Protoporphyrin IX (Pp IX) silica nanoparticles, developed for effective use in photodynamic therapy (PDT), were explored in in vitro and in vivo models with the ambition to improve knowledge on the role of biological factors in the photodamage. Pp IX silica nanoparticles are found efficient at temperature with extreme metabolic downregulation, which suggest a high proportion of passive internalization. For the first time, clearance of silica nanoparticles on tumor cells is established. Cell viability assessment in six tumor cell lines is reported. In all tumor types, Pp IX silica nanoparticles are more efficient than free Pp IX. A strong fluorescence signal of reactive oxygen species generation colocalized with Pp IX silica nanoparticles, correlates with 100% of cell death. In vivo studies performed in HCT 116, A549 and glioblastoma multiforme tumors-bearing mice show tumor uptake of Pp IX silica nanoparticles with better tumor accumulation than the control alone, highlighting a high selectivity for tumor tissues. As observed in in vitro tests, tumor cell type is likely a major determinant but tumor microenvironment could more influence this differential time accumulation dynamic. The present results strongly suggest that Pp IX silica nanoparticles may be involved in new alternative local applications of PDT.

Von Willebrand factor (VWF) is a multimeric protein, the size of which is regulated via ADAMTS13-mediated proteolysis within the A2-domain. We aimed to isolate nanobodies distinguishing between proteolyzed and non-proteolyzed VWF, leading to the identification of a nanobody (designated KB-VWF-D3.1) targeting the A3-domain, the epitope of which overlaps the collagen-binding site. While KB-VWF-D3.1 binds with similar efficiency to dimeric and multimeric derivatives of VWF, binding to VWF was lost upon proteolysis by ADAMTS13, suggesting that proteolysis in the A2-domain modulates exposure of its epitope in the A3-domain. We therefore used KB-VWF-D3.1 to monitor VWF degradation in plasma samples. Spiking experiments showed that a loss of 10% intact-VWF could be detected using this nanobody. By comparing plasma from volunteers to that of congenital VWD-patients, intact-VWF levels were significantly reduced for all VWD-types, and most severely in VWD-type 2A-group 2 in which mutations promote ADAMTS13-mediated proteolysis. Unexpectedly, we also observed increased proteolysis in some patients with VWD-type 1 and VWD-type 2M. A significant correlation (r=0.51, p<0.0001) between the relative amount of high molecular weight-multimers and levels of intact-VWF was observed. Reduced levels of intact-VWF were further found in plasmas from patients with severe aortic stenosis and patients receiving mechanical circulatory support. KB-VWF-D3.1 is thus a nanobody that detects changes in the exposure of its epitope within the collagen-binding site of the A3-domain. In view of its unique characteristics, it has the potential to be used as a diagnostic tool to investigate whether a loss of larger multimers is due to ADAMTS13-mediated proteolysis.

No abstract

Zeodration represents a new strategy to prepare PLTs with partly preserved aggregative properties after storage and rehydration. Z_PLTs have potential hemostatic properties provided it is possible to improve their transfusion efficacy.