DNA assembled gold nanoparticles polymeric network blocks modular highly sensitive electrochemical biosensors for protein kinase activity analysis and inhibition

Gold nanoparticles-based electrochemical method for the detection of protein kinase with a peptide-like inhibitor as the bioreceptor

This article presents a general method for the detection of protein kinase with a peptide-like kinase inhibitor as the bioreceptor, and it was done by converting gold nanoparticles (AuNPs)-based colorimetric assay into sensitive electrochemical analysis. In the colorimetric assay, the kinase-specific aptameric peptide triggered the aggregation of AuNPs in solution. However, the specific binding of peptide to the target protein (kinase) inhibited its ability to trigger the assembly of AuNPs. In the electrochemical analysis, peptides immobilized on a gold electrode and presented as solution triggered together the in situ formation of AuNPs-based network architecture on the electrode surface. Nevertheless, the formation of peptide-kinase complex on the electrode surface made the peptide-triggered AuNPs assembly difficult. Electrochemical impedance spectroscopy was used to measure the change in surface property in the binding events. When a ferrocene-labeled peptide (Fc-peptide) was used in this design, the network of AuNPs/Fc-peptide produced a good voltammetric signal. The competitive assay allowed for the detection of protein kinase A with a detection limit of 20 mU/mL. This work should be valuable for designing novel optical or electronic biosensors and likely lead to many detection applications.

Ultra-Sensitive Colorimetric Assay System Based on the Hybridization Chain Reaction-Triggered Enzyme Cascade Amplification

A versatile and ultrasensitive colorimetric detection platform has been developed based on the hybridization chain reaction (HCR)-triggered enzyme cascade amplification in this work. The proposal involves the preparation of two different hairpin DNA strands consisting of the H₁, modified with glucose oxidase (GOx-H₁) and H₂, modified with horseradish peroxidase (HRP-H₂). The H₁ and H₂ were composed of complementary sequence of nucleic acid target (T) and interlaced complementary stem-loop sequences. In the nucleic acid detection, the hybridization of T and its complementary sequence induces the autonomous assembly of GOx-H₁ and HRP-H₂ through the predictable HCR, accompanied by the formation of GOx/HRP enzyme pairs with a multiple enzymatic cascade. In contrast to the crude mixture of free GOx-H₁ and HRP-H₂, the catalytic performance of enzyme cascade reaction has been significantly enhanced, which can be determined by monitoring the absorbance change of 2, 2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS^2-), a typical substrate with hydrogen peroxide for the HRP. Furthermore, this platform can be utilized in the assay of biological substances by the introduction of corresponding aptamer (Apt), complementary strands (Com), and an assistant hairpin DNA strand (H_Assist). In view of the signal amplification of HCR and the enhanced catalytic performance of cascaded enzymes, our colorimetric assay system exhibits excellent sensitivity, and the detection limits have been calculated to be 5.2 fM and 0.8 pM for the nucleic acid target (T as a model) and biological substances (ATP as a model), respectively.

The improved sensitive detection of C-reactive protein based on the chemiluminescence immunoassay by employing monodispersed PAA-Au/Fe3O4 nanoparticles and zwitterionic glycerophosphoryl choline

Monodispersed PAA-Au/Fe₃O₄ NPs were engineered for highly sensitive CRP assay with zwitterionic glycerophosphoryl choline as the co-blocking agent.

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.

Ultrasensitive electrochemical detection of protein tyrosine kinase-7 by gold nanoparticles and methylene blue assisted signal amplification

We present here an ultrasensitive and simple strategy for protein tyrosine kinase-7 (PTK7) detection based on the recognition-induced structure change of sgc8 aptamer, and the signal change of methylene blue (MB) that interacted with sandwiched DNA complex. To construct such a sensor, an homogeneous nano-surface was formed firstly on the glass carbon electrode (GCE) by using negatively charged Nafion (Nf) as the inner layer and positively charged gold nanoparticles ((+)AuNPs) as the outer layer, followed by the immobilization of sgc8 aptamer based on Au-S bond. In the presence of helper probe (HP), sandwiched DNA complex was formed between the sgc8 aptamer and the DNA modified gold nanoparticle probe (DNA-AuNPs). Then, a strong current signal was produced due to the capture of abundant MB molecules by both the sandwiched DNA complex and the multiple DNAs that modified on AuNPs surface. However, the specific binding of sgc8 aptamer with PNK7 would trigger a structure transition of it, and directly prevented the following formation of sandwiched structure and the capture of MB. Thus, PTK7 detection could be realized based on monitoring the signal reduction of MB upon incubation of sgc8 aptamer with PTK7. Under optimal conditions, a low detection limit of 372 fM was obtained for PNK7 detection. Due to the employment of sgc8 aptamer, the proposed biosensor exhibited high selectivity to PNK7. Moreover, satisfactory results were obtained when the proposed method was applied for PNK7 detection in cellular debris.

Full Spectrum Visible LED Light Activated Antibacterial System Realized by Optimized Cu2O Crystals

Assisted by three-dimensional printing technology, we proposed and demonstrated a full spectrum visible light activated antibacterial system by using a combination of 500 nm sized Cu2O crystals and light-emitting diode (LED) lamps. Further improved antibacterial ratios were achieved, for the first time, with pure Cu2O for both Gram-positive bacteria and Gram-negative bacteria among all of the six different color LED lamps. For practical antibacterial applications, we revealed that the nonwoven fabric could act as excellent carrier for Cu2O crystals and provide impressive antibacterial performance. Furthermore, integrated with our self-developed app, the poly(ethylene terephthalate) film loaded with Cu2O crystals also showed significant antibacterial property, thus making it possible to be applied in field of touch screen. The present research not only provided a healthier alternative to traditional ultraviolet-based sterilization but also opened an auto-response manner to decrease the rate of microbial contamination on billions of touch screen devices.

Ultrasensitive electrochemical detection of nucleic acid by coupling an autonomous cascade target replication and enzyme/gold nanoparticle-based post-amplification

Owing to the intrinsic importance of nucleic acid as bio-targets, the development of isothermal and ultrasensitive electrochemical DNA biosensor is very essential for biological studies and medical diagnostics. Herein, the autonomous cascade DNA replication strategy was effectively married with the enzyme/gold nanoparticle-based post-amplification strategy to promote the detection performance toward target DNA. A hairpin DNA probe (HP) is designed that consists of an overhang at 3'-end as the recognition unit for target DNA, a recognition site for nicking endonuclease, and an alkane spacer to terminate polymerization reaction. The autonomous DNA replication-scission-displacement reaction operated by the nicking endonuclease/KF polymerase induced the autocatalytic opening of HP, which was then specifically bound by the enzyme/gold nanoparticles for further dual-signal amplification toward target-related sensing events. A low detection limit of 0.065 fM with an excellent selectivity toward target DNA could be achieved. The proposed biosensor could be also easily regenerated for target detection. The developed biosensor creates an opportunity for the effective coupling of the target replication with post-amplification strategies and thus opens a promising avenue for the detection of nucleic acid with low abundance in bioanalysis and clinical biomedicine.

Label-free and dual-amplified electrochemical detection of Hg2+ based on self-assembled DNA nanostructures and target-triggered exonuclease cleavage activity

An electrochemical biosensor for Hg²⁺ detection via HCR and Hg²⁺-triggered Exo III-assisted target recycling for signal amplification.

Phosphorylation-induced formation of a cytochrome c-peptide complex: a novel fluorescent sensing platform for protein kinase assay

A novel fluorescent sensing platform has been developed for protein kinase assay based on the phosphorylation-induced formation of a cytochrome c-peptide complex.

Ultratrace DNA Detection Based on the Condensing-Enrichment Effect of Superwettable Microchips

A sensitive nucleic acid detection platform based on superhydrophilic microwells spotted on a superhydrophobic substrate is fabricated. Due to the wettability differences, ultratrace DNA molecules are enriched and the fluorescent signals are amplified to allow more sensitive detection. The biosensing interface based on superwettable materials provides a simple and cost-effective way for ultratrace DNA sensing.

Magnetic zirconium hexacyanoferrate(II) nanoparticle as tracing tag for electrochemical DNA assay

Novel multifunctional magnetic zirconium hexacyanoferrate nanoparticles (ZrHCF MNPs) were prepared, which consisted of magnetic beads (MBs) inner core and zirconium hexacyanoferrate(II) (ZrHCF) outer shell. As an artificial peroxidase, the ZrHCF MNPs exhibited remarkable electrocatalytic properties in the reduction of H2O2 at 0.2 V vs saturated calomel electrode (SCE). On the basis of the bonding interaction between Zr (IV) of the shell ZrHCF framework and phosphonate groups, the 5'-phosphorylated ssDNA probes with a consecutive stretch of guanines as a spacer could be incorporated in ZrHCF MNPs easily. Thus, DNA-grafted ZrHCF MNPs could be simply obtained by magnetic separation. The prepared nanoelectrocatalyst was further used as signal nanoprobe for the ultrasensitive electrochemical DNA assay. Under optimal conditions, the proposed biosensor presents high sensitivity for detecting target DNA with a linear range from 1.0 fM to 1.0 nM and a low detection limit of 0.43 fM. Moreover, it exhibits good performance with excellent selectivity, high stability, and acceptable fabrication reproducibility.

A visible light induced photoelectrochemical aptsensor constructed by aligned ZnO@CdTe core shell nanocable arrays/carboxylated g-C3N4 for the detection of Proprotein convertase subtilisin/kexin type 6 gene

It was reported that Proprotein convertase subtilisin/kexin type 6 (PCSK6) can promote the progression of rheumatoid arthritis to a higher aggressive status. In this work, a novel visible light induced photoelectrochemical (PEC) platform was designed to detect PCSK6 gene. ZnO@CdTe nanocable arrays/carboxylated g-C3N4 used as the PEC signal generator. Hexagonal ZnO nanorods grew on ITO electrode firstly. CdTe were then electrodeposited on the ZnO nanorods surface to enhance the photogenerated h(+)/e(-) separation efficiency. Carboxylated g-C3N4 was utilized to improve h(+)/e(-) separation efficiency and anchor the capture probes of PCSK6 gene by the covalent bonding effect. The 5' and 3' primers captured PCSK6 ssDNA by the specific recognition. The linear range was 10 pg/mL to 20.0 ng/mL with a detection limit of 2 pg/mL.

Quantitative investigation of the poly-adenine DNA dissociation from the surface of gold nanoparticles

In recent years, poly adenine (polyA) DNA functionalized gold nanoparticles (AuNPs) free of modifications was fabricated with high density of DNA attachment and high hybridization ability similar to those of its thiolated counterpart. This nanoconjugate utilized poly adenine as an anchoring block for binding with the AuNPs surface thereby facilitated the appended recognition block a better upright conformation for hybridization, demonstrating its great potential to be a tunable plasmonic biosensor. It's one of the key points for any of the practical applications to maintaining stable conjugation between DNA oligonucleotides and gold nanoparticles under various experimental treatments. Thus, in this research, we designed a simple but sensitive fluorescence turn-on strategy to systematically investigate and quantified the dissociation of polyA DNA on gold nanoparticles in diverse experimental conditions. DNA desorbed spontaneously as a function of elevated temperature, ion strength, buffer pH, organic solvents and keeping time. What's more, evaluating this conjugate stability as affected by the length of its polyA anchor was another crucial aspect in our study. With the improved understanding from these results, we were able to control some of our experimental conditions to maintain a good stability of this kind of polyA DNA-AuNPs nanoconjugates.

Carbon nanotube enhanced label-free detection of microRNAs based on hairpin probe triggered solid-phase rolling-circle amplification

The detection of microRNAs (miRNAs) is imperative for gaining a better understanding of the functions of these biomarkers and has great potential for the early diagnosis of human disease. High sensitivity and selectivity for miRNA detection brings new challenges. Herein, an ultrasensitive protocol for electrochemical detection of miRNA is designed through carbon nanotube (CNT) enhanced label-free detection based on hairpin probe triggered solid-phase rolling-circle amplification (RCA). Traditionally, RCA, widely applied for signal enhancement in the construction of a variety of biosensors, has an intrinsic limitation of ultrasensitive detection, as it is difficult to separate the enzymes, templates, and padlock DNAs from the RCA products in the homogeneous solution. We purposely designed a solid-phase RCA strategy, using CNTs as the solid substrate, integrated with a hairpin structured probe to recognize target miRNA. In the presence of miRNA the stem-loop structure will be unfolded, triggering the CNT based RCA process. Due to the efficient blocking effect originating from the polymeric RCA products, the label-free assay of miRNA exhibits an ultrasensitive detection limit of 1.2 fM. Furthermore, the protocol possesses excellent specificity for resolving lung cancer-related let-7 family members which have only one-nucleotide variations. The high sensitivity and selectivity give the method great potential for applications in online diagnostics and in situ detection in long-term development.

Silver nanoclusters-based fluorescence assay of protein kinase activity and inhibition

A simple and sensitive fluorescence method for monitoring the activity and inhibition of protein kinase (PKA) has been developed using polycytosine oligonucleotide (dC12)-templated silver nanoclusters (Ag NCs). Adenosine-5'-triphosphate (ATP) was found to enhance the fluorescence of Ag NCs, while the hydrolysis of ATP to adenosine diphosphate (ADP) by PKA decreased the fluorescence of Ag NCs. Compared to the existing methods for kinase activity assay, the developed method does not involve phosphorylation of the substrate peptides, which significantly simplifies the detection procedures. The method exhibits high sensitivity, good selectivity, and wide linear range toward PKA detection. The inhibition effect of kinase inhibitor H-89 on the activity of PKA was also studied. The sensing protocol was also applied to the assay of drug-stimulated activation of PKA in HeLa cell lysates.

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.

Fe3O4NPs mediated nonenzymatic electrochemical immunosensor for the total protein of Nosema bombycis detection without addition of substrate

This work described an immunosensor for total protein of Nosema bombycis detection based on Fe₃O₄NPs as catalyst toward methylene blue with the aid of Fe₃O₄NPs–DNA dendrimers for signal amplification.

Conductive Composite Biosensor System for Electrochemical Indinavir Drug Detection

Indinavir is a protease inhibitor antiretroviral (ARV) drug, which forms part of the highly active antiretroviral therapy during the treatment of HIV/AIDS. Indinavir undergoes first-pass metabolism through the cytochrome P450 (CYP) enzymes in the human liver, of which CYP3A4 is the most influential isoenzyme. Multidrug combination therapy and, as such, therapeutic drug monitoring (TDM) during HIV/AIDS treatment are therefore critical, to prevent adverse interactions. The conventional sensitive and specific assays available for quantifying ARV drugs, however, suffer from distinct disadvantages. In this regard, biosensors can be used to provide real time information on the metabolic profile of the drug. In this study, a biosensor with cobalt(III) sepulchrate trichloride{CoSep3+}as diffusional mediator was constructed. The biosensor platform consisted of CYP3A4 immobilized onto a gold nanoparticle (GNP) overoxidized polypyrrole (OvOxPpy) carrier matrix. The biosensor exhibited reversible electrochemistry, with formal potential determined as −624 ± 5 mV, from voltammetric analysis, with overall electron transfer being diffusion controlled. The biosensor showed typical electrocatalytic response to dioxygen (O2), exemplified by the distinct increase in the cathodic peak current (Ip,c). A concentration-dependent increase inIp,cwas observed in response to consecutive additions of Indinavir.