Search

Ferroelectricity in metal-free perovskites (MFPs) has emerged as an academic hotspot for their lightweight, eco-friendly processability, flexibility, and degradability, with considerable progress including large spontaneous polarization, high Curie temperature, large piezoelectric response, and tailoring coercive field. However, their equivalent polarization axes as a key indicator are far from enough, although multiaxial ferroelectrics are highly preferred for performance output and application flexibility that profit from as many equivalent polarization directions as possible with easier reorientation. Here, by implementing the synergistic overlap of regulating anionic geometries (from spherical I - to octahedral [PF 6 ] - and to tetrahedral [ClO 4 ] - or [BF 4 ] - ) and cationic asymmetric modification, we successfully designed multiaxial MFP ferroelectrics CMDABCO-NH 4 -X 3 (CMDABCO = N -chloromethyl- N '-diazabicyclo[2.2.2]octonium; X = [ClO 4 ] - or [BF 4 ] - ) with the lowest P 1 symmetry. More impressively, systemic characterizations indicate that they possess 24 equivalent polarization axes (Aizu notations of 432F1 and m 3̅ m F1, respectively)─the maximum number achievable for ferroelectrics. Benefiting from the multiaxial feature, CMDABCO-NH 4 -[ClO 4 ] 3 has been demonstrated to have excellent piezoelectric sensing performance in its polycrystalline sample and prepared composite device. Our study provides a feasible strategy for designing multiaxial MFP ferroelectrics and highlights their great promise for use in microelectromechanical, sensing, and body-compatible devices.

Since the concept of "multiferroic" was first proposed in 1968, the coupling effect between different ferroic orders has attracted great interest in energy, information, and biomedical fields. However, the fully ferroelectric-fully ferroelastic effect has never been experimentally observed in hybrid perovskites, even though this effect was predicted to exist half a century ago. Realizing such cross-linking effects of polarization vectors and strain tensors has always been a huge challenge because of the complex difference in these two ferroic origins. Here, we report a multiferroic with full ferroelectricity and full ferroelasticity in two-dimensional (2D) hybrid perovskites based on ferroelectrochemistry. The dynamic molecular reorientations endow (cyclohexanemethylaminium) 2 PbCl 4 with a desired symmetry change of 4̅2 m F mm 2 at a Curie temperature of 411.8 K. More strikingly, the switchable evolution of ferroelastic domains was directly observed under the control of either electric or mechanical fields, which is the first experimental observation of a fully ferroelectric-fully ferroelastic effect in hybrid perovskites. This work would provide new insights into understanding the intrinsic cross-linking mechanism between ferroelectricity and ferroelasticity toward the development of multichannel interactive microelectronic devices.

The ability of drugs to cross the blood-brain barrier (BBB) is crucial for treating central nervous system (CNS) disorders. Inspired by natural viruses, here we report a glucose and polydopamine (GPDA) coating method for the construction of delivery platforms for efficient BBB crossing. Such platforms are composed of nanoparticles (NPs) as the inner core and surface functionalized with glucose-poly(ethylene glycol) (Glu-PEG) and polydopamine (PDA) coating. Glu-PEG provides selective targeting of the NPs to brain capillary endothelial cells (BCECs), while PDA enhances the transcytosis of the NPs. This strategy is applicable to gold NPs (AuNPs), silica, and polymeric NPs, which achieves as high as 1.87% of the injected dose/g of brain in healthy brain tissues. In addition, the GPDA coating manages to deliver NPs into the tumor tissue in the orthotopic glioblastoma model. Our study may provide a universal strategy for the construction of delivery platforms for efficient BBB crossing and brain drug delivery.

Metal-organic frameworks (MOFs) show tremendous promise for drug delivery due to their structural and functional versatility. However, MOFs are usually used as biologically inert carriers in most cases. The creation of intrinsically immunostimulatory MOFs remains challenging. In this study, a facile and green synthesis method is proposed for the preparation of a manganese ion (Mn 2+ )-based immunostimulatory MOF (ISAMn-MOF) for cancer metalloimmunotherapy. ISAMn-MOF significantly facilitates the activation of cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) related genes and signaling pathways in bone-marrow-derived dendritic cells (BMDCs). BMDCs treated with ISAMn-MOF secrete 4-fold higher type I interferon and 2- to 16-fold higher proinflammatory cytokines than those treated with equivalent MnCl 2 . ISAMn-MOF alone or its combination with immune checkpoint antibodies significantly suppresses tumor growth and metastasis and prolongs mouse survival. Mechanistic studies indicate that ISAMn-MOF treatment facilitates the infiltration of stimulatory immune cells in tumors and lymphoid organs. This study provides insight into the design of bioactive MOFs for improved cancer metalloimmunotherapy.

Enabling macrophages to phagocytose tumor cells holds great potential for cancer therapy but suffers from tremendous challenges because the tumor cells upregulate antiphagocytosis molecules (such as CD47) on their surface. The blockade of CD47 alone is insufficient to stimulate tumor cell phagocytosis in solid tumors due to the lack of "eat me" signals. Herein, a degradable mesoporous silica nanoparticle (MSN) is reported to simultaneously deliver anti-CD47 antibodies (aCD47) and doxorubicin (DOX) for cancer chemo-immunotherapy. The codelivery nanocarrier aCD47-DMSN was constructed by accommodating DOX within the mesoporous cavity, while adsorbing aCD47 on the surface of MSN. aCD47 blocks the CD47-SIRPα axis to disable the "don't eat me" signal, while DOX induces immunogenic tumor cell death (ICD) for calreticulin exposure as an "eat me" signal. This design facilitated the phagocytosis of tumor cells by macrophages, which enhanced antigen cross-presentation and elicited efficient T cell-mediated immune response. In 4T1 and B16F10 murine tumor models, aCD47-DMSN generated a strong antitumor effect after intravenous injection by increasing tumor-infiltration of CD8 + T cells. Taken together, this study offers a nanoplatform to modulate the phagocytosis of macrophages for efficacious cancer chemo-immunotherapy.

Two-dimensional transition-metal carbides/carbonitrides (MXenes) with both superb electrical conductivity and hydrophilicity are promising for fabricating multifunctional nanomaterials and nanocomposites. However, the construction of three-dimensional (3D) and lightweight MXene macroscopic assemblies with excellent electrical conductivity and mechanical performances has not been realized due to the weak gelation capability of MXene sheets. Herein, we demonstrate an efficient approach for constructing highly conductive 3D Ti 3 C 2 T x porous architectures by graphene oxide assisted hydrothermal assembly followed by directional freezing and freeze-drying. The resultant hybrid aerogels exhibit aligned cellular microstructure, in which the graphene sheets serve as the inner skeleton, while the compactly attached Ti 3 C 2 T x sheets present as shells of the cell walls. The porous and highly conductive architecture (up to 1085 S m -1 ) is highly efficient in endowing epoxy nanocomposite with a high electrical conductivity of 695.9 S m -1 and an outstanding electromagnetic interference (EMI)-shielding effectiveness of more than 50 dB in the X-band at a low Ti 3 C 2 T x content of 0.74 vol %, which are the best results for polymer nanocomposites with similar loadings of MXene so far. The successful assembly methodology of 3D and porous architectures of Ti 3 C 2 T x would greatly widen the practical applications of MXenes in the fields of EMI shielding, supercapacitors, and sensors.