Poly(dopamine) coated gold nanocluster functionalized electrochemical immunosensor for brominated flame retardants using multienzyme-labeling carbon hollow nanochains as signal amplifiers

Simple and Effective Approach to Prepare an Epoxy-Functionalized Polymer and Its Application for an Electrochemical Immunosensor

An epoxy-functionalized polymer based on a new skeleton has been prepared via an efficient method and it combined with aminated carbon nanotubes to form a new composite material. This new composite material was applied for the fabrication of an electrochemical immunosensor with good performance. The inexpensive and easily available IgG was used to test the performance of the prepared composite material. The levels of IgG were quantitatively analyzed using a differential pulse voltammetry detection system and the lowest detection limit was calculated to be 0.05 ng/mL. The detection system can also respond to IgG in the concentration range from 0.1 to 25 ng/mL.

Impedimetric monitoring of apoptosis using cytochrome-aptamer bioconjugated silver nanocluster

It is well known that cytochrome c (Cyt c) is a crucial death regulator that triggers programmed cell death, apoptosis. Here, we report on the successful application of an aptamer bioconjugated nanoclusters for the detection of apoptosis based on release of cytochrome c from mitochondria in lysates human embryonic kidney cells HEK293T. The aptamer-conjugated silver nanoclusters (Apt@AgNCs) were synthesized and immobilized on gold electrode for impedimetric detection of Cyt c over the range of 0.15-375nM. It was found that the presence of Ag(I) ions shell at the surface of prepared NCs could increase their affinity to the donor groups (COO^- and some amine groups in its deprotonated form, NH₂) of cysteine attached on the gold electrode surface. The use of NCs, which play the role of conductive holders, established a simple immobilization procedure based on a low cost non-functionalized DNA sequence. To diminish the probable nonspecific impedance changes and decrease time of measurement, a rapid single frequency measurements (SFM) was assessed based on recording total impedance |Z| in different individual frequencies.

Low molecular weight chitosan-coated polymeric nanoparticles for sustained and pH-sensitive delivery of paclitaxel

Low molecular weight chitosan (LMWC) is a promising polymer for surface modification of nanoparticles (NPs), which can impart both stealth effect and electrostatic interaction with cells at mildly acidic pH of tumors. We previously produced LMWC-coated NPs via covalent conjugation to poly(lactic-co-glycolic) acid (PLGA-LMWC NPs). However, this method had several weaknesses including inefficiency and complexity of the production as well as increased hydrophilicity of the polymer matrix, which led to poor drug release control. Here, we used the dopamine polymerization method to produce LMWC-coated NPs (PLGA-pD-LMWC NPs), where the core NPs were prepared with PLGA that served best to load and retain drugs and then functionalized with LMWC via polydopamine layer. The PLGA-pD-LMWC NPs overcame the limitations of PLGA-LMWC NPs while maintaining their advantages. First of all, PLGA-pD-LMWC NPs attenuated the release of paclitaxel to a greater extent than PLGA-LMWC NPs. Moreover, PLGA-pD-LMWC NPs had a pH-dependent surface charge profile and cellular interactions similar to PLGA-LMWC NPs, enabling acid-specific NP-cell interaction and enhanced drug delivery to cells in weakly acidic environment. Although the LMWC layer did not completely prevent protein binding in serum solution, PLGA-pD-LMWC NPs showed less phagocytic uptake than bare PLGA NPs.

Construction of portable electrochemical immunosensors based on graphene hydrogel@polydopamine for microcystin-LR detection using multi-mesoporous carbon sphere-enzyme labels

A portable electrochemical immunosensor was fabricated for the detection of microcystin-LR by using graphene hydrogel@polydopamine as the substrate material and multi-HRP-(MCSs/Thi@AuNPs)-Ab₂ as the signal label.

Rapid Legionella pneumophila determination based on a disposable core-shell Fe₃O₄@poly(dopamine) magnetic nanoparticles immunoplatform

A novel amperometric magnetoimmunoassay, based on the use of core-shell magnetic nanoparticles and screen-printed carbon electrodes, was developed for the selective determination of Legionella pneumophila SG1. A specific capture antibody (Ab) was linked to the poly(dopamine)-modified magnetic nanoparticles (MNPs@pDA-Ab) and incubated with bacteria. The captured bacteria were sandwiched using the antibody labeled with horseradish peroxidase (Ab-HRP), and the resulting MNPs@pDA-Ab-Legionella neumophila-Ab-HRP were captured by a magnetic field on the electrode surface. The amperometric response measured at -0.15 V vs. Ag pseudo-reference electrode of the SPCE after the addition of H2O2 in the presence of hydroquinone (HQ) was used as transduction signal. The achieved limit of detection, without pre-concentration or pre-enrichment steps, was 10(4) Colony Forming Units (CFUs) mL(-1). The method showed a good selectivity and the MNPs@pDA-Ab exhibited a good stability during 30 days. The possibility of detecting L. pneumophila at 10 CFU mL(-1) level in less than 3 h, after performing a membrane-based preconcentration step, was also demonstrated.

Electrochemical immunosensor based on hydrophilic polydopamine-coated prussian blue-mesoporous carbon for the rapid screening of 3-bromobiphenyl

A sensitive electrochemical immunosensor for 3-bromobiphenyl (3-BBP) detection was constructed by employing a new polydopamine coated prussian blue-mesoporous carbon (PDOP/PB/CMK-3) nanocomposite as the substrate platform and multi-horseradish peroxidase-double helix carbon nanotubes-secondary antibody (multi-HRP-DHCNTs-Ab2) as the signal label. PB/CMK-3 was firstly successfully in-situ synthesized with the aid of the CMK-3 reduction, which was characterized by transmission electron microscope (TEM), infrared spectroscopy (IR), X-ray diffraction (XRD) and N2 adsorption-desorption analysis. By using PDOP/PB/CMK-3 as the substrate, it can effectively enhance the specific surface for antigen loading due to the three-dimensional structure of the nanocomposites, while large amount of PB that fixed inside or outside the pore of CMK-3 successfully improved the electrochemical response and the PDOP film can provide a biocompatible environment to maintain the activity of antigen availability. Under the optimized conditions, the proposed immunosensor shows a good current response to 3-BBP in a linear range from 5 pM to 2 nM with a detection limit of 2.25 pM. In addition, the specificity, reproducibility and stability of the immunosensor were also proved to be acceptable, indicating its potential application in environmental monitoring.