Simple, clickable protocol for atomic force microscopy tip modification and its application for trace ricin detection by recognition imaging.
A simple two-step protocol for modification of atomic force microscopy (AFM) tip and substrate by using a "click reaction" has been developed. The modified tip and substrate would be applied to detect trace amounts of ricin by using atomic force microscopy. A key feature of the approach is the use of a PEG (polyethylene glycol) derivative functionalized with one thiol and one azide ending group. One end of the PEG was attached to the gold-coated AFM tip by a strong Au-thiol bond. The azide group hanging at the other end of the immobilized PEG was used for the attachment of an antiricin antibody modified with an alkyne group using a "click reaction". The latter reaction is highly efficient, compatible with the presence of many functional groups and could proceed under mild reaction conditions. In a separate step, ricin was immobilized on the gold substrate surface that was modified by active esters. For this process, a novel bifunctional reagent was employed containing an active ester and a thioctic acid moiety. By these modification processes, AFM recognition imaging was used to detect the toxin molecules and the results show fg/mL detection sensitivity, surpassing the existing detection techniques. With measurement of the unbinding force between the antiricin antibody and ricin, which was statistically determined to be 64.89 +/- 1.67 pN, the single molecular specificity of this sensing technique is realized.
Chen
Guojun
G
Molecular Nanoelectronics, Faculty of Engineering & Nanoscale Science and Engineering Center, University of Georgia, Athens, Georgia 30602, USA.
Ning
Xinghai
X
Park
Bosoon
B
Boons
Geert-Jan
GJ
Xu
Bingqian
B
D000937:Antigen-Antibody Reactions; D002621:Chemistry / Q000379:methods*; D004563:Electrochemistry / Q000379:methods; D004952:Esters / Q000737:chemistry; D006046:Gold / Q000737:chemistry; D018625:Microscopy, Atomic Force / Q000379:methods*; D008956:Models, Chemical; D011092:Polyethylene Glycols / Q000737:chemistry*; D011506:Proteins / Q000737:chemistry; D012276:Ricin / Q000737:chemistry*; D013438:Sulfhydryl Compounds / Q000737:chemistry; D013499:Surface Properties
D004952:Esters; D011506:Proteins; D013438:Sulfhydryl Compounds; D011092:Polyethylene Glycols; D006046:Gold; D012276:Ricin