A novel DNA sensor based on C60NPs-PAMAM-PtPNPs to detect VKORC1 gene for guiding rational clinical therapy with warfarin

Reports have indicated that warfarin is the most widely prescribed anticoagulant. However, traditionally prescribed doses for each patient may be too low or too high. The therapeutic effect is often hindered by a lack of evidence-based medical information. Herein, our aim is to provide this information. To accomplish this challenge, we report the development of a novel assay based on biotinylated tetrahedral DNA as a capture probe and fullerene (C₆₀)-based nanomaterial as a redox probe using an ultrasensitivity assay with the Vitamin K epoxide reductase complex, subunit 1 (VKORC1). Platinum porous nanoparticles (PtPNPs) were modified on amino-terminated polyamidoamine (PAMAM)-functionalized C₆₀ nanoparticles (C₆₀NPs). The resultant C₆₀NPs-PAMAM-PtPNPs were used as a redox probe. In this design, C₆₀ exhibited excellent redox activity that was triggered by tetraoctylammonium bromide (TOAB). To improve the immobilization of the tetrahedral DNA capture probe, avidin was introduced during the fabrication of the biosensor because it can provide more active sites for the immobilization capture probe. The free-standing probe on top of the tetrahedral DNA served as a receptor to hybridize with target DNA directly. Different pulse voltammetry (DPV) was applied to record the electrochemical signals, which increased linearly with the target DNA. Under optimal conditions, the prepared biosensor showed a wide linear relationship, from 1 pM to 10 nM, with detection limits of 0.33 pM. This strategy demonstrates a new avenue for the determination of tumour-related mutated nucleotides in biosamples.

Cerium dioxide-doped carboxyl fullerene as novel nanoprobe and catalyst in electrochemical biosensor for amperometric detection of the CYP2C19*2 allele in human serum

The disposition dose of clopidogrel is different in CYP2C19*2 gene carriers and non-carriers. High-dose clopidogrel has been recommended to overcome a low-responsiveness to clopidogrel in patients with the CYP2C19*2 gene. To guide the choice of clopidogrel dosage and catalyse a development in the field of personalized therapy, we developed an ultrasensitive electrochemical biosensor to detect CYP2C19*2 gene. We constructed a novel assay based on cerium dioxide (CeO₂)-functionalized carboxyl fullerene (c-C₆₀) supported by Pt nanoparticles (c-C₆₀/CeO₂/PtNPs) for signal amplification. Au nanoparticles @ Fe-MIL-88NH₂ (AuNPs@Fe-MOFs) were synthesized by one-step method as the support platform to enhance the conductivity and immobilize more biotin-modified capture probe (bio-CP) through the superior affinity and specificity between streptavidin and biotin. c-C₆₀/CeO₂/PtNPs were labeled with signal probe to form the signal label. After the sandwich reaction of CYP2C19*2 gene between capture probe and the signal label, a distinguishing electrochemical signal from the catalysis of H₂O₂ by signal label would be observed. Amperometry was applied to record electrochemical signals. Under optimized conditions, the approach showed a good linear dependence between current and the logarithm of CYP2C19*2 gene concentrations in the range of 1 fM to 50nM with a low detection limit of 0.33fM (S/N = 3). The proposed method showed good specificity to target DNA compared with possible interfering substances. More importantly, the fabricated biosensor achieved accurate quantitative detection of CYP2C19*2 gene in human serum samples demonstrated by excellent correlations with standard DNA sequencing and provided a promising strategy for electrochemical biosensor detection of other gene mutations.

Multifunctional substrate of label-free electrochemical immunosensor for ultrasensitive detection of cytokeratins antigen 21-1

Poly(thionine)-Au, a novel multifunctional substrate with excellent redox signal, enzyme-like activity, and easy antibody immobilisation, was synthesised using HAuCl₄ as the oxidising agent and thionine as the monomer. The prepared poly(thionine)-Au composite exhibited an admirable electrochemical redox signal at -0.15 V and excellent H₂O₂ catalytic ability. In addition, gold nanoparticles in this composite were found to directly immobilise antibodies and further improve conductivity. In addition, a label-free electrochemical immunosensor was developed using poly(thionine)-Au as the sensing substrate for ultrasensitive detection of cytokeratin antigen 21-1 (CYFRA 21-1), an immunoassay found in human serum. The prepared immunosensor showed a wide liner range from 100 ng mL^-1 to 10 fg mL^-1 and an ultralow detection limit of 4.6 fg mL^-1 (the ratio of signal to noise (S/N) = 3). Additionally, this method was used to analyse human serum samples and yielded results consistency with those of ELISA, implying its potential application in clinical research. The poly(thionine)-Au composite can be easily extended to other polymer-based nanocomposites, which is significant for other electrochemical immunoassays.

A novel non-invasive detection method for the FGFR3 gene mutation in maternal plasma for a fetal achondroplasia diagnosis based on signal amplification by hemin-MOFs/PtNPs

The small amount of cell-free fetal DNA (cffDNA) can be a useful biomarker for early non-invasive prenatal diagnosis (NIPD) of achondroplasia. In this study, a novel non-invasive electrochemical DNA sensor for ultrasensitive detecting FGFR3 mutation gene, a pathogenic gene of achondroplasia, based on biocatalytic signal materials and the biotin-streptavidin system are presented. Notably encapsulation of hemin in metal-organic frameworks-based materials (hemin-MOFs) and platinum nanoparticles (PtNPs) were used to prepare hemin-MOFs/PtNPs composites via a one-beaker-one-step reduction. We utilized hemin-MOFs/PtNPs for signal amplification because the promising hemin-MOFs/PtNPs nanomaterial has remarkable ability of catalyze H₂O₂ as well as excellent conductivity. To further amplify the electrochemical signal, reduced graphene oxide-tetraethylene pentamine (rGO-TEPA), gold nanoparticles and streptavidin were selected for modification of the electrode to enhance the conductivity and immobilize more biotin-modified capture probe (Bio-CP) through the high specificity and superior affinity between streptavidin and biotin. The electrochemical signal was primarily derived from the synergistic catalysis of H₂O₂ by hemin and PtNPs and recorded by Chronoamperometry. Under the optimal conditions, this newly designed biosensor exhibited sensitive detection of FGFR3 from 0.1fM to 1nM with a low detection limit of 0.033fM (S/N=3). We proposed that this ultrasensitive biosensor is useful for the early non-invasive prenatal diagnosis of achondroplasia.

Novel redox species polyaniline derivative-Au/Pt as sensing platform for label-free electrochemical immunoassay of carbohydrate antigen 199

A novel electrochemical redox-active nanocomposite was synthesized by a one-pot method using N,N'-diphenyl-p-phenylediamine as monomer, and HAuCl4 and K2PtCl4 as co-oxidizing agents. The as-prepared poly(N,N'-diphenyl-p-phenylediamine)-Au/Pt exhibited admirable electrochemical redox activity at 0.15 V, excellent H2O2 electrocatalytic ability and favorable electron transfer ability. Based on these, the evaluation of the composite as sensing substrate for label-free electrochemical immunosensing to the sensitive detection of carbohydrate antigen 199 was described. This technique proved to be a prospective detection tool with a wide liner range from 0.001 U mL(-1) to 40 U mL(-1), and a low detection limit of 2.3 × 10(-4) U mL(-1) (S/N = 3). In addition, this method was used for the analysis of human serum sample, and good agreement was obtained between the values and those of enzyme-linked immunosorbent assay, implying the potential application in clinical research. Importantly, the strategy of the present substrate could be extended to other polymer-based nanocomposites such as polypyrrole derivatives or polythiophene derivatives, and this could be of great significance for the electrochemical immunoassay.

Novel gold-decorated polyaniline derivatives as redox-active species for simultaneous detection of three biomarkers of lung cancer

Novel redox-active species including gold-poly(o-aminophenol) and gold-poly(p-phenylenediamine) were synthesized and applied for the electrochemical immunoassay of three tumor biomarkers.