Targeted drug delivery has great potential for improving therapeutic outcomes for many diseases. Polymeric nanocarriers can improve the targeted delivery of insoluble and toxic drugs but, to achieve this, it is important to tailor the particle properties. In this study, nanoparticles comprised of poly(ethylene oxide)-b-poly(Dplactic acid) (PEO-b-PDLLA) were made by flash nanoprecipitation while varying the compositions of the additives poly(L-lactic acid) (PLLA), a fluorophore 6,13-bis-(triisopropylsylylethynyl) (TIPS) pentacene, and poly(acrylic acid)-b-poly(D,L-lactic acid) (PAA-b-PDLLA) to characterize their effects on size, xi potential, fluorescence, and surface functionalization. The particle size was readily increased by addition of PLLA homopolymer up to similar to 40 wt % without significant change to the xi potential. The maximum nanoparticle fluorescence was at 0.5 wt % TIPS based on the PDLLA core and exhibited quenching that could be described by Forster resonant energy transfer. The cores of the particles were coupled with streptavidin through 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide coupling chemistry. Even without the added carboxylate groups from the PAA, the base PEO-b-PDLLA nanoparticles were conjugated with streptavidin at comparable levels while retaining the functionality of streptavidin for further biotinylated ligand binding.