Submicron magnetic core conducting polypyrrole polymer shell: Preparation and characterization

Optimized synthesis of polyacrylic acid-coated magnetic nanoparticles for high-efficiency DNA isolation and size selection

Solid-phase reversible immobilization (SPRI) bead technology is widely used in molecular biology for convenient DNA manipulation. However, commercial SPRI bead kits lack cost advantages and flexibility. It is, therefore, necessary to develop new and alternative cost-effective methods of on-par or better quality. Herein, an easy and cost-effective method is proposed for synthesizing polyacrylic acid-coated iron oxide nanoparticles (PAA-IONPs) through in situ polymerization at lab scale for high-efficiency nucleic acid extraction and size selection. A design of experiment (DoE) approach was used to investigate the influence of iron oxide nanoparticles (IONPs), acrylic acid (AA) monomer, and sodium dodecyl sulfate (SDS) surfactant amounts on the sizes and carboxyl group densities of PAA-IONPs. Thorough characterization by thermogravimetric analysis (TGA), attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) and vibrating sample magnetometry (VSM) highlights the importance of a low starting pH achieved by a high ratio of AA/IONPs, to yield the largest sizes (554 nm) and highest carboxyl group densities (2.13 mmol g-1) obtained in this study. An efficient DNA purification strategy is then presented using homemade beads-suspension buffer and optimized bead concentrations (17% PEG 8000, 2.5 M NaCl, and 3 mg mL-1 PAA-IONPs). This method shows comparable performance to the control (AMPure XP beads) for DNA recovery. An adjustable PAA-IONPs DNA purification system was also developed to be used for DNA-size selection at low DNA amounts (50-100 ng) with a high degree of resolution and recovery. In conclusion, this work offers an optimized PAA-IONPs synthesis protocol and a flexible DNA purification approach that will enable researchers to manipulate DNA under various conditions, holding the significant potential to benefit future molecular biology research and diagnostics.

Core-shell nanostructures: a simplest two-component system with enhanced properties and multiple applications

With the pace of time, synthesis of nanomaterials has paved paths to blend two or more materials having different properties into hybrid nanoparticles. Therefore, it has become possible to combine two different functionalities in a single nanoparticle and their properties can be enhanced or modified by coupling of two different components. Core-shell technology has now represented a new trend in analytical sciences. Core-shell nanostructures are in demand due to their specific design and geometry. They have internal core of one component (metal or biomolecules) surrounded by a shell of another component. Core-shell nanoparticles have great importance due to their high thermal stability, high solubility and lower toxicity. In this review, recent progress in development of new and sophisticated core-shell nanostructures has been explored. The first section covers introduction throwing light on basics of core-shell nanoparticles. Following section classifies core-shell nanostructures into single core/shell, multicore/single shell, single core/multishell and multicore/multishell nanostructures. Next main section gives a brief description on types of core-shell nanomaterials followed by processes for the synthesis of core-shell nanostructures. Ultimately, the final section focuses on the application areas such as drug delivery, bioimaging, solar cell applications etc.

A screen printed electrode modified with Fe3O4@polypyrrole-Pt core-shell nanoparticles for electrochemical detection of 6-mercaptopurine and 6-thioguanine

In this paper, Fe₃O₄@ppy-Pt core-shell nanoparticles (NPs) could be produced and utilized for the development of a novel electrochemical sensor to detect 6-mercaptopurine (6-MP). 6-MP determination was examined by cyclic voltammetry (CV), chronoamperometry (CHA), linear sweep voltammetry (LSV), and differential pulse voltammetry (DPV) at Fe₃O₄@ppy-Pt core-shell NPs modified screen printed electrode (Fe₃O₄@ppy-Pt/SPE) in phosphate buffered solution (PBS). The outcomes obtained from DPV demonstrated that the Fe₃O₄@ppy-Pt/SPE proved a linear concentration range among 0.04 and 330.0 μM having a detection limit of 10.0 nM for 6-MP. Also, modified electrode was satisfactorily utilized to detect 6-MP in the presence of 6-thioguanine (6-TG). This sensor showed two separate oxidative peaks at 530 mV for 6-MP and at 730 mV for 6-TG with a peak potential separation of 200 mV which was large enough for simultaneous detection of the two anticancer drugs. In addition, the proposed sensor presented long-term stability, good repeatability, and excellent reproducibility. Finally, the modified electrode demonstrated satisfactory outcomes while used in real samples, proposing the appropriate potential of Fe₃O₄@ppy-Pt/SPE in the case of clinical diagnosis, biological samples and pharmaceutical compounds analysis.

Multifunctional Magnetic Oxide Nanoparticle (MNP) Core-Shell: Review of Synthesis, Structural Studies and Application for Wastewater Treatment

The demand for water is predicted to increase significantly over the coming decades; thus, there is a need to develop an inclusive wastewater decontaminator for the effective management and conservation of water. Magnetic oxide nanocomposites have great potentials as global and novel remediators for wastewater treatment, with robust environmental and economic gains. Environment-responsive nanocomposites would offer wide flexibility to harvest and utilize massive untapped natural energy sources to drive a green economy in tandem with the United Nations Sustainable Development Goals. Recent attempts to engineer smart magnetic oxide nanocomposites for wastewater treatment has been reported by several researchers. However, the magnetic properties of superparamagnetic nanocomposite materials and their adsorption properties nexus as fundamental to the design of recyclable nanomaterials are desirable for industrial application. The potentials of facile magnetic recovery, ease of functionalization, reusability, solar responsiveness, biocompatibility and ergonomic design promote the application of magnetic oxide nanocomposites in wastewater treatment. The review makes a holistic attempt to explore magnetic oxide nanocomposites for wastewater treatment; futuristic smart magnetic oxides as an elixir to global water scarcity is expounded. Desirable adsorption parameters and properties of magnetic oxides nanocomposites are explored while considering their fate in biological and environmental media.

Development of Novel Magneto-Biosensor for Sulfapyridine Detection

In this work, we report the development of a highly sensitive biosensor for sulfapyridine detection based on an integrated bio micro-electromechanical system (Bio-MEMS) containing four gold working electrodes (WEs), a platinum counter electrode (CE), and a reference electrode (RE). Firstly, the cleaned WEs were modified with 4-aminophenylacetic acid (CMA). Then, (5-[4-(amino)phenylsulfonamide]-5-oxopentanoic acid (SA2BSA) was immobilized onto the transducers surface by carbodiimide chemistry. The analyte was quantified by competitive detection with SA2BSA immobilized on the WE toward a mixture of Ab155 antibody (with fixed concentration) and sulfapyridine. In order to obtain a highly sensitive biosensor, Ab155 was immobilized onto magnetic latex nanoparticles surface to create a 3D architecture (Ab-MLNp). Using electrochemical impedance spectroscopy (EIS), we investigated the influence of the Ab-MLNp on the sensitivity of our approach. The optimized system was analyzed, as competitive assay, with different concentrations of sulfapyridine (40 µM, 4 µM, and 2 nM) and with phosphate buffer solution. From data fitting calculations and graphs, it was observed that the EIS showed more linearity when Ab-MLNp was used. This result indicates that the magnetic latex nanoparticles increased the sensitivity of the biosensor.

Multifunctional Polypyrrole-Coated Mesoporous TiO2 Nanocomposites for Photothermal, Sonodynamic, and Chemotherapeutic Treatments and Dual-Modal Ultrasound/Photoacoustic Imaging of Tumors

TiO₂ nanoparticles have emerged as satisfactory sonosensitizers in sonodynamic therapy over the years, but shortcomings such as poor drug loading capability and inadequate techniques to construct suitable TiO₂ nanoparticles, limit their broader applications. Hence, in this paper, versatile nanocomposites that combine mesoporous TiO₂ nanoparticles (mTiO₂ s) with the promising photothermal material, polypyrrole (PPY) to exert synergistic therapeutic effects on tumors are fabricated. The PPY-coated mesoporous TiO₂ nanocomposites (mTiO₂ @PPYs) act as drug delivery vehicles and ultrasonically activated sonosensitizers as well as photothermal agents. Besides, mTiO₂ @PPY may have potential as an ultrasound/photoacoustic (US/PA) imaging contrast agent. The mTiO₂ @PPY shows a favorable drug loading and good photothermal conversion ability. Moreover, intracellular reactive oxygen species generation is verified. The in vitro cell experiments on HepG2 and 4T1 cells demonstrate that honokiol (HNK)-loaded mTiO₂ @PPY has satisfactory cytotoxicity under laser and US irradiation, and the results are further validated by animal experiments. The ability of mTiO₂ @PPY as a contrast agent for US and PA imaging is investigated both in vitro and in vivo. The results indicate that mTiO₂ @PPY-HNK has multitherapeutic effects and bimodal imaging property, which shows great prospect as a novel nanosystem in antitumor applications.

Ultrasensitive Immunosensor Array for TNF-α Detection in Artificial Saliva using Polymer-Coated Magnetic Microparticles onto Screen-Printed Gold Electrode

Tumor necrosis factor-α (TNF-α) is a biomarker of inflammation that occurs in patients suffering from heart failure (HF). Saliva can be sampled in a non-invasive way, and it is currently gaining importance as matrix alternative to blood in diagnostic and therapy monitoring. This work presents the development of an immunosensor array based on eight screen-printed gold electrodes to detect TNF-α in saliva samples. Two different functionalization strategies of electrodes were compared. In the first, anti-TNF-α antibodies were chemically bonded onto the electrode by functionalization with 4-carboxymethylaniline. The other functionalization procedure involved the binding of antibodies onto polymer-coated magnetic microparticles, which were then deposited onto the electrode by pulsed chronoamperometry. Finally, the chronoamperometry technique was applied to characterize the modified SPEAu. The use of a secondary antibody anti-TNF-α (Ab-TNF-α-HRP) labelled with horseradish peroxidase (HRP, 2 µg·mL⁻¹) was investigated using tetramethylbenzidine (TMB, pH = 3.75) as electrochemical substrate containing 0.2 mM of H₂O₂. A sandwich-type detection strategy with a secondary antibody anti-TNF-α provided chronoamperometric analyses in 10 s for each sample. Linearity, precision, limit of detection, and selectivity of devices were investigated. Interferences were evaluated by analyzing solutions containing other cytokine produced during the acute stage of inflammation. The immunosensor showed good performance within the clinically relevant concentration range, with a precision of 8%, and a limit of detection of 0.3 pg/mL. Therefore, it may represent a promising tool for monitoring HF in a non-invasive way.

DNA-magnetic Particle Binding Analysis by Dynamic and Electrophoretic Light Scattering

Isolation of DNA using magnetic particles is a field of high importance in biotechnology and molecular biology research. This protocol describes the evaluation of DNA-magnetic particles binding via dynamic light scattering (DLS) and electrophoretic light scattering (ELS). Analysis by DLS provides valuable information on the physicochemical properties of particles including particle size, polydispersity, and zeta potential. The latter describes the surface charge of the particle which plays major role in electrostatic binding of materials such as DNA. Here, a comparative analysis exploits three chemical modifications of nanoparticles and microparticles and their effects on DNA binding and elution. Chemical modifications by branched polyethylenimine, tetraethyl orthosilicate and (3-aminopropyl)triethoxysilane are investigated. Since DNA exhibits a negative charge, it is expected that zeta potential of particle surface will decrease upon binding of DNA. Forming of clusters should also affect particle size. In order to investigate the efficiency of these particles in isolation and elution of DNA, the particles are mixed with DNA in low pH (~6), high ionic strength and dehydration environment. Particles are washed on magnet and then DNA is eluted by Tris-HCl buffer (pH = 8). DNA copy number is estimated using quantitative polymerase chain reaction (PCR). Zeta potential, particle size, polydispersity and quantitative PCR data are evaluated and compared. DLS is an insightful and supporting method of analysis that adds a new perspective to the process of screening of particles for DNA isolation.

Morphology-Controlled Coating of Colloidal Particles with Silica: Influence of Particle Surface Functionalization

We present a general, convenient, and efficient synthetic concept for the coating of colloidal particles with a silica (SiO₂) shell of well-defined and precisely controlled morphology and porosity. Monodisperse submicroscopic polystyrene (PS) particles were synthesized via two-stage emulsifier-free emulsion polymerization and subsequent swelling polymerization, enabling selective particle surface modification by the incorporation of ionic (methacrylic acid, MAA) or nonionic (hydroxyethyl methacrylate, HEMA or methacrylamide, MAAm) comonomers, which could be proven by zeta potential measurements as well as by determining the three-phase contact angle of the colloidal particles adsorbed at the air-water and n-decane-water interface. The functionalized particles could be directly coated with silica shells of variable thickness, porosity, and controlled surface roughness in a seeded sol-gel process from tetraethoxysilane (TEOS), leading to hybrid PS@silica particles with morphologies ranging from core-shell (CS) to raspberry-type architectures. The experimental results demonstrated that the silica coating could be precisely tailored by the type of surface functionalization, which strongly influences the surface properties of the colloidal particles and thus the morphology of the final silica shell. Furthermore, the PS cores could be easily removed by thermal treatment, yielding extremely uniform hollow silica particles, while maintaining their initial shell architecture. These particles are highly stable against irreversible aggregation and could be readily dried, purified, and redispersed in various solvents. Herein we show a first example of coating semiconducting CdSe/ZnS nanocrystals with smooth and spherical silica shells by applying the presented method that are expected to be suitable systems for applications as markers in biology and life science by using fluorescence microscopy methods, which are also briefly discussed.

Synthesis and drug release profile of a dual-responsive poly(ethylene glycol) hydrogel nanocomposite

This work describes the synthesis, characterization and application of a pH- and magnetic-responsive PEG hydrogel (HG) nanocomposite as a platform for drug delivery.