Labeling of RGD peptides with near-infrared fluorophores yields optical probes for noninvasive imaging of tumors overexpressing ανβ3 integrins. An important prerequisite for optimum detection sensitivity in vivo is strongly absorbing and highly emissive probes with a known fluorescence lifetime. The RGD-Cy5.5 optical probe was derived by coupling Cy5.5 to a cyclic arginine–glycine–aspartic acid–D-phenylalanine–lysine (RGDfK) peptide via an aminohexanoic acid spacer. Spectroscopic properties of the probe were studied in different matrices in comparison to Cy5.5. For in vivo imaging, human glioblastoma cells were subcutaneously implanted into nude mice, and in vivo fluorescence intensity and lifetime were measured. The fluorescence quantum yield and lifetime of Cy5.5 were found to be barely affected on RGD conjugation but dramatically changed in the presence of proteins. By time domain fluorescence imaging, we demonstrated specific binding of RGD-Cy5.5 to glioblastoma xenografts in nude mice. Discrimination of unspecific fluorescence by lifetime-gated analysis further enhanced the detection sensitivity of RGD-Cy5.5-derived signals. We characterized RGD-Cy5.5 as a strongly emissive and stable probe adequate for selective targeting of ανβ3 integrins. The specificity and thus the overall detection sensitivity in vivo were optimized with lifetime gating, based on the previous determination of the probés fluorescence lifetime under application-relevant conditions.
In the literature there are not much data available to describe the corrosion behavior of titanium, nickel alloys and special stainless steels in acids at high temperature, in particular above the boiling point. Therefore, a laboratory testing program was performed with two titanium alloys (UNS R50400 and UNS R53400) to obtain corrosion data in formic acid, acetic acid, phosphoric acid, polyphosphoric acid, p-toluene sulfonic acid and lactic acid at 200 °C. Results were compared to previously published ones obtained on UNS N08031, UNS N06059 and UNS N10665.
From the results it can be concluded that titanium does not always show better corrosion resistance than Ni-based alloys.
UNS N06059 was the best choice for formic and acetic acids at temperatures of 200 °C. Both Ti-alloys are resistant in acetic acid. Some slight differences were observed for formic acid, where UNS R50400 is only resistant up to a 20 % solution and UNS R53400 in concentrated acid too. The phosphoric acid is extremely corrosive and none of the investigated materials was resistant. In the diluted acid (5 %) only UNS R53400 is resistant, whereas in 1 % solution all investigated materials performed satisfactory. UNS N10665 and UNS N06059 showed the best behavior in polyphosphoric acid. In 30 % concentrated p-toluene sulfonic acid at 200 °C all alloys tested were unsuitable. In very diluted acid (0.1 %) both Ti-alloys and the other three alloys behaved well. In lactic acid at 180 °C increased corrosion underneath deposits was detected; the best performance was observed for UNS N06059 and UNS R50400.
In the literature there are not much data available to describe the corrosion behavior of titanium, nickel alloys and special stainless steels in acids at high temperature, in particular above the boiling point. Therefore, a laboratory testing program was performed with two titanium alloys (grade 2 - UNS R50400 and grade 12 - UNS R53400) to obtain corrosion data in formic acid, acetic acid, phosphoric acid, polyphosphoric acid, p-toluene sulfonic acid and lactic acid at 200 °C. Results were compared to previously published ones obtained on alloy 31 (UNS N08031), alloy 59 (UNS N06059) and B-2 (UNS N10665).
From the results it can be concluded that titanium does not always Show better corrosion resistance than Ni-based alloys,
Alloy 59 was the best choice for formic and acetic acids at temperatures of 200°C. Both Ti-alloys are resistant in acetic acid. Some slight differences were observed for formic acid, where Ti grade 2 is only resistant up to a 20 % solution and grade 12 in concentrated acid too. The phosphoric acid is extremely corrosive and none of the investigated materials was resistant. In the diluted acid (5 %) only Ti grade 12 is resistant, whereas in 1 % solution all investigated materials withstand. Alloy B-2 and alloy 59 showed the best behavior in polyphosphoric acid. In 30 % concentrated p-toluene sulfonic acid at 200 °C all alloys tested were unsuitable. In very diluted acid (0.1 %) both Ti-alloys and the other three alloys behaved well. In lactic acid at 180 °C increased corrosion underneath deposits was detected; the best performance was observed for alloy 59 and Ti grade 2.