Unnatural Amino Acids for Biological Spectroscopy and Microscopy.

Due to advances in methods for site-specific incorporation of unnatural amino acids (UAAs) into proteins, a large number of UAAs with tailored chemical and/or physical properties have been developed and used in a wide array of biological applications. In particular, UAAs with specific spectroscopic characteristics can be used as external reporters to produce additional signals, hence increasing the information content obtainable in protein spectroscopic and/or imaging measurements. In this Review, we summarize the progress in the past two decades in the development of such UAAs and their applications in biological spectroscopy and microscopy, with a focus on UAAs that can be used as site-specific vibrational, fluorescence, electron paramagnetic resonance (EPR), or nuclear magnetic resonance (NMR) probes. Wherever applicable, we also discuss future directions.

Engineering contact curved interface with high-electronic-state active sites for high-performance potassium-ion batteries.

Potassium-ion batteries (PIBs) have attracted ever-increasing interest due to the abundant potassium resources and low cost, which are considered a sustainable energy storage technology. However, the graphite anodes employed in PIBs suffer from low capacity and sluggish reaction kinetics caused by the large radius of potassium ions. Herein, we report nitrogen-doped, defect-rich hollow carbon nanospheres with contact curved interfaces (CCIs) on carbon nanotubes (CNTs), namely CCI-CNS/CNT, to boost both electron transfer and potassium-ion adsorption. Density functional theory calculations validate that engineering CCIs significantly augments the electronic state near the Fermi level, thus promoting electron transfer. In addition, the CCIs exhibit a pronounced affinity for potassium ions, promoting their adsorption and subsequently benefiting potassium storage. As a result, the rationally designed CCI-CNS/CNT anode shows remarkable cyclic stability and rate capability. This work provides a strategy for enhancing the potassium storage performance of carbonaceous materials through CCI engineering, which can be further extended to other battery systems.

Cooperative Dynamic Game-Based Optimal Power Control in Wireless Sensor Network Powered by RF Energy.

This paper focuses on optimal power control in wireless sensor networks powered by RF energy, under the simultaneous wireless information and power transfer (SWIFT) protocol, where the information and power can be transmitted at the same time. We aim to maximize the utility for each sensor through the optimal power control, considering the influences of both the SINR and the harvested energy. The utility maximization problem is formulated as a cooperative dynamic game of a given time duration. All the sensors cooperate together to control their transmission power to maximize the utility and agree to act cooperatively so that a team optimum can be achieved. As a result, a feedback Nash equilibrium solution for each sensor is given based on the dynamic programming theory. Simulation results verify the effectiveness of the proposed approach, by comparing the grand coalition solutions with the non-cooperative solutions.

Shape Memory Polyester Scaffold Promotes Bone Defect Repair through Enhanced Osteogenic Ability and Mechanical Stability.

Bone tissue engineering involving scaffolds is recognized as the ideal approach for bone defect repair. However, scaffold materials exhibit several limitations, such as low bioactivity, less osseointegration, and poor processability, for developing bone tissue engineering. Herein, a bioactive and shape memory bone scaffold was fabricated using the biodegradable polyester copolymer's four-dimensional fused deposition modeling. The poly(ε-caprolactone) segment with a transition temperature near body temperature was selected as the molecular switch to realize the shape memory effect. Another copolymer segment, i.e., poly(propylene fumarate), was introduced for post-cross-linking and improving the regulation effect of the resulting bioadaptable scaffold on osteogenesis. To mimic the porous structures and mechanical properties of the native spongy bone, the pore size of the printed scaffold was set as ∼300 µm, and a comparable compression modulus was achieved after photo-cross-linking. Compared with the pristine poly(ε-caprolactone), the scaffold made from fumarate-functionalized copolymer considerably enhanced the adhesion and osteogenic differentiation of MC3T3-E1 cells in vitro. In vivo experiments indicated that the bioactive shape memory scaffold could quickly adapt to the defect geometry during implantation via shape change, and bone regeneration at the defect site was remarkably promoted, providing a promising strategy to treat bone defects in the clinic, substantial bone defects with irregular geometry.

4D Printing of Biocompatible Scaffolds via In Situ Photo-crosslinking from Shape Memory Copolyesters.

The complexity of surgical treatments for large-area soft tissue injuries makes placing large implants into injury sites challenging. Aliphatic polyesters are often used for scaffold preparation in tissue engineering owing to their excellent biodegradability and biocompatibility. Scaffolds with shape-memory effect (SME) can also avoid large-volume trauma during the implantation. However, the complexity and diversity of diseases require more adaptable and precise processing methods. Four-dimensional (4D) printing, a booming smart material additive manufacturing technology, provides a new opportunity for developing shape memory scaffolds. With the aim of personalized or patient-adaptable soft tissues such as blood vessels, we developed a feasible strategy for fabricating scaffolds with fine architectures using 4D printing crosslinkable shape memory linear copolyesters using fused deposition modeling (FDM). To overcome the weak bonding strength of each printed layer during FDM, a catalyst-free photo-crosslinkable functional group derived from biocompatible cinnamic acid was embedded into the linear copolyesters as in situ crosslinking points during FDM printing. Under ultraviolet-assisted irradiation, the resulting 4D scaffold models demonstrated excellent SME, desirable mechanical performance, and good stability in a water environment owing to the chemical bonding between each layer. Moreover, the excellent biocompatibility of the scaffold was evaluated in vitro and in vivo. The developed composite scaffolds could be used for minimally invasive soft tissue repair.

Electrospun carbon-based nanomaterials for next-generation potassium batteries.

Rechargeable potassium (K) batteries that are of low cost, with high energy densities and long cycle lives have attracted tremendous interest in affordable and large-scale energy storage. However, the large size of the K-ion leads to sluggish reaction kinetics and causes a large volume variation during the ion insertion/extraction processes, thus hindering the utilization of active electrode materials, triggering a serious structural collapse, and deteriorating the cycling performance. Therefore, the exploration of suitable materials/hosts that can reversibly and sustainably accommodate K-ions and host K metals are urgently needed. Electrospun carbon-based materials have been extensively studied as electrode/host materials for rechargeable K batteries owing to their designable structures, tunable composition, hierarchical pores, high conductivity, large surface areas, and good flexibility. Here, we present the recent developments in electrospun CNF-based nanomaterials for various K batteries (e.g., K-ion batteries, K metal batteries, K-chalcogen batteries), including their fabrication methods, structural modulation, and electrochemical performance. This Feature Article is expected to offer guidelines for the rational design of novel electrospun electrodes for the next-generation K batteries.