CD44 is an endocytic hyaluronic acid (HA) receptor, and is overexpressed in many carcinomas. This has encouraged the use of HA to design CD44‐targeting carriers. This paper is about dissecting the mechanistic role of CD44. Here, HA‐decorated nanoparticles are used to deliver siRNA to both tumoral (AsPC‐1, PANC‐1, HT‐29, HCT‐116) and non‐tumoral (fibroblasts, differently polarized THP‐1 macrophages, HUVEC) human cell lines, evaluating the initial binding of the nanoparticles, their internalization rate, and the silencing efficiency (cyclophilin B (PPIB) gene). Tumoral cells internalize faster and experience higher silencing than non‐tumoral cells. This is promising as it suggests that, in a tumor, HA nanocarriers may have limited off‐target effects. More far‐reaching is the inter‐relation between the four parameters of the study: CD44 expression, HA binding on cell surfaces, internalization rate, and silencing efficiency. No correlation is found between binding (an early event) and any of the other parameters, whereas silencing correlates both with speed of the internalization process and CD44 expression. This study confirms on one hand that HA‐based carriers can perform a targeted action, but on the other it suggests that this may not be due to a selective binding event, but rather to a later recognition leading to selective internalization.

This study is about fine tuning the targeting capacity of peptide-decorated nanoparticles to discriminate between cells that express different integrin make-ups. Using microfluidic-assisted nanoprecipitation, we have prepared poly(lactic acid-co-glycolic acid) (PLGA) nanoparticles with a PEGylated surface decorated with two different arginine-glycine-aspartic acid (RGD) peptides: one is cyclic (RGDFC) and has specific affinity towards α_vβ₃ integrin heterodimers; the other is linear (RGDSP) and is reported to bind equally α_vβ₃ and α₅β₁. We have then evaluated the nanoparticle internalization in two cell lines with a markedly different integrin fingerprint: ovarian carcinoma A2780 (almost no α_vβ₃, moderate in α₅β₁) and glioma U87MG (very high in α_vβ₃, moderate/high in α₅β₁). As expected, particles with cyclic RGD were heavily internalized by U87MG (proportional to the peptide content and abrogated by anti-α_vβ₃) but not by A2780 (same as PEGylated particles). The linear peptide, on the other hand, did not differentiate between the cell lines, and the uptake increase vs. control particles was never higher than 50%, indicating a possible low and unselective affinity for various integrins. The strong preference of U87MG for cyclic (vs. linear) peptide-decorated nanoparticles was shown in 2D culture and further demonstrated in spheroids. Our results demonstrate that targeting specific integrin make-ups is possible and may open the way to more precise treatment, but more efforts need to be devoted to a better understanding of the relation between RGD structure and their integrin-binding capacity.