The main objective of this study was to evaluate macrophage-targeted alginate nanoparticles as a noncondensing gene delivery system for potential anti-inflammatory therapy. An external gelation method was employed to form plasmid DNA-encapsulated alginate nanoparticles. The nanoparticle surface was modified with a peptide sequence containing tuftsin (TKPR), and transfection efficiency was determined in J774A.1 macrophages. The effect of transfected mIL-10 in blocking expression of tumor necrosis factor-alpha (TNF-alpha) was evaluated in lipopolysaccharide (LPS)-stimulated cells. Scrambled peptide- and tuftsin-modified cross-linked alginate nanoparticles efficiently encapsulated plasmid DNA and protected against DNase I degradation. The transgene expression efficiencies, measured using GFP and mIL-10 expressing plasmid DNA, were highest with tuftsin-modified nanoparticles. Levels of TNF-alpha were significantly lower (p < 0.0001) in LPS-stimulated cells that were transfected with mIL-10 using alginate nanoparticles. The results of the study show that noncondensing alginate nanoparticles can efficiently deliver plasmid DNA, leading to sustained in vitro gene expression in macrophages.