3D calcite heterostructures for dynamic and deformable mineralized matrices

Matrix-Directed Mineralization for Bulk Structural Materials

Mineral-based bulk structural materials (MBSMs) are known for their long history and extensive range of usage. The inherent brittleness of minerals poses a major problem to the performance of MBSMs. To overcome this problem, design principles have been extracted from natural biominerals, in which the extraordinary mechanical performance is achieved via the hierarchical organization of minerals and organics. Nevertheless, precise and efficient fabrication of MBSMs with bioinspired hierarchical structures under mild conditions has long been a big challenge. This Perspective provides a panoramic view of an emerging fabrication strategy, matrix-directed mineralization, which imitates the in vivo growth of some biominerals. The advantages of the strategy are revealed by comparatively analyzing the conventional fabrication techniques of artificial hierarchically structured MBSMs and the biomineral growth processes. By introducing recent advances, we demonstrate that this strategy can be used to fabricate artificial MBSMs with hierarchical structures. Particular attention is paid to the mass transport and the precursors that are involved in the mineralization process. We hope this Perspective can provide some inspiring viewpoints on the importance of biomimetic mineralization in material fabrication and thereby spur the biomimetic fabrication of high-performance MBSMs.

Synergistic Coupling Derived Cobalt Oxide with Nitrogenated Holey Two-Dimensional Matrix as an Efficient Bifunctional Catalyst for Metal-Air Batteries

Developing cost-effective, efficient bifunctional electrocatalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is the heart of metal-air batteries as a renewable-energy technology. Herein, well-distributed nanopolyhedron (NP) Co₃O₄ grown on iron (Fe) encapsulated in graphitic layers on a nitrogenated, porous two-dimensional (2D) structure, namely, a C₂N matrix, (NP Co₃O₄/Fe@C₂N), presents an outstanding bifunctional catalytic activity with a comparable overpotential and Tafel slope to those of benchmark Pt/C and IrO₂. The rationally designed atomic configuration of Co₃O₄ on the C₂N matrix has a well-controlled NP morphology with a (111) plane, leading to bifunctional activities for the ORR and OER. Interestingly, the specific interaction between the NP Co₃O₄ nanoparticles and the C₂N matrix introduces synergistic coupling and changes the electronic configuration of Co atoms and the C₂N framework. Benefiting from the synergistic coupling of Co₃O₄ with the C₂N matrix, the NP Co₃O₄/Fe@C₂N electrocatalyst exhibits exceptionally high stability and an even lower charge-discharge overpotential gap of 0.85 V at 15 mA cm^-2 than that of the Pt/C+IrO₂ catalyst (1.01 V) in Zn-air batteries. This work provides insights into the rational design of a metal oxide on a C₂N matrix for bifunctional, low-cost electrochemical catalysts.

Close-loop dynamic nanohybrids on collagen-ark with in situ gelling transformation capability for biomimetic stage-specific diabetic wound healing

A self-regulated dynamic nanohybrid that can sensitively respond to hyperglycemic microenvironment is developed. The nanohybrid with a core/shell structure is produced through a single-step microfluidics nanoprecipitation method, where drugs-loaded porous silicon (PSi) nanoparticles are encapsulated by H₂O₂ responsive polymeric matrix.

Biomimetic Approaches Toward Smart Bio-hybrid Systems

Bio-integrated materials and devices can blur the interfaces between living and artificial systems. Microfluidics, bioelectronics and engineered nanostructures, with close interactions with biology at the cellular or tissue levels, have already yielded a spectrum of new applications. Many new designs emerge, including those of organ-on-a-chip systems, biodegradable implants, electroceutical devices, minimally invasive neuro-prosthetic tools, and soft robotics. In this review, we highlight a few recent advances on the fabrication and application of the smart bio-hybrid systems, with a particular emphasis on the three-dimensional (3D) bio-integrated devices that mimick the 3D feature of tissue scaffolds. Moreover, neurons integrated with engineered nanostructures for wireless neuromodulation and dynamic neural output will be briefly discussed. We will also go over the progress in the construction of cell-enabled soft robotics, where a tight coupling of the synthetic and biological parts is crucial for efficient functions. Finally, we summarize the approaches for enhancing bio-integration with biomimetic micro- and nanostructures.

Talking to cells: semiconductor nanomaterials at the cellular interface

The interface of biological components with semiconductors is a growing field with numerous applications. For example, the interfaces can be used to sense and modulate the electrical activity of single cells and tissues. From the materials point of view, silicon is the ideal option for such studies due to its controlled chemical synthesis, scalable lithography for functional devices, excellent electronic and optical properties, biocompatibility and biodegradability. Recent advances in this area are pushing the bio-interfaces from the tissue and organ level to the single cell and sub-cellular regimes. In this progress report, we will describe some fundamental studies focusing on miniaturizing the bioelectric and biomechanical interfaces. Additionally, many of our highlighted examples involve freestanding silicon-based nanoscale systems, in addition to substrate-bound structures or devices; the former offers new promise for basic research and clinical application. In this report, we will describe recent developments in the interfacing of neuronal and cardiac cells and their networks. Moreover, we will briefly discuss the incorporation of semiconductor nanostructures for interfacing non-excitable cells in applications such as probing intracellular force dynamics and drug delivery. Finally, we will suggest several directions for future exploration.