Superparamagnetic iron oxide nanoparticles (SPIONs) with a rigid cross-linked poly(ethylene glycol)-co-fumarate (PEGF) coating are developed for imaging and drug delivery applications. The coating addresses two major challenges in magnetic nanoparticle use: the burst effect, where a large portion of the drug is released immediately upon injection, and the degradation of the coating inside cells, which can expose the nanoparticles to cellular components and affect cell integrity. The PEGF coating, formed by cross-linking unsaturated aliphatic polyesters, provides stability and reduces the burst effect. The study shows that cross-linked PEGF-coated nanoparticles have a 21% lower burst effect compared to non-cross-linked ones. The nanoparticles were tested for biocompatibility using the MTT assay, which confirmed their compatibility with cells even at high concentrations. The PEGF coating also enhances the stability of the nanoparticles in biological environments, reducing protein interaction and prolonging circulation time. The results suggest that PEGF-coated SPIONs are promising for drug and gene delivery applications due to their stability, reduced burst effect, and biocompatibility. The study also highlights the potential of PEGF as a coating material for SPIONs, offering improved performance in biomedical applications.Superparamagnetic iron oxide nanoparticles (SPIONs) with a rigid cross-linked poly(ethylene glycol)-co-fumarate (PEGF) coating are developed for imaging and drug delivery applications. The coating addresses two major challenges in magnetic nanoparticle use: the burst effect, where a large portion of the drug is released immediately upon injection, and the degradation of the coating inside cells, which can expose the nanoparticles to cellular components and affect cell integrity. The PEGF coating, formed by cross-linking unsaturated aliphatic polyesters, provides stability and reduces the burst effect. The study shows that cross-linked PEGF-coated nanoparticles have a 21% lower burst effect compared to non-cross-linked ones. The nanoparticles were tested for biocompatibility using the MTT assay, which confirmed their compatibility with cells even at high concentrations. The PEGF coating also enhances the stability of the nanoparticles in biological environments, reducing protein interaction and prolonging circulation time. The results suggest that PEGF-coated SPIONs are promising for drug and gene delivery applications due to their stability, reduced burst effect, and biocompatibility. The study also highlights the potential of PEGF as a coating material for SPIONs, offering improved performance in biomedical applications.