A　new　hypoxia-sensitive　coordination　compound,　bis(2-(2＇-benzothienyl)pyridinato-N,C3＇)iridium[poly(n-butyl　cyanoacrylate)],　hereafter　denoted　as　(btp)(2)Ir(PBCA),　is　synthesized　and　characterized　by　C-13　nuclear　magnetic　resonance　(NMR)　and　Fourier　transform　infrared　spectroscopy　(FTIR).　(btp)(2)Ir(PBCA)/chitosan　[(btp)(2)Ir(PBCA)/CS]　nanoparticles　(NPs)　with　a　core-shell　structure　are　prepared　by　a　two-step　fabrication　process.　The　size　distributions　of　these　NPs　are　measured　with　a　Malvern　size　analyzer,　and　their　morphology　is　observed　by　transmission　electron　microscopy　(TEM).　The　functional　groups　on　the　surface　are　confirmed　by　FTIR.　Phosphorescence　spectra　are　obtained　and　lifetimes　are　determined　with　a　spectrophotofluorometer　and　a　time-correlated　single　photon　counting　(TCSPC)　apparatus,　respectively.　HeLa　and　CT26　cell　lines　are　used　to　examine　the　cytotoxicity　by　the　MTT　assay,　as　well　as　to　determine　the　imaging　capability　of　the　samples　in　air　and　nitrogen　atmospheres,　respectively.　Tumor-bearing　mouse　models　of　colon　adenocarcinoma　are　used　for　tumor　imaging　in　vivo,　and　the　imaging　effect　is　evaluated　with　a　Maestro　2　fluorescence　imaging　system.　Compared　with　the　hypoxia-associated　probe　bis(2-(2＇-benzothienyl)pyridinato-N,C3＇)iridium(acetylacetonate)　(BTP),　the　phosphorescence　lifetime　of　(btp)(2)Ir(PBCA)/CS　NPs　significantly　decreases,　but　the　hypoxia-sensitivity　increases　after　preparation　of　NPs.　Apart　from　the　significantly　lower　cytotoxicity,　(btp)(2)Ir(PBCA)/CS　NPs　also　enhance　the　tumor　imaging　effect　by　more　than　10　times,　maintaining　the　phosphorescence　signal　in　tumor　tissue　for　over　24　h　and　significantly　decreasing　the　phosphorescence　signal　in　normal　tissue　in　vivo　compared　with　the　BTP　probe.