NanoSafe III: A User Friendly Safety Management System for Nanomaterials in Laboratories and Small Facilities.

Research in nanoscience continues to bring forward a steady stream of new nanomaterials and processes that are being developed and marketed. While scientific committees and expert groups deal with the harmonization of terminology and legal challenges, risk assessors in research labs continue to have to deal with the gap between regulations and rapidly developing information. The risk assessment of nanomaterial processes is currently slow and tedious because it is performed on a material-by-material basis. Safety data sheets are rarely available for (new) nanomaterials, and even when they are, they often lack nano-specific information. Exposure estimations or measurements are difficult to perform and require sophisticated and expensive equipment and personal expertise. The use of banding-based risk assessment tools for laboratory environments is an efficient way to evaluate the occupational risks associated with nanomaterials. Herein, we present an updated version of our risk assessment tool for working with nanomaterials based on a three-step control banding approach and the precautionary principle. The first step is to determine the hazard band of the nanomaterial. A decision tree allows the assignment of the material to one of three bands based on known or expected effects on human health. In the second step, the work exposure is evaluated and the processes are classified into three "nano" levels for each specific hazard band. The work exposure is estimated using a laboratory exposure model. The result of this calculation in combination with recommended occupational exposure limits (rOEL) for nanomaterials and an additional safety factor gives the final "nano" level. Finally, we update the technical, organizational, and personal protective measures to allow nanomaterial processes to be established in research environments.

Real-time, in vivo measurement of tissular pO2 through the delayed fluorescence of endogenous protoporphyrin IX during photodynamic therapy.

Tissular oxygen concentration plays a key role during photodynamic therapy (PDT). Therefore, monitoring its local oxygen partial pressure (pO2) may help predict and/or control the outcome of a PDT treatment. The first real-time, in vivo measurements of the pO2 in the chicken egg's chorioallantoic membrane, using the delayed fluorescence of photoactivable porphyrins (PAPs), including protoporphyrin IX (PpIX), as monitored with a dedicated optical, fiber-based, time-resolved spectrometer, are reported here. The formation of PAPs/PpIX, photosensitizers of extensive clinical use, was induced in the chicken egg's chorioallantoic membrane (CAM) with aminolevulinic acid. An excellent correlation between the vascular damage induced by PDT and the reduction in tissular pO2 is found. This study suggests that clinical measurement of the pO2 using the PAPs'/PpIX's delayed fluorescence (DF) may be used to individualize in real time the PDT light dose applied.

Population branching in the conical intersection of the retinal chromophore revealed by multipulse ultrafast optical spectroscopy.

The branching ratio of the excited-state population at the conical intersection between the S(1) and S(0) energy surfaces (Φ(CI)) of a protonated Schiff base of all-trans retinal in protic and aprotic solvents was studied by multipulse ultrafast transient absorption spectroscopy. In particular, pump-dump-probe experiments allowed to isolate the S(1) reactive state and to measure the photoisomerization time constant with unprecedented precision. Starting from these results, we demonstrate that the polarity of the solvent is the key factor influencing the Φ(CI) and the photoisomerization yield.

Dependence of photochemical reactivity of the all-trans retinal protonated Schiff base on the solvent and the excitation wavelength.

An all-optical experimental technique aimed at measuring photoisomerization quantum yield (phi) of the all-trans protonated Schiff base of retinal in solution has been implemented. Upon the increase in the excitation wavelength from 400 to 540 nm a slight increase in phi from 0.16 +/- 0.03 to 0.20 +/- 0.02 is observed in the chromophore dissolved in methanol, whereas the phi value of the one dissolved in acetonitrile varies only from 0.22 +/- 0.03 (400 nm) to 0.23 +/- 0.04 (540 nm). The results suggest that dissipation of the excited-state vibrational energy excess, along with environment-induced modifications of the potential energy surfaces are necessary for an efficient retinal photoisomerization in both solvent and protein environment.