Estudo de liberação do marcador fluorescente IR780 a partir de nanopartículas poliméricas : IR780 encapsulado versus ligado covalentemente ao polímero.

The success of cancer treatments is compromised by side and toxic effects due to the use of conventional antineoplastic drugs. The lack of selectivity of drugs for the tumor tissues also causes them to reach healthy tissues, being one of the main barriers to cancer treatment. The evolution of technology expanded the possibilities of tools applicable for teranostic of cancer, highlighting: molecular imaging techniques and photodynamic and photothermal therapies. In this context, the fluorescent probe IR780, a photosensitizer, has been described in numerous studies as a potential substance in the treatment of tumors. IR780 has an excitation and emission wavelength of 780 nm and 810 nm, respectively, in near infrared, what is an advantage due to the absence of interference from the autofluorescence of tissues in these wavelengths, enabling its use as a fluorescent dye in follow-up of tumors, as well as in diagnosis in small animals in imaging studies in vivo. In addition, because of the lipophilic characteristic of this drug, an alternative is to load it in nanocarriers for its delivery, in order to delivery the molecule to tumor tissues. Therefore, the aim of this study was to evaluate the release profile of IR780 physically encapsulated in polymeric nanocapsules or covalently linked to polymer. For this, the kinetic profile of the release of the substance was evaluated in similar conditions to in vivo using the direct dialysis method. The solubility of the dye in PBS containing 1% tween was 101,65 µg/mL. The physically encapsulated IR780 presented a low percentage of release in simulated physiological environment (<10%), while the IR780 covalently linked to PLA polymer was not released under the same conditions. Thus, it showed great potential as a fluorescent dye to be applied in biodistribution studies by in vivo image, especially when the IR780 is linked to the PLA, ensuring reliable tracking of the nanocarrier.