Electrogenerated Chemiluminescence Of New Nanomaterials For Small Biomolecule Bio-sensing

Electrochemiluminescence (ECL) biosensors have exhibited unique advantages and broad application prospects in detecting and recognizing small biomolecules, due to their advantages of high sensitivity, good selectivity, simple equipment and eazsy miniaturization. Nanomaterials, as a new type of ECL luminophor, could be easily functionalized with biomolecules through physical absorption, electrostatic interaction, and covalent binding, which is beneficial to build a good platform for ECL conduc-tion. Therefore, it’s the ongoing motivation of current research to find new ECL lu-minophores, combine with modern sensing strategy, and realize low potential, and high selective, high sensitive detection staregy of small biomolecules. Based on the effort of previous reaseachers, this paper further studied a new ECL nano-luminophor and its’ ECL behavior and property. Combining with new analytical methodology, this paper mainly studied on the construction of ECL biosensors for the detection of small biomolecules as follows:1. Anodic Electrochemiluminescence of Graphitic-phase C3N4 Nanosheets for Sensitive BiosensingThis work observed the anodic electrochemiluminescence (ECL) of C3N4 nanosheets (CNNS) for the first time. The ECL emission was 40 times stronger than that from bulk g-C3N4 in the presence of triethylamine (Et3N) as a coreactant due to large surface-to-volume ratio, which enhanced the sensitivity for biosensing. At pH 7.0, the CNNS modified electrode prepared with 0.75 mg mL-1 CNNS in 0.025% chi-tosan solution possesses good stability and acceptable reproducibility in the presence of 30 mM Et3N. The ECL mechanism of CNNS/Et3N system was proposed to be emitted from the excited CNNS, which was produced during the reaction between the oxidation product of dopamine (DA·+) and Et3N· radical, a quenching-based method was established for sensitive and specific detection of dopamine ranging from 1.0 nM to 100 nM with a detection limit of 96 pM by using the CNNS as an ECL emitter. The proposed method showed excellent specificity, high sensitivity and low detection limit, could be applied in analysis of real samples.2. An "Off-On" Electrochemiluminescence System for Sensitive Detection of ATP via Target-Induced Structure SwitchingAn "off-on" electrochemiluminescence (ECL) strategy was constructed for highly sensitive and selective detection of adenosine 5’-triphosphate (ATP) with a quantum dots (QDs) modified electrode and a DNAzyme signal probe. The immobilized QDs were functionalized with a DNA sequence (DNA1) and then aptamer for recognition of target analyte. The signal probe was prepared by assembling another DNA se-quence (DNA2) and G-quadruplex on gold nanoparticle via Au-S chemistry, which was used to bind the probe to electrode surface through a hybridization reaction with aptamer and hemin for forming G-quadruplex/hemin DNAzyme, respectively. Upon the sandwich hybridization of DNAl-aptamer-DNA2, the signal probe could be cap-tured on the aptasensor to catalyze the reduction of dissolved oxygen, the coreactant for cathodic ECL emission of QDs, leading to a decrease of ECL intensity and thus the "off" state. In the presence of target, its recognition by aptamer led to the release of aptamer from electrode surface and decreased the amount of captured signal probe, thus the ECL emission was in its "on" state. The "off-on" strategy resulted from the target-induced structure switching could be used for specific detection of ATP with a linear range of 8 to 2000 nM and a detection limit of 7.6 nM. The proposed aptasensor could be successfully applied in the ECL detection of ATP in human serum. This method could resist environmental interferents and be extended for sensitive and reli-able detection of a wide range of analytes in complex sample.