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.

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.

Hollow spheres have shown fascinating application in bionanotechnology recently, including bioanalysis, diagnostics, drug delivery and therapeutics. However the exploration of hollow spheres via template- and surfactant-free synthesis and using them as sensing material is still at an early stage. In this regard, we described a novel solution-based chemical process to fabricate Ni(OH)2 hollow spheres (Ni(OH)2-HS) assembled from nanosheet building blocks. Ni(OH)2-HS can be obtained with this template-free approach under one-step hydrothermal method. Various techniques, including X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), were used to characterize the morphology and the structure of the as-prepared samples. It was confirmed that the products possess a hollow microsphere structure constructed by interconnecting nanosheet framework. The as-obtained hierarchical structured Ni(OH)2-HS showed excellent catalytic activity toward the oxidation of glucose in alkaline solutions, which enables the Ni(OH)2-HS to be used in enzyme-free amperometric sensors for glucose determination. Furthermore, Ni(OH)2-HS modified glassy carbon electrode (Ni(OH)2-HS/GCE) exhibited a good ability to suppress the background current from large excess ascorbic acid (AA), uric acid (UA) and L-cysteine. Under the optimal conditions, selective detection of glucose in a linear concentration range of 0.8749 μM-7.781 mM was obtained with the limit of 0.1 μM (S/N = 3). Meanwhile, the sensors were also applied to the detection of glucose content in real serum sample with satisfactory results.

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.