Analytical strategies to study the formation and drug delivery capabilities of ferritin-encapsulated cisplatin in sensitive and resistant cell models.

One of the limitations in the use of cisplatin is its low penetration into cells. In addition, some cells develop the so called resistance, a multifactorial event that decreases significantly the intracellular cisplatin concentration. To circumvent these limitations, recent studies are focused on the use of nanocarriers that permit, among others, to achieve higher drug uptake. In this work, ferritin is evaluated as a nanostructured cisplatin-delivery system in cell models of ovarian cancer. One of the key aspects is the characterization of the encapsulated product, and for this aim, a battery of analytical techniques, including size exclusion chromatography (SEC) coupled to UV detection and to inductively coupled plasma mass spectrometry (ICP-MS) together with transmission electron microscopy (TEM), is conducted. Higher level of incorporation occurs when using initial concentrations of the Fe-containing form of the protein at 10 mg/mL and 1 mg/mL cisplatin solution. The incorporation of the free and encapsulated cisplatin is addressed in A2780 and A2780CIS, sensitive and cisplatin-resistant cell lines, respectively, showing a significantly higher uptake of the encapsulated form. These values ranged from 5- to 9-fold in the sensitive line and 2-4 in the resistant model, being always more pronounced at the lower doses. Functionality of the drug after encapsulation is addressed by monitoring the presence of Pt in DNA and normalizing DNA concentration through simultaneous P and Pt measurements by ICP-MS. Time elapsed between exposure and Pt detection in DNA proved to be critical in the encapsulated model, showing the slower drug release mechanism from the ferritin nanocage that could be advantageously used for a controlled therapy. Graphical abstract.

Evaluation of the uptake, storage and cell effects of nano-iron in enterocyte-like cell models.

The therapy with nanocompounds is widely used to treat Fe deficiency and an emerging trend to inhibit tumor growth. The present work aims to address the management of different FeONP, comparing sucrose covered FeONP and Fe nanoparticles in the form of the ferritin with non-particulated inorganic Fe (II) by enterocytes-like colon cancer cell lines (Caco-2 and HT-29). Iron uptake results revealed significantly higher Fe incorporation in the case of nanoparticulated Fe, first in the form of FeONP and second in the form of ferritin with respect to inorganic Fe (II). Furthermore, the intracellular Fe fractionation, conducted by size exclusion chromatography coupled on line to inductively coupled plasma mass spectrometry (SEC-ICP-MS) showed a significant increase of the Fe-ferritin peak upon exposure of cells to the following compounds ferritin > FeONP > FeSO4. Such results point out that the sucrose coated FeONP released Fe into the cell cytosol that was used to replenish the existing cytosolic ferritin without inducing changes in the protein concentration. On the other hand, the increase of the Fe-ferritin peak in cells exposed to ferritin as iron source is due to a significant increase on the intracellular protein concentration, as proved by using an ICP-MS linked ferritin sandwich immune assay. Cell viability experiments conducted with concentrations up to 1000 µmol L-1 (as Fe) of each compound under scrutiny did not reveal significant differences among Fe species regarding global cellular toxicity. However, significant cell DNA damage was detected when treating the cells with FeONP (500 µmol L-1).