Gemeente Leiden

A new strategy for efficient in vivo image-guided photodynamic therapy (PDT) has been demonstrated utilizing a ligand-exchange constructed upconversion-C60 nanophotosensitizer. This theranostic platform is superior to the currently reported nanophotosensitizers in (i) directly bonding photosensitizer C60 to the surface of upconversion nanoparticles (UCNPs) by a smart ligand-exchange strategy, which greatly shortened the energy transfer distance and enhanced the (1)O2 production, resulting in the improvement of the therapeutic effect; (ii) realizing in vivo NIR 808 nm image-guided PDT with both excitation (980 nm) and emission (808 nm) light falling in the biological window of tissues, which minimized auto-fluorescence, reduced light scatting and improved the imaging contrast and depth, and thus guaranteed noninvasive diagnostic accuracy. In vivo and ex vivo tests demonstrated its favorable bio-distribution, tumor-selectivity and high therapeutic efficacy. Owing to the effective ligand exchange strategy and the excellent intrinsic photophysical properties of C60, (1)O2 production yield was improved, suggesting that a low 980 nm irradiation dosage (351 J cm(-2)) and a short treatment time (15 min) were sufficient to perform NIR (980 nm) to NIR (808 nm) image-guided PDT. Our work enriches the understanding of UCNP-based PDT nanophotosensitizers and highlights their potential use in future NIR image-guided noninvasive deep cancer therapy.

At an excavation of the late medieval St Margaretha Convent in Leiden (The Netherlands), archaeobotanical results could be compared with historical data. Both wood and macroremains were analysed to reconstruct the local vegetation and seek evidence of the cultivation of plants. The historical sources available for this estate are a charter prepared in 1572, which listed all trees present just after the abandonment of the convent, and an illustration from 1574 of the convent and its grounds. The charter mentions Salix and Alnus as the most numerous trees present, followed by several other taxa. The archaeological evidence from the wood remains, mostly construction timber with a dominance of Quercus, shows the use of indigenous taxa and some non-indigenous material, which was partly re-used. It is possible that some of the Coniferae were very early home-grown specimens. The trees represented in the macroremains were most probably growing in the immediate vicinity. They specify some of the taxa found as wood or mentioned in the historical text. The identified cultivated plants could all have been grown locally. The vegetation is in general represented by ruderal taxa and plants growing in wet conditions, which form an assemblage typical of an abandoned rural area.