The metalloproteinase BMP-1 (bone morphogenetic protein-1) plays a major role in the control of extracellular matrix (ECM) assembly and growth factor activation. Most of the growth factors activated by BMP-1 are members of the TGF-β superfamily known to regulate multiple biological processes including embryonic development, wound healing, inflammation and tumor progression. In this study, we used an iTRAQ (isobaric tags for relative and absolute quantification)-based quantitative proteomic approach to reveal the release of proteolytic fragments from the cell surface or the ECM by BMP-1. Thirty-eight extracellular proteins were found in significantly higher or lower amounts in the conditioned medium of HT1080 cells overexpressing BMP-1 and thus, could be considered as candidate substrates. Strikingly, three of these new candidates (betaglycan, CD109 and neuropilin-1) were TGF-β co-receptors, also acting as antagonists when released from the cell surface, and were chosen for further substrate validation. Betaglycan and CD109 proved to be directly cleaved by BMP-1 and the corresponding cleavage sites were extensively characterized using a new mass spectrometry approach. Furthermore, we could show that the ability of betaglycan and CD109 to interact with TGF-β was altered after cleavage by BMP-1, leading to increased and prolonged SMAD2 phosphorylation in BMP-1-overexpressing cells. Betaglycan processing was also observed in primary corneal keratocytes, indicating a general and novel mechanism by which BMP-1 directly affects signaling by controlling TGF-β co-receptor activity. The proteomic data have been submitted to ProteomeXchange with the identifier PXD000786 and doi: 10.6019/PXD000786 .

Nanometric TiO2 has been reported to be cytotoxic and genotoxic in different in vitro models when activated by UV light. However, a clear picture of the species mediating the observed toxic effects is still missing. Here, a nanometric TiO2 powder has been modified at the surface to completely inhibit its photo-catalytic activity and to inhibit the generation of all reactive species except for singlet oxygen. The prepared powders have been tested for their ability to induce strand breaks in plasmid DNA and for their cytotoxicity and genotoxicity toward human keratinocyte (HaCaT) cells (100-500 μg mL(-1), 15 min UVA/B exposure at 216-36 mJ m(-2) respectively). The data reported herein indicate that the photo-toxicity of TiO2 is mainly triggered by particle-derived singlet oxygen. The data presented herein contribute to the knowledge of structure-activity relationships which are needed for the design of safe nanomaterials.

Hydrophobicity is an important parameter for the risk assessment of chemicals, but standardised quantitative methods for the determination of hydrophobicity cannot be applied to nanomaterials. Here we describe a method for the direct quantification of the surface energy and hydrophobicity of nanomaterials. The quantification is obtained by comparing the nanomaterial binding affinity to two or more engineered collectors, i.e. surfaces with tuned hydrophobicity. In order to validate the concept, the method is applied to a set of nanoparticles with varying degrees of hydrophobicity. The technique described represents an alternative to the use of other methods such as hydrophobic interaction chromatography or water-octanol partition, which provide only qualitative values of hydrophobicity.