Drug delivery system studies aim to improve nanoparticle (NP) formulation to enable efficient delivery of NPs to tumors. However, NPs must be transported by blood or through direct injection. How NPs leave the circulatory system and how NPs diffuse into a tumor remain unclear, and this
uncertainty is a limitation of drug delivery systems. The intimate connection between these questions and metabolism may be related to their biosafety in vivo. Thus, in this study, classical carrier SiO2 NPs were used as typical transport NPs, and fluorescein isothiocyanate
(FITC) was used as the representative drug and tracer. As exosome and tunneling nanotubes (TNTs) are the most relevant mechanism for NP transportation and considering the local situation in a tumor, we focused on identifying this phenomenon and investigating TNTs. In conclusion, we effectively
demonstrated that NPs can be transferred from cell to cell. Nanotubes may play an important role in this process.
Background To identify candidate external quality assessment (EQA) materials for normetanephrine and metanephrine measurements, we assessed the commutability of eight processed human plasma samples. The agreement between routine assays and the candidate reference measurement procedure (cRMP) was also evaluated. Methods Fifty-three clinical samples and eight processed plasma samples were prepared. The processed samples included pooled and individual plasma samples spiked with pure normetanephrine and metanephrine and non-spiked pooled and individual plasma samples. The clinical and processed samples were subjected to four routine isotope dilution tandem mass spectrometry assays and cRMP. Commutability was assessed based on two approaches recommended by the CLSI and International Federation of Clinical Chemistry (IFCC). Passing–Bablok regression and Bland–Altman analysis were used to evaluate the agreement between the routine assays and cRMP. Results The commutability results of the CLSI approach were better than those of the IFCC approach. For the CLSI approach, spiked individual plasma samples and spiked high-concentration pooled plasma samples were commutable for all routine assays for both analytes. The non-spiked pooled plasma sample was commutable for two out of four routine assays for metanephrine and three out of four routine assays for normetanephrine. The agreement between the routine assays and the cRMP was satisfactory, except for one routine assay showing significant bias. Conclusions High-concentration spiked pooled plasma samples and spiked individual plasma samples are candidate EQA materials for normetanephrine and metanephrine measurements.
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