A　novel　approach　to　improve　the　antiviral　efficacy　of　nucleoside　reverse　transcriptase　inhibitors　(NRTIs)　and　reduce　their　side　effects　was　developed　by　constructing　a　nanosized　NRTI　monophosphate-polymer　conjugate　using　d4T　as　a　model　NRTI.　Firstly,　a　novel　chitosan-O-isopropyl-5＇-O-d4T　monophosphate　conjugate　with　a　phosphoramidate　linkage　was　efficiently　synthesized　through　Atherton-Todd　reaction　under　mild　conditions.　The　anti-HIV　activity　and　cytotoxicity　of　the　polymeric　conjugate　were　evaluated　in　MT4　cell　line.　Then　the　conjugate　nanoparticles　were　prepared　by　the　process　of　ionotropic　gelation　between　TPP　and　chitosan-d4T　conjugate　to　improve　their　delivery　to　viral　reservoirs,　and　their　physicochemical　properties　were　characterized　by　transmission　electron　microscopy　(TEM),　dynamic　light　scattering　(DLS)　techniques　and　X-ray　diffraction　(XRD).　In　vitro　drug　release　studies　in　pH　1.1　and　pH　7.4　suggested　that　both　chitosan-d4T　conjugate　and　its　nanoparticles　prefer　to　release　d4T　5＇-(O-isopropyl)　monophosphate　than　free　d4T　for　prolonged　periods,　which　resulted　in　the　enhancement　of　anti-HIV　selectivity　of　the　polymeric　conjugate　relative　to　free　d4T　due　to　bypassing　the　metabolic　bottleneck　of　monophosphorylation.　Additionally,　the　crosslinked　conjugate　nanoparticles　can　prevent　the　coupled　drug　from　leaking　out　of　the　nanoparticles　before　entering　the　target　viral　reservoirs　and　provide　a　mild　sustained　release　of　d4T　5＇-(O-isopropyl)　monophosphate　without　the　burst　release.　The　results　suggested　that　this　kind　of　chitosan-O-isopropyl-5＇-O-d4T　monophosphate　conjugate　nano-prodrugs　may　be　used　as　a　targeting　and　sustained　polymeric　prodrugs　for　improving　therapy　efficacy　and　reducing　side　effects　in　antiretroviral　treatment.　(C)　2009　Elsevier　Ltd.　All　rights　reserved.