title: Immobilization of enzymes through one-pot chemical preoxidation and electropolymerization of dithiols in enzyme-containing aqueous suspensions to develop biosensors with improved performance.
abstract: A protocol of one-pot chemical preoxidation and electropolymerization of monomers (CPEM) in enzyme-containing aqueous suspensions (or solutions) was proposed as a universal strategy for high-activity and high-load immobilization of enzymes to construct amperometric biosensors, which was proven to be effective for the monomer of 1,4-benzenedithiol (BDT), 1,6-hexanedithiol, o-phenylenediamine, o-aminophenol or pyrrole, the preoxidant of K3Fe(CN)6 or p-benzoquinone, and the enzyme of glucose oxidase (GOx) or alkaline phosphatase (AP) to develop GOx-based glucose biosensors or AP-based disodium phenyl phosphate biosensors. As a case examined in detail, a well-dispersed aqueous suspension of the poorly soluble BDT was obtained through its dispersion assisted by ultrasonication and coexisting GOx, which was then subject to chemical preoxidation through adding K3Fe(CN)6, yielding many composites of insoluble BDT oligomers with lots of high-activity enzyme molecules entrapped. Some insoluble composites were then electrochemically codeposited with poly(1,4-benzenedithiol) on an Au electrode, yielding an enzyme film with high-load and high-activity enzyme immobilized. The glucose biosensor prepared here from the CPEM protocol showed much better performance than that from the preoxidant-free conventional electropolymerization (CEP) protocol, with a detection sensitivity increase by a factor of 32 in this case. The GOx-based and AP-based first-generation biosensors developed from the present CPEM protocol all exhibited notably improved performance compared with the analogues from the preoxidant-free CEP protocol. The electrochemical quartz crystal microbalance (EQCM) technique was used to investigate various electrode modification processes. The values of quantity and enzymatic specific activity (ESA) of the immobilized enzymes were evaluated through the EQCM and the conventional UV-vis spectrophotometric method, given that the CPEM protocol notably improved the quantity and the ESA of immobilized enzymes as compared with the preoxidant-free CEP protocol. The proposed CPEM protocol may be interesting in a number of fields, including biosensing, biocatalysis, biofuel cells, bioaffinity chromatography, and biomaterials, and the successful electropolymerization of dithiols in aqueous suspensions (two-phase electropolymerization) may open a new avenue for many monomers that are poorly soluble in neutral aqueous solutions to in situ immobilize biomolecules for bioapplications.
authors.affiliation: Key Laboratory of Chemical Biology and Traditional Chinese Medicine Research (Ministry of Education of China), College of Chemistry and Chemical Engineering, Hunan Normal University, Changsha 410081, PR China.
authors.forename: Yingchun
authors.initials: Y
authors.lastname: Fu
authors.forename: Chao
authors.initials: C
authors.lastname: Chen
authors.forename: Qingji
authors.initials: Q
authors.lastname: Xie
authors.forename: Xiahong
authors.initials: X
authors.lastname: Xu
authors.forename: Can
authors.initials: C
authors.lastname: Zou
authors.forename: Qingmei
authors.initials: Q
authors.lastname: Zhou
authors.forename: Liang
authors.initials: L
authors.lastname: Tan
authors.forename: Hao
authors.initials: H
authors.lastname: Tang
authors.forename: Youyu
authors.initials: Y
authors.lastname: Zhang
authors.forename: Shouzhuo
authors.initials: S
authors.lastname: Yao
mesh_terms: D000469:Alkaline Phosphatase; D015374:Biosensing Techniques / Q000379:methods*; D004563:Electrochemistry / Q000379:methods*; D004800:Enzymes, Immobilized / Q000138:chemical synthesis* / Q000737:chemistry; D005947:Glucose / Q000032:analysis; D005949:Glucose Oxidase; D010755:Organophosphates / Q000032:analysis; D011108:Polymers / Q000138:chemical synthesis; D013535:Suspensions; D014050:Toluene / Q000031:analogs & derivatives / Q000737:chemistry
chemical_list: D004800:Enzymes, Immobilized; D010755:Organophosphates; D011108:Polymers; D013535:Suspensions; D014050:Toluene; C074782:phenylphosphate; D005949:Glucose Oxidase; D000469:Alkaline Phosphatase; D005947:Glucose; C004848:dithiol