Detection　of　disease-related　small　biomolecules　was　of　great　significance　for　clinical　diagnostics　and　treatment.　In　this　work,　we　synthesized　defect-rich　knotted　graphene　nanotubes　(k-GNTs)　via　chemical　oxidative　etching　of　stacked-up　carbon　nanotubes　(SC-CNTs)　followed　by　chemical　reduction,　to　detect　disease-related　small　biomolecules.　We　further　studied　the　electrochemical　properties　using　three　representative　redox　probes　and　analyzed　their　biosensitivity　using　five　biomolecules.　The　k-GNT-modified　electrodes　exhibited　excellent　electrochemical　response,　with　the　lowest　ΔEp　and　the　highest　k0.　Besides,　the　modified　electrodes　could　simultaneously　detect　and　discriminate　between　dopamine　(DA),　ascorbic　acid　and　uric　acid　(UA),　as　well　as　differentiate　phenethylamine　(PEA)　and　epinephrine　(EP)　existed　in　newborn　rat　serum,　providing　the　wide　linear　detection　ranges　with　high　sensitivities　for　DA,　UA,　PEA,　and　EP.　These　excellent　electrocatalytic　properties　could　be　ascribe　to　the　unique　knotted　graphene　nanotube　structure　with　high　proportion　of　defect/edge　sites,　large,　accessible,　three-dimensional,　accessible　surface　area,　fewer　oxygen-containing　groups　and　doped　N　atoms.　Our　work　reveals　defect-rich　k-GNTs　as　a　promising　platform　for　further　applications　in　electrochemical　biosensing　and　electrocatalysis.　©　2016　Elsevier　Ltd