In Situ Polymerization of Dopamine on Graphene Framework for Charge Storage Applications

Polydopamine, a functional coating material, is redox active as cathode materials for both Li‐ and Na‐ion batteries or hybrid capacitors. Here, a polydopamine coating onto 3D graphene framework is introduced through a simple hydrothermal process, during which graphene oxide serves not only as an oxidant for assisting the polymerization of dopamine, but also as a template for the conformal growth of polydopamine. High‐density films are fabricated by compressing the polydopamine‐coated graphene aerogels, which can be directly used as free‐standing and flexible cathodes in both Li‐ and Na‐cells. The compact electrodes deliver high capacities of ≈230 mAh g⁻¹ in Li‐cells and ≈211 mAh g⁻¹ in Na‐cells based on the total mass of electrodes. These compact electrodes also exhibit exceptional cycling stability and high rate performance due to the unique structure in which polydopamine is uniformly coated on the 3D structured graphene.     

Drug‐Controlled Release Based on Complementary Base Pairing Rules for Photodynamic–Photothermal Synergistic Tumor Treatment

Controlled drug release systems can enhance the safety and availability but avoid the side effect of drugs. Herein, the concept of DNA complementary base pairing rules in biology is used to design and prepare a photothermal‐triggered drug release system. Adenine (A) modified polydopamine nanoparticles (A‐PDA, photothermal reagent) can effectively bind with thymine (T) modified Zinc phthalocyanine (T‐ZnPc, photosensitizer) forming A‐PDA = T‐ZnPc (PATP) complex based on A = T complementary base pairing rules. Similar to DNA, whose base pairing in double strands will break by heating, T‐ZnPc can be effectively released from A‐PDA after near infrared irradiation–triggered light‐thermal conversion to obtain satisfactory photodynamic–photothermal synergistic tumor treatment. In addition, PDA can carry abundant Gd³⁺ to provide magnetic resonance imaging guided delivery and theranostic function.     

Mussel Adhesion‐Inspired Reverse Transfection Platform Enhances Osteogenic Differentiation and Bone Formation of Human Adipose‐Derived Stem Cells

Using small interfering RNA (siRNA) to regulate gene expression is an emerging strategy for stem cell manipulation to improve stem cell therapy. However, conventional methods of siRNA delivery into stem cells based on solution‐mediated transfection are limited due to low transfection efficiency and insufficient duration of cell‐siRNA contact during lengthy culturing protocols. To overcome these limitations, a bio‐inspired polymer‐mediated reverse transfection system is developed consisting of implantable poly(lactic‐co‐glycolic acid) (PLGA) scaffolds functionalized with siRNA‐lipidoid nanoparticle (sLNP) complexes via polydopamine (pDA) coating. Immobilized sLNP complexes are stably maintained without any loss of siRNA on the pDA‐coated scaffolds for 2 weeks, likely due to the formation of strong covalent bonds between amine groups of sLNP and catechol group of pDA. siRNA reverse transfection with the pDA‐sLNP‐PLGA system does not exhibit cytotoxicity and induces efficient silencing of an osteogenesis inhibitor gene in human adipose‐derived stem cells (hADSCs), resulting in enhanced osteogenic differentiation of hADSCs. Finally, hADSCs osteogenically committed on the pDA‐sLNP‐PLGA scaffolds enhanced bone formation in a mouse model of critical‐sized bone defect. Therefore, the bio‐inspired reverse transfection system can provide an all‐in‐one platform for genetic modification, differentiation, and transplantation of stem cells, simultaneously enabling both stem cell manipulation and tissue engineering.     

Conductive Cellulose Bio-Nanosheets Assembled Biostable Hydrogel for Reliable Bioelectronics

Biostable electronic materials that can maintain their super mechanical and conductive properties, even when exposed to biofluids, are the fundamental basis for designing reliable bioelectronic devices. Herein, cellulose-derived conductive 2D bio-nanosheets as electronic base materials are developed and assembled into a conductive hydrogel with ultra-high biostability, capable of surviving in harsh physiological environments. The bio-nanosheets are synthesized by guiding the in situ regeneration of cellulose crystal into a 2D planar structure using the polydopamine-reduced-graphene oxide as supporting templates. The nanosheet-assembled hydrogel exhibits stable electrical and mechanical performances after undergoing aqueous immersion and in vivo implantation. Thus, the hydrogel-based bioelectronic devices are able to conformally integrate with the human body and stably record electrophysiological signals. Owing to its tissue affinity, the hydrogel further serves as an “E-skin,” which employs electrotherapy to aid in the faster healing of chronic wounds in diabetic mice through transcutaneous electrical stimulation. The nanosheet-assembled biostable, conductive, flexible, and cell/tissue affinitive hydrogel lays a foundation for designing electronically and mechanically reliable bioelectronic devices.     

A Heterostructure Coupling of Bioinspired,Adhesive Polydopamine,and Porous Prussian Blue Nanocubics as Cathode for High‐Performance Sodium‐Ion Battery

Prussian blue (PB) and its analogues are recognized as promising cathodes for rechargeable batteries intended for application in low‐cost and large‐scale electric energy storage. With respect to PB cathodes, however, their intrinsic crystal regularity, vacancies, and coordinated water will lead to low specific capacity and poor rate performance, impeding their application. Herein, nanocubic porous Na_xFeFe(CN)₆ coated with polydopamine (PDA) as a coupling layer to improve its electrochemical performance is reported, inspired by the excellent adhesive property of PDA. As a cathode for sodium‐ion batteries, the Na_xFeFe(CN)₆ electrode coupled with PDA delivers a reversible capacity of 93.8 mA h g^?1 after 500 cycles at 0.2 A g^?1, and a discharge capacity of 72.6 mA h g^?1 at 5.0 A g^?1. The sodium storage mechanism of this Na_xFeFe(CN)₆ coupled with PDA is revealed via in situ Raman spectroscopy. The first‐principles computational results indicate that Fe^II sites in PB prefer to couple with the robust PDA layer to stabilize the PB structure. Moreover, the sodium‐ion migration in the PB structure is enhanced after coating with PDA, thus improving the sodium storage properties. Both experiments and computational simulations present guidelines for the rational design of nanomaterials as electrodes for energy storage devices.     

A Photoresponsive Red‐Hair‐Inspired Polydopamine‐Based Copolymer for Hybrid Photocapacitive Sensors

Inspired by the powerful photosensitizing properties of the red hair pigments pheomelanins, a photoresponsive cysteine‐containing variant of the adhesive biopolymer polydopamine (pDA) is developed via oxidative copolymerization of dopamine (DA) and 5‐S‐cysteinyldopamine (CDA) in variable ratios. Chemical and spectral analysis indicate the presence of benzothiazole/benzothiazine units akin to those of pheomelanins. p(DA/CDA) copolymers display ­impedance properties similar to those of biological materials and a marked photoimpedance response to light stimuli. The use of the p(DA/CDA) copolymer to implement a solution‐processed hybrid photocapacitive/resistive metal‐insulator‐semiconductor (MIS) device disclosed herein is the first example of technological exploitation of photoactive, red‐hair‐inspired biomaterials as soft enhancement layer for silicon in an optoelectronic device. The bio‐inspired materials described herein may provide the active component of new hybrid photocapacitive sensors with a chemically tunable response to visible light.