Summary Modeling the in vivo microenvironment typically involves placing cells in a three-dimensional (3D) extracellular matrix (ECM) in physiologically relevant context with respect to other cells. The mechanical and chemical features of 3D microenvironments play important roles in tissue engineering, tumor growth and metastasis, and in defining stem cell niches, and it is increasingly recognized that cells behave much differently when surrounded by a 3D ECM than when anchored to a 2D substrate. To create microenvironments that more closely mimic in vivo settings, here we describe a novel microfluidic device that allows multiple discrete constructs of 3D cell-laden hydrogels to be patterned in a sequence of simple steps. The microfluidic platform allows for real time imaging of the interactions between multiple cell types exposed to both autocrine and paracrine signaling molecules, all within a 3D ECM environment. Detailed modeling determined that surface tension, hydrophobic interactions, and spatial geometry were important factors in containing the gels within distinct separate channels during the filling process. This allowed us to pattern multiple gel types side-by-side and pattern 3D gels spatially with tight dimensional control. Cells embedded in gels could be patterned by culturing MDA-MB-231 metastatic breast cancer cells and RAW 264.1 macrophage cells within distinct collagen type I and Matrigel ECM environments, respectively. Over a 7 day culture experiment, RAW cells invaded into neighboring gels containing MDA-MB-231 cells, but not into gels lacking cells. These studies demonstrate the versatility and potential of this new microfluidic platform to engineer 3D microscale architectures to investigate cell-cell and cell-matrix interactions.

Targeted drug delivery using nanoparticles can minimize the side effects of conventional pharmaceutical agents and enhance their efficacy. However, translating nanoparticle-based agents into clinical applications still remains a challenge due to the difficulty in regulating interactions on the interfaces between nanoparticles and biological systems. Here, we present a targeting strategy for nanoparticles incorporated with a supramolecularly pre-coated recombinant fusion protein in which HER2-binding affibody combines with glutathione-S-transferase. Once thermodynamically stabilized in preferred orientations on the nanoparticles, the adsorbed fusion proteins as a corona minimize interactions with serum proteins to prevent the clearance of nanoparticles by macrophages, while ensuring systematic targeting functions in vitro and in vivo. This study provides insight into the use of the supramolecularly built protein corona shield as a targeting agent through regulating the interfaces between nanoparticles and biological systems.

While the realization of clean and sustainable energy conversion systems primarily requires the development of highly efficient catalysts, one of the main issues had been designing the structure of the catalysts to fulfill minimum cost as well as maximum performance. Until now, noble metal-based nanocatalysts had shown outstanding performances toward the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER). However, the scarcity and high cost of them impeded their practical use. Recently, hollow nanostructures including nanocages and nanoframes had emerged as a burgeoning class of promising electrocatalysts. The hollow nanostructures could expose a high proportion of active surfaces while saving the amounts of expensive noble metals. In this review, we introduced recent advances in the synthetic methodologies for generating noble metal-based hollow nanostructures based on thermodynamic and kinetic approaches. We summarized electrocatalytic applications of hollow nanostructures toward the ORR, OER, and HER. We next provided strategies that could endow structural robustness to the flimsy structural nature of hollow structures. Finally, we concluded this review with perspectives to facilitate the development of hollow nanostructure-based catalysts for energy applications.

Pt-based intermetallic nanostructures have demonstrated higher electrocatalytic performances compared to random alloy structures. However, the origin of their enhanced catalytic properties remains elusive. Furthermore, a robust synthetic strategy for well-defined intermetallic nanostructures represents a challenge. Here, we reveal by combining theoretical and experimental results that the activity enhancement in intermetallic structures for the oxygen reduction reaction (ORR) originates from an intensified ligand effect. We prepared well-defined model nanocatalysts via confined nanospace-directed synthesis using mesoporous silica templates, which allows precise control over the size and shape of nanostructures. Importantly, this method can transform disordered alloy nanostructures into intermetallic analogues without agglomeration, enabling decoupling of an atomic ordering effect in catalysis. The prepared ordered intermetallic Pt3Co nanowires (O-Pt3Co NWs) can benefit from an intensified ligand effect, Pt-skin layer, and agglomeration-tolerant contiguous structure, which led to their enhanced ORR activity and durability compared to disordered alloy Pt3Co nanowires (D-Pt3Co NWs) and Pt/C catalysts. The multifunctionality of O-Pt3Co NWs is demonstrated with their higher activity and durability in the alkaline hydrogen evolution reaction and acidic methanol oxidation reaction than those of D-Pt3Co NWs and Pt/C catalysts. Furthermore, a proton exchange membrane fuel cell cathode based on O-Pt3Co NWs shows much better durability than a Pt/C-based one.

Microrobots that are light and agile yet require no artificial power input can be widely used in medical, military, and industrial applications. As an actuation system to drive such robots, here we report a biologically inspired bilayer structure that harnesses the environmental humidity energy, with ratchets to rectify the motion. We named this actuator-ratchet system the hygrobot. The actuator uses a hygroscopically responsive film consisting of aligned nanofibers produced by directional electrospinning, which quickly swells and shrinks in lengthwise direction in response to the change of humidity. The ratchets based on asymmetric friction coefficients rectify oscillatory bending motion in a directional locomotion. We mathematically analyzed the mechanical response of the hygrobot, which allowed not only prediction of its performance but also the optimal design to maximize the locomotion speed given geometric and environmental constraints. The hygrobot sterilized a trail across an agar plate without any artificial energy supply.

EPSCC was identified in various sites, with the most common primary site being the uterine cervix. Regardless of the primary site or disease stage, EPSCC of sites other than cervix was usually a fatal disease with a discouraging outcome for various treatment modalities.

Noble metal binary alloy nanoframes have emerged as a new class of fuel cell electrocatalysts because of their intrinsic high catalytic surface area and accompanied high catalytic activity. However, their inferior structural and compositional stability during catalysis pose as formidable huddles to their practical applications. Herein, it is reported that introduction of an additional component to the binary catalytic system may serve as a simple and effective means of enhancing the structural and compositional stability of nanoframe‐based electrocatalysts. It is demonstrated that in situ doping of Co to the PtCu alloy nanoframe yields a ternary PtCuCo rhombic dodecahedral nanoframe (Co‐PtCu RNF) with a reinforced vertex structure. Co‐PtCu RNF exhibits superior electrocatalytic activity and durability for the oxygen reduction reaction to those of PtCu rhombic dodecahedral nanoframe (PtCu RNF) and Pt/C catalysts, due to its ternary composition and vertex‐strengthened frame structure. Furthermore, Co‐PtCu RNF shows enhanced activity for the methanol oxidation reaction as compared to PtCu RNF and Pt/C.

Nanoframe alloy structures represent a class of high-performance catalysts for the oxygen reduction reaction (ORR), owing to their high active surface area, efficient molecular accessibility, and nanoconfinement effect. However, structural and chemical instabilities of nanoframes remain an important challenge. Here, we report the synthesis of PtCu nanoframes constructed with an atomically ordered intermetallic structure (O-PtCuNF/C) showing high ORR activity, durability, and chemical stability. We rationally designed the O-PtCuNF/C catalyst by combining theoretical composition predictions with a silicacoating-mediated synthesis. The O-PtCuNF/C combines intensified strain and ligand effects from the intermetallic PtCu L1 1 structure and advantages of the nanoframes, resulting in superior ORR activity to disordered alloy PtCu nanoframes (D-PtCuNF/C) and commercial Pt/C catalysts. Importantly, the O-PtCuNF/C showed the highest ORR mass activity among PtCu-based catalysts. Furthermore, the O-PtCuNF/C exhibited higher ORR durability and far less etching of constituent atoms than D-PtCuNF/C and Pt/C, attesting to the chemically stable nature of the intermetallic structure.