Starting with the enhanced permeability and retention (EPR) effect discovery, nanomedicine has gained a crucial role in cancer treatment. The advances in the field have led to the approval of nanodrugs with improved safety profile and still inspire the ongoing investigations. However, several restrictions, such as high manufacturing costs, technical challenges, and effectiveness below expectations, raised skeptical opinions within the scientific community about the clinical relevance of nanomedicine. In this review, we aim to give an overall vision of the current hurdles encountered by nanotherapeutics along with their design, development, and translation, and we offer a prospective view on possible strategies to overcome such limitations.
Active targeting of nanoparticles to tumours can be achieved by conjugation with specific antibodies. Specific active targeting of the HER2 receptor is demonstrated in vitro and in vivo with a subcutaneous MCF-7 breast cancer mouse model with trastuzumab-functionalized gold nanoparticles. The number of attached antibodies per nanoparticle was precisely controlled in a way that each nanoparticle was conjugated with either exactly one or exactly two antibodies. As expected, in vitro we found a moderate increase in targeting efficiency of nanoparticles with two instead of just one antibody attached per nanoparticle. However, the in vivo data demonstrate that best effect is obtained for nanoparticles with only exactly one antibody. There is indication that this is based on a size-related effect. These results highlight the importance of precisely controlling the ligand density on the nanoparticle surface for optimizing active targeting, and that less antibodies can exhibit more effect.
PLGA nanoparticles are among the most studied polymer nanoformulations for several drugs against different kinds of malignant diseases, thanks to their in vivo stability and tumor localization exploiting the well-documented "enhanced permeation and retention" (EPR) effect. In this paper, we have developed uniform curcumin-bearing PLGA nanoparticles by a single-emulsion process, which exhibited a curcumin release following a Fickian-law diffusion over 10 days in vitro. PLGA nanoparticles were about 120 nm in size, as determined by dynamic light scattering, with a surface negative charge of -30 mV. The loading ratio of encapsulated drug in our PLGA nanoformulation was 8 wt%. PLGA encapsulation provided efficient protection of curcumin from environment, as determined by fluorescence emission experiments. Next, we have investigated the possibility to study the intracellular degradation of nanoparticles associated with a specific G2/M blocking effect on MCF7 breast cancer cells caused by curcumin release in the cytoplasm, which provided direct evidence on the mechanism of action of our nanocomplex. This study was carried out using Annexin V-based cell death analysis, MTT assessment of proliferation, flow cytometry, and confocal laser scanning microscopy. PLGA nanoparticles proved to be completely safe, suggesting a potential utilization of this nanocomplex to improve the intrinsically poor bioavailability of curcumin for the treatment of severe malignant breast cancer.
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