Immuno-silent polymer capsules encapsulating nanoparticles for bioimaging applications

The Influence of Defects on the Luminescence of Trivalent Terbium in Nanocrystalline Yttrium Orthovanadate

Terbium-doped YVO₄ has been considered a nonluminescent solid since the first classic studies on rare-earth-doped phosphors in the 1960s. However, we demonstrate that defect engineering of YVO₄:Tb³⁺ nanoparticles overcomes the metal-metal charge transfer (MMCT) process which is responsible for the quenching of the Tb³⁺ luminescence. Tetragonal (Y_1-xTb_x)VO₄ nanoparticles obtained by colloidal precipitation showed expanded unit cells, high defect densities, and intimately mixed carbonates and hydroxides, which contribute to a shift of the MMCT states to higher energies. Consequently, we demonstrate unambiguously for the first time that Tb³⁺ luminescence can be excited by VO₄^3- → Tb³⁺ energy transfer and by direct population of the ⁵D₄ state in YVO₄. We also discuss how thermal treatment removes these effects and shifts the quenching MMCT state to lower energies, thus highlighting the major consequences of defect density and microstructure in nanosized phosphors. Therefore, our findings ultimately show nanostructured YVO₄:Tb³⁺ can be reclassified as a UV-excitable luminescent material.

Revealing the Phagosomal pH Regulation and Inflammation of Macrophages after Endocytosing Polyurethane Nanoparticles by A Ratiometric pH Nanosensor

The effect of the intracellular pH of macrophages after taking up biodegradable polymer nanoparticles (NPs) on immunomodulating functions has not been explored so far. Previous studies have demonstrated that biodegradable polyurethane (PU) NPs exhibit immunosuppressive activity. Yet, the intracellular mechanism is not clearly understood. In this study, a uniquely designed pH nanosensor is employed for tracking the intracellular pH value of macrophages to reveal the intracellular journey of PU NPs and to clarify the intracellular pH effect on the corresponding inflammatory response. First, fluorescent mesoporous silica nanoparticles (FRMSNs) is used to detect the pH change in macrophages after endo/phagocytosis of PU NPs. Second, PU is coated on the external surface of FRMSNs to examine the intracellular trafficking process of PU in the macrophages. The results show that the majority of PU-coated FRMSNs remain to stay at the cytosol-early endosome/phagosome regions. The intracellular pH value and other supporting results show that the immune response of PU NPs may be correlated to their internalization journey. The retardation in the degradation process of the PU NPs may intervene with the lysosome activity and repress the immunostimulatory effect, which contributes to the low immune response of PU NPs.