Functional Nanoparticles with Magnetic 3D Covalent Organic Framework for the Specific Recognition and Separation of Bovine Serum Albumin.

Glutathione functionalized magnetic 3D covalent organic frameworks combined with molecularly imprinted polymer (magnetic 3D COF-GSH MIPs) were developed for the selective recognition and separation of bovine serum albumin (BSA). Ultrasonication was used to prepare magnetic 3D COFs with high porosity (~1 nm) and a large surface area (373 m2 g-1). The magnetic 3D COF-GSH MIP nanoparticles had an imprinting factor of 4.79, absorption capacity of 429 mg g-1, magnetic susceptibility of 32 emu g-1, and five adsorption-desorption cycles of stability. The proposed method has the advantages of a shorter equilibrium absorption time (1.5 h), higher magnetic susceptibility (32 emu g-1), and larger imprinting factor (4.79) compared with those reported from other studies. The magnetic 3D COF-GSH MIPs used with BSA had selectivity factors of 3.68, 2.76, and 3.30 for lysozyme, ovalbumin, and cytochrome C, respectively. The successful recognition and separation of BSA in a real sample analysis verified the capability of the magnetic 3D COF-GSH MIP nanoparticles.

Petrological features of volcanic scoriae from the southern part of the Cameroon Volcanic Line and their supplementary cementations application.

Volcanic scoriae from the southern part of the Cameroon Volcanic Line (Limbé, Loum-Tombel, Yamba, Doupé, Njinkouo, Foumbot, Manjo-manengollé, Galim and Djoungo) were investigated in order to determine their chemical and mineralogical composition, to deduce their origin and to identify their natural characteristics which may be useful to the cement industry. The mineralogical composition was determined by X-ray Diffractometer (XRD); X-ray Fluorescence (XRF) and Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) instruments provided geochemical data. In order to establish the relationship between the natural characteristics of volcanic scoriae and the properties of cements, the amount of amorphous phases was determined by dissolution using sodium hydroxide solution and the pozzolanic activity by thermogravimetric analysis. Field observations show that these rocks are basalts, basanites, hawaiites and picrobasalts. Their mineralogical composition includes augite, olivine, plagioclase, enstatite, feldspars, ettringite, portlandite and Fe-Ti minerals. Overall, they are characterized by high MgO, Fe2O3, CaO, and TiO2 contents. The behavior of major and trace elements suggests that volcanic scoriae have an evolution dominated by partial melting. Besides, high chondrite normalized La/Yb (8-22), Tb/Yb (>1.9) and Dy/Yb (>2) values suggest that the melting corresponds to the garnet lherzolite stability field. The scoriae exhibit good pozzolanic reactivity after 28 days according to their considerable amount of amorphous phases, low CaO contents and their large specific surface area. According to ASTM C618 standard, the sum of SiO2, Al2O3 and Fe2O3 (SAI = 65.96-76.34 wt.%); LOI (-0.1-16.99 wt.%), and of CaO, Fe2O3 and MgO (CIM = 23.43-34.06 wt.%) suggest that those less weathered materials seem appropriate as an additive in cement manufacture. The suitable use of volcanic scoriae in the cement industry closely depends on the petrological features of amorphous phases.

Rapid Preparation of Fluorescent Carbon Dots from Pine Needles for Chemical Analysis.

Fluorescent carbon dots with blue, green, and red emissions were rapidly prepared from modified pine needles through microwave irradiation in a one-pot reaction. The fluorescence intensity and emission versatility for a carbon source were experimentally optimized. The reaction times were under 10 min and the reaction temperatures were lower than 220 °C. Potential applications of magnetic fluorescence-linked immunoassays of carcinoembryonic antigen (CEA) and tumor necrosis factor-alpha (TNF-α) were presented. The detection limits for CEA and TNF-α (3.1 and 2.8 pg mL-1, respectively) are lower than those presented in other reports, whereas the linear ranges for CEA and TNF-α (9 pg mL-1 to 18 ng mL-1 and 8.5 pg mL-1 to 17 ng mL-1, respectively) are wider than those presented in other reports. Magnetic immunoassays with fluorescent CDs prepared from pine needles can enable rapid, sensitive, and selective detections for biochemical analysis.

Differential effects of an electronic symptom monitoring intervention based on the age of patients with advanced cancer.

BACKGROUND: Symptom monitoring interventions enhance patient outcomes, including quality of life (QoL), health care utilization, and survival, but it remains unclear whether older and younger patients with cancer derive similar benefits. We explored whether age moderates the improved outcomes seen with an outpatient electronic symptom monitoring intervention. PATIENTS AND METHODS: We carried out a secondary analysis of data from a randomized trial of 766 patients receiving chemotherapy for metastatic solid tumors. Patients received an electronic symptom monitoring intervention integrated with oncology care or usual oncology care alone. The intervention consisted of patients reporting their symptoms, which were provided to their physicians at clinic visits, and nurses receiving alerts for severe/worsening symptoms. We used regression models to determine whether age (older or younger than 70 years) moderated the effects of the intervention on QoL (EuroQol EQ-5D), emergency room (ER) visits, hospitalizations, and survival outcomes. RESULTS: Enrollment rates for younger (589/777 = 75.8%) and older (177/230 = 77.0%) patients did not differ. Older patients (median age = 75 years, range 70-91 years) were more likely to have an education level of high school or less (26.6% versus 20.9%, P = 0.029) and to be computer inexperienced (50.3% versus 23.4%, P < 0.001) compared with younger patients (median age = 58 years, range 26-69 years). Younger patients receiving the symptom monitoring intervention experienced lower risk of ER visits [hazard ratio (HR) = 0.74, P = 0.011] and improved survival (HR = 0.76, P = 0.011) compared with younger patients receiving usual care. However, older patients did not experience significantly lower risk of ER visits (HR = 0.90, P = 0.613) or improved survival (HR = 1.06, P = 0.753) with the intervention. We found no moderation effects based on age for QoL and risk of hospitalizations. CONCLUSIONS: Among patients with advanced cancer, age moderated the effects of an electronic symptom monitoring intervention on the risk of ER visits and survival, but not QoL. Symptom monitoring interventions may need to be tailored to the unique needs of older adults with cancer.

Microwave Synthesis of Gold Nanoclusters with Garlic Extract Modifications for the Simple and Sensitive Detection of Lead Ions.

Novel bovine serum albumin (BSA)-gold nanoclusters with garlic extract modifications (mw_G-BSA-AuNCs) were prepared through microwave-assisted rapid synthesis. The modified nanoclusters were characterized and used for the simple and sensitive detection of Pb2+ ions. Both turn-on and turn-off methods were used and compared for Pb2+ ion detection. For Pb2+ ions, the preparation time for the modified nanoclusters was 10 min, and the detection time for the nanoclusters was 6 min. The modified nanoclusters were stable, and their fluorescence intensities changed by less than 10% in 60 days. The detection limit and linear range for the "off-on" method of mw_G-BSA-AuNCs for Pb2+ ion detection were 0.28 and 1-20 nM, respectively. The recoveries of the mw_G-BSA-AuNCs probe used for the detection of the Pb(II) ion in tap water ranged from 93.8% to 102.2%, with an average of 97.1%. The "off-on" method of mw_G-BSA-AuNCs can provide a lower detection limit, higher selectivity, and better recovery than the commonly used "turn-off" methods of mw_BSA-AuNCs for Pb2+ ion detection. The proposed method is superior to other methods proposed from 2018 to 2019 because it can provide a shorter preparation time and a lower detection limit with good selectivity. The microwave-assisted novel compound, mw_G-BSA-AuNCs, can be rapidly synthesized in a green manner and can provide a low detection limit, good selectivity, and a simple and fast reaction for Pb2+ ion detection.

A magneto-microfluidic platform for fluorescence immunosensing using quantum dot nanoparticles.

This study reports the online fluorescent detection of carcinoembryonic antigen (CEA) and α-fetoprotein (AFP) biomarker proteins in microfluidic channels using functional nanoparticles. Functional magnetic nanoparticles labeled with two antibodies were predeposited on separated microfluidic channels. Antigens were passed through each microfluidic channel to react with the respective antibodies. Two types of fluorescent nanoparticles labeled with antibodies were then used to detect and confirm antigens in the immunocomplex. Results indicate that online fluorescent detection of proteins can provide advantages for real-time monitoring and diagnostic applications. The running time was less than 20 min for each trial. The detection limits of CEA and AFP were found to be 0.6 and 0.2 pg ml-1. These detection limits are lower than those of ELISA. The linear ranges of CEA and AFP detection were from 1.8 pg ml-1 to 1.8 ng ml-1 and from 0.68 pg ml-1 to 0.68 ng ml-1 for two deposition zones in a magnetic sandwich immunoassay. The linear ranges of this method are wider than those of ELISA and those of most other methods. The measurements of CEA and AFP in serum samples from this method differed from ELISA results by 11% and 9.4%, respectively. The detection limit of online detection has achieved the same range as those of previous offline detection. This method has a good potential for automation and multichannel analysis to increase the throughput with some modifications in the future. The proposed method can provide simple, fast, and sensitive online detection for biomarkers.

Pilot randomized trial of an electronic symptom monitoring intervention for hospitalized patients with cancer.

BACKGROUND: Hospitalized patients with cancer experience a high symptom burden, which is associated with poor health outcomes and increased health care utilization. However, studies investigating symptom monitoring interventions in this population are lacking. We conducted a pilot randomized trial to assess the feasibility and preliminary efficacy of a symptom monitoring intervention to improve symptom management in hospitalized patients with advanced cancer. PATIENTS AND METHODS: We randomly assigned patients with advanced cancer who were admitted to the inpatient oncology service to a symptom monitoring intervention or usual care. Patients in both arms self-reported their symptoms daily (Edmonton Symptom Assessment System and Patient Health Questionnaire-4). Patients assigned to the intervention had their symptom reports presented graphically with alerts for moderate/severe symptoms during daily team rounds. The primary end point of the study was feasibility. We defined the intervention as feasible if >75% of participants hospitalized >2 days completed >2 symptom reports. We observed daily rounds to determine whether clinicians discussed and developed a plan to address patients' symptoms. We used regression models to assess intervention effects on patients' symptoms throughout their hospitalization, readmission risk, and hospital length of stay (LOS). RESULTS: Among 150 enrolled patients (81.1% enrollment), 94.2% completed >2 symptom reports. Clinicians discussed 60.4% of the symptom reports and developed a plan to address the symptoms highlighted by the symptom reports 20.8% of the time. Compared with usual care, intervention patients had a greater proportion of days with lower psychological distress (B = 0.12, P = 0.008), but no significant difference in the proportion of days with improved Edmonton Symptom Assessment System-physical symptoms (B = 0.07, P = 0.138). Intervention patients had lower readmission risk (hazard ratio = 0.68, P = 0.224), although this difference was not significant. We found no significant intervention effects on hospital LOS (B = 0.16, P = 0.862). CONCLUSIONS: This symptom monitoring intervention is feasible and demonstrates encouraging preliminary efficacy for improving patients' symptoms and readmission risk.ClinicalTrials.gov identifier NCT02891993.

Magnetofluorescent nanocomposites and quantum dots used for optimal application in magnetic fluorescence-linked immunoassay.

Magnetofluorescent nanocomposites with optimal magnetic and fluorescent properties were prepared and characterized by combining magnetic nanoparticles (iron oxide@polymethyl methacrylate) with fluorescent nanoparticles (rhodamine 6G@mSiO2). Experimental parameters were optimized to produce nanocomposites with high magnetic susceptibility and fluorescence intensity. The detection of a model biomarker (alpha-fetoprotein) was used to demonstrate the feasibility of applying the magnetofluorescent nanocomposites combined with quantum dots and using magnetic fluorescence-linked immunoassay. The magnetofluorescent nanocomposites enable efficient mixing, fast re-concentration, and nanoparticle quantization for optimal reactions. Biofunctional quantum dots were used to confirm the alpha-fetoprotein (AFP) content in sandwich immunoassay after mixing and washing. The analysis time was only one third that required in ELISA. The detection limit was 0.2 pg mL-1, and the linear range was 0.68 pg mL-1-6.8 ng mL-1. This detection limit is lower, and the linear range is wider than those of ELISA and other methods. The measurements made using the proposed method differed by less than 13% from those obtained using ELISA for four AFP concentrations (0.03, 0.15, 0.75, and 3.75 ng mL-1). The proposed method has a considerable potential for biomarker detection in various analytical and biomedical applications. Graphical abstract Magnetofluorescent nanocomposites combined with fluorescent quantum dots were used in magnetic fluorescence-linked immunoassay.

Multifunctional nanoparticles for protein detections in thin channels.

This paper presents a method for simultaneous detection of two proteins by using multifunctional nanoparticles with a magnetic immunoassay in thin channels. Biofunctional magnetic graphene quantum dots (GQDs) combined with two biofunctional quantum dots (QDs) were used for simultaneously detecting two proteins. Magnetic GQDs enabled selective and quantitative nanoparticle deposition with blue emission. Biofunctional QDs confirmed the two protein detections with orange and green emissions. We used two model biomarkers [alpha-fetoprotein (AFP) and cancer antigen 125 (CA125)] to demonstrate the feasibility of the proposed method. The detection limits (0.06pg/mL AFP and 0.001U/mL CA125) and linear ranges (0.2pg/mL-0.68ng/mL AFP and 0.003-25U/mL CA125) of this method are the same as those of single protein detection within experimental errors. These detection limits are substantially lower and the linear ranges are considerably wider than those of enzyme-linked immunosorbent assay (ELISA) and other immunoassay methods. The differences between the proposed method and an ELISA method in AFP and CA125 measurements of serum samples were less than 12%. The proposed method demonstrates favorable detection of biomarkers with advantages of speed, sensitivity, selectivity, and throughput.

Estimation of Molecular Interaction Force Using Atomic Force Microscopy for Bioapplication.

We report a method that involves using atomic force microscopy to estimate molecular interaction forces for bioapplications. Experimental parameters, comprising the labeling concentrations of tips and substrates and the loading rates of tips, were optimized for estimating molecular interaction forces for three pairs of model molecules (IgG/anti-IgG, BSA/anti-BSA, streptavidin/biotin). The estimated molecular interaction forces of IgG/anti-IgG, BSA/anti-BSA, and streptavidin/biotin were 121 ± 3, 185 ± 4, and 241 ± 4 pN, respectively. The measured values were consistent and within the range of values reported in the literature. Estimation of molecular interaction forces in force-distance curves for bioapplication is still challenging. There are many potential bioapplications with further investigations. Providing additional screening reference for microsensing applications is one example. This method demonstrates favorable potential for effectively estimating molecular interaction forces for various applications of protein-ligand, antibody-antigen, ligand-receptor complexes, and other bioreactions. This method is also useful for studies of the structures and properties of molecular, cellular, and bacterial surfaces.

Detection of c-reactive protein based on a magnetic immunoassay by using functional magnetic and fluorescent nanoparticles in microplates.

We report the preparation and application of biofunctional nanoparticles to detect C-reactive protein (CRP) in magnetic microplates. A CRP model biomarker was used to test the proposed detection method. Biofunctional magnetic nanoparticles, CRP, and biofunctional fluorescent nanoparticles were used in a sandwich nanoparticle immunoassay. The CRP concentrations in the samples were deduced from the reference plot, using the fluorescence intensity of the sandwich nanoparticle immunoassay. When biofunctional nanoparticles were used to detect CRP, the detection limit was 1.0 ng ml(-1) and the linear range was between 1.18 ng ml(-1) and 11.8 µg ml(-1). The results revealed that the method involving biofunctional nanoparticles exhibited a lower detection limit and a wider linear range than those of the enzyme-linked immunosorbent assay (ELISA) and most other methods. For CRP measurements of serum samples, the differences between this method and ELISA in CRP measurements of serum samples were less than 13%. The proposed method can reduce the analysis time to one-third that of ELISA. This method demonstrates the potential to replace ELISA for rapidly detecting biomarkers with a low detection limit and a wide dynamic range.

Electrochemical sensing of hepatocyte viability.

We investigated the use of amperometric and chronoamperometric methods with a double mediator system and screen-printed electrodes (SPEs) for the electrochemical sensing of hepatocyte viability. Cell counts were determined based on measuring cellular respiration via interaction of electroactive redox mediators. The oxidation currents of chronoamperometric measurement were proportional to the concentrations of ferrocyanide which was produced via interaction of cellular respiration, succinate and ferricyanide. The integrated oxidation charges increased linearly with the density of the cultured primary rat hepatocytes over a range of 1 × 10(5) to 5 × 10(5) cells per well (slope = 1.98 (±0.08) µC per 10(5) cells; R(2) = 0.9969), and the detection limit was 7600 (±300) cells per well based on S/N = 3. Each density of cells was cultured in triple replicates and individual cell samples were evaluated. The results of the cytotoxic effect of the chronoamperometric method are comparable to those of the tetrazolium-based colorimetric assay. The chronoamperometric method with ferricyanide and succinate mediators is an efficient, alternative method for assessing the viability of primary hepatocytes which can be completed in 20 min. Succinate did not provide an efficient electron shuttle between cytosolic respiratory redox activity of cancer cells and extracellular ferricyanide, an effect that may be useful for distinguishing hepatocarcinoma cells from healthy hepatocytes.

Effects of particle characteristics on magnetic immunoassay in a thin channel.

The effects of size and porosity of particles on magnetic immunoassay in a thin channel were studied. Experimental parameters were investigated and compared using a model immunoassay complex of carcinoembryonic antigen (CEA)/anti-CEA. The rate constant for the affinity reaction between functional particles increased as the size of magnetic nanoparticles (800-80 nm) decreased. The affinity reaction between functional particles had no significant effect on the sizes of microparticles (1.0-4.4 µm) at commonly used thin channel flow-rates of 0.001-0.025 ml/min. Competitive and sandwich reactions of CEA/anti-CEA were studied for CEA detection. Microparticles of different porosities produced similar linear ranges of detection and limits of detection. The limits of detection for CEA were 0.29 pg/ml and 0.21 pg/ml for competitive and sandwich reactions, respectively. The linear ranges of detection were from 0.49 pg/ml to 4.9 ng/ml for both competitive and sandwich reactions. The detection limits were lower, and the linear ranges were wider than those of literature. There was a 9% difference in CEA detection measurements between competitive and sandwich magnetic immunoassay. The measurements of two magnetic immunoassays differed by less than 13% from the ELISA reference measurements. The running time was less than 30 min. Magnetic immunoassay in a thin channel has great potential for biochemical analysis and immunoassay-related applications.

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

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.

Competitive magnetic immunoassay for protein detection in thin channels.

Functional magnetic nanoparticles are prepared and characterized for protein detection in a magnetic separation channel. This detection method is based on a competitive immunoassay of magnetic separation in thin channels using functional magnetic nanoparticles. We used protein A-IgG complex to demonstrate the feasibility. Free IgG and fixed number of IgG-labeled microparticles were used to compete for limited sites of protein A on the magnetic nanoparticles. Several experimental parameters were investigated for protein detection. The deposited percentages of IgG-labeled microparticles at various concentrations of free IgG were determined and used as a reference plot. The IgG concentration in a sample was deduced and determined based on the reference plot using the deposited percentage of IgG-labeled microparticles from the sample. The linear range of IgG detection was from 5.0 x 10(-8) to 1.0 x 10(-11) M. The detection limit was 3.69 x 10(-12) M. The running time was less than 10 min. Selectivities were higher than 92% and the relative errors were less than 7%. The IgG concentration of serum was determined to be 3.6 mg ml(-1). This measurement differed by 8.3% from the ELISA measurement. The recoveries of IgG spiked in serum were found to be higher than 94%. This method can provide simple, fast, and selective analysis for protein detection and other immunoassay-related applications.

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

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.

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

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 microg/mL for deposited percentages of CRP-labeled particles. The detection limit of this method was 0.12 microg/mL which was approximately 8-fold lower than the typical clinical cutoff concentration (1 microug/mL). This method can provide a fast, simple, and sensitive way for protein detection based on competitive immunoassay using magnetic nanoparticles under magnetic fields.

Analytical and preparative applications of magnetic split-flow thin fractionation on several ion-labeled red blood cells.

BACKGROUND: Magnetic Split-flow thin (SPLITT) fractionation is a newly developed technique for separating magnetically susceptible particles. Particles with different field-induced velocities can be separated into two fractions by adjusting applied magnetic forces and flow-rates at inlets and outlets. METHODS: Magnetic particles, Dynabeads, were used to test this new approach of field-induced velocity for susceptibility determination using magnetic SF at different magnetic field intensities. Reference measurements of magnetic susceptibility were made using a superconducting quantum interference device (SQUID) magnetometer. Various ion-labeled red blood cells (RBC) were used to study susceptibility determination and throughput parameters for analytical and preparative applications of magnetic SPLITT fractionation (SF), respectively. Throughputs were studied at different sample concentrations, magnetic field intensities, and channel flow-rates. RESULTS: The susceptibilities of Dynabeads determined by SPLITT fractionation (SF) were consistent with those of reference measurement using a superconducting quantum interference device (SQUID) magnetometer. Determined susceptibilities of ion-labeled RBC were consistent within 9.6% variations at two magnetic intensities and different flow-rates. The determined susceptibilities differed by 10% from referenced measurements. The minimum difference in magnetic susceptibility required for complete separation was about 5.0 x 10(-6) [cgs]. Sample recoveries were higher than 92%. The throughput of magnetic SF was approximately 1.8 g/h using our experimental setup. CONCLUSION: Magnetic SF can provide simple and economical determination of particle susceptibility. This technique also has great potential for cell separation and related analysis. Continuous separations of ion-labeled RBC using magnetic SF were successful over 4 hours. The throughput was increased by 18 folds versus early study. Sample recoveries were 93.1 +/- 1.8% in triplicate experiments.

Solid-phase microextraction coupled with liquid chromatography for determination of beta-carotene in food.

Beta-carotene in vegetables and nutritional products is analyzed using solid-phase microextraction (SPME) coupled with liquid chromatography (LC) to improve the speed of analysis and to reduce the consumption of organic solvents. The relative standard deviations (RSDs) of this analytical method for beta-carotene determinations in vegetables and nutritional products are approximately 10% and 5%, respectively. The amount of beta-carotene was found to vary from 0.35 +/- 0.05 ppm to 76.5 +/- 6.9 ppm for several vegetables in Taiwan. This method was linear over the range of 0.4-40 ppm with correlation coefficients higher than 0.997. The experimentally determined level of beta-carotene in nutritional products varied from 3.8 +/- 0.2 ppm to 24.6 +/- 1.1 ppm following SPME-LC. The recoveries of beta-carotene for these measurements following SPME were all higher than 97% +/- 2% (n = 3). The detection limits of beta-carotene for this method were from 0.027 to 0.054 ppm. Conventional solvent extractions take approximately 4-6 h for extraction and reconcentration but SPME takes approximately 1 h. From several tens to hundreds of milliliters, organic solvents can be saved using SPME. SPME provides better analyses on beta-carotene than conventional solvent extraction for nutritional products in terms of speed, precision, simplicity, and solvent consumption.

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

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.