Li Yao

Amphiphilic Janus Particles Generated via a Combination of Diffusion-Induced Phase Separation and Magnetically Driven Dewetting and Their Synergistic Self-Assembly

Amphiphilic Janus particles are successfully obtained via a powerful strategy combining diffusion-induced phase separation and magnetically driven dewetting. A large-area, amphiphilic monolayer is been formed via a self-assembly paradigm based on a synergy between the amphiphilicity, shape anisotropy, and external magnetic field. This functionality holds great promise for practical applications in intelligent coatings, anti-bioadhesion, and antifouling surfaces.

Recent advances in biological detection with magnetic nanoparticles as a useful tool

Magnetic nanoparticles have emerged as a powerful tool for magnetic resonance imaging, biodetection, drug delivery, and hyperthermia. This review focuses on the biological detection of magnetic nanoparticles as well as their physicochemical properties. Substantial progress in the sensitivity of detection has been made by developing variety of methods. Five applications of magnetic nanoparticles in biological detection are discussed in this review: magnetic separation, magnetic sensing, magnetic manipulation, magnetic catalysis, and signal enhancer for surface plasmon resonance (SPR). Finally, some future trends and perspectives in these research areas are outlined.

Well-Defined and Sequence-Specific Noncovalent Binding Forces of DNA

The specific binding between the two DNA strands in a double helix is one of the most fundamental and influential molecular interactions in biochemistry. Using force-induced remnant magnetization spectroscopy (FIRMS), we obtained well-defined binding forces of DNA oligomers, with a narrow force distribution of 1.8 pN. The narrow force distribution allows for directly resolving two DNA duplexes with a single base-pair difference in the same sample. Therefore, binding force can serve as a discriminating parameter for probing different DNA interactions. Furthermore, we observed that the binding forces depend on the position of the mismatching base pair. Our results show that FIRMS is capable of high-precision mechanical measurements of biochemical processes involving multiple DNA interactions and has the potential for characterizing the binding strength of materials based on DNA origami.

Magnetic Ni/SiO2 composite microcapsules prepared by one-pot synthesis

The Ni/SiO2 composite microcapsules were prepared by a one-pot synthesis via thermally decomposing Ni(acac)2·2H2O in 2-pyrrolidone in the presence of tetraethyloxysilane and 3-aminopropyltrimethoxysilane (APS). Transmission electron microscopy and powder X-ray diffraction were used to characterize the general morphology of the resultant capsules as well as the crystalline phases of the Ni nanocrystals incorporated. Ultraviolet photoelectron spectroscopy and ultraviolet photoionization mass spectroscopy were adopted to analyze the gaseous species released during the reaction to elucidate the mechanism behind the formation of the Ni/SiO2 composite microcapsules. Preliminary experiments were designed to show the catalytic ability of the resultant capsules which were collectable by applying an external magnetic field.

Generation, Characterization, and Application of Hierarchically Structured Self-Assembly Induced by the Combined Effect of Self-Emulsification and Phase Separation.

Hierarchically structured magnetic single-hole hollow spheres (MSHS) have been successfully obtained via a facile self-assembly strategy. This methodology allows the double emulsions generated via the combined effect of self-emulsification and phase separation to provide confinement for directing the self-assembly of magnetic nanoparticles (MNPs). The resulting MSHS fully capitalize on both the multifunctional properties of MNPs and container features of single-hole hollow spheres. Moreover, the magnetic properties showed obvious improvement and can be tuned by modulating the assembled structure. Thus, MSHS can be used as a smart platform with multiple functionalities including image contrast enhancement, selective encapsulation for biomacromolecules, on-demand release, and magnetically guided transport. This strategy is very promising in the design of hierarchically structured assemblies for desired applications in biomedicine and other fields.

Force-induced selective dissociation of noncovalent antibody-antigen bonds.

Specific noncovalent binding between antibody and antigen molecules is the basis for molecular recognition in biochemical processes. Quantitative investigation of the binding forces could lead to molecular specific analysis and potentially mechanical manipulation of these processes. Using our force-induced remnant magnetization spectroscopy, we revealed a well-defined binding force for the bonds between mouse immunoglobulin G and magnetically labeled α-mouse immunoglobulin G. The force was calibrated to be 120 ± 15 pN. In comparison, the binding force was only 17 ± 3 pN for physisorption and much higher than 120 pN for biotin-streptavidin bonds. A unique rebinding method was used to confirm the dissociation of the antibody-antigen bonds. A well-defined and molecule-specific binding force opens a new avenue for distinguishing different noncovalent bonds in biochemical processes.

Optical atomic magnetometer at body temperature for magnetic particle imaging and nuclear magnetic resonance

Optical atomic magnetometers are often bulky and operate at elevated temperatures that impose restrictions on studying biological samples. Here we report a miniaturized Cs-based magnetometer, in contrast to conventionally used K- and Rb-based ones, with high sensitivity. The magnetic shield employed is more compact, and the optimal operation temperature of 37 degrees C is lower than previous magnetometers and is suitable for biological research. Applications include scanning magnetic imaging of functionalized magnetic particles and nuclear magnetic resonance of water. We reveal that the stability and sensitivity of the apparatus are not significantly affected by the absence of a laser stabilization device.

Detection of magnetic nanomaterials in molecular imaging and diagnosis applications

Abstract Advances in bionanotechnology promise to allow medical diagnosis and therapy through the channel of molecular imaging. Combining biological science and modern detection techniques, molecular imaging has the ability to penetrate biomedical processes at the molecular and cellular level. Magnetic nanoparticles (MNP), broadly defined as particles of tens of nm to approximately 2 μm in diameter in this review, are playing an increasingly important role in molecular imaging. They act as contrast agents to remarkably enhance the signal. The precise determination of the position and quantity of MNP is critical for these applications. This review describes the advances in the development of detection techniques for magnetic particles used in molecular imaging and diagnosis. The techniques are categorized as high magnetic field techniques and low magnetic field techniques. The high-field studies focus on magnetic resonance imaging (MRI). The ultra-low-field (ULF) studies include several of the most recent techniques: giant magnetoresistance sensors, superconducting quantum interference devices, atomic magnetometers, and magnetic particle imaging. The advantages and disadvantages of each method are discussed.

Applications of optically detected MRI for enhanced contrast and penetration in metal.

We report quantitative measurements using optically detected magnetic resonance imaging (MRI) for enhanced pH contrast and flow inside porous metals. Using a gadolinium chelate as the pH contrast agent, we show the response is 0.6s(-1) mM(-1) per pH unit at the ambient magnetic field for the pH range 6-8.5. A stopped flow scheme was used to directly measure T(1) relaxation time to determine the relaxivity. Flow profiles and images were obtained for a series of porous metals with different average pore sizes. The signal amplitudes and spatial distributions were compared. A clogged region in one of the samples was revealed using optically detected MRI but not optical imaging or scanning electron microscopy. These applications will significantly broaden the impact of optically detected MRI in chemical imaging and materials research.

Dual-Phase Separation in a Semiconfined System: Monodispersed Heterogeneous Block-Copolymer Membranes for Cell Encoding and Patterning

Block copolymers (BCPs) have the capacity to self-assemble into a myriad of well-defined aggregate structures, offering great promise for the construction of drug delivery, photolithographic templates, and complex nanoscale assemblies. A uniqueness of these materials is their propensity to become kinetically frozen in non-equilibrium states, implying that the process of self-assembly can be utilized to remodel the resulting structures. Here, a new semiconfined system for processing the BCP self-assembly is constructed, in which an unusual dual-phase separation occurs, including nonsolvent-induced microphase separation and osmotically driven macrophase separation, ultimately yielding heterogeneous BCP membranes. These membranes with cellular dimensions show unique anisotropy that can be used for cell encoding and patterning, which are highly relevant to biology and medicine. This processing method not only provides new levels of tailorability to the structures and encapsulated contents of BCP assemblies, but can also be generalized to other block polymers, particularly those with attractive electronic and/or optical properties.