期刊
ACS APPLIED MATERIALS & INTERFACES
卷 7, 期 36, 页码 20068-20075出版社
AMER CHEMICAL SOC
DOI: 10.1021/acsami.5b05146
关键词
DNA; hybridization; intrinsic molecular charge; label-free detection; field-effect capacitive sensor; polyelectrolyte; layer-by-layer technique
资金
- Bundesministerium fur Bildung und Forschung (DiaCharge project) [031A192D]
- National Natural Science Foundation of China [31470956]
- Zhejiang Provincial Natural Science Foundation of China [LY13H180002]
Miniaturized setup, compatibility with advanced micro- and nanotechnologies, and ability to detect biomolecules by their intrinsic molecular charge favor the semiconductor field-effect platform as one of the most attractive approaches for the development of label-free DNA chips. In this work, a capacitive field-effect EIS (electrolyte insulator semiconductor) sensor covered with a layer-by-layer prepared, positively charged weak polyelectrolyte layer of PAN (poly(allylamine hydrochloride)) was used for the label-free electrical detection of DNA (deoxyribonucleic acid) immobilization and hybridization. The negatively charged probe single-stranded DNA (ssDNA) molecules were electrostatically adsorbed onto the positively charged PAN layer, resulting in a preferentially flat orientation of the ssDNA molecules within the Debye length, thus yielding a reduced charge-screening effect and a higher sensor signal. Each sensor-surface modification step (PAN adsorption, probe ssDNA immobilization, hybridization with complementary target DNA (cDNA), reducing an unspecific adsorption by a blocking agent, incubation with noncomplementary DNA (ncDNA) solution) was monitored by means of capacitance voltage and constant-capacitance measurements. In addition, the surface morphology of the PAN layer was studied by atomic force microscopy and contact-angle measurements. High hybridization signals of 34 and 43 mV were recorded in low-ionic strength solutions of 10 and 1 mM, respectively. In contrast, a small signal of 4 mV was recorded in the case of unspecific adsorption of fully mismatched ncDNA. The density of probe ssDNA and dsDNA molecules as well as the hybridization efficiency was estimated using the experimentally measured DNA immobilization and hybridization signals and a simplified double-layer capacitor model. The results of field-effect experiments were supported by fluorescence measurements, verifying the DNA-immobilization and hybridization event.
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