The presence of rare but highly tumorigenic cancer stem cells (CSCs) within the tumors is recognized as one of the major reasons of failure of conventional chemotherapies, mainly attributed to the development of drug resistance and increasing metastatic potential. Here, we propose a therapeutic strategy based on the simultaneous delivery of docetaxel (DTX) and the photosensitizer meso-tetraphenyl chlorine disulfonate (TPCS_2a) using hyaluronic acid (HA) coated polymeric nanoparticles (HA-NPs) for the targeting and killing of CD44 over-expressing breast cancer (BC) cells, both differentiated and CSCs (CD44^high/CD24^low population), thus combining chemotherapy and photodynamic therapy (PDT). Using the CD44^high MDA-MB-231 and the CD44^low MCF-7 cells, we demonstrated the occurrence of CD44-mediated uptake of HA-NPs both in monolayers and mammosphere cultures enriched in CSCs. Cell treatments showed that combination therapy using co-loaded NPs (HA@DTX/TPCS_2a-NPs) had superior efficacy over monotherapies (HA@DTX-NPs or HA@TPCS_2a-NPs) in reducing the self-renewal capacity, measured as mammosphere formation efficiency, and in eradicating the CSC population evaluated with aldehyde dehydrogenase activity assay and CD44/CD24 immunostaining. In summary, these in vitro studies demonstrated for the first time the potential of the combination of DTX-chemotherapy and TPCS_2a-PDT for killing CSCs using properly designed NPs.

Nanoparticles (NPs) based on amphiphilic block copolymers of polyethylene glycol (PEG) and biodegradable polyesters are of particular current interest in drug nanodelivery due to their easily manipulated properties. The interaction of these NPs with biological environments is highly influenced by shell features, which drive biological identity after administration. To widen the strategies available for tuning particle surface chemistry, here we developed a panel of amine-bearing PEGylated NPs with a poly(ε-caprolactone) (PCL) core for the delivery of lipophilic drugs, and investigated the impact of NP modifications on their interaction with abundant circulating proteins (human serum albumin—HSA—and mucin), as well as their transport through biological barriers (artificial mucus—AM, extracellular matrix—ECM). We prepared NPs based on a diamino-terminated PCL (amine-NPs) and its mixture with PEG-PCL copolymers (amine/PEG-NPs) at different PEG molecular weights by nanoprecipitation, as well as corresponding NPs of PEG-PCL (PEG-NPs). The presence of an amine-bearing polymer resulted in NPs with a net positive charge and a zeta potential dependent on the length of PEG in the copolymer. Amine/PEG-NPs had a larger fixed aqueous layer thickness as compared to PEG-NPs, suggesting that PEG conformation is affected by the presence of positive charges. In general, amine-bearing NPs promptly interacted with the dysopsonic protein HSA, due to electrostatic interactions, and lose stability, thereby undergoing time-related aggregation. On the other hand, amine/PEG-NPs interaction with mucin induced switching to a negative surface charge but did not alter the quality of the dispersion. The transport kinetics of NPs through a layer of artificial mucus and tumor extracellular matrix was studied by means of fluorescent NPs based upon FRET. Amine/PEG-NPs did not cross the ECM, but they were promptly transported through the AM, with swifter transport noted at increasing MWs of PEG in the copolymer. Finally, we demonstrated that all the different NP types developed in this study are internalized by human monocytes and, despite the positive charge, they did not induce a measurable inflammatory effect. In conclusion, we showed that the concurrent presence of both PEG and amine groups on NP surface is a promising strategy for directing their interaction with body compartments. While PEG-NPs are confirmed for their capacity to cross ECM-like compartments, amine/PEG-NPs are revealed as a powerful platform to widen the arsenal of nanotools available for overcoming mucus-covered epithelia.

Given the limited number of materials available to design delivery platforms for nutrients, the rational combination of raw materials already approved as food ingredients and their processing through nano-micro technology can offer a unique tool for innovation. Here, we propose a nano-in-micro strategy to produce powders based on the hydrophobic protein zein, useful for the oral delivery of a hydrophilic iron source (iron bisglycinate) in anaemic patients. Iron-loaded powders were prepared through a two-step strategy consisting in the formation of a zein pseudolatex followed by a spray-drying step. To extend the manipulation space for zein and entrap iron bisglycinate, β-cyclodextrin (βCD) was selected as helping excipient. Addition of βCD allowed iron loading in the pseudolatex and greatly increased product yields after the drying process as compared to zein alone. Iron-loaded micro-sized powders were characterised by attenuated total reflectance–Fourier transform infrared (ATR-FTIR) spectra, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) to elucidate the role of βCD as a compatibilizer for the zein–iron system. Remarkably, micropowders released only 20% of FeBIS in a simulated gastric fluid, whereas release in a simulated intestinal fluid was almost completed in 7 h. In summary, βCD association to zein is a novel strategy to expand applications in the oral delivery of iron bisglycinate and, prospectively, to micronutrient chelates.