Correction: Clickable iron oxide NPs based on catechol derived ligands: synthesis and characterization.

Correction for 'Clickable iron oxide NPs based on catechol derived ligands: synthesis and characterization' by Esther Pozo-Torres et al., Soft Matter, 2020, 16, 3257-3266, DOI: 10.1039/C9SM02512J.

Passive targeting of high-grade gliomas via the EPR effect: a closed path for metallic nanoparticles?

Passive tumor targeting via the enhanced permeability and retention (EPR) effect has long been considered the most effective mechanism for the accumulation of nanoparticles inside solid tumors. However, several studies have demonstrated that the EPR effect is largely dependent on the tumor type and location. Particularly complex is the situation in brain tumors, where the presence of the blood-brain tumor barrier (BBTB) adds an extra limiting factor in reaching the tumor interstitium. However, it remains unclear whether these restraints imposed by the BBTB prevent the EPR effect from acting as an efficient tumor targeting mechanism for metallic nanoparticles. In this work, we have studied the EPR effect of metallic magnetic nanoparticles (MMNPs) in a glioblastoma (GBM) model by parametric MRI. Our results showed that only MMNPs ≤50 nm could reach the tumor interstitium, whereas larger MMNPs were unable to cross the BBTB. Furthermore, even for MMNPs around 30-50 nm, the amount of them found within the tumor was scarce and restricted to the vicinity of large tumor vessels, indicating that the BBTB strongly limits the passive accumulation of metallic nanoparticles in brain tumors. Therefore, active targeting becomes the most reasonable strategy to target metallic nanoparticles to GBMs.

Magnetic Nanoparticles as MRI Contrast Agents.

Iron oxide nanoparticles (IONPs) have emerged as a promising alternative to conventional contrast agents (CAs) for magnetic resonance imaging (MRI). They have been extensively investigated as CAs due to their high biocompatibility and excellent magnetic properties. Furthermore, the ease of functionalization of their surfaces with different types of ligands (antibodies, peptides, sugars, etc.) opens up the possibility of carrying out molecular MRI. Thus, IONPs functionalized with epithelial growth factor receptor antibodies, short peptides, like RGD, or aptamers, among others, have been proposed for the diagnosis of various types of cancer, including breast, stomach, colon, kidney, liver or brain cancer. In addition to cancer diagnosis, different types of IONPs have been developed for other applications, such as the detection of brain inflammation or the early diagnosis of thrombosis. This review addresses key aspects in the development of IONPs for MRI applications, namely, synthesis of the inorganic core, functionalization processes to make IONPs biocompatible and also to target them to specific tissues or cells, and finally in vivo studies in animal models, with special emphasis on tumor models.

Clickable iron oxide NPs based on catechol derived ligands: synthesis and characterization.

Clickable magnetic nanoparticles have attracted great attention as potential nanoplatforms for biomedical applications because of the high functionalization efficiency of their surfaces with biomolecules, which facilitates their bio-compatibilization. However, the design and synthesis of clickable NPs is still challenging because of the complexity of the chemistry on the magnetic NP surface, thus robust methods that improve the ligand synthesis and the transfer of magnetic NPs in physiological media being in high-demand. In this work, we developed a versatile and enhanced synthetic route to fabricate potentially clickable IONPs of interest in nanomedicine. Catechol anchor ligands with different stereo-electronic features were synthetized from a hetero bi-functional PEG spacer backbone. The resulting catechol ligands transferred in good yields and high stability to magnetic NPs by an improved energetic ligand exchange method that combines sonication and high temperature. The azido functionalized IONPs exhibited excellent characteristics as T2 MRI contrast agents with low cytotoxicity, making these clickable magnetic NPs promising precursors for nanomedicines.

Diosgenin Functionalized Iron Oxide Nanoparticles as Novel Nanomaterial Against Breast Cancer.

Iron oxide nanoparticles (IONPs) have gained immense importance recently as drug nanocarriers due to easy multifunctionalization, simultaneous targeting, imaging and cancer hyperthermia. Herein, we report a novel nanomedicine comprising of IONPs core functionalized with a potent anticancer bioactive principle, diosgenin from medicinal plant Dioscorea bulbifera via citric acid linker molecule. IONPs were synthesized by reverse co-precipitation and characterized using field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM) and dynamic light scattering (DLS). Diosgenin functionalization was confirmed using fourier transform infrared spectroscopy (FTIR) and biochemical methods. Synthesized IONPs, citrate linked IONPs (IONPs-CA), diosgenin functionalized IONPs (IONPs-D) along with free citric acid and diosgenin were checked for anticancer activity against MCF7 breast cancer cells by MTT assay, wound migration assay, confocal microscopy and protein expression by western blotting. Size of IONPs, IONPs-CA and IONPs-D gradually increased ranging from 12 to 21 nm as confirmed by FESEM and HRTEM. Signature peaks of diosgenin at 2914, 1166 and 1444 cm-1 IONPs-D, revealed in FTIR indicated the presence of functionalized diosgenin. IONPs-D exhibited 51.08 ± 0.37% antiproliferative activity against MCF7 cells, which was found to be superior to free citric acid (17.71 ± 0.58%) and diosgenin (33.31 ± 0.37%). Treatment with IONPs-D exhibited reduced wound migration upto 40.83 ± 2.91% compared to bare IONPs (89.03 ± 2.58%) and IONPs-CA (50.35 ± 0.48%). IONPs-D and diosgenin exhibited apoptosis induction, confirmed by Alexa Fluor 488 annexin V/PI double-stained cells indicating extensive cell membrane damage coupled with PI influx leading to nuclear staining in treated cells. IONPs-D mediated selective PARP cleavage strongly rationalized it as superior apoptotic inducers. Based on these findings, IONPs-D can be considered as first diosgenin functionalized novel magnetic nanomedicine with antiproliferative, migration inhibiting and apoptosis inducing properties against breast cancer.