The development of a safe and effective adjuvant that amplifies the immune response to an antigen is important for vaccine delivery. In this study, we developed pristine mesoporous carbon hollow spheres as high-capacity vaccine protein nanocarriers and safe adjuvants for boosting the immune response. Mono-dispersed invaginated mesostructured hollow carbon spheres (IMHCSs) have an average particle size of ~200 nm, large pore size of 15 nm, and high pore volume of 2.85 cm³·g^-1. IMHCSs exhibited a very high loading capacity (1, 040 μg·mg^-1) towards ovalbumin (OVA, a model antigen), controlled OVA release behavior, excellent safety profile to normal cells, and high antigen delivery efficacy towards macrophages. In vivo immunization studies in mice demonstrated that OVA-loaded IMHCSs induced a 3-fold higher IgG response compared to a traditional adjuvant QuilA used in veterinary vaccine research. OVA delivered by IMHCSs induced a higher IgG1 concentration than IgG2a, indicating a T-helper 2 (Th2)-polarized response. Interferon-γ and interleukin-4 concentration analysis revealed both T-helper 1 (Th1) and Th2 immune responses induced by OVA-loaded IMHCSs. IMHCSs are safer adjuvants than QuilA. Our study revealed that pure IMHCSs without further functionalization can be used as a safe adjuvant for promoting Th2-biased immune responses for vaccine delivery.

Hollow nanostructures have attracted considerable attention owing to their large surface area, tunable cavity, and low density. In this study, a unique flower-like C@SnO_X@C hollow nanostructure (denoted as C@SnO_X@C-1) was synthesized through a novel one-pot approach. The C@SnO_X@C-1 had a hollow carbon core and interlaced petals on the shell. Each petal was a SnO₂ nanosheet coated with an ultrathin carbon layer ~2 nm thick. The generation of the hollow carbon core, the growth of the SnO₂ nanosheets, and the coating of the carbon layers were simultaneously completed via a hydrothermal process using resorcinol-formaldehyde resin-coated SiO₂ nanospheres, tin chloride, urea, and glucose as precursors. The resultant architecture with a large surface area exhibited excellent lithium-storage performance, delivering a high reversible capacity of 756.9 mA·h·g^–1 at a current density of 100 mA·g^–1 after 100 cycles.

The rational design of nano-carriers is critical for modern enzyme immobilization for advanced biocatalysis. Herein, we report the synthesis of octadecylalkyl- modified mesoporous-silica nanoparticles (C18-MSNs) with a high C18 content (~19 wt.%) and tunable pore sizes (1.6–13 nm). It is demonstrated that the increased hydrophobic content and a tailored pore size (slightly larger than the size of lipase) are responsible for the high performance of immobilized lipase. The optimized C18-MSNs exhibit a loading capacity of 711 mg/g and a specific activity 5.23 times higher than that of the free enzyme. Additionally, 93% of the initial activity is retained after reuse five times, which is better than the best performance reported to date. Our findings pave the way for the robust immobilization of lipase for biocatalytic applications.

Selenium sulfide/double-layered hollow carbon sphere (SeS₂/DLHC) composites have been designed as high-performance cathode materials for novel Li–SeS₂ batteries. In the constructed composite, SeS₂ is predominantly encapsulated in the interlayer space of DLHCs with a high loading of 75% (weight percentage) and serves as the active component for lithium storage. The presence of Se in the composite and the carbon framework not only alleviate the shuttling of polysulfide, but also improve the conductivity of electrodes. Migration of active materials from the interlayer void to the hollow cavity of DLHCs after cycling, which further mitigates the loss of active materials and the shuttle effect, is observed. As a result, the SeS₂/DLHC composite delivers a high specific capacity (930 mA·h·g^-1 at 0.2 C) and outstanding rate capability (400 mA·h·g^-1 at 6 C), which is much better than those of SeS₂/single-layered hollow carbon sphere, Se/DLHC, and S/DLHC composites. Notably, the SeS₂/DLHC composite shows an ultralong cycle life with 89% capacity retention over 900 cycles at 1 C, or only 0.012% capacity decay per cycle. Our study reveals that both SeS₂ and the double-layered structures are responsible for the excellent electrochemical performance.

Silica-based nanoparticles are promising carriers for gene delivery applications. To gain insights into the effect of particle size on gene transfection efficiency, amine-modified monodisperse Stöber spheres (NH₂-SS) with diameters of 125, 230, 330, 440, and 570 nm were synthesized. The in vitro transfection efficiencies of NH₂-SS for delivering plasmid DNA encoding green fluorescent protein (GFP) (pcDNA3-EGFP, abbreviated as pcDNA, 6.1 kbp) were studied in HEK293T cells. NH₂-SS with a diameter of 330 nm (NH₂-SS330) showed the highest GFP transfection level compared to NH₂-SS particles with other sizes. The transfection efficiency was found as a compromise between the binding capacity and cellular uptake performance of NH₂-SS330 and pcDNA conjugates. NH₂-SS330 also demonstrated the highest transfection efficiency for plasmid DNA (pDNA) with a bigger size of 8.9 kbp. To our knowledge, this study is the first to demonstrate the significance of particle size for gene transfection efficiency in silica-based gene delivery systems. Our findings are crucial to the rational design of synthetic vectors for gene therapy.