A Sandwich-Type Electrochemical Immunosensor Using Antibody-Conjugated Pt-Doped CdTe QDs as Enzyme-Free Labels for Sensitive HER2 Detection Based on a Magnetic Framework.

Tumor markers are highly sensitive and play an important role in the early diagnosis of cancer. We developed an electrochemical sandwich-type immunosensor that detects human epidermal growth factor receptor 2 (HER2). Magnetic framework (Fe3O4@ TMU-24) and AuNPs (Fe3O4@ TMU-24 -AuNPs) are utilized in this sensing platform. In addition to their high specific surface area and excellent biocompatibility, Fe3O4@ TMU-24-AuNPs nanocomposites exhibited excellent electrocatalytic properties. The primary antibody of HER2 (Ab1) was immobilized on the surface of the Fe3O4@ TMU-24-AuNPs. In this sensing method, palatine doped to CdTe QDs (Pt: CdTe QDs) is utilized as a novel labeling signal biomolecule (secondary antibodies). Pt: CdTe QDs own good biocompatibility and excellent catalytic performance. The amperometric technique was used to achieve the quantitative determination of HER2 by using a sandwich-type electrochemical immunosensor. Under the optimum conditions, the dependency of the current signal and HER2 concentration showed a linear region from 1 pg ml-1-100 ng ml-1 with 0.175 pg ml-1 as the limit of detection. This biosensing device also showed long stability and good reproducibility, which can be used for the quantitative assay of HER2.

Signal amplification of novel sandwich-type genosensor via catalytic redox-recycling on platform MWCNTs/Fe3O4@TMU-21 for BRCA1 gene detection.

The MWCNTs/Fe3O4@TMU-21 as a novel electrochemical sandwich-type genosensor was fabricated to detect the BRCA1 gene using the redox-cycling ferrocene functionalized reporter label probe (r-Fc-DNA). In the designed genosensor, the capture probe (cDNA) and r-Fc-DNA were used to detect the BRCA1 gene in sandwich-type genosensor, in which DNA sequences are well -hybridized with the BRCA1 gene (t-DNA). The cDNA was immobilized on the multiwall carbon nanotube and metal-organic framework with Fe3O4 nanoparticle core, which is the sensor platform. Target DNA was assayed by redox-recycling reporter probe (r-Fc-DNA) using the electro-catalytic activity of ferri/ferrocyanide, which results in significantly enhanced the oxidation peak current of r-Fc-DNA. The electrochemical redox cycling led to a high signal-to-noise ratio for gene assay. MWCNTs and Fe3O4@TMU-21 were applied to increase the platform conductivity and suitable binding of the recognition elements. This constructed genosensor plays an influential role in increasing the sensitivity of BRCA1 gene sequence recognition. So that under optimal conditions, this genosensor illustrated a wide linear range from 1.0×10-15 to 1.0×10-10 M with a detection limit of 0.57 × 10-15 M. Moreover, the genosensor exhibited high selectivity, stability, and reproducibility. The obtained recoveries (between 91 and 105%) of the BRCA1 gene assay in human blood samples satisfactory, which can be used for BRCA1 gene measurement in the laboratory.

Application of magnetic nanomaterials in magnetic in-tube solid-phase microextraction.

Development of magnetic nanomaterials has greatly promoted the innovation of in-tube solid-phase microextraction. This review article gives an insight into recent advances in the modifications and applications of magnetic nanomaterials for in-tube solid-phase microextraction. Also, different magnetic nanomaterials which have recently been utilized as in-tube solid-phase microextraction sorbents are classified. This study shows that magnetic nanomaterials have gained significant attention owing to large specific surface area, selective absorption, and surface modification. Magnetic in-tube solid-phase microextraction has been applied for the analysis of food samples, biological, and environmental. However, for full development of magnetic in-tube SPME, effort is still needed to overcome limitations, such as mechanical stability, selectivity and low extraction efficiency. To achieve these objectives, research on magnetic in-tube SPME is mainly focused in the preparation of new extractive phases.

Facile magnetization of metal-organic framework TMU-6 for magnetic solid-phase extraction of organophosphorus pesticides in water and rice samples.

In the present work, a magnetic metal-organic framework composite (Fe3O4@TGA@TMU-6) was synthesized and used as an adsorbent for magnetic solid-phase extraction (MSPE) of some organophosphorus pesticides (phosalone, chlorpyrifos and, profenofos) in rice and environmental water samples. Extraction, separation and determination of the analytes were performed by MSPE-HPLC-UV. Due to the large surface area and unique porous structure of the metal-organic frameworks (MOFs) as well as π-π and hydrophobic interactions between the analytes and the MOF ligands, the prepared sorbents showed a high affinity towards the target analytes. The affecting parameters on the extraction efficiency, including type and volume of eluent, pH, amount of MFC, extraction time, salt effect and desorption time were investigated and optimized. Under optimum conditions, calibration curves were found to be linear in the range of 7.5-75 µg L-1, 10-100 µg L-1, and 10-150 µg L-1 for phosalone, chlorpyrifos, and profenofos in water samples, respectively. The LODs (based on S/N = 3) were 0.5, 1 and 0.5 µg L-1 for phosalone, chlorpyrifos, and profenofos in water samples, respectively.

Enzyme-free sandwich-type electrochemical immunosensor for highly sensitive prostate specific antigen based on conjugation of quantum dots and antibody on surface of modified glassy carbon electrode with core-shell magnetic metal-organic frameworks.

The early diagnosis of cancer increases the chance of its treatment. In this study, an enzyme-free sandwich type of immunosensors is presented for prostate specific antigen (PSA), as prostate cancer biomarker. In this regard, the quantum dots (QDs) and magnetic metal-organic frameworks (MOFs) were used for labeling the secondary anybody and modifying the electrode surface, respectively. Herein, a bare glassy carbon electrodes is modified with iron magnetic nanoparticles with a core shell MOFs (magnetic framework Fe3O4@ TMU-10) and the primary antibodies (Ab1) are immobilized on the modified electrode. Moreover, the second antibody is successfully conjugated to a nickel-cadmium quantum dots as an electroactive non-enzymatic probe. The prepared immunosensor shows a linear range between 1 pg mL-1- 100 ng mL-1 and the detection limit of 0.45 pg mL-1 with acceptable selectivity, reproducibility and stability. The proposed sensor is also applied for determination of PSA in human serum samples and the results is confirmed by a reference method, which indicates its ability for clinical monitoring of the tumor marker.

Magnetic framework composite as sorbent for magnetic solid phase extraction coupled with high performance liquid chromatography for simultaneous extraction and determination of tricyclic antidepressants.

In this study, magnetic framework composites (MFCs) (Fe3O4@TMU-10) microspheres were successfully fabricated and applied as an effective sorbent for preconcentration of the two model tricyclic antidepressants (TCAs) amitriptyline and imipramine from biological samples. MFCs were fabricated by a step-by-step assembly, novel, simple and efficient strategy. The shell thickness of the Metal-organic frameworks (MOFs) could also be easily controlled by tuning the number of assembly cycles. By coupling magnetic solid-phase extraction (MSPE) with high-performance liquid chromatography with UV detector (HPLC-UV), a simple, reliable, fast, sensitive and cost-effective method for simultaneous determination of TCAs was developed. Under optimal conditions, the preconcentration factors and relative recoveries of the studied compounds were obtained in the range of 43-50 and 90.5-99.0% respectively. The calibration curves were obtained in the range of 5-800 µg L-1 with reasonable linearity (R2 > 0.9904) and the limits of detection (LODs) ranged between 2 and 4 µg L-1 (based on S/N = 3). The relative standard deviations of intra- and inter-day tests ranged from 3.1 to 4.6% and from 4.3 to 5.2%, respectively. The results demonstrate that Fe3O4@TMU-10 core-shell magnetic microspheres combine advantages of MOFs and magnetic nanoparticles, and are the promising sorbents for rapid and efficient extraction of target analytes from urine and plasma complex biological samples.

Magnetic frame work composite as an efficient sorbent for magnetic solid-phase extraction of plasticizer compounds.

Two metal-organic frameworks (MOFs) TMU-23 and TMU-24, containing amide-functionalized pores, have been fabricated. Their applications were evaluated for the magnetic solid phase extraction of plasticizer compounds benzylbutylphthalate (BBP), di-2-(ethylhexyl) phthalate (DEHP) and di-n-butyl phthalate (DBP) prior to analysis by gas chromatography with flame ionization detector (GC-FID). Due to the large surface area and unique porous structure of the MOFs as well as hydrogen bonding formation, π-π and hydrophobic interactions between the analytes and the MOF ligands, the prepared sorbents showed a high affinity towards the target analytes. The studies reveal that TMU-24 has a better adsorption capability than TMU-23. A magnetic TMU-24 was then fabricated by in-situ synthesis of a magnetic core-shell nanocomposite. The material was chosen as an efficient sorbent for the extraction of the target analytes, followed by their determination by GC-FID. Under optimal conditions, preconcentration factors and relative recoveries of the studied compounds were obtained in the range of 189-278 and 92.0-102.0% respectively. The calibration curves were obtained in the range of 0.5-250 µg L-1 with reasonable linearity (R2 >0.99) and the limits of detection (LODs) ranged between 0.2 and 0.4 µg L-1 (based on S/N = 3). The precision of the method, expressed as relative standard deviation for extraction and determination of the 100 µg L-1 analytes in the samples solution was in the range of 3.9-5.9%.

Simultaneous determination of steroid drugs in the ointment via magnetic solid phase extraction followed by HPLC-UV.

The copper-coated iron oxide nanoparticles with core-shell were produced by deposition of a Cu shell on Fe3O4 NPs through reduction of Cu2+ ions in solution using NaBH4. Subsequently, the organosulfur compound, bis-(2,4,4-trimethylpentyl)-dithiophosphinic acid (b-TMP-DTPA), was used to form self-assembled monolayer in order to modify sorbent's surface via covalent bonding between Cu and thiol (-SH) terminal groups. The prepared magnetic nanoparticles were characterized by using Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscope (TEM), vibrating sample magnetometer (VSM) and thermo gravimetric analysis (TGA). Then, the application of this new sorbent was investigated to extract the steroid drugs in ointment samples with the aid of ultrasound. An external magnetic field was applied to collect the magnetic nanoparticles (MNPs). The extracted analytes were desorbed using acetonitrile. The obtained extraction solution was analyzed by HPLC-UV. The main affecting factors on the extraction efficiency including pH, sonication time, amount of sorbent, salt concentration, and desorption conditions were optimized in detail. Under the optimum conditions, good linearity was obtained in the range of 2.5-250.0 µg/ L with reasonable linearity (R2 > 0.99) and the limits of detection (LODs) ranged between 0.5 and 1.0 µg/L (based on S/N = 3). Repeatability (intra-day precision) based on five replicates and preconcentration factors were calculated to be 3.6%-4.7% and 87-116, respectively. Relative recoveries in ointment samples at two spiked levels of the target analytes were obtained in the range of 90.0%-103.2%. The results illustrated that the Fe3O4@Cu@ b-TMP-DTPA NPs have the capability of extraction of steroid drugs from ointment samples.

On-line packed magnetic in-tube solid phase microextraction of acidic drugs such as naproxen and indomethacin by using Fe3O4@SiO2@layered double hydroxide nanoparticles with high anion exchange capacity.

The authors describe a 3-component nanoparticle system composed of a silica-coated magnetite (Fe3O4) core and a layered double (Cu-Cr) hydroxide nanoplatelet shell. The sorbent has a high anion exchange capacity for extraction anionic species. A simple online system, referred to as "on-line packed magnetic-in-tube solid phase microextraction" was designed. The nanoparticles were placed in a stainless steel cartridge via dry packing. The cartridge was then applied to the preconcentration acidic drugs including naproxen and indomethacin from urine and plasma. Extraction and desorption times, pH values of the sample solution and flow rates of sample solution and eluent were optimized. Analytes were then quantified by HPLC with UV detection. Under optimal conditions, the limits of detection range from 70 to 800 ng L-1, with linear responses from 0.1-500 µg L-1 (water samples), 0.6-500 µg L-1 (spiked urine), and 0.9-500 µg L-1 (spiked plasma). The inter- and intra-assay precisions (RSDs, for n = 5) are in the range of 2.2-5.4%, 2.8-4.9%, and 2.0-5.2% at concentration levels of 5, 25 and 50 µg L-1, respectively. The method was applied to the analysis of the drugs in spiked human urine and plasma, and good results were achieved. Graphical abstract Fe3O4@SiO2@CuCr-LDH magnetic nanoparticles were synthesized and packed in to a stainless steel column. The column was applied to solid phase microextraction of acidic drugs from biological samples.

Simultaneous determination of steroid drugs in the ointment via magnetic solid phase extraction followed by HPLC-UV / 药物分析学报

The copper-coated iron oxide nanoparticles with core-shell were produced by deposition of a Cu shell on Fe3O4 NPs through reduction of Cu2+ ions in solution using NaBH4. Subsequently, the organosulfur compound, bis-(2,4,4-trimethylpentyl)-dithiophosphinic acid (b-TMP-DTPA), was used to form self-assembled monolayer in order to modify sorbent's surface via covalent bonding between Cu and thiol (-SH) terminal groups. The prepared magnetic nanoparticles were characterized by using Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscope (TEM), vibrating sample magnetometer (VSM) and thermo gravimetric analysis (TGA). Then, the application of this new sorbent was investigated to extract the steroid drugs in ointment samples with the aid of ultrasound.An external magnetic field was applied to collect the magnetic nanoparticles (MNPs). The extracted analytes were desorbed using acetonitrile. The obtained extraction solution was analyzed by HPLC-UV. The main affecting factors on the extraction efficiency including pH, sonication time, amount of sorbent, salt concentration, and desorption conditions were optimized in detail. Under the optimum conditions, good linearity was obtained in the range of 2.5-250.0 μg/ L with reasonable linearity (R2 > 0.99) and the limits of detection (LODs) ranged between 0.5 and 1.0 μg/L (based on S/N = 3). Repeatability (intra-day precision) based on five replicates and preconcentration factors were calculated to be 3.6％-4.7％ and 87116,respectively.Relative recoveries in ointment samples at two spiked levels of the target analytes were obtained in the range of 90.0％-103.2％. The results illustrated that the Fe3O4@Cu@ b-TMP-DTPA NPs have the capability of extraction of steroid drugs from ointment samples.

On-line electrochemically controlled in-tube solid phase microextraction of inorganic selenium followed by hydride generation atomic absorption spectrometry.

In this work, for the first time, a rapid, simple and sensitive microextraction procedure is demonstrated for the matrix separation, preconcentration and determination of inorganic selenium species in water samples using an electrochemically controlled in-tube solid phase microextraction (EC-in-tube SPME) followed by hydride generation atomic absorption spectrometry (HG-AAS). In this approach, in which EC-in-tube SPME and HG-AAS system were combined, the total analysis time, was decreased and the accuracy, repeatability and sensitivity were increased. In addition, to increases extraction efficiency, a novel nanostructured composite coating consisting of polypyrrole (PPy) doped with ethyleneglycol dimethacrylate (EGDMA) was prepared on the inner surface of a stainless-steel tube by a facile electrodeposition method. To evaluate the offered setup and the new PPy-EGDMA coating, it was used to extract inorganic selenium species in water samples. Extraction of inorganic selenium species was carried out by applying a positive potential through the inner surface of coated in-tube under flow conditions. Under the optimized conditions, selenium was detected in amounts as small as 4.0 parts per trillion. The method showed good linearity in the range of 0.012-200 ng mL(-1), with coefficients of determination better than 0.9996. The intra- and inter-assay precisions (RSD%, n = 5) were in the range of 2.0-2.5% and 2.7-3.2%, respectively. The validated method was successfully applied for the analysis of inorganic selenium species in some water samples and satisfactory results were obtained.

Extraction and preconcentration of formaldehyde in water by polypyrrole-coated magnetic nanoparticles and determination by high-performance liquid chromatography.

In this study, a simple and rapid extraction method based on the application of polypyrrole-coated Fe3 O4 nanoparticles as a magnetic solid-phase extraction sorbent was successfully developed for the extraction and preconcentration of trace amounts of formaldehyde after derivatization with 2,4-dinitrophenylhydrazine. The analyses were performed by high-performance liquid chromatography followed by UV detection. Several variables affecting the extraction efficiency of the formaldehyde, i.e., sample pH, amount of sorbent, salt concentration, extraction time and desorption conditions were investigated and optimized. The best working conditions were as follows: sample pH, 5; amount of sorbent, 40 mg; NaCl concentration, 20% w/v; sample volume, 20 mL; extraction time, 12 min; and 100 µL of methanol for desorption of the formaldehyde within 3 min. Under the optimal conditions, the performance of the proposed method was studied in terms of linear dynamic range (10-500 µg/L), correlation coefficient (R(2) ≥ 0.998), precision (RSD% ≤ 5.5) and limit of detection (4 µg/L). Finally, the developed method was successfully applied for extraction and determination of formaldehyde in tap, rain and tomato water samples, and satisfactory results were obtained.

Speciation of chromium in environmental samples by dual electromembrane extraction system followed by high performance liquid chromatography.

This study proposes the dual electromembrane extraction followed by high performance liquid chromatography for selective separation-preconcentration of Cr(VI) and Cr(III) in different environmental samples. The method was based on the electrokinetic migration of chromium species toward the electrodes with opposite charge into the two different hollow fibers. The extractant was then complexed with ammonium pyrrolidinedithiocarbamate for HPLC analysis. The effects of analytical parameters including pH, type of organic solvent, sample volume, stirring rate, time of extraction and applied voltage were investigated. The results showed that Cr(III) and Cr(VI) could be simultaneously extracted into the two different hollow fibers. Under optimized conditions, the analytes were quantified by HPLC instrument, with acceptable linearity ranging from 20 to 500 µg L(-1) (R(2) values≥0.9979), and repeatability (RSD) ranging between 9.8% and 13.7% (n=5). Also, preconcentration factors of 21.8-33 that corresponded to recoveries ranging from 31.1% to 47.2% were achieved for Cr(III) and Cr(VI), respectively. The estimated detection limits (S/N ratio of 3:1) were less than 5.4 µg L(-1). Finally, the proposed method was successfully applied to determine Cr(III) and Cr(VI) species in some real water samples.