The article provides a comprehensive review of nanoparticle-based drug delivery systems. Nanoparticles, defined as particulate dispersions or solid particles ranging from 10 to 1000 nm in size, have been widely used to improve the pharmacokinetic and pharmacodynamic properties of various drugs. The review covers the preparation methods of nanoparticles, including dispersion of preformed polymers, polymerization of monomers, ionic gelation, and supercritical fluid technology. Key aspects such as particle size, surface properties, and drug loading are discussed, highlighting their impact on drug release and therapeutic efficacy. The article also explores the applications of nanoparticulate delivery systems, including tumor targeting, long-circulating nanoparticles, multidrug resistance reversal, oral delivery of peptides and proteins, gene delivery, and brain drug delivery. Despite the advantages of nanoparticle-based systems, challenges such as particle aggregation and limited drug loading remain to be addressed. The review concludes by emphasizing the potential of nanoparticle technology as a next-generation drug delivery system, with ongoing research aimed at optimizing its performance and practical applications.The article provides a comprehensive review of nanoparticle-based drug delivery systems. Nanoparticles, defined as particulate dispersions or solid particles ranging from 10 to 1000 nm in size, have been widely used to improve the pharmacokinetic and pharmacodynamic properties of various drugs. The review covers the preparation methods of nanoparticles, including dispersion of preformed polymers, polymerization of monomers, ionic gelation, and supercritical fluid technology. Key aspects such as particle size, surface properties, and drug loading are discussed, highlighting their impact on drug release and therapeutic efficacy. The article also explores the applications of nanoparticulate delivery systems, including tumor targeting, long-circulating nanoparticles, multidrug resistance reversal, oral delivery of peptides and proteins, gene delivery, and brain drug delivery. Despite the advantages of nanoparticle-based systems, challenges such as particle aggregation and limited drug loading remain to be addressed. The review concludes by emphasizing the potential of nanoparticle technology as a next-generation drug delivery system, with ongoing research aimed at optimizing its performance and practical applications.