A　highly　sensitive　and　selective　electrochemiluminescent　(ECL)　biosensor　for　the　determination　of　adenosine　was　developed.　Single　DNA　(capture　DNA)　was　immobilized　on　the　gold　electrode　through　Au-thiol　interaction　at　first.　Another　DNA　modified　with　tris(2,2＇-bipyridyl)　ruthenium(II)-doped　silica　nanoparticles　(Ru-SNPs)　that　contained　adenosine　aptamer　was　then　modified　on　the　electrode　surface　through　hybridizing　with　the　capture　DNA.　In　the　presence　of　adenosine,　adenosine-aptamer　complex　is　produced　rather　than　aptamer-DNA　duplex,　resulting　with　the　dissociation　of　Ru-SNPs-labeled　aptamer　from　the　electrode　surface　and　the　decrease　in　the　ECL　intensity.　The　decrease　of　ECL　intensity　has　a　direct　relationship　with　the　logarithm　of　adenosine　concentration　in　the　range　of　1.0×10-10　to　5.0×10-6molL-1.　The　detection　limit　of　the　proposed　method　is　3.0×10-11molL-1.　The　existence　of　guanosine,　cytidine　and　uridine　has　little　interference　with　adenosine　detection,　demonstrating　that　the　developed　biosensor　owns　a　high　selectivity　to　adenosine.　In　addition,　the　developed　biosensor　also　demonstrates　very　good　reusability,　as　after　being　reused　for　30　times,　its　ECL　signal　still　keeps　91%　of　its　original　state.　©　2010　Elsevier　B.V.