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Psoriasis is a chronic skin inflammation influenced by dysregulated skin microbiota, with the role of microbiota in psoriasis gaining increasing prominence. Bacterial extracellular vesicles (bEVs) serve as crucial regulators in the interaction between hosts and microbiota. However, the mechanism underlying the therapeutic potential of bEVs from commensal bacteria in psoriasis remains unclear. Here, we investigated the therapeutic role of Cutibacterium acnes (C. acnes)-derived extracellular vesicles (CA-EVs) in psoriasis treatment. To prolong the active duration of CA-EVs, we encapsulated them in gelatin methacrylate (GelMA) to fabricate hydrogel microspheres (CA-EVs@GHM) with sustained release properties. As GelMA degraded, CA-EVs were gradually released, maintaining a high concentration in mouse skin even 96 h post-treatment. In human keratinocyte cells (HaCaT), CA-EVs@GHM enhanced resistance to Staphylococcus aureus (S. aureus), promoted proliferation and migration of HaCaT cells exposed to S. aureus , and significantly reduced the expression of inflammatory genes such as interleukin (IL)-6 and C-X-C motif chemokine ligand 8 (CXCL8). In vivo , CA-EVs@GHM, more potent than CA-EVs alone, markedly attenuated proinflammatory gene expression, including tumor necrosis factor (TNF), Il6, Il17a, Il22 and Il23a in imiquimod (IMQ)-induced psoriasis-like mice, and restored skin barrier function. 16S rRNA sequencing revealed that CA-EVs@GHM might provide therapeutic effects against psoriasis by restoring microbiota diversity on the back skin of mice, reducing Staphylococcus colonization, and augmenting lipid metabolism. Furthermore, flow cytometry analysis showed that CA-EVs@GHM prevented the conversion of type 2 innate lymphoid cells (ILC2) to type 3 innate lymphoid cells (ILC3) in psoriasis-like mouse skin, reducing the pathogenic ILC3 population and suppressing the secretion of IL-17 and IL-22. In summary, our findings demonstrate that the long-term sustained release of CA-EVs alleviated psoriasis symptoms by controlling the transformation of innate lymphoid cells (ILCs) subgroups and restoring skin microbiota homeostasis, thus offering a promising therapy for psoriasis treatment. Cutibacterium acnes , which is reduced in psoriasis skin, has been reported to promote skin homeostasis by regulating immune balance. Compared to live bacteria, bacterial extracellular vesicles (bEVs) are less prone to toxicity and safety concerns. bEVs play a pivotal role in maintaining bacterial homeostasis and modulating the immune system. However,bEVs without sustained release materials are unable to function continuously in chronic diseases. Therefore, we utilized hydrogel microspheres to encapsulate Cutibacterium acnes (C. acnes)-derived extracellular vesicles (CA-EVs), enabling long term sustained release. Our findings indicate that, CA-EVs loaded gelatin methacrylate hydrogel microspheres (CA-EVs@GHM) showed superior therapeutic effects in treating psoriasis compared to CA-EVs. CA-EVs@GHM exhibited a more significant regulation of pathological type 3 innate lymphoid cells (ILC3) and skin microbiota, providing a promising approach for microbiota-derived extracellular vesicle therapy in the treatment of skin inflammation. [Display omitted] [ABSTRACT FROM AUTHOR]

Boron carbide-alumina (B 4 C–Al 2 O 3) composite ceramics were fabricated using boron carbide (B 4 C) as the matrix and alumina (Al 2 O 3) as the second phase by hot-press sintering at 1950 °C. The phase composition, microstructure, relative density, mechanical properties, and toughening mechanism of the composite ceramics were evaluated. When the content of Al 2 O 3 is 30 wt%, the composite ceramics show the best comprehensive mechanical properties. The relative density, Vickers hardness, flexural strength, and fracture toughness of the obtained B 4 C-30 wt%Al 2 O 3 composite ceramics reach up to 98.8 %, 24.7 GPa, 477 MPa, and 4.64 MPa m1/2, respectively. The introduction of Al 2 O 3 as the second phase can significantly improve the fracture toughness of the B 4 C ceramics. Firstly, when cracks extend to the Al 2 O 3 grains, the cleavage fracture of the Al 2 O 3 grains resulting from its crystal structure causes the crack deflection along the cleavage plane. Secondly, due to the mismatch of the coefficient of thermal expansion between B 4 C and Al 2 O 3 , residual stress is generated at the grain boundary of the two phases and within the grains. The tensile stress at the grain boundary can cause some cracks to extend along the grain boundary, making cracks deflected, and the compressive stress within the B 4 C grains can inhibit crack extension. Thirdly, submicron-sized Al 2 O 3 grains wrapped within the B 4 C grains form a subboundary structure, which can lead to crack extension along the subboundary. All of these factors consume the crack extension energy, which can contribute to increasing the fracture toughness of B 4 C–Al 2 O 3 composite ceramics. [ABSTRACT FROM AUTHOR]

The friction and wear of B 4 C ceramics with different contents of Al 2 O 3 /Y 2 O 3 sintering additives were studied under dry sliding. With the increase of Al 2 O 3 /Y 2 O 3 content, the friction coefficient of B 4 C ceramics decreases first and then increases, and the wear rate of B 4 C ceramics decreases gradually. The friction coefficient of B 4 C ceramics is related to the amount of wear debris generated on the sliding interface, which is determined by the competition between the number of pores that can trap the wear debris and the degree of grain pullout and grain fracture. When the content of Al 2 O 3 /Y 2 O 3 is 5 wt%, the amount of wear debris on the sliding interface is the least, leading to the lowest friction coefficient. The wear rates of B 4 C ceramics are controlled by the competition of the beneficial effect of improved relative density and mechanical properties and the adverse effect of weak bonding between B 4 C grains due to the formation of intergranular phase. The gradually decreased wear rate of B 4 C ceramics with the increased content of Al 2 O 3 /Y 2 O 3 is attributed to the improved relative density and mechanical properties. [ABSTRACT FROM AUTHOR]