RESUMO
The human matrix metalloprotease 9 (hMMP-9) is involved in many physiological processes such as tissue remodeling. Its overexpression in tumors promotes the release of cancer cells thus contributing to tumor metastasis. It is a relevant marker of malignant tumors. We selected an RNA aptamer containing 2'-fluoro, pyrimidine ribonucleosides, that exhibits a strong affinity for hMMP-9 (K(d) = 20 nM) and that discriminates other human MMPs: no binding was detected to either hMMP-2 or -7. Investigating the binding properties of different MMP-9 aptamer variants by surface plasmon resonance allowed the determination of recognition elements. As a result, a truncated aptamer, 36 nucleotides long, was made fully resistant to nuclease following the substitution of every purine ribonucleoside residue by 2'-O-methyl analogues and was conjugated to S-acetylmercaptoacetyltriglycine for imaging purposes. The resulting modified aptamer retained the binding properties of the originally selected sequence. Following (99m)Tc labeling, this aptamer was used for ex vivo imaging slices of human brain tumors. We were able to specifically detect the presence of hMMP-9 in such tissues.
Assuntos
Aptâmeros de Nucleotídeos , Metaloproteinase 9 da Matriz/metabolismo , Neoplasias/diagnóstico , Neoplasias/enzimologia , Compostos Radiofarmacêuticos , Tecnécio Tc 99m Mertiatida , Aptâmeros de Nucleotídeos/síntese química , Aptâmeros de Nucleotídeos/química , Humanos , Imuno-Histoquímica , Estrutura Molecular , Neoplasias/metabolismo , Compostos Radiofarmacêuticos/síntese química , Compostos Radiofarmacêuticos/química , Tecnécio Tc 99m Mertiatida/síntese química , Tecnécio Tc 99m Mertiatida/químicaRESUMO
OBJECTIVE: Our objective was to investigate the safety of radioactive blood samples from patients receiving 131I and whether the radioactivity affects the validity of assays. METHODS: First, the activity of samples from patients given 131I was measured by 3 methods and compared with the upper threshold. Then, pilot sera were spiked with 131I, and possible interference was investigated using 2 immunoradiometric assays. RESULTS: The activity of 13 of the 15 samples was below the European limit; the other 2 samples were from patients with reduced renal clearance rates. No differences in thyroglobulin level or thyroid-stimulating hormone level were found between sera that were spiked with 131I and sera that were not. CONCLUSION: These blood samples are safe because they contain negligible activity, and the use of radioimmunoassays or immunoradiometric assays on them produces reliable results.