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Pharmacogenetic testing technology can effectively determine the individual differences among patients and scientifically assist doctors to select the most suitable drugs for each patient. In this study, an electrochemical biosensor based on magnetic α-Fe2O3/Fe3O4 heterogeneous nanosheets was constructed to detect Vitamin K epoxide reductase complex 1 type AA (VKORC1*2). Firstly, we fabricated magnetic α-Fe2O3/Fe3O4 heterogeneous nanosheets as the substrate material for electrochemical biosensors. Subsequently, the material surface was modified with Au nanoparticles to facilitate the connection of sensing probes and enhance current signal amplification. The electrochemical biosensor showed a negative linear relationship with the concentrations of target DNA (tDNA, VKORC1*2 gene) within 1 pM − 1 μM, a limit of detection was (LOD) = 0.36 pM, and a limit of quantification was (LOQ) = 1.19 pM. The biosensor demonstrated exceptional specificity, reproducibility, and stability. In real sample analysis, it exhibited a recovery range of 96.63 % − 110.57 % (RSD ≤ 3.07 %) for various tDNA concentrations, thereby indicating its promising potential in clinical diagnostics.

A "turn-on" aptasensor for label-free and cell-free EpCAM detection was constructed by employing magnetic α-Fe2O3/Fe3O4@Au nanocomposites as a matrix for signal amplification and double-stranded complex (SH-DNA/Apt probes) immobilization through Au-S binding. α-Fe2O3/Fe3O4@Au could be efficiently assembled into uniform and stable self-assembly films via magnetic-induced self-assembly technique on a magnetic glassy carbon electrode (MGCE). The effectiveness of the platform for EpCAM detection was confirmed through differential pulse voltammetry (DPV). Under optimized conditions, the platform exhibited excellent specificity for EpCAM, and a strong linear correlation was observed between the current and the logarithm of EpCAM protein concentration in the range 1 pg/mL–1000 pg/mL (R2 = 0.9964), with a limit of detection (LOD) of 0.27 pg/mL. Furthermore, the developed platform demonstrated good stability during a 14-day storage test, with fluctuations remaining below 93.33% of the initial current value. Promising results were obtained when detecting EpCAM in spiked serum samples, suggesting its potential as a point-of-care (POC) testing. [ABSTRACT FROM AUTHOR]

Magnetically induced self-assembly technology was used to construct a label-free electrochemical biosensor based on magnetic Mg0.5Cu0.5Fe2O4-Au nanocomposites for the sensitive detection of cancer antigen 125 (CA125). To aim for this, Mg0.5Cu0.5Fe2O4 nanoparticles were first prepared via the rapid combustion process. The average diameter of the nanoparticles calcined at 800 °C with the absolute ethanol volume of 20 mL was about 169.3 nm. Then Au was used for the surface modification by NaBH4 reduction reaction approach. The magnetic glassy carbon electrode (MGCE) was modified by Mg0.5Cu0.5Fe2O4-Au via a magnetic induction self-assembly process. The reduced thiol-modified single-stranded DNA was attached to the Mg0.5Cu0.5Fe2O4-Au nanocomposites by Au-S bonds without any coupling agent. CA125 antigen was grabbed directly by its aptamer DNA due to its specific identification with the aptamer. Finally, the modified electrodes were blocked with BSA and then characterized. Finally, DPV analysis was used for CA125 detection, the novel fabricated biosensor demonstrated good detection properties for CA125 with a linear range of 5–125 U/mL and a detection limit of 4.4 U/mL. The results showed that the aptamer sensor had good specificity, repeatability, and stability. The feasibility of our sensor for the determination of CA125 was also demonstrated by measuring CA125 levels in serum using the Roche gold-standard instrument of the People’s Hospital of Danyang as the reference value. The recoveries of real serum samples were 94.65–101.71%, and RSDs were 1.26–4.65%. Moreover, the surface of the electrode could be cleaned and reused by magnetic separation, greatly reducing the cost and providing the possibility for a point-of-care test (POCT). This work demonstrated a new strategy for integrating both nanostructures and biocompatibility to build advanced cancer biomarker sensors with wide applications.

Magnetic α-Fe 2 O 3 /Fe 3 O 4 nanosheets with surface-loaded gold nanoparticles were fabricated and employed as signal amplification substrates for electrochemical detection, and the PNA probes were bound to the α-Fe 2 O 3 /Fe 3 O 4 @Au surfaces via Au-S bonds to form the electrochemical biosensor. Subsequently, based on the principle of base complementary pairing, APOE ε4 was specifically recognized, captured, and detected. The biosensor exhibited lower LOD, high specificity, excellent stability, superior reproducibility, regeneration capability as well as satisfactory recovery rate in human serum samples. [Display omitted] • The sheet-like magnetic α-Fe 2 O 3 /Fe 3 O 4 @Au nanocomposites were fabricated via the hydrothermal-calcination reduction process. • A label-free and magnetic self-assembly biosensor was constructed via PNA-DNA hybridization for APOE ε4 detection. • The biosensor exhibited low LOD, excellent specificity, reproducibility, stability, renewability, and satisfactory recovery. A label-free electrochemical DNA detection strategy based on self-assembled α-Fe 2 O 3 /Fe 3 O 4 nanosheets with PNA-DNA hybridization process was developed for ultrasensitive detection of APOE ε4 gene, one of the most robust genetic risks for Alzheimer's Disease (AD). In this work, magnetic α-Fe 2 O 3 /Fe 3 O 4 heterogeneous nanosheets were prepared by hydrothermal-calcined reduction method and loaded with Au nanoparticles (AuNPs) on their surfaces. The magnetic α-Fe 2 O 3 /Fe 3 O 4 @Au nanocomposites significantly enhanced the electrochemical response as a signal amplification matrix and were able to bind to the magnetic glassy carbon electrode (MGCE) surface by magnetic self-assembly. Moreover, owing to the high specificity and stable binding capacity of PNA with respect to the target DNA, the biosensor not only enabled accurate (the limit of detection was estimated to be 0.147 pM) and rapid detection of the APOE ε4 gene, but also exhibited excellent specificity, stability and regeneration capability. Additional, the satisfactory recoveries were also obtained in real samples of human serum, ranging from 92.83 % to 106.22 % with relative standard deviation (RSD) between 0.25 % and 1.85 %. The results possessed important reference value for exploring the application of DNA biosensor technology in the diagnosis of APOE gene mutation. [ABSTRACT FROM AUTHOR]

In this paper, a detection strategy based on Surface-enhanced Raman Scattering (SERS) was proposed to quickly and simply separate target molecules from samples. Fe 3 O 4 @SiO 2 @Ag (FSA) magnetic particles modified with flower-like silver nanosheets were employed for efficient enrichment of target molecules, followed by their self-assembly onto the NdFeB substrate surface in fluid medium. The SERS sensitivity was indirectly adjusted by changing the reaction time to control the morphology of flower-like silver nanosheets on the surface of magnetic particles. SERS experiment showed that the substrate prepared by this detection strategy had high sensitivity, Rhodamine 6G (R6G) could be detected at the concentration of 10−8M and Methylene Blue (MB) could be detected at the concentration of 10−7M, the calculated enhancement factor was 1.34 × 105. In addition, the uniformity of the substrate was evaluated by SERS mapping using 10-6 M R6G, the RSD value of 8.89% was obtained. This detection strategy provides a new idea for simple and rapid SERS detection of organic dye. • A SERS detection strategy based on self-assembly magnetic particles onto hard magnetic materials substrate is proposed. • SERS substrate shows high uniformity with RSD of 8.89%. • A high EF of 1.34x105 is realized. • The proposed strategy is workable for rapid and simple water quality detection. [ABSTRACT FROM AUTHOR]

Abstract The importance of mechanical signals in regulating the fate of macrophages is gaining increased attention recently. However, the recently used mechanical signals normally rely on the physical characteristics of matrix with non‐specificity and instability or mechanical loading devices with uncontrollability and complexity. Herein, we demonstrate the successful fabrication of self‐assembled microrobots (SMRs) based on magnetic nanoparticles as local mechanical signal generators for precise macrophage polarization. Under a rotating magnetic field (RMF), the propulsion of SMRs occurs due to the elastic deformation via magnetic force and hydrodynamics. SMRs perform wireless navigation toward the targeted macrophage in a controllable manner and subsequently rotate around the cell for mechanical signal generation. Macrophages are eventually polarized from M0 to anti‐inflammatory related M2 phenotypes by blocking the Piezo1‐activating protein‐1 (AP‐1）‐CCL2 signaling pathway. The as‐developed microrobot system provides a new platform of mechanical signal loading for macrophage polarization, which holds great potential for precise regulation of cell fate.‐

Early-stage colorectal cancer (CRC) is often asymptomatic, leading to late diagnoses and impacting treatment outcomes. Timely detection and diagnosis are crucial, with serum carcinoembryonic antigen (CEA) levels playing a key role in CRC diagnosis and prognosis. To enhance precision, a label-free electrochemical nano-biosensor utilizing magnetic self-assembly (MSA) technology was developed for sensitive CEA detection. The biosensor's core was the α-Fe 2 O 3 /Fe 3 O 4 nanorods prepared by the hydrolysis-calcination reduction process. Its unique magnetism was the cornerstone of MSA technology. The biosensor exhibited excellent mechanical strength, ensuring stability during storage at 4 °C for at least one month. The aptamer probe (CEAA) self-assembled on the nanorods' surface via an Au–S bond, creating the magnetic probe (CEAA/α-Fe 2 O 3 /Fe 3 O 4 @Au). Upon capturing CEA, the current response decreased, indicating a "turn-off" nano-biosensor type as observed through differential pulse voltammetry (DPV) monitoring. In this research, the biosensor not only exhibited robust specificity and superior anti-interference ability but also demonstrated successful regeneration. The limit of detection (LOD) was 0.197 pg/mL, the recovery rate for real serum samples was between 94.15 % and 105.08 %, and the relative standard deviation (RSD) ranged from 1.40 % to 2.09 %. This biosensor showed promise in enhancing the accuracy and effectiveness of CRC diagnostic and prognostic protocols, offering a new direction for point-of-care testing. • A hydrolysis and calcination-reduction process using PEG 2000 was developed for the fabrication of magnetic α-Fe 2 O 3 /Fe 3 O 4 nanorods. • Rapid detection of CEA was achieved by employing magnetic α-Fe 2 O 3 /Fe 3 O 4 NRs by magnetic self-assembly. • The "label-free" nano-biosensor revealed an expanded linear range, a lower LOD of 0.197 pg/mL, and excellent performance. • The recovery rate for real serum samples was between 94.15% and 105.08%, with an RSD ranging from 1.40% to 2.09%. [ABSTRACT FROM AUTHOR]

Pharmacogenetic testing technology can effectively determine the individual differences among patients and scientifically assist doctors to select the most suitable drugs for each patient. In this study, an electrochemical biosensor based on magnetic α-Fe 2 O 3 /Fe 3 O 4 heterogeneous nanosheets was constructed to detect Vitamin K epoxide reductase complex 1 type AA (VKORC1*2). Firstly, we fabricated magnetic α-Fe 2 O 3 /Fe 3 O 4 heterogeneous nanosheets as the substrate material for electrochemical biosensors. Subsequently, the material surface was modified with Au nanoparticles to facilitate the connection of sensing probes and enhance current signal amplification. The electrochemical biosensor showed a negative linear relationship with the concentrations of target DNA (tDNA, VKORC1*2 gene) within 1 pM − 1 μM, a limit of detection was (LOD) = 0.36 pM, and a limit of quantification was (LOQ) = 1.19 pM. The biosensor demonstrated exceptional specificity, reproducibility, and stability. In real sample analysis, it exhibited a recovery range of 96.63 % − 110.57 % (RSD ≤ 3.07 %) for various tDNA concentrations, thereby indicating its promising potential in clinical diagnostics. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Cornlike structure was successfully prepared by magnetic self-assembly. • OH-Fe 3 O 4 @NC presents high capacity and excellent rate performance. • Successive carbon shell is beneficial for providing high electronic conductivity. • Cornlike structure buffer the volume expansion during cycling. Abstract Cornlike ordered N-doped carbon coated hollow Fe 3 O 4 (OH-Fe 3 O 4 @NC) composites are prepared through a facile strategy. The unique structure is composed of hundreds of N-doped carbon coated hollow Fe 3 O 4 nanospheres. Successive carbon shell and hollow structure address the irreversibility issue of Fe 3 O 4 -based electrodes. Owing to the unique cornlike ordered structure, the as-prepared OH-Fe 3 O 4 @NC composites exhibit appealing electrochemical performance as anode materials for lithium-ion batteries (LIBs). It delivers a high reversible capacity of 1316 mA h g−1 at 0.1 A g−1 after 50 cycles and a remarkable rate performance (725, 551 and 361 mA h g−1 at 1, 4, and 10 A g−1, respectively). Our results demonstrate that the OH-Fe 3 O 4 @NC composites are the promising anode materials with high capacity for next generation LIBs. [ABSTRACT FROM AUTHOR]

Magnetically induced self-assembly technology was used to construct a label-free electrochemical biosensor based on magnetic Mg 0.5 Cu 0.5 Fe 2 O 4 -Au nanocomposites for the sensitive detection of cancer antigen 125 (CA125). To aim for this, Mg 0.5 Cu 0.5 Fe 2 O 4 nanoparticles were first prepared via the rapid combustion process. The average diameter of the nanoparticles calcined at 800 °C with the absolute ethanol volume of 20 mL was about 169.3 nm. Then Au was used for the surface modification by NaBH 4 reduction reaction approach. The magnetic glassy carbon electrode (MGCE) was modified by Mg 0.5 Cu 0.5 Fe 2 O 4 -Au via a magnetic induction self-assembly process. The reduced thiol-modified single-stranded DNA was attached to the Mg 0.5 Cu 0.5 Fe 2 O 4 -Au nanocomposites by Au-S bonds without any coupling agent. CA125 antigen was grabbed directly by its aptamer DNA due to its specific identification with the aptamer. Finally, the modified electrodes were blocked with BSA and then characterized. Finally, DPV analysis was used for CA125 detection, the novel fabricated biosensor demonstrated good detection properties for CA125 with a linear range of 5–125 U/mL and a detection limit of 4.4 U/mL. The results showed that the aptamer sensor had good specificity, repeatability, and stability. The feasibility of our sensor for the determination of CA125 was also demonstrated by measuring CA125 levels in serum using the Roche gold-standard instrument of the People's Hospital of Danyang as the reference value. The recoveries of real serum samples were 94.65–101.71%, and RSDs were 1.26–4.65%. Moreover, the surface of the electrode could be cleaned and reused by magnetic separation, greatly reducing the cost and providing the possibility for a point-of-care test (POCT). This work demonstrated a new strategy for integrating both nanostructures and biocompatibility to build advanced cancer biomarker sensors with wide applications. [ABSTRACT FROM AUTHOR]

Magnetite (FeO) nanoparticles anchored over the different active carbon supports were developed by a simple wet solution method. The developed nanostructures were magnetically self-assembled over the electrode surface and exploited as anode catalysts in mediatorless microbial fuel cells (MFC). The morphological characterizations revealed that 3∼8-nm-sized FeO nanoparticles were homogeneously anchored over the different carbon matrices and the obtained diffraction patterns ensured the cubic inverse spinel structure of prepared FeO nanoparticles. The morphology, size, and structure of FeO nanoparticles anchored over the different active carbon supports were maintained identical, and the influence of active carbon support toward the effectual MFC performances was evaluated under various electrochemical regimes and conditions by using Escherichia coli as a catalytic microorganism. The electrochemical characterizations revealed that carbon nanotube (CNT)-supported FeO nanoparticles exhibited lower charge transfer resistance and high coulombic efficiency in comparison with the graphene and graphite nanofiber-supported composites. Among the studied anode catalysts, FeO/CNT composite exhibited the maximum MFC power density of 865 mW m associated with excellent durability performances, owing to the specific interaction exerted between the microorganisms and the FeO/CNT composite. Thus, the binder-free electrode modification process, mediatorless environment, rapid electron transfer kinetics, high power generation, and long durability performances achieved for the developed system paved futuristic dimensions for the high performance MFCs. [ABSTRACT FROM AUTHOR]

In this paper, we demonstrate a novel self-assembly method for non-contact and high precision handling of ultra-thin chips. The chips are manipulated by the magnetic interactions between an externally applied magnetic field and nickel contact pads present on the chip. The asymmetric layout of magnetic material on the chip and the gradient in the applied magnetic field allows achieving a unique rotational alignment. The repeatability of the process is 3 σ = 25 μ m in translation and 3 σ = 2 ° in rotation, with an alignment duration of 0.2 s. [ABSTRACT FROM AUTHOR]

A self-assembly process is developed for the placement and alignment of Ultra-Thin Chips (UTCs) to polymer foils. The chips are presented within the working range of a magnetic force field, and subsequently driven to and aligned at a target location. A low-viscosity die attach adhesive layer supports chip mobility during alignment, and is UV-cured after assembly to generate a mechanical bond. An adaptive electrical interconnection scheme compensates the position errors present after assembly. Standard Ni + Au bumps provide sufficient magnetization to generate the required alignment force. Numerical modeling confirms that over a long range magnetic forces operate on a chip and drive it to a target location. Also, an asymmetric bump arrangement supports achieving a unique in-plane orientation. Experimentally, chips with a thickness of 20 \mum were successfully trapped and aligned with a repeatability of \pm 100\ \mum in \mbi x and \mbi y-direction, and the best achieved cycle time is below 1.0 s. The cycle time depends considerably on the viscosity of the die attach adhesive. The presence of unique in-plane orientations, depending on the bump arrangement, is demonstrated. [ABSTRACT FROM AUTHOR]

Mechanically robust, cell encapsulating microdevices fabricated using photolithographic methods can lead to more efficient immunoisolation in comparison to cell encapsulating hydrogels. There is a need to develop adhesive bonding methods which can seal such microdevices under physiologically friendly conditions. We report the bonding of SU-8 based substrates through (i) magnetic self assembly, (ii) using medical grade photocured adhesive and (iii) moisture and photochemical cured polymerization. Magnetic self-assembly, carried out in biofriendly aqueous buffers, provides weak bonding not suitable for long term applications. Moisture cured bonding of covalently modified SU-8 substrates, based on silanol condensation, resulted in weak and inconsistent bonding. Photocured bonding using a medical grade adhesive and of acrylate modified substrates provided stable bonding. Of the methods evaluated, photocured adhesion provided the strongest and most stable adhesion. [ABSTRACT FROM AUTHOR]

This paper demonstrates and characterizes magnetically-directed self-assembly of 1 mm x 1 mm x 500 µm silicon components into an ordered array on a planar substrate. Each silicon component includes an embedded, microfabricated magnet on one surface that bonds to a corresponding magnetic receptor site (another embedded magnet) on the substrate. Two different magnet sizes are explored, corresponding to 25% and 75% of the bonding surface area. Using a shaker apparatus for mixing in a dry environment, studies are conducted to determine the assembly rates and yields. For the smaller magnets, a 4 x 4 array of components is shown to assemble onto a substrate with 97.5% yield in 10 s. The larger magnets indicate a 98.7% yield in 7 s. [ABSTRACT FROM AUTHOR]

Abstract: We provide the design method of multi-step magnetic self-assembly using ferromagnetic-hinged structures. The process uses the magnetostatic torque generated by an external magnetic field perpendicular to the substrate to lift hinged structures. Hinged structure is composed of a rigid plate connected by elastic hinges to one side of a substrate. If hinged structures are raised in sequential order, it is possible to assemble like Japanese “origami” complex three-dimensional structures. In our previous study, we found that a dimensionless factor that depends on its shape determines the sensitivity of the hinged microstructures to a magnetic field. This factor can be used as a criterion in designing a process for sequential batch self-assembly, because the factor indicates the differences in the sensitivity. In this study, we designed multi-step sequential assembly by using the dimensionless factor. Four-step sequential batch assembly was demonstrated using this method. This method will be useful for optical systems, which consist of many complex three-dimensional structures. [Copyright &y& Elsevier]

The assembly of nanoparticles into polymer-like architectures is challenging and usually requires highly defined colloidal building blocks. Here, we show that the broad size-distribution of a simple dispersion of magnetic nanocolloids can be exploited to obtain various polymer-like architectures. The particles are assembled under an external magnetic field and permanently linked by thermal sintering. The remarkable variety of polymer-analogue architectures that arises from this simple process ranges from statistical and block copolymer-like sequencing to branched chains and networks. This library of architectures can be realized by controlling the sequencing of the particles and the junction points via a size-dependent self-assembly of the single building blocks.