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.

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 CD_s prepared from pine needles can enable rapid, sensitive, and selective detections for biochemical analysis.

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.

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.

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 × 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.

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.

Solid-Phase Microextraction Coupled with Liquid Chromatography for Determination of -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.

New method of blood typing using analytical magnetapheresis

We report a new method of blood typing based on the agglutination of red blood cell (RBC) with serum-treated magnetic particles in analytical magnetapheresis. Blood typing of ABO was demonstrated. The agglutination patterns of RBCs are different for different blood types and can be used to determine the ABO blood typing in analytical magnetapheresis. Six samples can be tested in each run. The running time was less than 10 min. Magnetic particles were prepared in the laboratory. The amount of RBCs needed for the agglutination test was about 1.0 microl of adult blood. The blood typing of ABO was used to illustrate the capable applications of analytical magnetapheresis to nonmagnetic samples like cells without magnetic labels. Analytical magnetapheresis has a great potential for cell related analysis.

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

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 3-150 ppm 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.

Determination of magnetic susceptibility of various ion-labeled red blood cells by means of analytical magnetapheresis

Analytical magnetapheresis is a newly developed technique for separating magnetically susceptible particles. The magnetically susceptible particles are deposited on a bottom plate after flowing through a thin (< 0.05 cm) separation channel under a magnetic field applied perpendicular to the flow. Particles with various magnetic susceptibilities can be selectively deposited and separated by adjusting the applying magnetic force and flow rates. Magnetic susceptibility is an important parameter for magnetic separation. Magnetic susceptibility determination of various ion-labeled red blood cells (RBCs) using analytical magnetapheresis with a simple theoretical treatment is reported in this study. Susceptibility determination is based on the balance between maximal channel flow rate and magnetically induced flow rate for deposition. We tried a new approach to determine particle magnetic susceptibilities using a balance of magnetic and drag forces to control magnetically induced particle velocities. The Er3+, Fe3+, Cu2+, Mn2+, Co2+, and Ni2+ ions were used to label RBC at various labeling concentrations for susceptibility determination. The susceptibilities determined for various ion-labeled RBC under two magnetic field intensities fell within a 10% range. The average viabilities of various ion-labeled RBCs were 96.1 +/- 0.8%. The susceptibility determination generally took less than 10 min. Determined susceptibilities from analytical magnetapheresis differed by 10% from reference measurements using a superconducting quantum interference device (SQUID) magnetometer. The cost and time for analysis is much less using analytical magnetapheresis. This technique can provide a simple, fast, and economical way for particle susceptibility determinations.

Particle magnetic susceptibility determination using analytical split-flow thin fractionation

Magnetic split-flow thin (SPLITT) fractionation is a newly developed S

Analytical magnetapheresis of magnetically susceptible particles

Analytical magnetapheresis is a newly developed technique for analyzing magnetic particles. The magnetically susceptible particles form deposition patterns after flowing through a separation channel in a magnetic field. The separation channel requirements for analytical magnetapheresis are an excellent seal for the carrier flow and ease of disassembly after magnetapheresis. Previously used separation channels often exhibit variable channel leakage and unstable flow velocities. We improved the separation channel assembly to ensure stable, high flow velocities and characterized the system with various magnetically susceptible and labeled particles. Our new separation channel featured silicone sealant with embedded nylon wires and met analytical magnetapheresis requirements. Characterization of this system was performed using several magnetically susceptible particles, and we studied a variety of diamagnetic sample labels with paramagnetic ions and magnetically susceptible particles at different flow-rates and solution pH values. The minimal labeling concentration for complete deposition was determined to be approximately 2.50 x 10(10) ions per particle for test samples at a flow velocity of 0.67 mm s(-1) and a magnetic field gradient of 2.8 T mm(-1). Silicas, yeasts and blood cells were used for these studies. We determined that the minimal difference in magnetic susceptibility (delta(chi)) for successful separation was approximately 2.00 x 10(-6) [SI]. The magnetic susceptibilities of Dynabeads M-450 at several separation distances and flow-rates were determined to be 0.25 [SI], within 2% of values published by other workers. The magnetic susceptibilities of various ion-labeled yeasts and cells were determined and most varied by less than 5% at different flow-rates. The results of this study provide very important references for analytical magnetapheresis applications.

Magnetic split-flow thin fractionation of magnetically susceptible particles

We recently built a magnetic separation system to extend the applications of split-flow thin (SPLITT) fractionation to magnetically susceptible particles. Here, we characterize the magnetic SPLITT system using magnetically susceptible particles and ion-labeled particles. The flow axis of separation channel was orientated parallel and perpendicular to gravitational forces to exclude and include, respectively, gravitational effects on separation. Both operating modes were used to test the theory experimentally, with emphasis on the parallel mode. The magnetic susceptibilities of carrier and ion-labeled particles were varied, and various ion-labeled and unlabeled particles were studied experimentally, resulting in successful separation of labeled particles, yeasts, and cells from unlabeled ones. The minimal difference in magnetic susceptibility (delta(chi)) required for complete particle separation was about 1.75 x 10(-5) [cgs], corresponding to about 10(9) labeling ions per particle in this study. The throughput was around 7.2 x 10(8) particles/h using the present setup. Magnetic SPLITT fractionation shows good potential for use in obtaining particles magnetic susceptibilities from a simple theoretical treatment.

Immunomagnetic isolation of magnetoferritin-labeled cells in a modified ferrograph

Pan T, helper, and cytotoxic lymphocytes were isolated from the human peripheral blood mononuclear cell fraction by antibody staining, ferritin labeling, and deposition on glass slides. Two distinct forms of ferritin were used: one was native horse spleen ferritin, and the other was magnetoferritin. Magnetoferritin was obtained by reconstituting the horse spleen ferritin iron core with superparamagnetic magnetite instead of the usual paramagnetic ferrihydrite crystal. The cell deposition on microscopic glass slides in the magnetic field was obtained by an instrument that was adapted from an industrial magnetic deposition analyzer, the ferrograph. The identity of cells in the magnetic deposits was confirmed by comparing the cell fractions in the feed and in the eluate with the use of flow cytometry. The immunostaining protocol amplified the number of ferritin molecules per cell surface antigen 20-70 times. Magnetoferritin, but not native ferritin, imparted a sufficient magnetic moment to cells to deplete the labeled cell population between 67 and 88% of its initial concentration in a magnetic field of 1.67 Tesla (T), a field gradient of 2.57 T/mm, and a flow rate of 0.01 ml/min. This study showed that the magnetic moment of magnetoferritin was sufficient for immunomagnetic isolation of lymphocytes from mononuclear cell preparations in the modified ferrograph.

Analytical magnetapheresis of ferritin-labeled lymphocytes

Analytical magnetapheresis is a technique for analyzing magnetic particles in suspension. The magnetically susceptible particles form a deposition pattern from the suspending medium under carefully controlled flow and magnetic field conditions. This technique was used to determine the effective magnetic volumetric susceptibility, delta chi, of human lymphocytes labeled with an iron-rich protein, ferritin. Dynabeads M450, monodisperse polymeric beads doped with magnetite, of a diameter 4.5 microns, close to that of human lymphocytes, were used as a reference. The experiment showed an almost complete deposition of ferritin-labeled lymphocytes at an average flow velocity of 0.28 mm/s, a representative magnetic field of 1.67 T, and a magnetic field gradient of 2.57 T/mm. The calculated delta chi was (2.92 +/- 0.24) x 10(-6)[SI] (ferritin-labeled lymphocytes), and the corresponding number of ferritin molecules per lymphocyte was (1.75 +/- 0.44) x 10(7). In comparison, an almost complete deposition of the Dynabeads was observed at a much higher average flow velocity, 15 mm/s, a much lower field, 0.164 T, and a much lower field gradient, 0.025 T/mm. These results corresponded to a much higher delta chi = 0.245[SI] (Dynabeads M450). These results offer important guidelines in evaluating the use of ferritin as a soluble magnetic cell label.

Isolation of human blood cells, platelets, and plasma proteins by centrifugal SPLITT fractionation

Centrifugal SPLITT fractionation, a technique designed for the continuous high-resolution separation of colloids and low-density particles, is applied here to fresh human blood, producing six purified fractions consisting of proteins and lipoproteins, platelets, red blood cells, lymphocytes, monocytes, and neutrophils. Production of the six fractions requires five steps, each yielding two fractions. These five steps are carried out in sequence using a single apparatus, with conditions varying from step to step in accordance with theoretical guidelines in order to achieve the desired cut points. In the first step, a stream of diluted blood is separated into one fraction consisting of platelets and plasma and another containing blood cells. The throughput of diluted blood is 162 mL/h and that of whole blood is about 2 mL/h or approximately 10(10) cells/h; guidelines are given for significantly increasing throughput. The purity of the blood cell fractions ranged from 92 to 98%, and the viability fell in the range 97-99%.

Rapid diffusion coefficient measurements using analytical SPLITT fractionation: application to proteins

This work reports a new technique for the rapid measurement of diffusion coefficients using a special flow cell called a SPLITT cell. Such SPLITT cells, designed for continuous SPLITT fractionation, utilize differential transport across a thin (approximately 100 microns) ribbonlike lamina flowing through the cell. The liquid stream in the cell is split into two substreams at the outlet. The relative concentration in the two outlet substreams of a dilute component introduced into one of two inlet substreams is mathematically related to the appropriate transport coefficient, in this case the diffusion coefficient D. Thus D can be calculated from measured values of relative outlet concentrations. This approach has been tested using a number of dilute protein solutions. The results at different stream-splitting ratios are reasonably self-consistent and agree with most literature values for D within 5%. This approach provides a simple, rapid, and predictable means for determining the diffusion coefficients of proteins and other substances.