10.1021/acsami.7b11659.s001 Dang-Dang Xu Dang-Dang Xu Cui Liu Cui Liu Cheng-Yu Li Cheng-Yu Li Chong-Yang Song Chong-Yang Song Ya-Feng Kang Ya-Feng Kang Chu-Bo Qi Chu-Bo Qi Yi Lin Yi Lin Dai-Wen Pang Dai-Wen Pang Hong-Wu Tang Hong-Wu Tang Dual Amplification Fluorescence Assay for Alpha Fetal Protein Utilizing Immunohybridization Chain Reaction and Metal-Enhanced Fluorescence of Carbon Nanodots American Chemical Society 2017 hairpin fluorescence intensity amplification fluorescence sensor sensitivity quantum acid radiative decay rate HCR probe AFP molecules immunohybridization chain reaction MEF-capable immunohybridization reactions sandwich immunoassay method Alpha Fetal Protein Utilizing Immunohybridization Chain Reaction detection antibodies-conjugated oligonucleotide initiator gold nanoisland film Dual Amplification Fluorescence Assay analysis 2017-10-10 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Dual_Amplification_Fluorescence_Assay_for_Alpha_Fetal_Protein_Utilizing_Immunohybridization_Chain_Reaction_and_Metal-Enhanced_Fluorescence_of_Carbon_Nanodots/5514712 As an emerging fascinating fluorescent nanomaterial, carbon nanodots (CDs) have attracted much attention owing of their unique properties such as small size, antiphotobleaching, and biocompatibility. However, its use in biomedical analysis is limited because of its low quantum yield. Herein, we constructed a dual amplification fluorescence sensor by incorporating immunohybridization chain reaction (immuno-HCR) and metal-enhanced fluorescence (MEF) of CDs for the detection of alpha fetal protein (AFP). The immunoplasmonic slide and detection antibodies-conjugated oligonucleotide initiator are served to capture and probe AFP molecules, respectively. Then, CD-tagged hairpin nucleic acids were introduced to trigger the HCR, in which the hairpin nucleic acid and oligonucleotide initiator are complementary. The interaction between CDs and the gold nanoisland film greatly improves the radiative decay rate, increases the quantum yield, and enhances the fluorescence emission of the CDs. Furthermore, the HCR provides secondary amplification of fluorescence intensity. Therefore, the MEF-capable immunohybridization reactions provide obvious advantages and result in exceptional sensitivity. In addition, the sandwich immunoassay method offers high specificity. The results show a wide linearity between the fluorescence intensity and AFP concentration over 5 orders of magnitude (0.0005–5 ng/mL), and the detection limit reaches as low as 94.3 fg/mL. This method offers advantages of high sensitivity and reliability, wide detection range, and versatile plasmonic chips, thus presenting an alternative for the technologies in biomedical analysis and clinical applications.