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To solve the problem of ice condensation and adhesion, it is urgent to develop new anti-icing and deicing technologies. This study presented the development of a highly efficient photothermal-enhanced superhydrophobic PDMS/Ni@Ti 3 C 2 T x composite film ( m -NMPA) fabricated cost-effectively and straightforwardly. This film was fabricated utilizing PDMS as a hydrophobic agent, adhesive, and surface protector, while Ni@Ti 3 C 2 T x as a magnetic photothermal filler innovatively. Through a simple spraying method, the filler is guided by a strong magnetic field to self-assemble into an eyelash-like microstructure array. The unique structure not only imparts superhydrophobic properties to the surface but also constructs an efficient "light-capturing" architecture. Remarkably, the m -NMPA film demonstrates outstanding superhydrophobic passive anti-icing and efficient photothermal active deicing performance without the use of fluorinated chemicals. The micro-/nanostructure of the film forms a gas layer, significantly delaying the freezing time of water. Particularly under extreme cold conditions (-30 °C), the freezing time is extended by a factor of 7.3 compared to the bare substrate. Furthermore, under sunlight exposure, surface droplets do not freeze. The excellent photothermal performance is attributed to the firm anchoring of nickel particles on the MXene surface, facilitating effective "point-to-face" photothermal synergy. The eyelash-like microarray structure enhances light-capturing capability, resulting in a high light absorption rate of 98%. Furthermore, the microstructure aids in maintaining heat at the uppermost layer of the surface, maximizing the utilization of thermal energy for ice melting and frost thawing. Under solar irradiation, the m -NMPA film can rapidly melt approximately a 4 mm thick ice layer within 558 s and expel the melted water promptly, reducing the risk of secondary icing. Additionally, the ice adhesion force on the surface of the m -NMPA film is remarkably low, with an adhesion strength of approximately 4.7 kPa for a 1 × 1 cm 2 ice column. After undergoing rigorous durability tests, including xenon lamp weathering test, pressure resistance test, repeated adhesive tape testing, xenon lamp irradiation, water drop impact testing, and repeated brushing with hydrochloric acid and particles, the film's surface structure and superhydrophobic performance have remained exceptional. The photothermal superhydrophobic passive anti-icing and active deicing technology in this work rely on sustainable solar energy for efficient heat generation. It presents broad prospects for practical applications with advantages such as simple processing method, environmental friendliness, outstanding anti-icing effects, and exceptional durability.

Magnetic nanoparticles as drug carriers, despite showing immense promises in preclinical trials, have remained to be only of limited use in real therapeutic practice primarily due to unresolved anomalies concerning their grossly contrasting controllability and variability in performance in artificial test benches as compared to human tissues. To circumvent the deficits of reported in vitro drug testing platforms that deviate significantly from the physiological features of the living systems and result in this puzzling contrast, here, we fabricate a biomimetic microvasculature in a flexible tissue phantom and demonstrate distinctive mechanisms of magnetic-field-assisted controllable penetration of biocompatible iron oxide nanoparticles across the same, exclusively modulated by tissue deformability, which has by far remained unraveled. Our experiments deciphering the transport of magnetic nanoparticles in a blood analogue medium unveil a decisive interplay of the flexibility of the microvascular pathways, magnetic pull, and viscous friction toward orchestrating the optimal vascular penetration and targeting efficacy of the nanoparticles in colorectal tissue-mimicking bioengineered media. Subsequent studies with biological cells confirm the viability of using localized magnetic forces for aiding nanoparticle penetration within cancerous lesions. We establish nontrivially favorable conditions to induce a threshold force for vascular rupture and eventual target of the nanoparticles toward the desired extracellular site. These findings appear to be critical in converging the success of in vitro trials toward patient-specific targeted therapies depending on personalized vascular properties obtained from medical imaging data.

Efficient gas enrichment approaches are of great importance for the storage and transportation of clean energy and the sequestration of carbon dioxide. Of special interest is the regulated gas hydrate-based method; however, its operation requires adequate additives to overcome the low-storage capacity issue. Thus, this method is not economically feasible or environmentally friendly. In this work, a novel recyclable hydrate promoter of copolystyrene-sodium styrenesulfonate@Fe 3 O 4 (PNS) nanoparticles with an integrated core-shell structure was synthesized through emulsion polymerization. This was found to effectively reduce the induction time of methane hydrate formation by one-third compared with the widely used sodium dodecyl sulfate (SDS); the corresponding gas storage capacity was also comparable, up to 155 v/v. In addition, the PNS nanoparticles showed a good performance in foam inhibition upon hydrate decomposition, which frequently occurred with the use of SDS and other surfactant-based promoters. In particular, the new promoters contributed to a more than 30% increase in CO 2 storage capacity, coacting with the fine sediments that mimic a marine environment. This provided further possibilities of sequestering CO 2 in the form a gas hydrate under the seafloor. The underlying mechanism was proposed to involve anchored surfactants on the surface and tiny channels between the nanoparticles that lead to rapid hydrate nucleation and controlled growth. The results showed that the integrated magnetically recovering nanoparticles developed in this study could improve the efficiency of gas storage by forming gas hydrates; the excellent recycling performance paved the way for solving the economic and environmental problems encountered in additive usage.

In the present study, a magnetic mimic multi-enzyme system was developed by encapsulating the aryloxyphenoxypropionate (AOPP) herbicide hydrolase QpeH and alcohol oxidase (AOx) in zeolitic imidazolate framework (ZIF-8) nanocrystals with magnetic Fe 3 O 4 nanoparticles (MNPs) to detect AOPP herbicides. The structural, protein loading capacity and loading ratio, porosity, and magnetic properties of QpeH/AOx@mZIF-8 were characterized by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, nitrogen sorption, and vibrating sample magnetometry. An AOPP herbicide colorimetric biosensor made with QpeH/AOx@mZIF-8 had the highest sensitivity toward quizalofop-P-ethyl (QpE) with a limit of detection of 8.2 μM. This system was suitable to detect two other AOPP herbicides, including fenoxaprop-P-ethyl (FpE) and haloxyfop-P-methyl (HpE). The practical application of the biosensor was verified through quantitative analysis of QpE residues in industrial wastewater and field soils. Furthermore, QpeH/AOx@mZIF-8 exhibited excellent long-term storage stability (at least 50 days), easy separation by magnet, and reusability (at least 10 cycles), supporting its promising role in simple and low-cost detection of AOPP herbicides in real environmental samples.

With the ongoing global pandemic of coronavirus disease 2019 (COVID-19), there is an increasing quest for more accessible, easy-to-use, rapid, inexpensive, and high-accuracy diagnostic tools. Traditional disease diagnostic methods such as qRT-PCR (quantitative reverse transcription-PCR) and ELISA (enzyme-linked immunosorbent assay) require multiple steps, trained technicians, and long turnaround time that may worsen the disease surveillance and pandemic control. In sight of this situation, a rapid, one-step, easy-to-use, and high-accuracy diagnostic platform will be valuable for future epidemic control, especially for regions with scarce medical resources. Herein, we report a magnetic particle spectroscopy (MPS) platform for the detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) biomarkers: spike and nucleocapsid proteins. This technique monitors the dynamic magnetic responses of magnetic nanoparticles (MNPs) and uses their higher harmonics as a measure of the nanoparticles' binding states. By anchoring polyclonal antibodies (pAbs) onto MNP surfaces, these nanoparticles function as nanoprobes to specifically bind to target analytes (SARS-CoV-2 spike and nucleocapsid proteins in this work) and form nanoparticle clusters. This binding event causes detectable changes in higher harmonics and allows for quantitative and qualitative detection of target analytes in the liquid phase. We have achieved detection limits of 1.56 nM (equivalent to 125 fmole) and 12.5 nM (equivalent to 1 pmole) for detecting SARS-CoV-2 spike and nucleocapsid proteins, respectively. This MPS platform combined with the one-step, wash-free, nanoparticle clustering-based assay method is intrinsically versatile and allows for the detection of a variety of other disease biomarkers by simply changing the surface functional groups on MNPs.

Remote control of cells and single molecules by magnetic nanoparticles in nonheating external magnetic fields is a perspective approach for many applications such as cancer treatment and enzyme activity regulation. However, the possibility and mechanisms of direct effects of small individual magnetic nanoparticles on such processes in magneto-mechanical experiments still remain unclear. In this work, we have shown remote-controlled mechanical dissociation of short DNA duplexes (18-60 bp) under the influence of nonheating low-frequency alternating magnetic fields using individual 11 nm magnetic nanoparticles. The developed technique allows (1) simultaneous manipulation of millions of individual DNA molecules and (2) evaluation of energies of intermolecular interactions in short DNA duplexes or in other molecules. Finally, we have shown that DNA duplexes dissociation is mediated by mechanical stress and produced by the movement of magnetic nanoparticles in magnetic fields, but not by local overheating. The presented technique opens a new avenue for high-precision manipulation of DNA and generation of biosensors for quantification of energies of intermolecular interaction.

Helicobacter pylori infection is one of the leading causes of several gastroduodenal diseases, such as gastritis, peptic ulcer, and gastric cancer. In fact, H. pylori eradication provides a preventive effect against the incidence of gastric cancer. Amoxicillin is a commonly used antibiotic for H. pylori eradication. However, due to its easy degradation by gastric acid, it is necessary to administer it in a large dosage and to combine it with other antibiotics. This complexity and the strong side effects of H. pylori eradication therapy often lead to treatment failure. In this study, the chitosan/poly (acrylic acid) particles co-loaded with superparamagnetic iron oxide nanoparticles and amoxicillin (SPIO/AMO@PAA/CHI) are used as drug nano-carriers for H. pylori eradication therapy. In vitro and in vivo results show that the designed SPIO/AMO@PAA/CHI nanoparticles are biocompatible and could retain the biofilm inhibition and the bactericidal effect of amoxicillin against H. pylori . Moreover, the mucoadhesive property of chitosan allows SPIO/AMO@PAA/CHI nanoparticles to adhere to the gastric mucus layer and rapidly pass through the mucus layer after exposure to a magnetic field. When PAA is added, it competes with amoxicillin for chitosan, so that amoxicillin is quickly and continuously released between the mucus layer and the gastric epithelium and directly acts on H. pylori . Consequently, the use of this nano-carrier can extend the drug residence time in the stomach, reducing the drug dose and treatment period of H. pylori eradication therapy.

Discontinuous dewetting (DD) is an attractive technique that enables the production of large liquid arrays in microwells and is applicable to the synthesis of anisotropic microparticles with complex morphologies. However, such loading of liquids into microwells presents a significant challenge, as the liquids used in this technique should exhibit low mold surface wettability. This study introduces DD in a degassed mold (DM), a simple yet powerful technique that achieves uniform loading of microparticle precursors into large microwell arrays within 1 min. Using this technique, hydrogel microparticles are produced by different polymerization mechanisms with various shapes and sizes, ranging from a few micrometers to hundreds of micrometers. Hydrophobic oil microparticles are produced by the simple plasma treatment of the DM, and agarose microparticles encapsulating bovine serum albumin (in a well-dispersed state) are produced by submerging the DM in fluorinated oil. To demonstrate additional functionality of microparticles using this technique, high concentrations of magnetic nanoparticles are loaded into microparticles for particle-based immunoassays performed in a microwell plate, and the immunoassay performance is comparable to that of ELISA.

Despite the widely explored biomaterial scaffolds in vascular tissue engineering applications lately, no ideal platform has been provided for small diameter synthetic vascular grafts mainly due to the thrombosis issue. Endothelium is the only known completely non-thrombogenic material; so, functional endothelialization onto vascular biomaterials is critical in maintaining the patency of vascular networks. Bacterial cellulose (BC) is a natural biomaterial with superior biocompatibility and appropriate hydrophilicity as potential vascular grafts. In previous studies, surface modification of active peptides such as Arg-Gly-Asp (RGD) sequences onto biomaterials has been proven to achieve accelerated and selective endothelial cell (EC) adhesion. In our study, we demonstrated a new strategy to remotely regulate the adhesion of endothelial cells based on an oscillating magnetic field and achieve successful endothelialization on the modified BC membranes. In details, we synthesized bacterial cellulose (BC), magnetic BC (MBC), and RGD peptide-grafted magnetic BC (RMBC), modified with the HOOC-PEG-COOH-coated iron oxide nanoparticles (PEG-IONs). The endothelial cells were cultured on the three materials under different frequencies of an oscillating magnetic field, including "stationary" (0 Hz), "slow" (0.1 Hz), and "fast" (2 Hz) groups. Compared to BC and MBC membranes, the cells on RMBC membranes generally show better adhesion and proliferation. Meanwhile, the "slow" frequency of a magnetic field promotes this phenomenon on RMBC and achieves endothelialization after culture for 4 days, whereas "fast" inhibits the cellular attachment. Overall, we demonstrate a non-invasive and convenient method to regulate the endothelialization process, with promising applications in vascular tissue engineering.

Heavy-metal pollution is becoming a worldwide problem severely threatening our health and ecosystem. In this study, we constructed a genetic-engineering-driven coassembly of synthetic bacterial cells and magnetic nanoparticles (MNPs) for capturing heavy metals. The Escherichia coli cells were genetically engineered by introducing a de novo synthetic heavy-metal-capturing gene (encoding a protein SynHMB containing a six-histidine tag, two cystine-rich peptides, and a metallothionein sequence) and a synthetic type VI secretory system (T6SS) cluster of Pseudomonas putida , endowing the synthetic cells (SynEc2) with high ability of displaying the heavy-metal-capturing SynHMB on cell surface. MNPs were synthesized by a coprecipitation method and further modified by polyethylenimine (PEI) and diethylenetriaminepentaacetic acid (DTPA). Owing to the surface exposure of six-histidine tag on the synthetic bacteria and carboxyl groups on the modified MNPs (MNP@SiO 2 -PEI-DTPA), the synthetic bacterial cells and MNPs coassembled to form biotic/abiotic complex exhibiting a self-developing characteristic. In the culture medium containing both Cd 2+ and Pb 2+ , the coassemblies captured these heavy metals with high removal efficiency (>90% even at 50 mg/L of Cd 2+ and 50 mg/L of Pb 2+ ) and were conveniently recycled by artificial magnetic fields. Moreover, the coassemblies realized coremoval of organic carbon pollutants with the removal efficiency of >80%. This study builds a novel biotic/abiotic coassembling platform facilitated by genetic engineering and sheds light on development of artificial magnetic biological systems for efficient treatment of environmental pollution.

Actin cytoskeleton disruption is a promising and intriguing anticancer strategy, but their efficiency is frequently compromised by severe side effects of the actin cytoskeleton-disrupting agents. In this study, we constructed the biocompatible actin cytoskeleton-targeting multivalent supramolecular assemblies that specifically target and disrupt the tumor actin cytoskeleton for cancer therapy. The assemblies were composed of β-cyclodextrin-grafted hyaluronic acid (HACD) and iron oxide magnetic nanoparticles (MNPs) grafted by an actin-binding peptide (ABP) and adamantane (Ada)-modified polylysine. Owing to the multivalent binding between cyclodextrin and Ada, HACD, and peptide-grafted MNPs (MNP-ABP-Ada) could self-assemble to form MNP-ABP-Ada⊂HACD nanofibers in a geomagnetism-dependent manner. Furthermore, the presence of ABP rendered the assemblies to efficiently target the actin cytoskeleton. Interestingly, with the acid of a low-frequency alternating magnetic field (200 Hz), the actin cytoskeleton-targeting nanofibers could induce severe actin disruption, leading to a remarkable cell cycle arrest and drastic cell death of tumor cells both in vitro and in vivo, but showed no obvious toxicity to normal cells. The actin cytoskeleton-targeting/disrupting supramolecular assembly implies an excellent strategy for realizing efficient cancer therapy.

Biologically inspired structural color hydrogels with magnetic- and photothermal-controlled self-healable abilities were fabricated by integrating magnetic-responsive photonic crystals into gelatin hydrogels. The self-healable ability of the hydrogel systems was derived from the magnetic response and light-absorbing abilities of the magnetic nanoparticles. When the hydrogels deteriorate or get damaged, magnetic nanoparticles could absorb heat under near-infrared irradiation and external magnetic fields, which stimulates phase transformation in the hydrogels to fill or heal the hydrogels. In addition, the hydrogel systems were demonstrated with high biocompatibility and plasticity. These features of magnetic self-healable structural color hydrogels make them have broad application prospects in the fields of biological engineering and cell engineering.

Magnetic nanoparticles (MNPs) have been extensively used as contrasts and tracers for bioimaging, heating sources for tumor therapy, carriers for controlled drug delivery, and labels for magnetic immunoassays. Here, we describe a MNP Brownian relaxation dynamics-based magnetic particle spectroscopy (MPS) method for the quantitative detection of molecular biomarkers. In MPS measurements, the harmonics of oscillating MNPs are recorded and used as a metric for the freedom of rotational motion, which indicates the bound states of the MNPs. These harmonics can be collected from microgram quantities of iron oxide nanoparticles within 10 s. As the harmonics are largely dependent on the quantity of the MNPs in the sample, the MPS bioassay results could be biased by the deviations of MNP quantities in each sample, especially for the very low-concentration biomarker detection scenarios. Herein, we report three MNP concentration/quantity-independent metrics for characterizing the bound states of MNPs in MPS. Using a streptavidin-biotin binding system as a model, we demonstrate the feasibility of using MPS and MNP concentration/quantity-independent metrics to sense these molecular interactions, showing that this method can achieve rapid, wash-free bioassays, and is suitable for future point-of-care, sensitive, and versatile diagnosis.

Inspired by natural biological machines, lots of effort has been invested in developing artificially functional micromotors which can convert energy into movement for carrying out tasks in diverse areas. Here, we present a capillary microfluidic system with dual inner injections for one-step generation of composite structured polymer micromotors with two distinct cores of platinum (Pt) nanoparticle-integrated and iron oxide (Fe 3 O 4 ) nanoparticle-dispersed hydrogels. Because the flow rates of the prepolymerized fluids can be precisely tuned in the microfluidics, the diameters of the micromotors as well as the sizes and numbers of the inner cores can be well tailored to optimize the parameters of the resultant micromotors. When exposed to a hydrogen peroxide (H 2 O 2 ) medium, the Pt-integrated cores of the micromotors could provide propulsion by expelling bubbles produced from the catalytic decomposition of H 2 O 2 , while the Fe 3 O 4 -dispersed cores could impart magnetic guidance for the micromotors. Benefiting from the close cooperation of these two types of cores, the micromotors were imparted with a strong propulsion and prominent recyclability for the delivery of both microscale and macroscale objects. These results manifest that this kind of composite micromotor has great diversity in various applications.

Small magnetic nanoparticles that have surfaces decorated with stimuli-responsive polymers can be reversibly aggregated via a stimulus, such as temperature, to enable efficient and rapid biomarker separation. To fully realize the potential of these particles, the synthesis needs to be highly reproducible and scalable to large quantity. We have developed a new synthesis for temperature-responsive magnetic nanoparticles via an in situ co-precipitation process of Fe 2+ /Fe 3+ salts at room temperature with poly(acrylic acid)- block-poly( N-isopropylacrylamide) diblock co-polymer template, synthesized via the reversible addition-fragmentation chain-transfer polymerization method. These particles were 56% polymer by weight with a 6.5:1 Fe/COOH ratio and demonstrated remarkable stability over a 2 month period. The hydrodynamic diameter remained constant at ∼28 nm with a consistent transition temperature of 34 °C, and the magnetic particle separation efficiency at 40 °C was ≥95% over the 2 month span. These properties were maintained for all large-scale synthesis batches. To demonstrate the practical utility of the stimuli-responsive magnetic nanoparticles, the particles were incorporated into a temperature-responsive binary reagent system and efficiently separated a model protein biomarker (mouse IgG) as well as purified extracellular vesicles derived from a human biofluid, seminal plasma. The ease of using these particles will prove beneficial for various biomedical applications.

Magnetic particles are widely used as labels in magnetoresistive sensors. To use magnetic particles as labels, several important characteristics should be considered, such as superparamagnetism, a high magnetic moment per particle (m), facile surface functionalization and biomolecule immobilization, colloidal stability, and analyte specificity. In this paper, we describe the preparation of magnetic labels with a high m, using colloidal assemblies of superparamagnetic zinc ferrite nanoparticles (ZFNPs, ∼9 nm). Also, several properties of these particles are compared with those of commercially available magnetic beads, Dynabeads and TurboBeads. The colloidally assembled zinc ferrite magnetic beads (ZFMBs, ∼160 nm) were synthesized by assembling ZFNPs via an emulsion-based assembly approach. While retaining superparamagnetism at room temperature, the m of ZFMBs is ∼4000× higher than that of the constituent ZFNPs. Surface functionalization with a layer of polyacrylic acid stabilized the ZFMBs in aqueous solution and enabled conjugation with streptavidin via carbodiimide linking chemistry. The streptavidinated ZFMBs can be suspended in aqueous buffer for ≥24 h, whereas 1.05 μm Dynabeads and 30 nm TurboBeads undergo ballistic deposition and instantaneous aggregation in solution, respectively. Finally, the streptavidinated ZFMBs were employed as labels in an immunoassay for the detection of osteopontin, a potential pancreatic cancer marker, proving superior to the commercial particles in terms of limit of detection and dynamic range. We expect that the work presented in this article can be extended to other biological applications, especially where superparamagnetic particles with a high m and colloidal stability are needed.

MnFe 2 O 4 @SiO 2 -NH 2 magnetic nanocomposite (AFMNC) adsorbent with a particle size of ∼50 nm was successfully synthesized using a facile approach. The as-prepared composite particles showed a fast binding of Pt(IV) with easy magnetic solid-liquid separation. The kinetic data were fitted to both pseudo-first and second-order rate models, indicating that AFMNC exhibited a much higher rate of Pt(IV) binding (0.125 g mg -1 min -1 ) compared to that of commercial ion-exchange resin Amberjet 4200 (0.0002 g mg -1 min -1 ). The equilibrium adsorption data were fitted to the Langmuir isotherm model with a relatively high sorption capacity of 380 mg/g. Scanning transmission electron microscopy analysis demonstrated the presence of platinum chloride after sorption on AFMNC, suggesting an adsorbate-adsorbent anion-exchange interaction. In addition, due to its magnetic characteristics, AFMNC can be easily separated from the aqueous medium after the sorption process. The novel nanocomposite may facilitate recovery of Pt(IV) from waste solutions.

DNA hydrogel has aroused widespread attention because of its unique properties. In this work, the DNA-modified magnetic nanoparticles were integrated into the mainframe of DNA hydrogel, resulting in DNA-MNP hydrogel. Under the magnetic field, this hydrogel can be remotely deformed into various shapes, driven to jump between two planes and even climb the hill. By applying various triggers, such as temperature, enzyme, and magnetic field, DNA-MNP hydrogel can specifically undergo sol-gel transition. This work not only imparts DNA hydrogel with a new fold of property but also opens a unique platform of such smart materials for its further applications.

Stimuli-responsive membranes that can adjust mass transfer and interfacial properties "on demand" have drawn large interest over the last few decades. Here, we designed and prepared a novel magnetoresponsive separation membrane with remote switchable molecular sieving effect by simple one-step and scalable nonsolvent induced phase separation (NIPS) process. Specifically, poly(ether sulfone) (PES) as matrix for an anisotropic membrane, prefabricated poly(N-isopropylacrylamide) (PNIPAAm) nanogel (NG) particles as functional gates, and iron oxide magnetic nanoparticles (MNP) as localized heaters were combined in a synergistic way. Before membrane casting, the properties of the building blocks, including swelling property and size distribution for NG, and magnetic property and heating efficiency for MNP, were investigated. Further, to identify optimal film casting conditions for membrane preparation by NIPS, in-depth rheological study of the effects of composition and temperature on blend dope solutions was performed. At last, a composite membrane with 10% MNP and 10% NG blended in a porous PES matrix was obtained, which showed a large, reversible, and stable magneto-responsivity. It had 9 times higher water permeability at the "on" state of alternating magnetic field (AMF) than at the "off"-state. Moreover, the molecular weight cutoff of such membrane could be reversibly shifted from ∼70 to 1750 kDa by switching off or on the external AMF, as demonstrated in dextran ultrafiltration tests. Overall, it has been proved that the molecular sieving performance of the novel mixed matrix composite membrane can be controlled by the swollen/shrunken state of PNIPAAm NG embedded in the nanoporous barrier layer of a PES-based anisotropic porous matrix, via the heat generation of nearby MNP. And the structure of such membrane can be tailored by the NIPS process conditions. Such membrane has potential as enabling material for remote-controlled drug release systems or devices for tunable fractionations of biomacromolecule/-particle mixtures.

Development of efficient and rapid protocols for diversification of functional magnetic nanoparticles (MNPs) would enable identification of promising candidates using high-throughput protocols for applications such as diagnostics and cure through early detection and localized delivery. Polymer brush coated magnetic nanoparticles find use in many such applications. A protocol that allows modular diversification of a pool of parent polymer coated nanoparticles will lead to a library of functional materials with improved uniformity. In the present study, polymer brush coated parent magnetic nanoparticles obtained using reversible addition-fragmentation chain transfer (RAFT) polymerization are modified to obtain nanoparticles with different "clickable" groups. In this design, trithiocarbonate group terminated polymer brushes are "grafted from" MNPs using a catechol group bearing initiator. A postpolymerization radical exchange reaction allows installation of "clickable" functional groups like azides and maleimides on the chain ends of the polymers. Thus, modified MNPs can be functionalized using alkyne-containing and thiol-containing moieties like peptides and dyes using the alkyne-azide cycloaddition and the thiol-ene conjugation, respectively. Using the approach outlined here, a cell surface receptor targeting cyclic peptide and a fluorescent dye are attached onto nanoparticle surface. This multifunctional construct allows selective recognition of cancer cells that overexpress integrin receptors. Furthermore, the approach outlined here is not limited to the installation of azide and maleimide functional groups but can be expanded to a variety of "clickable" groups to allow nanoparticle modification using a broad range of chemical conjugations.

Sepsis and bacteremia are life-threatening clinical syndromes associated with significant patient morbidity and mortality. Rapid and sensitive detection of pathogenic bacteria is the key to improve patient survival rates. Herein, we have rationally constructed a simple aptamer-based capture platform to shorten the time needed for confirmation of bacterial bloodstream infection in clinical blood samples. This capture platform is made of a mesoporous TiO2-coated magnetic nanoparticle and is modified with target aptamer. It features excellent bacterial enrichment efficiency of about 80% even at low bacterial concentrations (10-2000 CFU mL(-1)). More importantly, the bacteria can be enriched within 2 h, and the time for bacterial identification is effectively shortened in comparison to the "gold standard" in clinical diagnosis of bloodstream infection. The aptamer-based capture platform may pave a way for the detection of biomarkers and find potential applications in disease diagnosis.

The introduction of functional molecules to the surface of magnetic iron oxide nanoparticles (NPs) is of critical importance. Most previously reported methods were focused on surface ligand attachment either by physisorption or covalent conjugation, resulting in limited ligand loading capacity. In this work, we report the seeded growth of a nucleotide coordinated polymer shell, which can be considered as a special form of adsorption by forming a complete shell. Among all of the tested metal ions, Fe(3+) is the most efficient for this seeded growth. A diverse range of guest molecules, including small organic dyes, proteins, DNA, and gold NPs, can be encapsulated in the shell. All of these molecules were loaded at a much higher capacity compared to that on the naked iron oxide NP core, confirming the advantage of the coordination polymer (CP) shell. In addition, the CP shell provides better guest protein stability compared to that of simple physisorption while retaining guest activity as confirmed by the entrapped glucose oxidase assay. Use of this system as a peroxidase nanozyme and glucose biosensor was demonstrated, detecting glucose as low as 1.4 μM with excellent stability. This work describes a new way to functionalize inorganic materials with a biocompatible shell.

Studying protein interactions is of vital importance both to fundamental biology research and to medical applications. Here, we report on the experimental proof of a universally applicable label-free homogeneous platform for rapid protein analysis. It is based on optically detecting changes in the rotational dynamics of magnetically agitated core-shell nanorods upon their specific interaction with proteins. By adjusting the excitation frequency, we are able to optimize the measurement signal for each analyte protein size. In addition, due to the locking of the optical signal to the magnetic excitation frequency, background signals are suppressed, thus allowing exclusive studies of processes at the nanoprobe surface only. We study target proteins (soluble domain of the human epidermal growth factor receptor 2 - sHER2) specifically binding to antibodies (trastuzumab) immobilized on the surface of our nanoprobes and demonstrate direct deduction of their respective sizes. Additionally, we examine the dependence of our measurement signal on the concentration of the analyte protein, and deduce a minimally detectable sHER2 concentration of 440 pM. For our homogeneous measurement platform, good dispersion stability of the applied nanoprobes under physiological conditions is of vital importance. To that end, we support our measurement data by theoretical modeling of the total particle-particle interaction energies. The successful implementation of our platform offers scope for applications in biomarker-based diagnostics as well as for answering basic biology questions.

Noninvasive and longitudinal monitoring of gene expression in living cells is essential for understanding and monitoring cellular activities. Herein, a smart magnetic nanosensor is constructed for the real-time, noninvasive, and longitudinal monitoring of cellular mRNA expression through the layer-by-layer deposition of molecular beacons (MBs) and polyethylenimine on the iron oxide nanoparticles. The loading of MBs, responsible for the signal intensity and the tracking time, was easily tuned with the number of layers incorporated. The idea was first demonstrated with the magnetic nanosensors for glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA, which was efficiently internalized into the cells under the influence of magnetic field. This nanosensor allowed the continuous monitoring of the cellular GAPDH mRNA expression for 1 month. Then this platform was further utilized to incorporate two kinds of MBs for alkaline phosphatase (ALP) and GAPDH mRNAs, respectively. The multifunctional nanosensors permitted the simultaneous monitoring of the reference gene (GAPDH mRNA) and the early osteogenic differentiation marker (ALP mRNA) expression. When the fluorescence signal ratio between ALP mRNA MBs and GAPDH mRNA MBs was taken, the dynamic osteogenic differentiation process of MSCs was accurately monitored.

A magnetically responsive diacetylene (DA) powder was developed for the visualization of latent fingerprints. A mixture of the DA and magnetite nanoparticles, applied to a surface containing latent fingermarks, becomes immobilized along the ridge patterns of the fingerprints when a magnetic field is applied. Alignment along the ridge structures is a consequence of favorable hydrophobic interactions occurring between the long alkyl chains in the DAs and the lipid-rich, sebaceous latent fingermarks. UV irradiation of the DA-magnetite composite immobilized on the latent fingerprint results in the generation of blue-colored PDAs. Heat treatment of the blue-colored image promotes a blue-to-red transition as well as fluorescence turn-on. A combination of the aligned pale brown-colored monomeric state, UV irradiation generated blue-colored PDA state, as well as the heat treatment generated red-colored and fluorescent PDA state enables efficient visual imaging of a latent fingerprint, which is deposited on various colored solid surfaces.

Facile and efficient detection of cancer cells at their preclinical stages is one of the central challenges in cancer diagnostics. A direct, rapid, highly sensitive and specific biosensor for detection of cancer biomarkers is desirable in early diagnosis and prognosis of cancer. In this work, we developed, for the first time, an easy and intuitive dispersion-dominated colorimetric strategy for cancer cell detection based on combining multi-DNA released from an aptamer scaffold with cyclic enzymatic amplification, which was triggered by aptamer DNA conformational switch and demonstrated by non-cross-linking gold nanoparticles (Au NPs) aggregation. First, five kinds of messenger DNAs (mDNAs) were aligned on the cancer cell aptamers modified on magnetic beads (MBs) to form mDNAs-Apt-MBs biocompatible nanosensors. In the presence of target cells, the aptamer would bind to the receptors on the cell membranes, and mDNAs would be released, resulting in the first amplification that one biological binding event would cause the release of multiple kinds of mDNAs simultaneously. After magnetic separation, the released mDNAs were introduced into the cyclic enzymatic amplification to cleave more single strand DNA (ssDNA) fragments. Instead of modification of Au NPs, these fragments and mDNAs could be adsorbed on the surface of Au NPs to prevent particle aggregation and ensure the stability and color of solution in high salt environments. The linear response for HL-60 cells in a concentration range from 10 to 10(4) cells was obtained with a detection limit of four cells in buffer solution. Moreover, the feasibility of the proposed strategy was demonstrated in a diluted serum sample. This dual signal amplification method can be extended to other types of cancer cells, which has potential application in point-of-care cancer diagnosis.

Fluorescent-magnetic particles (FMPs) play important roles in modern materials, especially as nanoscale devices in the biomedical field. The interesting features of FMPs are attributed to their dual detection ability, i.e., fluorescent and magnetic modes. Functionalization of FMPs can be performed using several types of polymers, allowing their use in various applications. The synergistic potentials for unique multifunctional, multilevel targeting nanoscale devices as well as combination therapies make them particularly attractive for biomedical applications. However, the synthesis of FMPs is challenging and must be further developed. In this review article, we summarized the most recent representative works on polymer-based FMP systems that have been applied particularly in the bioanalytical field.

We report the synthesis of a magnetofluorescent biocompatible nanoprobe-following room temperature complexation reaction between Fe3O4-ZnS nanocomposite and 8-hydroxyquinoline (HQ). The composite nanoprobe exhibited high luminescence quantum yield, low rate of photobleaching, reasonable excited-state lifetime, luminescence stability especially in human blood serum, superparamagnetism and no apparent cytotoxicity. Moreover, the nanoprobe could be used for spatio-controlled cell labeling in the presence of an external magnetic field. The ease of synthesis and cell labeling in vitro make it a suitable candidate for targeted bioimaging applications.

Iron oxide nanoparticles of diameter ca. 12 nm were dispersed into polyelectrolyte complexes made from poly(styrenesulfonate) and poly(diallyldimethylammonium). These nanocomposites were plasticized with salt water and extruded into dense, tough fibers. Magnetometry of these composites showed they retained the superparamagnetic properties of their constituent nanoparticles with saturation magnetization that scaled with the loading of nanoparticles. Their superparamagnetic response allowed the composites to be heated remotely by radiofrequency fields. While the modulus of fibers was unaffected by the presence of nanoparticles the toughness and tensile strength increased significantly.