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Aptamer-based molecular probes: a multidisciplinary pipeline
* 1 , 1 , 1 , 2 , 1
1  Aptamer Group, Centro de Investigaciones Nucleares. Facultad de Ciencias, Universidad de la República, Montevideo-Uruguay.
2  Computational Biophysics Group, Department of Biological Sciences, CENUR Litoral Norte (UdelaR), Montevideo-Uruguay.
Academic Editor: Maria Emília Sousa (registering DOI)

Aptamers are small oligonucleotides that specifically recognize a molecular target with high affinity and specificity. Based on their versatility and physicochemical properties, several techniques were developed to exploit the advantages of aptamers as probes for molecular imaging. In our previous work, a DNA aptamer which exhibits specific binding for PTK7 receptor, was used as a molecular imaging probe. This aptamer was modified at 5'-position with several chelator agents and radiolabeled with technetium-99m or gallium-67. An Alexa647 derivative was also used as near infrared dye. All probes were physicochemical and biologically evaluated in BALB/c mice bearing lymphoma-tumor. In order to increase the specificity, the RP-HPLC purification procedure of probes was very strict. The chemical modifications were confirmed by mass spectrometry and RP-HPLC-gamma detection. Confocal microscopy and flow cytometry were performed in several tumor cells with the fluorescent probe. In vivo images were obtained in mice using X-ray, gamma and optical imaging strategies. After 24 h of injection, the probes were retained in the tumor and ratios tumor/non-target organ with values over 20 were obtained. In addition, in vivo specificity was evaluated in competition assays. The retention over time of the probe in the tumor and its quick excretion support the utility of labeled aptamers as molecular probes for diverse image strategies. Currently, a multidisciplinary pipeline is being developed to design and create bispecific aptamers against epitopes of interest, combining theoretical strategies together with experimental approaches using cell lines and ex vivo tumor samples, to guide the structural fine-tuning of selected aptamers.

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