| Objective: The single-walled carbon nanotubes(SWNTs) were oxidized by concen trated sulfuric and nitric acid to prepare carboxylated single-walled carbon nanotubes(SWNTs-COOH) and characterized. According to the principle of the conductivity cha nge of the whole network caused by the variation of its bandgap and the contact resis tance between tubes, the prepared SWNTs-COOH suspension was used for dipping por ous fiber to make a simple, efficient biological sensor for the detection of carcinoemb ryonic antigen(CEA).Methods:(1) The single-walled carbon nanotubes(SWNTs) were oxidized by con centrated sulfuric and nitric acid to prepare carboxylated single-walled carbon nanotube s(SWNTs-COOH) and then dispersed with a amphiphilic Pluronic F127((PEO)99(PPO)65(PEO)99) triblock copolymer under the condition of magnetic stirring, shock and ultra sound to prepare the suspension of SWNTs-COOH/F127.The dispersion and stability w ere conducted by static observation. The characterizations of SWNTs、F127 modified S WNTs、carboxylated SWNTs and carboxylated SWNTs modified by F127 dispersions were carried out by laser particle size analyzer, scanning electron microscope, transmis sion electron microscopy, fourier-transform infrared spectra, UV–vis spectroscopy and Raman spectroscopy to compare their difference.(2) According to the principle of the conductivity change of the whole network caused by the variation of its bandgap and the contact resistance between tubes, carbon nanotubes was used for dipping porous fi ber to prepare a simple, efficient biological sensor for the detection of carcinoembryon ic antigen(CEA). Uniform, stable dispersion was firstly prepared where anti-CEA was in further added in. Subsequently, filter paper was dipped into the solution to prepare the paper sensor. Finally, CEA was dropped onto the paper sensor. The rapid, accura te CEA detection can be conducted by measuring the conductivity changes of the pap er sensor caused by immune reaction.Results:(1) The optimal mass ratio of SWNTs-COOH and F127 was 1:30 and t he concentration of SWNTs in the dispersion firstly increased and then decreased withthe increasing of F127 concentration. Carboxylated SWNTs in F127 solution were sin gle or small bundles. The mixed acid treatment could not only introduce carboxyl gro ups on their surface, but also improve the hydrophilicity and biocompatibility of carbo n nanotubes, contributing to the further modification. F127 combined on SWNTs by n on-covalent bond, without damaging the structure of carbon nanotubes.(2) A new typ e of immune paper sensor based on carbon nanotubes for the CEA detection was esta blished. The resistance changes before and after identification of CEA and CEA conce ntration showed a linear relationship between 0.1875ng/m L~100ng/mL. The paper sens or can complete detection within 5 min and the same note can detect multiple sample s. The use method of the paper sensor was simple and the cost was greatly reduced.The paper sensor based on carbon nanotubes for the detection of AFP showed high se nsitivity and accuracy.Conclusion: The single-walled carbon nanotubes were modified with carboxyl gro ups after treatment with mixed acid successfully. Compared with the pristine SWNTs,the dispersion and stability in water of modified SWNTs have greatly improved. The SWNTs-COOH/F127 suspension has no deposition after centrifugation for 30 min with4000r/min and can stand at room temperature for more than 30 days without flocculat ion. The sensitivity and detection limit are comparable to the traditional ELISA kit, B ut the analysis time is shortened by 28 times, the operation method is simple, the cos t is greatly reduced and is expected to become a new diagnosis method for other dise ases. |
PDF Full Text Request