The nanoprecipitation method was used to formulate ε-polycaprolactone (PCL) into fluorescent nanoparticles. Two methods of mixing the phases were evaluated: introducing the organic phase into the aqueous phase dropwise and via a specially designed microfluidic device. As a result of the nanoprecipitation process, fluorescein-loaded nanoparticles (NPs) with a mean diameter of 127 ± 3 nm and polydispersity index (PDI) of 0.180 ± 0.009 were obtained. The profiles of dye release were determined in vitro using dialysis membrane tubing, and the results showed a controlled release of the dye from NPs. In addition, the cytotoxicity of the NPs was assessed using an MTT assay. The PCL NPs were shown to be safe and non-toxic to L929 and MG63 cells. The results of the present study have revealed that PCL NPs represent a promising system for developing new drug delivery systems.

Polydopamine (PDA) is widely used to functionalize materials and enhance cell attachment. At the same time, the potential of the dopamine precursor tyrosine in its polymerized form (polytyrosine, PTYR) remains underexplored despite its biological activity. In this study, we developed nanostructured PDA and PTYR layers on stainless steel 316L via a novel in situ oxidation process and evaluated their physicochemical properties and cellular interactions at the nano/microscale. Surface characterization revealed that the polymeric coatings formed a homogenous layer with distinct topographical features and thickness in the nanometer range for PTYR and in the micrometer range in case of PDA. Compared to PDA, PTYR coatings exhibited a nanoparticulate surface morphology and higher stability under physiological conditions. Wettability, roughness, and amine group density were systematically analyzed to determine their influence on interactions with fibroblasts and platelets. Our results show that PTYR nanocoatings significantly reduced platelet adhesion and activation, whereas PDA coatings, due to their higher primary amine content, could in some cases enhance platelet adhesion. Furthermore, fibroblast attachment was primarily influenced by coating roughness, with a specific threshold beyond which adhesion did not increase or was negatively impacted. These findings highlight the potential of engineered PTYR nanocoatings for developing advanced hemocompatible surfaces for biomedical implants.