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Functionalized MCM-41 is a class of new nanoporous biomaterials extensively studied as drug carriers of a diversity of therapeutic agents due to its suitable properties. In the present study, two oxindolimine complexes based on copper(ii) and zinc(ii) were immobilized in two selective delivery systems, namely, unmodified and modified MCM-41, which can act as carriers of water-insoluble anticancer metallodrugs. Morphological and structural characterizations of these materials were accomplished, and their cytotoxic effect was evaluated on three different cancer cell lines, SKMEL-147, SKMEL-05 and HeLa, in comparison to a non-tumor cell line (fibroblast P4). Cytotoxicity assays showed that both complexes coordinated to the modified matrix were more active and selective than those immobilized into the unmodified matrix, particularly toward SKMEL-147 cells. In contrast, P4 cells were much less affected by the presence of these compounds, with very high IC50 values. Further, the release of the complexes from these materials was monitored in vitro by X-ray fluorescence, which indicated a significant delivery after 2 h at 37 °C. By using CytoViva™ images, it was possible to observe the presence of such nanoparticles inside the cells, as well as the formation of apoptotic bodies due to the action of these antitumor compounds. A high damage on the nucleus was verified by comet and DNA cleavage assays, pointing to DNA as an important target of such metallodrugs. The matrices also contribute to the potential therapeutic action of these metal complexes, significantly increasing their cytotoxicity against melanoma and cervical carcinoma cells. [ABSTRACT FROM AUTHOR]