optical properties. However, information on their health effects, particularly in the reproductive system, is limited. The present study focuses on the effects of intravenous injection of CdSe/ZnS QDs on the reproductive system and embryo development at various stages of pregnancy in mice. The CdSe/ZnS QDs intravenously injected in mice during pregnancy accumulated in the maternal liver, uterus and placenta. This accumulation affected the growth and development of the embryo during the early and middle stages of pregnancy. Moreover, genotoxicity to the placenta after exposure to CdSe/ZnS QDs was demonstrated by the increased expression levels of genes related to oxidative stress and apoptosis and the reduced expression levels of genes related to the nutrient and waste transportation. Alterations in the gene expression levels have hindered the transport of metabolites across the placenta, which in turn affected the ability of the fetus to obtain nutrients.

In this study, a fluorescence-positioned hybridization chain reaction (HCR) system for the detection of single-stranded DNA (ssDNA) specific to Salmonellawas developed. Target ssDNA captured by magnetic beads was used to trigger the HCR, forming multiple double-stranded DNAs (dsDNAs). SYBR Green I was applied to intercalate with the minor groove of the dsDNA forming MBs + dsDNA + SYBR Green I. Magnetic separation was used to isolate the MBs + dsDNA + SYBR Green I from the excess reagents before recording the fluorescence intensity (FI). This fluorescence-positioned HCR method for the quantitative detection of Salmonellashowed a limit of detection (LOD) as low as 4.2 × 101CFU mL−1in 0.01 M phosphate-buffered saline (PBS). When the method was applied in spiked milk samples, the LOD was recorded at 4.2 × 102CFU mL−1. The fluorescence-positioned HCR method provided a modification-free and fluorescence-positioned strategy for sensitive detection of target DNA which holds promise for sensitive and selective bacterial detection.

Because of the lack of early screening strategies, ovarian cancer is the most deadly cause of gynecologic malignancies. This paper describes an effective method for the separation and detection of ovarian cancer cells from female whole blood, using folic acid (FA) conjugated magnetic iron oxide nanoparticles (IO–FA nanoparticles). The IO nanoparticles were synthesized by thermal decomposition and then covalently conjugated with FA. The IO–FA nanoparticles were stably attached to the surface of ovarian cancer cells by coupling to the over-expressed folate receptor (FR), thereby making the cells magnetic. These “magnetic cells” were separated from the complex blood matrix without destruction under a magnetic field. The separation efficiency was as high as 61.3% when the abundance of spiked ovarian cancer SKOV3 cells was as low as 5 × 10−5%. We also successfully detected five (5) out of ten (10) metastatic ovarian cancer patients’ whole blood. This study suggested the feasibility of early detecting of metastatic ovarian cancer cells, which may potentially improve the ovarian cancers patients’ overall survival rate for clinical applications.

Bifidobacteriumis well known to have an inhibitory effect on the survival, growth, and proliferation of various foodborne pathogens, but the mechanism of the molecular action of B. longumin blocking the invasion of Listeria monocytogenesis not yet well defined. In the present study, following RNA extraction and cDNA synthesis, differential expression of virulence and stress fitness genes in L. monocytogenesand B. longumwas determined by real-time PCR. The results indicate that L. monocytogenesvirulence factors, including actA, hly, inlA, and plcA, showed significantly downregulated expression during co-incubation of B. longumand L. monocytogenesin phosphate-buffered saline. The relative mRNA levels of oppAand serpin, two stress fitness genes in B. longum, were significantly higher than for the control group. These results indicate that downregulation of L. monocytogenesvirulence factors during co-incubation with B. longummight be responsible for the inhibitory effects.

Nanomaterials are currently being developed for various biomedical applications. Engineered nanomaterials such as quantum dots, metal and semiconductor nanoparticles, and magnetic nanoparticles are among the new materials being studied for medical applications. Nanomaterials have unique properties that include diameters from 3-50 nm, high quantum yields, resistance against photobleaching, high magnetic and electric properties, and simultaneous excitation of multiple fluorescent colors. Quantum dots have unique emission spectra even with ordinary source of light. Magnetic nanoparticles are unique because of their highly magnetic nature. Magnetic nanoparticles are used in magnetic resonance imaging and targeted drug delivery while quantum dots are increasingly being used for biomedical imaging. We report the results of our studies on the applications of nanomaterials in medicine. These include cell imaging, tissue imaging, protein detection, drug delivery, and cell targeting. Preliminary studies indicated promising applications of nanomaterials in molecular imaging and in vitro diagnostics.

Engineered nanomaterials (eNMs) are dominating the 21st century in industrial, biological, and medical applications. ENMs are the emerging new materials for sunscreens, medical imaging , solar cell, cosmetics, sports gadgets, consumer products, as well as biological detection materials. One of the major concerns in the application of ENMs like quantum dots (QDs) in life sciences research and clinical diagnostics is non-specific binding (NSB) or nonspecific uptake (NSU) in biological materials such as cells, proteins, or DNA. Elimination of non-specific uptake of ENMs is essential in order to utilize the maximum potential for detection of different biological molecules resulting from the >50% higher emission intensity of QDs in comparison with organic dyes. Furthermore, ENMs are small enough to be used in biological systems making them useful for clinical applications such as drug delivery and/or magnetic resonance imaging. Since QDs are size tunable they can be modified for the detection of single or multiple analyte. However, NSU and/or NSB must be minimized or eliminated before these can be used for the detection of biological analytes. Studies on the development of blocking buffers to minimize or eliminate NSB/NSU have been initiated. Blockers such as bovine serum albumin, polyvinyl pyrrolidone and detergents such as tween 20 and triton X 100 have been used to minimize NSB/NSU. Results of blocking nonspecific uptake of ENMs will be discussed.

Quantum dots (QDs) are a new generation of fluorescent labeling agents which have recently attracted researcher's attention for a variety of biomedical applications. Literature on the applications of quantum dots in the life sciences has recently significantly increased in number that is in line with predictions that nanotechnology in life sciences research will contribute $3.4 billion by 2010 while the National Science Foundation is predicting that the market for nanotechnology and corresponding products will reach $1 trillion in 10 to 15 years. The chemical sensor industry, which is a $2.9 billion US industry, is predicted to grow while applications of nanomaterials have been estimated to have a market impact of over US$ 340 billion within a decade. In this present work, we developed a QD-based protein sensor using mouse IgG as the model analyte. The sensor was designed using a combination of capture antibody (rabbit anti-mouse IgG antibody) and QDs conjugated goat anti-mouse IgG for detection. In order to eliminate the non-specific binding of QD-labeled antibody, a super blocker BBB was used for the assay. Thus, we successfully demonstrated the use of QDs for protein sensing.

Nanotechnology, the area of study involving nanoparticles, century; medical fields. The nanotechnology is one of the fastest growing sectors of the high-tech economy in the 21st industry, it is currently undergoing unprecedented development in nowadays especially in areas of biological research for clinical, environmental and life science applications. The most frequently used nanoparticles are superparamagnetic iron oxide (SPIO) nanoparticles and semiconductor quantum dots (QDs). SPIO nanoparticles with nanometer sizes and superparamagnetic properties are widely used for labeling and sorting cells or organelles, magnetic resonance imaging, targeted drug delivery, and hyperthermia. QDs combined the unique size-dependent physical properties, excellent chemical and photochemical stability, controlled and increased endocytosis, enhanced cooperative binding activity, and easy introduction of multi-functionality for targeted delivery and imaging, and became the most promising labeling tool for life science studies. Both types of nanomaterials provide special approaches for complex studies and play very important roles in modern biomedical research. However, non-specific uptake of QDs and SPIO nanoparticles is a major concern because it can lead to false positives or false results. Hence, we report cellular uptake studies on SPIO nanoparticles and QDs conducted on breast cancer cell line SK-BR3. The results show that both QDs and SPIO nanoparticles have very strong non-specific cellular uptake. With specially designed blocking buffer (BBB) the non-specific signals were significantly decreased.

A self-contained microelectrochemical immunoassay detection of Bacillus anthracis protective antigen (PA) has been developed. A microcavity array (VEG4x1{trade mark, serif}) of 50-mm diameter cavities with self-contained microelectrodes were used for the detection of as low as 2.5 pg of B. anthracis Protective Antigen in a less than 12 min total assay time from capture to signal generation. The micro-electrochemical sandwich enzyme-linked immunoassay involved covalent immobilization of the capture antibody on the free end of mercaptoundecanol self-assembled monolayers at the bottom Au-microdisk electrode that also serves as the bottom of the microcavities. Signal generation involved alkaline phosphatase hydrolysis of the enzyme substrate p-aminophenyl phosphate to p-aminophenol that is detected with the wall middle layer gold as the detecting electrode and the top layer gold as the pseudoreference/auxiliary electrodes. The microelectrodes in the cavity exhibited background signals lower than signal for the lowest concentration detected that was 2.5 pg.

An electrochemical enzyme-linked solid phase DNA-hybridization assay for the detection of Plasmodium falciparum is reported. The DNA-hybridization assay involves attachment of biotinylated primary DNA probe (10P) via its 5'-amine-terminus to the streptavidin- coated microwells in a 96-well plate. The 10P was used to capture the target by hybridization to a complementary sequence. A 36-mer secondary DNA probe labeled with alkaline phosphatase (20P~AP) on the 3'end was hybridized to a complementary base sequence on the 5' end of the target. The electrochemical detection involved the wall electrode (TNB, 8 um2) as the detecting electrode and top layer gold (0.7 mm2 when 200 nL is placed on top of microcavity) as pseudoreference/auxiliary electrodes. The peak current from cyclic voltammograms of PAPP incubated inside modified microwells gave a linear relationship with the concentration of the target at 2- 50 ng/mL, where 10P and 20P~AP were 50 ng/mL. A detection limit of 1.4 ng/mL (or 70 pg) of the DNA target was obtained. The electrochemical signals were not affected in the presence of human hepatocytes, pig liver, or chicken serum indicating the viability of this assay in real clinical samples.

Screen-printed gold (SPG, Dupont gold conductor 5734) on low-temperature co-fired ceramic (LTCC) materials (Dupont dielectric tape 951, mostly composed of alumina and silica) has been demonstrated to be a substrate for electrochemical enzyme-linked immunosorbant assays. The effect of two different cleaning treatments and the extent of nonspecific adsorption on the SPG/LTCC and plain LTCC surfaces were also evaluated. LTCC materials hold promise for constructing a new generation of devices for microelectrochemical sensing and assays. Facile fabrication in three dimensions with integrated conducting elements makes them attractive. A standard sandwich immunoassay for a model analyte, mouse IgG, was used to evaluate the LTCC materials. After the assembly of components onto chips of SPG/LTCC and plain LTCC, p-aminophenol that was generated enzymatically by the enzyme label was detected electrochemically with a separate glassy carbon electrode. Cleaning SPG/LTCC with a piranha solution (7:1 vol/vol of concentrated H2SO4/30% H2O2), traditionally used for other gold surfaces prior to SAM assembly, resulted in a notable decrease in assay signal and an increase in nonspecific adsorption when compared to cleaning with water alone. Assay components assemble specificallyon plain LTCC, with only a small percent attributed to NSA. Environmental scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy reveal the tremendous chemical heterogeneity and complexity of both SPG/LTCC and plain LTCC surfaces and aid in the explanation of assay results. A 10% acetate Tween bovine serum albumin solution and an ethanolic solution of 4 mM 1-butanol eliminate assay signals originating from plain LTCC. The outcomes of these studies can now be used to achieve miniaturized electrochemical immunoassays on LTCC materials where both plain and SPG surfaces are present.

Studies toward the development of automated, rapid, sensitive, low-cost, and reliable biomedical and environmental assays using arrays of microcavities with three individually addressable electrodes is reported. Each microcavity in the array contains a bottom electrode called recessed microdisk electrode (or RMD), a middle layer electrode found along the wall called tubular nanoband electrode (or TNB), and a rim/top electrode. The microelectrode TNB was used to detect the signal from a microwell assay for as low as 100 pg of Plasmodium falciparum CSP gene over 5-min enzyme substrate incubation. A self-contained microelectrochemical assay for Cryptosporidium parvum was generated using the RMD for capture, the TNB as the detecting electrode, and the rim/top as the pseudoreference/auxiliary electrodes. The 4-um distance of the capture surface to the TNB detecting electrode provided close proximity to the assay components which allowed for a rapid response where the first signal was recorded within 30 s of enzyme substrate incubation. The self-contained nature of the microcavity provided low cost assays with the use of reagents down to 200 nL. The self-contained microelectrochemical microarrays were compatible with automation that was demonstrated in the detection of 25 pg Bacillus anthracis anti-PA IgG in < 25 min total assay time.

Sensors applications represent one of the most promising commercial products developments. The Global Industry Analysts predicted that in 2017, the global market for biosensors in medical diagnostics would reach US$16.5 billion. The increased R&D focused on highly accurate real-time diagnosis using biosensors and the demand for biosensors based equipment drives this market. The emergence of new technologies including nanomaterials based-sensors, microfluidics, and non-invasive sensors also act as other market drivers. Until 2016, diagnostic sensors for point of care will continue to drive the market while biodefense and environmental markets are predicted to have the highest CAGRs at 13%–15%. This paper will focus on the preliminary studies in the development of nano and bio sensors for life sciences applications. Data gathered for detection of disease biomarkers using nanotechnology, electrochemistry, and colorimetric methods will be discussed. Studies on the development of lateral flow strip tests, glass slide-based sensors, and 96-well plate assays using quantum dots fluorescence, absorbance, and electrochemical detection methods will be presented.

Nanomaterials are currently being developed for various biomedical applications. Engineered nanomaterials such as quantum dots, metal and semiconductor nanoparticles, and magnetic nanoparticles are among the new materials being studied for medical applications. Nanomaterials have unique properties that include diameters from 3-50 nm, high quantum yields, resistance against photobleaching, high magnetic and electric properties, and simultaneous excitation of multiple fluorescent colors. Quantum dots have unique emission spectra even with ordinary source of light. Magnetic nanoparticles are unique because of their highly magnetic nature. Magnetic nanoparticles are used in magnetic resonance imaging and targeted drug delivery while quantum dots are increasingly being used for biomedical imaging. We report the results of our studies on the applications of nanomaterials in medicine. These include cell imaging, tissue imaging, protein detection, drug delivery, and cell targeting. Preliminary studies indicated promising applications of nanomaterials in molecular imaging and in vitro diagnostics.

Quantum dots (QDs) are a new generation of fluorescent labeling agents which have recently attracted researcher's attention for a variety of biomedical applications. Literature on the applications of quantum dots in the life sciences has recently significantly increased in number that is in line with predictions that nanotechnology in life sciences research will contribute $3.4 billion by 2010 while the National Science Foundation is predicting that the market for nanotechnology and corresponding products will reach $1 trillion in 10 to 15 years. The chemical sensor industry, which is a $2.9 billion US industry, is predicted to grow while applications of nanomaterials have been estimated to have a market impact of over US$ 340 billion within a decade. In this present work, we developed a QD-based protein sensor using mouse IgG as the model analyte. The sensor was designed using a combination of capture antibody (rabbit anti-mouse IgG antibody) and QDs conjugated goat anti-mouse IgG for detection. In order to eliminate the non-specific binding of QD-labeled antibody, a super blocker BBB was used for the assay. Thus, we successfully demonstrated the use of QDs for protein sensing.

Nanotechnology, the area of study involving nanoparticles, century; medical fields. The nanotechnology is one of the fastest growing sectors of the high-tech economy in the 21st industry, it is currently undergoing unprecedented development in nowadays especially in areas of biological research for clinical, environmental and life science applications. The most frequently used nanoparticles are superparamagnetic iron oxide (SPIO) nanoparticles and semiconductor quantum dots (QDs). SPIO nanoparticles with nanometer sizes and superparamagnetic properties are widely used for labeling and sorting cells or organelles, magnetic resonance imaging, targeted drug delivery, and hyperthermia. QDs combined the unique size-dependent physical properties, excellent chemical and photochemical stability, controlled and increased endocytosis, enhanced cooperative binding activity, and easy introduction of multi-functionality for targeted delivery and imaging, and became the most promising labeling tool for life science studies. Both types of nanomaterials provide special approaches for complex studies and play very important roles in modern biomedical research. However, non-specific uptake of QDs and SPIO nanoparticles is a major concern because it can lead to false positives or false results. Hence, we report cellular uptake studies on SPIO nanoparticles and QDs conducted on breast cancer cell line SK-BR3. The results show that both QDs and SPIO nanoparticles have very strong non-specific cellular uptake. With specially designed blocking buffer (BBB) the non-specific signals were significantly decreased.

Engineered nanomaterials (eNMs) are dominating the 21st century in industrial, biological, and medical applications. ENMs are the emerging new materials for sunscreens, medical imaging , solar cell, cosmetics, sports gadgets, consumer products, as well as biological detection materials. One of the major concerns in the application of ENMs like quantum dots (QDs) in life sciences research and clinical diagnostics is non-specific binding (NSB) or nonspecific uptake (NSU) in biological materials such as cells, proteins, or DNA. Elimination of non-specific uptake of ENMs is essential in order to utilize the maximum potential for detection of different biological molecules resulting from the >50% higher emission intensity of QDs in comparison with organic dyes. Furthermore, ENMs are small enough to be used in biological systems making them useful for clinical applications such as drug delivery and/or magnetic resonance imaging. Since QDs are size tunable they can be modified for the detection of single or multiple analyte. However, NSU and/or NSB must be minimized or eliminated before these can be used for the detection of biological analytes. Studies on the development of blocking buffers to minimize or eliminate NSB/NSU have been initiated. Blockers such as bovine serum albumin, polyvinyl pyrrolidone and detergents such as tween 20 and triton X 100 have been used to minimize NSB/NSU. Results of blocking nonspecific uptake of ENMs will be discussed.

We report the development of early stage detection of breast cancer cells using quantum dots (QDs) as fluorescent signal generator for detection. The QDs based imaging of breast cancer cells involved two kinds of antibodies: the first was for labeling the cells and the second was for imaging the breast cancer cells. Anti-Her2/neu (10Ab) was used for labeling the captured SK-BR3 cells. The second antibody against anti-Her2/neu (20Ab) that was conjugated to QDs (20Ab~QDs) forms the complete assay, SK-BR3 + 10Ab + 20Ab~QDs, to generate the fluorescent cells for imaging. Fluorescent images of the complete assay for SK-BR3 cells were evaluated under a microscope with a UV light source. The preliminary results showed that the breast cancer cell SK-BR3 in the complete assay were successfully observed as fluorescent cells that had brighter signals compared with those labeled with organic dye using similar parameters and the same number of cells.

A self-contained microelectrochemical immunoassay detection of Bacillus anthracis protective antigen (PA) has been developed. A microcavity array (VEG4x1{trade mark, serif}) of 50-mm diameter cavities with self-contained microelectrodes were used for the detection of as low as 2.5 pg of B. anthracis Protective Antigen in a less than 12 min total assay time from capture to signal generation. The micro-electrochemical sandwich enzyme-linked immunoassay involved covalent immobilization of the capture antibody on the free end of mercaptoundecanol self-assembled monolayers at the bottom Au-microdisk electrode that also serves as the bottom of the microcavities. Signal generation involved alkaline phosphatase hydrolysis of the enzyme substrate p-aminophenyl phosphate to p-aminophenol that is detected with the wall middle layer gold as the detecting electrode and the top layer gold as the pseudoreference/auxiliary electrodes. The microelectrodes in the cavity exhibited background signals lower than signal for the lowest concentration detected that was 2.5 pg.

An electrochemical enzyme-linked solid phase DNA-hybridization assay for the detection of Plasmodium falciparum is reported. The DNA-hybridization assay involves attachment of biotinylated primary DNA probe (10P) via its 5'-amine-terminus to the streptavidin- coated microwells in a 96-well plate. The 10P was used to capture the target by hybridization to a complementary sequence. A 36-mer secondary DNA probe labeled with alkaline phosphatase (20P~AP) on the 3'end was hybridized to a complementary base sequence on the 5' end of the target. The electrochemical detection involved the wall electrode (TNB, 8 μm2) as the detecting electrode and top layer gold (0.7 mm2 when 200 nL is placed on top of microcavity) as pseudoreference/auxiliary electrodes. The peak current from cyclic voltammograms of PAPP incubated inside modified microwells gave a linear relationship with the concentration of the target at 2- 50 ng/mL, where 10P and 20P~AP were 50 ng/mL. A detection limit of 1.4 ng/mL (or 70 pg) of the DNA target was obtained. The electrochemical signals were not affected in the presence of human hepatocytes, pig liver, or chicken serum indicating the viability of this assay in real clinical samples.

By adding redox species, both aqueous and nonaqueous solutions can be pumped along the length of a microfluidic channel when low voltages (to produce current) are applied across the channel’s breadth in the presence of a magnetic field applied across its height. Control of flow rate is possible by varying the magnitudes of the voltage and magnetic field and by changing the redox concentration. Direction is determined by the voltage polarity and magnetic field orientation. We have demonstrated a dc redox magnetohydrodynamic (MHD) pump in microchannels (270μmwide ×640μmdeep ×2cmlong) that were constructed from low-temperature cofired ceramics with screen-printed gold electrodes on opposing sidewalls. Redox MHD involves the generation of current between the electrodes in a solution through the oxidation/reduction of redox species in the presence of a magnetic field. When the current and magnetic fields are perpendicular, a Lorentz force results, causing fluid flow along the length of the channel. The pumping performance was investigated as a function of type and concentration of redox species, magnetic flux density, applied voltage, and time scale. Studies show bidirectional capability by changing the direction of the current. Flow velocities of up to 5.0mm∕swere observed in a solution of 0.5Mnitrobenzene (NB) and 0.5Mtetrabutylammonium hexafluorophosphate (TBAPF6)in acetonitrile using a 0.41TNdFeBpermanent magnet, at an applied voltage of −1.3Vvs Ag∕AgCl(saturated KCl) (approximately a potential difference of 1.2–1.7Vbetween wall electrodes in the microchannel) and the corresponding current enhancements (caused by the increased convection) were as large as 145%. Flow rates for 0.1MNB and 0.25MNB in 0.1MTBAPF6in acetonitrile were measured at three different applied voltages near the redox potential of NB. Comparisons were also made to theory. A mixture of oxidized and reduced forms of the same redox couple, instead of a single species like NB, can avoid electrode dissolution at the oxidizing electrode (or bubble generation at either electrode). One example of this approach involves a solution of 0.125MFe2+and 0.125MFe3+in 3.0MKCland another involves a solution of 0.125MFe(CN)63−and 0.125MFe(CN)64−in 2.0MKCl, where potential differences between wall electrodes in the microchannel can be less than 0.4V. Findings from these studies should be useful in development of sealed microanalytical devices using redox MHD pumps with possible lab-on-a-chip applications.

Studies toward the development of automated, rapid, sensitive, low-cost, and reliable biomedical and environmental assays using arrays of microcavities with three individually addressable electrodes is reported. Each microcavity in the array contains a bottom electrode called recessed microdisk electrode (or RMD), a middle layer electrode found along the wall called tubular nanoband electrode (or TNB), and a rim/top electrode. The microelectrode TNB was used to detect the signal from a microwell assay for as low as 100 pg of Plasmodium falciparum CSP gene over 5-min enzyme substrate incubation. A self-contained microelectrochemical assay for Cryptosporidium parvum was generated using the RMD for capture, the TNB as the detecting electrode, and the rim/top as the pseudoreference/auxiliary electrodes. The 4-μm distance of the capture surface to the TNB detecting electrode provided close proximity to the assay components which allowed for a rapid response where the first signal was recorded within 30 s of enzyme substrate incubation. The self-contained nature of the microcavity provided low cost assays with the use of reagents down to 200 nL. The self-contained microelectrochemical microarrays were compatible with automation that was demonstrated in the detection of 25 pg Bacillus anthracis anti-PA IgG in < 25 min total assay time.