Highly sensitive electrogenerated chemiluminescence biosensor in profiling protein kinase activity and inhibition using a multifunctional nanoprobe

Phosphopeptide-bridged NH2-TiO2-mediated carbon dots self-enhancing and electrochemiluminescence microsensors for label-free protein kinase A detection

A novel electrochemiluminescence (ECL) method was developed for determination of protein kinase A (PKA) ultra-sensitively based on amidated nano-titanium (NH2-TiO2) embellished carbon dots (Mg@N-CDs) fluorescent probe, which integrated the target recognition and ECL signal enhancement. The Cys-labeled kemptides were employed to build a serine-rich synthetic substrate-heptapeptide (Cys-kemptide) on the Au-electrode surface. Then, the PKA-induced biosensor was triggered as a signal switch to introduce the large amounts of TiO2 decorated Mg@N-CD nanohybrid (Ti@NMg-CDs) into AuE/Cys-phosphopeptides for signal output. In particular, the presence of PKA could induce the formation of Cys-phosphopeptides by the catalytic reaction between specific substrate (kemptide) and PKA, which acts as an initiator to link the Ti@NMg-CDs according to the bridge interactions Ti-O-P. In this way, multiple Cys-phosphopeptides were adsorbed onto a single Ti@NMg-CDs, and the Ti@NMg-CDs not only provided high specific selectivity but also large surface area, as well as unprecedented high ECL efficiency. Using this PKA-induced enhanced sensor, the limit of detection of the PKA was 4.89 × 10-4 U/mL (S/N = 3). The proposed ECL biosensor was also universally applicable for the screening of PKA inhibitors and determining of other kinases activity. Our sensing system has excellent performance of specificity and the screening of kinase inhibitors, as well as it will inspire future effort in clinical diagnostics and new drug discovery.

A review of electrogenerated chemiluminescent biosensors for assays in biological matrices

Electrogenerated chemiluminescence (ECL) is the production of light via electron transfer reactions between electrochemically produced reagents. ECL-based biosensors use specific biological interactions to recognize an analyte and produce a luminescent signal. Biosensors fabricated with novel biorecognition species have increased the number of analytes detected. Some of these analytes include peptides, cells, enzymes and nucleic acids. ECL biosensors are selective, simple, sensitive and have low detection limits. Traditional methods use ruthenium complexes or luminol to generate ECL. Nanomaterials can be incorporated into ECL biosensors to improve efficiency, but also represent a new class of ECL emitters. This article reviews the application of ruthenium complex, luminol and nanomaterial-based ECL biosensors to making measurements in biological matrices over the past 4 years.

Zirconium-metalloporphyrin frameworks as a three-in-one platform possessing oxygen nanocage, electron media, and bonding site for electrochemiluminescence protein kinase activity assay

A Zr-based metal-organic framework with zinc tetrakis(carboxyphenyl)-porphyrin (ZnTCPP) groups (MOF-525-Zn) was utilized to develop a novel electrochemiluminescence (ECL) biosensor for highly sensitive protein kinase activity assay. In this work, in terms of ECL measurements and cyclic voltammetry, the cathodic ECL behaviors of MOF-525-Zn in aqueous media were thoroughly investigated for the first time. The photoelectric active groups ZnTCPP on the MOF-525-Zn frameworks could promote the generation of singlet oxygen ((1)O2) via a series of electrochemical and chemical reactions, resulting in a strong and stable red irradiation at 634 nm. Additionally, the surfactant tetraoctylammonium bromide (TOAB) further facilitated dissolved oxygen to interact with the active sites ZnTCPP of MOF-525-Zn. Furthermore, the inorganic Zr-O clusters of MOF-525-Zn were simultaneously served as the recognition sites of phosphate groups. And then, an ultrasensitive ECL sensor was proposed for protein kinase A (PKA) activity detection with a linear range from 0.01 to 20 U mL(-1) and a sensitive detection limit of 0.005 U mL(-1). This biosensor can also be applied for quantitative kinase inhibitor screening. Finally, it exhibits good performance with high stability and acceptable fabrication reproducibility, which provide a valuable strategy for clinic diagnostics and therapeutics.

Dye-Sensitized and Localized Surface Plasmon Resonance Enhanced Visible-Light Photoelectrochemical Biosensors for Highly Sensitive Analysis of Protein Kinase Activity

A novel visible-light photoelectrochemical (PEC) biosensor based on localized surface plasmon resonance (LSPR) enhancement and dye sensitization was fabricated for highly sensitive analysis of protein kinase activity with ultralow background. In this strategy, DNA conjugated gold nanoparticles (DNA@AuNPs) were assembled on the phosphorylated kemptide modified TiO2/ITO electrode through the chelation between Zr(4+) ions and phosphate groups, then followed by the intercalation of [Ru(bpy)3](2+) into DNA grooves. The adsorbed [Ru(bpy)3](2+) can harvest visible light to produce excited electrons that inject into the TiO2 conduction band to form photocurrent under visible light irradiation. In addition, the photocurrent efficiency was further improved by the LSPR of AuNPs under the irradiation of visible light. Moreover, because of the excellent conductivity and large surface area of AuNPs that facilitate electron-transfer and accommodate large number of [Ru(bpy)3](2+), the photocurrent was significantly amplified, affording an extremely sensitive PEC analysis of kinase activity with ultralow background signals. The detection limit of as-proposed PEC biosensor was 0.005 U mL(-1) (S/N = 3). The biosensor also showed excellent performances for quantitative kinase inhibitor screening and PKA activities detection in MCF-7 cell lysates under forskolin and ellagic acid stimulation. The developed dye-sensitization and LSPR enhancement visible-light PEC biosensor shows great potential in protein kinases-related clinical diagnosis and drug discovery.

A dual-potential electrochemiluminescence ratiometric approach based on graphene quantum dots and luminol for highly sensitive detection of protein kinase activity

A novel Au NP mediated dual-potential ECL ratiometric approach based on GQDs and luminol for sensitive PKA detection is developed.

Multiplexed electrochemical detection of trypsin and chymotrypsin based on distinguishable signal nanoprobes

In this work, we developed a novel multisignal output for simultaneous detection of multiple proteases by using nanoprobes labeled with distinguishable electrochemical probes. First, biotinylated peptide1 (S1) and biotinylated peptide2 (S2) were associated with biotinylated DNA1 and DNA2 via biotin-streptavidin interaction, forming DNA1-S1 and DNA2-S2, respectively. Two distinguishable signal nanoprobes (DNA1'-Au NPs-Thi and DNA2'-Au NPs-Fc) were prepared by initial assembling DNA1' and DNA2' on the Au NPs surface, respectively, and then carrying corresponding thionine (Thi) and 6-(Ferrocenyl)hexanethiol (Fc). Then, the peptide substrates (DNA1-S1 and DNA2-S2) were immobilized on gold electrode surface through Au-S bonds, and the DNA1'-Au NPs-Thi and DNA2'-Au NPs-Fc were assembled to the peptide-DNA-modified electrode surface via DNA hybridization. The targets of trypsin and chymotrypsin can specifically recognize and cleave peptides with different sequences, releasing DNA1'-Au NPs-Thi and DNA2'-Au NPs-Fc from the electrode surface into solution, thus decreasing the current of Thi and Fc. The decrease in the electrochemical currents of the two signal nanoprobes enables us to simultaneously and quantitatively determine the targets trypsin and chymotrypsin. More importantly, this strategy can be extended easily by designing various proteases-specific peptide substrates and utilizing corresponding electrochemical detectable elements for simultaneous multiplex protease assay in various biosystems.