Poly (ethylenimine)(PEI), a polymer with monomers composed of amine groups bound to ethylene molecules, has gained increasing interest as a material for nanoparticulate drug delivery systems. However, its high toxicity due to excessive positive charge hinders the versatility of PEI in biomedical applications. Thus, this work aimed to develop and characterize novel PEI-based nanoparticles as a drug delivery system, with reduced surface charge, through polyelectrolyte complexation with a negatively charged compound. Among three candidates, fibroin, sodium docusate (DO) and alginate, DO yielded the best results. Further coating the PEI–DO nanoparticles with fibroin significantly reduced the system surface charge from+ 57.3 to+ 39.3 mV. The fibroin-coated PEI–DO nanoparticles were loaded with the model drug α-mangostin, which had a spherical shape with a hydrodynamic size of 260 nm, surface charge of+ 39.3 mV, entrapment efficiency of 94.6%, and drug loading capacity of 2.96%. The system increased the α-mangostin solubility up to 25 times and showed a fast drug released characteristic within 30 min. Finally, the developed nanoparticles significantly reduced the α-mangostin hematotoxicity. In conclusion, the novel fibroin-coated PEI–DO nanoparticles could be further studied as a potential drug delivery system.