Micro-Fluidic Diffusion Coefficient Measurement

A new method for diffusion coefficient measurement applicable to micro-fluidics is pre- sented. The method Iltilizes an analytical model describing laminar dispersion in rect- anglllar ~llicro_channe]s. The Illethod ~vas verified throllgh measllremen~ of fllloresceill diffusivity in water and aqueolls polymer solutions of differing concentration. The diffll- sivity of flllorescein was measlmed as 0.64 x 10-gm2/s in water, 0.49 x 10-gm2/s in the 4 gm/dl dextran solution and 0.38 x 10-9n12/s in the 8 gnl/dl dextran solution

The treatment and outcomes of early-stage epithelial ovarian cancer: have we made any progress?

The objective of this study is to determine the progress and trends in the treatment and survival of women with early-stage (I–II) epithelial ovarian cancer. Data were obtained from the SEER database between 1988 and 2001. Kaplan–Meier and Cox regressions methods were employed for statistical analyses. Of the 8372 patients, the median age was 57 years (range: 12–99 years). A total of 6152 patients (73.4%) presented with stage I and 2220 (26.5%) with stage II disease. Over the periods 1988–1992, 1993–1997, and 1998–2001, 3-year disease-specific survivals increased from 86.1 to 87.2 to 88.8% (P=0.076). The number of patients that underwent lymphadenectomy has increased significantly from 26.2 to 38.7 to 54.2% over the study period (P<0.001). Of those patients who underwent staging procedures with lymphadenectomy, there was no improvement in survival over the three study periods (from 93.2 to 93.5 to 93.1%; P=0.978). On multivariate analysis, younger age, nonclear cell histology, earlier stage, lower grade, surgery, and lymphadenectomy were significant independent prognostic factors for improved survival. After adjusting for surgical staging with lymphadenectomy, the year of diagnosis was no longer an important prognostic factor. In conclusion, the use of lymphadenectomy during surgery for early-stage ovarian cancer has doubled over the last 14 years. The marginal improvement in survival demonstrated over time is potentially attributed to the increased use of staging procedures with lymphadenectomy

Separation method based on affinity reaction between magnetic and nonmagnetic particles for the analysis of particles and biomolecules

[[abstract]]A separation method is reported for particle and biochemical analysis based on affinity interactions between particle surfaces under magnetic field. In this method, magnetic particles with immunoglobulin G (IgG) or streptavidin on the surface are flowed through a separation channel to form a deposition matrix for selectively capturing nonmagnetic analytes with protein A or biotin on the surface due to specific antigen (Ag)-antibody (Ab) interactions. This separation method was demonstrated using model reactions of IgG-protein A and streptavidin-biotin on particle surface. The features of this new separation method are (1) the deposited Ag-Ab complex can be examined and further analyzed under the microscope, (2) a kinetic study of complex binding is possible, and (3) the predeposited matrix can be formed selectively and changed easily. The detection limits were about 10(-11) g. The running time was less than 10 min. The selectivities of studied particles were 94% higher than those of label-controlled particles. This method extends the applications of analytical magnetapheresis to nonmagnetic particles. Preliminary study shows that this separation method has a great potential to provide a simple, fast, and selective analysis for particles, blood cells, and immunoassay related applications. (c) 2006 Elsevier B.V. All rights reserved.[[note]]SC

Detection of alpha-fetoprotein in magnetic immunoassay of thin channels using biofunctional nanoparticles

[[abstract]]This paper presents the use of fluorescent biofunctional nanoparticles (10-30 nm) to detect alpha-fetoprotein (AFP) in a thin-channel magnetic immunoassay. We used an AFP model biomarker and s-shaped deposition zones to test the proposed detection method. The results show that the detection using fluorescent biofunctional nanoparticle has a higher throughput than that of functional microparticle used in previous experiments on affinity reactions. The proposed method takes about 3 min (versus 150 min of previous method) to detect 100 samples. The proposed method is useful for screening biomarkers in clinical applications, and can reduce the run time for sandwich immunoassays to less than 20 min. The detection limits (0.06 pg/ml) and linear ranges (0.068 pg/ml-0.68 ng/ml) of AFP using fluorescent biofunctional nanoparticles are the same as those of using functional microparticles within experimental errors. This detection limit is substantially lower and the linear range is considerably wider than those of enzyme-linked immunosorbent assay (ELISA) and other methods in sandwich immunoassay methods. The differences between this method and an ELISA in AFP measurements of serum samples were less than 12 %. The proposed method provides simple, fast, and sensitive detection with a high throughput for biomarkers.[[note]]SC

Detection of c-reactive protein based on immunoassay using antibody-conjugated magnetic nanoparticles

[[abstract]]We report a detection method for C-reactive protein (CRP) based on competitive immunoassay using magnetic nanoparticles under magnetic fields: Functional magnetic nanoparticles were prepared and conjugated with anti-CRP for immunoassay. Magnetic nanoparticles labeled with anti-CRP were flowed through a separation channel to form depositions for selective capture of CRP under magnetic fields. Free CRP and a fixed number of CRP-labeled particles were used to compete for a limited number of anti-CRP binding sites on the magnetic nanoparticles. The deposited percentages of CRP-labeled particles at various concentrations of free CRP were determined and used as a reference plot. The determination of CRP in the unknown sample was deduced from the reference plot using the deposited percentages. The running time was less than 10 min. The CRP concentration of serum sample was linearly over the range of 1.2-310 mu g/mL for deposited percentages of CRP-labeled particles. The detection limit of this method was 0.12 mu g/ mL which was similar to 8-fold lower than the typical clinical cutoff concentration (1 mu g/mL). This method can provide a fast, simple, and sensitive way for protein detection based on competitive immunoassay using magnetic nanoparticles under magnetic fields.[[note]]SC

Impurity analysis of 1,4-dioxane in nonionic surfactants and cosmetics using headspace solid-phase microextraction coupled with gas chromatography and gas chromatography-mass spectrometry

[[abstract]]1,4-Dioxane impurity in nonionic surfactants and cosmetics were analyzed using solid-phase microextraction (SPME) coupled with gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). Experimental results show that there is no significant difference using SPME-GC and SPME-GC-MS for analysis of 1,4-dioxane in three types of nonionic surfactants at the 95% confidence level. The relative standard deviation (R.S.D.) values of each analytical method were smaller than 3%. The amount of 1,4-dioxane was found to vary from 11.6 +/- 0.3 ppm to 73.5 +/- 0.5 ppm in 30% of nonionic surfactants from manufacturers in Taiwan. These methods were linear over the studied range of 3-150ppm with correlation coefficients higher than 0.995. The recoveries of 1,4-dioxane for these nonionic surfactants following SPME were all higher than 96 +/- 1% (n = 3). The detection limits of 1,4-dioxane for these nonionic surfactants following SPME were from 0.06 ppm to 0.51 ppm. The experimentally determined level of 1,4-dioxane in cosmetics from manufacturers in Taiwan varied from 4.2 +/- 0.1 ppm to 41.1 +/- 0.6 ppm in 22% of daily used cosmetics following SPME coupled with GC and GC-MS. Conventional solvent extraction takes around 1 h for extraction and reconcentration but SPME takes only around 10 min. SPME provides better analyses of 1,4-dioxane in nonionic surfactants and cosmetics than conventional solvent extraction and head space pretreatments in term of simplicity, speed, precision, detection limit, and solvent consumption. (c) 2004 Elsevier B.V. All rights reserved.[[note]]SC

Magnetic immunoassay detection of tumor necrosis factor-alpha in different deposited zones of thin channels using functional particles

[[abstract]]This study reports the magnetic immunoassay detection of tumor necrosis factor-alpha (TNF-alpha) in different deposited zones of thin channels using functional particles. Deposited zones with linear and s-shape geometries were tested and compared to detect a TNF-alpha model biomarker. Results show that the deposited zone of s-shape geometry is faster than that of linear geometry for affinity reactions. Using the s-shape deposited zones, the running time can be reduced to less than 20 min. The detection limits of linear and s-shape deposited zones were found to be the same as 1.0 pg/mL within experimental errors. The detection limit is lower than that of ELISA. The linear ranges of TNF-alpha detection were from 1.7 pg/mL to 1.7 ng/mL for two deposited zones in sandwiched magnetic immunoassay. The linear range of this method is wider than those of ELISA and other methods. The measurements of TNF-alpha in serum samples from this method differed from ELISA results by about 10%. The proposed method can provide simple, fast, and sensitive detection for biomarkers. (C) 2012 Elsevier B.V. All rights reserved.[[note]]SC

Determination of hepatitis B surface antigen using magnetic immunoassays in a thin channel

[[abstract]]We report novel methods for detection of hepatitis B surface antigen (HBsAg) based on competitive and sandwiched magnetic immunoassays using functional magnetic nanoparticles in a thin channel. Magnetic nanoparticles labeled with hepatitis B antibody are flowed through a thin channel to form a predeposition layer for capturing HBsAg. Competitive and sandwiched magnetic immunoassays were studied and detection limit, linear range, and sample selectivity were compared. The detection limits of competitive and sandwiched magnetic immunoassays were found to be 0.26 and 0.25 pg/ml, respectively. The linear range of HBsAg concentration was 0.26 pg/ml-2.6 ng/ml for competitive magnetic immunoassay and was 0.89 pg/ml-8.9 ng/ml for sandwiched magnetic immunoassay. The advantages of these methods over ELISA and other methods for HBsAg detection are lower detection limits and wider linear ranges. The running time was less than 30 min. Competitive magnetic immunoassay was faster than sandwiched magnetic immunoassay for detection of HBsAg. The measurements of HBsAg in serum samples from these methods differed by about 10% from those of ELISA. These methods can provide simple, fast, and sensitive detections of biomarkers and other immunoassay-related samples. (C) 2010 Elsevier B.V. All rights reserved.[[note]]SC

Integrating the QCM detection with magnetic separation for on-line analysis

[[abstract]]We investigate the feasibility of coupling the quartz crystal microbalance (QCM) with magnetic separation for on-line analysis. A flow cell was integrated with QCM and magnetic force for the analysis of magnetic and nonmagnetic samples. The resonant frequency change (Delta f) of QCM was related to the amount of deposited magnetic nanoparticles. This experiment demonstrates that QCM can be used as an on-line detector for magnetic separation. The QCM also gives a characteristic response of the binding between the streptavidin and biotin labeled On the magnetic nanoparticles. Biotin-labeled magnetic nanoparticles were flowed through a gold electrode of QCM to deposit as a matrix for selective capturing streptavidin. The resonant frequency change of QCM was proportional to the amounts of streptavidin captured by biotin. This technique can provide a simple, economic, and automatic method for on-line detection of biomarkers. (C) 2008 Elsevier B.V. All rights reserved.[[note]]SC