Doxorubicin (Dox), a widely used anti-cancer drug, was encapsulated within new special-tailored proteinoid
nanoparticles (NPs), with the intention to overcome side effects while keeping the drug potency. The synthesis and
characterization of four newly-made proteinoids of very high molecular weights (122-149 kDa) and low polydispersity
(1.01-1.03) is presented. The proteinoids were synthesized from L-lysine, L-arginine, L-histidine, L-phenylalanine
and poly-L-lactic acid (PLLA) segments, and are named P(KRHF-PLLA). Using this selection of amino acids
provides basic positive-charged novel tailored proteinoids, with a rigid and biodegradable backbone, achieved by the
incorporation of PLLA. The proteinoids self-assemble to yield NPs of a narrow-size distribution. This self-assembly
procedure was utilized to encapsulate Dox within the NP core. The optimal Dox-encapsulated NPs were chosen by a
study of their size, size distribution and Dox content. The chosen NPs, 15% Dox-loaded P(KRHF-PLLA) NPs were
checked for their stability in different conditions. In order to improve tumor uptake and time of circulation in the
blood, the chosen NPs were further PEGylated and the effects of PEGylation of the NPs, as well as the effect of the
environment, on the release rate of Dox from the NPs were investigated. Additionally, the cytotoxicity of the PEGylated
and non-PEGylated Dox-containing NPs was studied by XTT assay and their generation of immune-response was
investigated by cytokines induction assay. Overall, the Dox-loaded NPs were found stable, non-immunogenic and
showed good cell toxicity, making them good candidates to be used against cancer, while PEGylation improved all
parameters.