Abstract
Water soluble and biocompatible 3-mercaptopropionic acid capped gallium selenide nanocrystals, were synthesized from hydrated gallium (III) perchlorate and selenide ions. The 3-mercaptopropionic acid capped gallium selenide nanocrystals, was non-fluorescent but showed a sharp UV-vis absorption maximum at 250 nm.The synthesized nanoparticle was used to develop an electrochemical biosensor for the detection of 17-alpha-ethinyl estradiol, an estrogenic endocrine disrupting compound (e-EDC). The biosensor was fabricated by potentiostatic deposition of novel gallium selenide nanocrystals on a L-cystine modified gold electrode, followed by covalent coupling of genetically engineered cytochrome P450-3A4 (CYP3A4), a Heme containing enzyme. The biosensor gave an electrochemical response at about-220 mV. The results revealed that 3-Mecarptopropanoic acid capped Gallium Selenide nanocrystals can be used in conjunction with CYP3A4 as an electrode modifier for the detection of 17-alpha ethinyl estradiol. The 3-Mecarptopropanoic acid capped Gallium Selenide nanoparticles exhibited a semiconductor like behaviour.
Highlights
17-alpha-ethinyl estradiol (17EE), a natural/ synthetic hormone that is one of the main active elements in birth control pills and hormone replacement therapy, has been classified as an estrogenic endocrine compound (e-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC))
Among the many metal selenide known, gallium selenide which is a member of III–VI group has a number of interesting properties for electrical and nonlinear optical applications [19,20]
This paper describes an approach for the determination of 17EE using 3-mercaptopropionic acid capped Ga2Se3 nanoparticles/ cytochrome P450-3A4 (CYP3A4) modified gold electrode
Summary
17-alpha-ethinyl estradiol (17EE), a natural/ synthetic hormone that is one of the main active elements in birth control pills and hormone replacement therapy, has been classified as an estrogenic endocrine compound (e-EDC). Conventional methods have been reported for the detection of estrogenic endocrine disruptors These include methods such as chemiluminescence enzyme immunoassay [5,6], high performance liquid chromatography (HPLC) [7,8,9], as well as enzyme linked Immunosorbent assay (ELISA) [10]. CYP3A4 oxidatively metabolizes 17EE to estrone as described in (Fig.1) Though this cycle involves electronic transfer but this is very poor for electrochemical detection, we have employed nanoparticles as part of our electrode modification. Analytical grade zinc nitrate hexahydrate, 3-mercaptopropionic acid (HSCH2CH2CO2H) [3-MPA], sodium hydroxide, selenium powder, sodium borohydrate, gallium, perchloric acid disodium hydrogen phosphate, sodium dihydrogen phosphate, potassium ferricyanide, potassium ferrocyanide, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS), L-cystine, ethanol, 17-alpha ethinylestradiol, ethanol were of analytical grade and were all purchased from Sigma-Aldrich (Cape Town, South Africa). 0.10 M phosphate buffer solution, pH 7.40, was prepared from disodium hydrogen phosphate and sodium dihydrogen phosphate. 5 mM (1:1) solution of K3Fe(CN) and K4Fe(CN) was prepared in 100 mL of PBS at pH 7.5
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