In nanoparticle-based drug delivery, nanoscale materials are employed to deliver certain therapeutic agents to specific targeting sites. A major benefit of this approach lies in the ability to control the parameters of the nanocarrier, such as size, shape, density, or surface coating, which allows for a controlled and sustained delivery of therapeutics. [2] Several types of nanocarriers to encapsulate drugs of interest have been developed for efficient drug delivery to the targeting site, including lipid nanoparticles, [3] inorganic nanoparticles, [4] protein-based nanoparticles, [5] and polymeric nanoparticles. [6] The appropriate carrier type is selected based on the desired drug release profile and also depends on the interactions between the drug and the carrier particle; drugs might be encapsulated by means of covalent bonding, hydrogen bonding interactions, electrostatic interactions, or van der Waals interactions. [1] Polyester-based nanoparticles (NPs), such as poly(lactic-co-glycolic acid) (PLGA) NPs, combine chemical versatility with degradability, and they are thus often studied as potential drug delivery vehicles. [7,8] PLGA is an FDA-approved, biocompatible polymer, and PLGA NPs have been extensively studied for biomedical applications due This study examines the potential of poly(lactic-co-glycolic acid) (PLGA) nanoparticles functionalized with poly(zwitterion)-mannose brushes to target macrophages. Uptake studies with RAW 264.7 macrophages indicate that multiple mannose-binding sites in the grafted brushes facilitate interaction with the mannose receptor of the macrophages, resulting in approximately four times higher cellular uptake than nanoparticles with mannose monolayer coatings. To test the feasibility of the nanoparticles as longcirculating drug delivery vehicles, their multicomponent aggregation in blood plasma is analyzed using nanoparticle tracking analysis and compared to poly(ethylene glycol)-coated (PEGylated) particles, which are known to reduce aggregation. There is no significant difference in the aggregation behavior of the poly(zwitterion)-mannose grafted particles and the PEGylated control particles (≈760 particles in aggregates per 105 particles). In addition, the particle size in blood plasma is compared, which includes the protein corona, after 0, 8, and 15 h. Whereas there is no significant difference at longer time scales, the overall particle size of the poly(zwitterion)-mannose brush-grafted nanoparticles is ≈130 nm smaller than that of the PEGylated nanoparticles at shorter time scales, suggesting a smaller protein corona. All these results suggest that poly(lactic-co-glycolic acid nanoparticles functionalized with poly(zwitterion)-mannose brush grafts may be excellent candidates for targeted drug delivery to macrophages.The ORCID identification number(s) for the author(s) of this article can be found under