Search

Excessive residues of semicarbazide (SEM) can accumulate in animals after the original drug has been abused, posing a risk to human health. Herein, based on multifunctional silica-initiated dual mode signal response, a novel competitive-type immunosensor was constructed for ultrasensitive detection of SEM. As a preliminary signal amplification platform for immunosensors, polyethyleneimine reduced graphene oxide composite gold nanorods (PEI-rGO/AuNRs) modified gold electrodes (AuE) provide a high specific surface area and high electrical conductivity. The thionine-aminated silica nanospheres-AuPt (thi-SiO

Herein, an aptasensor based on target-induced strand displacement (TISD) strategy was developed for sensitive detection of T-2 toxin. Gold nanoparticles@ aminated manganese dioxide (AuNPs@NH

A fluorescent aptasensor was constructed to detect lead ion (Pb2+). Complementary DNA with sulfhydryl group (SH-cDNA) were loaded on gold nanoflowers materials (Au NFs) through Au–S bonds. Then, based on complementary base pairing between FAM modified Pb2+ aptamer (FAM-Apt) and Au NFs/SH-cDNA system, a Au NFs/SH-cDNA/FAM-Apt aptasensor was constructed. The fluorescence of FAM was quenched by Au NFs due to the fluorescence resonance energy transfer (FRET). Upon addition of Pb2+ and RecJf exonuclease (RecJf Exo) for 1.5 h, the Apt changed to a G-quadruplex structure due to the high affinity between Pb2+ and its aptamers, which lead to a large recovery in the fluorescence intensity. Under the optimized conditions, the presented aptasensor revealed high selectivity toward Pb2+ in the concentration range of 0.5 nM–1 μM, with a limit of detection (LOD) of 0.285 nM. Besides, the designed aptasensor was successfully used to recognize Pb2+ with excellent selectivity, reproducibility and stability in tap water and tea, providing a potential platform for Pb2+ detection in actual samples.

The feasibility of developing a multispectral imaging method using important wavelengths from hyperspectral images selected by genetic algorithm (GA), successive projection algorithm (SPA) and regression coefficient (RC) methods for modeling and predicting protein content in peanut kernel was investigated for the first time. Partial least squares regression (PLSR) calibration model was established between the spectral data from the selected optimal wavelengths and the reference measured protein content ranged from 23.46% to 28.43%. The RC-PLSR model established using eight key wavelengths (1153, 1567, 1972, 2143, 2288, 2339, 2389 and 2446 nm) showed the best predictive results with the coefficient of determination of prediction (R2P) of 0.901, and root mean square error of prediction (RMSEP) of 0.108 and residual predictive deviation (RPD) of 2.32. Based on the obtained best model and image processing algorithms, the distribution maps of protein content were generated. The overall results of this study indicated that developing a rapid and online multispectral imaging system using the feature wavelengths and PLSR analysis is potential and feasible for determination of the protein content in peanut kernels.

Herein, PtPd nanoparticles compound polyethyleneimine-functionalized reduced graphene oxide (PtPd NPs/PEI-rGO) was used as the substrate material, Exonuclease III (Exo III)-assisted triple-amplified was integrated into electrochemical platform for the detection of deoxynivalenol (DON). PtPd NPs/PEI-rGO as the substrate material increased the surface area of the electrode and improved the conductivity of the electrode. The specific binding of the DON and the aptamer triggered Exo III-assisted cyclic amplification in sample solution and generated trigger (Tr) (cycle I). The hybridization of Tr and Locking probe (LP) activated DNA Walker (W-DNA) (cycle II). Then, W-DNA run continuously with the assistance of Exo III, eventually the current signal was decreased (cycle III). However, in the absence of DON, DNA machine was not driven and the electric signal was relatively high. Under optimal conditions, the detection limit of the aptasensor is 6.9 × 10−9 mg mL−1, and the detection range from 1 × 10−8 mg mL−1 to 1 × 10−4 mg mL−1. In addition, the stability, reproducibility, and real sample detection ability of the aptasensor were studied and obtained satisfactory results.

The authors designed a sensitive label-free electrochemical aptasensor for the detection of sulfaquinoxaline (SQX), including the AuPd NPs@UiO-66-NH2/CoSe2 nanocomposites and RecJf exonuclease-assisted target recycle signal amplification strategy. AuPd NPs@UiO-66-NH2/CoSe2 nanocomposite with excellent conductivity and numerous active sites was successfully synthesized to provide a favorable sensing platform and load more double-strand DNA (dsDNA) on the electrode surface. The negatively charged phosphate group of the oligonucleotide and [Fe (CN)6] 3-/4- repel each other electrostatically, resulting in very low electrical signals. In the presence of SQX, its corresponding aptamer will be released from the double-stranded structure and then digested by RecJf exonuclease, which resulted in the SQX being released to initiate the next recycling to help amplify the DPV signal. Under the optimal conditions, the peak current has a linear relationship with the logarithmic of SQX concentration in the range of 1 pg/mL∼100 ng/mL and the obtained detection limit was 0.547 pg/mL. Furthermore, the contrasted aptasensor possess reliable specificity, reproducibility and stability toward SQX, and has been applied to detect SQX in pork samples with a satisfied recovery varied from 94.40% to 95.98%.

In this work, a sensitive dual mode competitive electrochemical immunosensor based on differential pulse voltammetry (DPV) and square wave voltammetry (SWV) response modes for quantitative determination of dibutyl phthalate (DBP) was successfully established. According to diethylenetriamine (DETA) assisted hydrothermal strategy, a novel N-doped graphene/CoSe2 nanobelt composite was prepared. Afterwards, PEI functionalized NG-CoSe2 and gold nanowires (AuNWs) were further compounded as a preliminary signal amplification platform for immunosensor. Thionine (Thi)-loaded Au@Pt and secondary antibody (Ab2) connected as a signal label. The immobilized coating antigen DBP-BSA and the DBP compete for limited antibody binding sites. The concentration of DBP can be determined by DPV detect the Thi signal loaded on the Thi-Au@Pt-Ab2 label. It can also be determined by SWV mode to detect the current generated by the reaction system of H2O2 and o-phenylenediamine (o-PD) catalyzed by Thi-Au@Pt with peroxidase like properties. Under optimum conditions, the linear ranges of the DPV and SWV modes were 1 pg mL−1∼1 μg mL−1. And LOD were 0.486 pg mL-1 (DPV) and 0.711 pg mL-1 (SWV), respectively. Besides, it exhibited outstanding selectivity, reproducibility, stability and can be used for sensitive detection of DBP in real samples.

A sensitive electrochemical biosensor was constructed for Hg2+ detection based on peonylike Cu-MOFs in situ growth of PtPd NPs bimetallic label S1 and Mg2+-dependent DNAzyme-driven DNA Walker dual amplification signal strategy. The hairpin DNA (HP) and signal label Cu-MOFs@PtPd NPs/S1 were first used to self-assemble on the gold nanorods/poly (diallyldimethylammonium chloride) functionalized graphene (AuNRs/PDDA-Gr) modified electrode, at this time, Cu ions can undergo a valence change to produce a larger initial signal. Here, we designed S2 that can perform dual functions and contains two sequences, on was a substrate sequence of the Mg2+-dependent DNAzyme and the other was a sequence complementary to HP. In the presence of target Hg2+, HP was opened and hybridized with enzymatically sequenced DNA Walker (S2) to preferentially form thymine-Hg2+-thymine (T-Hg2+-T). Then, DNA Walker exhibited catalytic activity of DNAzyme in the presence of Mg2+ to continuously cleave Cu-MOFs@PtPd NPs/S1, resulting in a decrease of electrochemical signal. Under optimal conditions, the change of current was linearly related to the negative logarithm of the Hg2+ concentration in the detection range of 0.001–100 nM with a low detection limit of 0.52 pM. Moreover, the proposed aptasensor was successfully applied in detection of milk powder samples.

A sensitive and selective electrochemical Pb2+ sensor was developed based on GR-5 DNAzyme and exonuclease III-assisted target recycling amplification. When target Pb2+ existed, GR-5 DNAzyme was cleaved into two free DNA fragments. One of the fragments could open the hairpin DNA (HP1) modified on the electrode to form DNA duplex with blunt end at the 3′-terminus and triggered Exo III cleavage process. A large amount of residual part of HP1 were obtained by the Exo III-aided recycling which could hybridized with another hairpin DNA labeled with methylene blue, resulting in the dramatic increase of current. The electrochemical signal of methylene blue positive correlated with the Pb2+ concentration. The proposed sensor has the concentration ranging from 10−11 to 8×10−6 mol/L with a detection limit of 2.74 p mol/L. Moreover, the analysis of Pb2+ concentration in real water revealed that the proposed biosensor has a promising application in environment monitoring.

The ICP34.5 protein of herpes simplex virus type 1 is a neurovirulence factor that plays critical roles in viral replication and anti-host responses. One of its functions is to recruit protein phosphatase 1 (PP1) that leads to the dephosphorylation of the α subunit of translation initiation factor eIF2 (eIF2α), which is inactivated by infection-induced phosphorylation. As PP1 is a protein phosphatase with a wide range of substrates, the question remains to be answered how ICP34.5 directs PP1 to specifically dephosphorylate eIF2α. Here we report that ICP34.5 not only binds PP1 but also associates with eIF2α by in vitro and in vivo assays. The binding site of eIF2α is identified at amino acids 233–248 of ICP34.5, which falls in the highly homologous region with human gene growth arrest and DNA damage 34. The interaction between ICP34.5 and eIF2α is independent of the phosphorylation status of eIF2α at serine 51. Deletion mutation of this region results in the failure of dephosphorylation of eIF2α by PP1 and, consequently, interrupts viral protein synthesis and replication. Our data illustrated that the binding between viral protein ICP34.5 and the host eIF2α is crucial for the specific dephosphorylation of eIF2α by PP1. We propose that herpes simplex virus protein ICP34.5 bridges PP1 and eIF2α via their binding motifs and thereby facilitates the protein synthesis and viral replication.

Chemical compounds activating innate responses may present potential adjuvants for the vaccine development. Levamisole (LMS), demonstrated as a potent adjuvant for DNA and viral killed vaccines in our previous studies, may activate such responses. To confirm this notion, LMS combined with the recombinant HBsAg (rHBsAg) was investigated. Compared to the vaccination with rHBsAg alone, LMS could up-regulate the expressions of TLR7&8, MyD88, IRF7 and their downstream pro-inflammatory cytokines including IFN-α and TNF-α, which promote DCs activation. Strikingly, we find that the combination of LMS and alum adjuvant synergistically enhances immunogenicity of rHBsAg and leads to a robust cell-mediated response demonstrated by the higher level of IgG2a/IgG1, T cell proliferation, and importantly, a high level of antigen-specific CTL and IFN-γ production within these activated CD8 + T cells. The achieved robust responses are at a comparative level with CpG + alum used as a positive control adjuvant in mice. The combination of LMS + alum with rHBsAg may provide a cost-effective, safe, and effective therapy to treat those individuals chronically infected by HBV, since antigen-specific cellular immunity is implicated for the clearance of HBV chronic infection.

Aerosol transmission of foot and mouth disease virus (FMDV) is believed to be an important route of infection. Induction of mucosal response is thought to be effective way against such infection. Various approaches have been developed including the use of molecules adjuvant and polymers delivery for the mucosal delivery of DNA vaccine. In this study, using low molecular weight chitosan as a delivery vehicle, we investigated whether co-administration intranasally of the FMDV DNA vaccine, pcD-VP1 and a construct expressing IL-15 as the molecular adjuvant can enhance mucosal and systemic immune responses in animals. Compared to the group intranasally immunized with pcD-VP1 alone, the group immunized with the molecular adjuvant not only was induced higher level of mucosal sIgA but also serum IgG. Interestingly, intranasal delivery of the IL-15 construct with pcD-VP1 significantly enhanced the cell-mediated immunity (CMI) compared to the pcD-VP1 alone, as evidenced by the higher level of antigen-specific T-cell proliferation, cytotoxic T lymphocyte (CTL) response and higher expressions of IFN-gamma in both CD4+ and CD8+ T cells inform the spleen and mucosal sites. Consistently, IL-15 as adjuvant provided higher level of FMDV neutralizing antibody against FMDV and high secretions of IgA producing cells in mucosal tissues. Taken together, the results demonstrated that intranasal delivery of IL-15 as a mucosal adjuvant can enhance the antigen-specific mucosal and systemic immune responses, which may provide a protection against the FMDV initial infection.

To improve efficacy of DNA vaccination, various approaches have been developed, including the use of plasmid expressing co-stimulatory molecules as molecular adjuvants. In this study, we investigated whether co-inoculation of a construct expressing either 4-1BBL or OX40L as the molecular adjuvant with FMDV DNA vaccine, pcD-VP1, can increase immune responses and protective efficacies. Compared to the group immunized with pcD-VP1 alone, the co-inoculation of either molecular adjuvant induced a higher ratio of IgG2a/IgG1, higher levels of expression of IFN-gamma in CD4(+) and CD8(+) T cells and antigen-specific CTL responses, and more importantly provided an enhanced protection against the live FMDV challenge in animals. Concurrently, 4-1BBL as the molecular adjuvant dramatically reduced the viral loads of FMDV in vivo after the challenge. Together, the results demonstrate that co-stimulatory molecules 4-1BBL and OX40L can enhance the antigen-specific cell-mediated responses elicited by VP1 DNA vaccine and provide an enhanced protective efficacy with the reduced viral loads.

To explore adjuvants that are capable of promoting Th1-biased immune response, we investigated the usefulness of levamisole (LMS) as one such adjuvant for two different preparations of killed viral vaccines, derived from the foot mouth disease virus (FMDV) or the porcine respiratory reproductive syndrome virus (PRRSV) and tested respectively in BALB/c or C57 BL/6 mice. The results showed that LMS induced different types of immune responses in the host, depending on its dosage. While a high level of serum IgG was induced by using LMS at 2%, the most robust T cell proliferation was induced with LMS at 0.5%. The Th1 and Th2 cytokine profiles, which tracked well with the antibody and T cell responses, were similarly influenced by the dose of LMS. Moreover, the enhanced T cell response correlated with increased expression of MHC and co-stimulatory molecules and decreased expression of the suppressors of cytokine signaling molecules (SOCS1 and SOCS3) in the spleen, suggesting that it is mediated by the antigen presentation, co-stimulator signaling, and cytokine production pathways. These results establish that LMS can be used to induce Th1-biased immune responses when combined with killed-virus-based antiviral vaccines and that such adjuvant effect depends on the optimal LMS dosage.

Although immunization has been used for eliciting immune response, here we show that it can also induce immune suppression. When a DNA vaccine encoding a viral antigen such as the VP1 protein from the foot and mouth disease virus is administered together with its recombinant protein antigen or a viral preparation containing the same antigen, the immunized animals developed significantly reduced antigen-specific T cell-mediated responses and became impaired to subsequent rechallenge with the same antigen. The induction of immune suppression is mediated by suppressor T cells, as demonstrated by an adoptive transfer experiment and mixed lymphocyte reactions. The induction of immune suppression in immunized animals is also correlated with a shift of cytokine balance, as reflected by an elevated level of IL-10 and reduced level of IFN-γ or IL-2. Hence, co-immunization with DNA- and protein-based vaccines may represent a novel means for inducing active suppression against untoward immunity.

Vaccination against the SARS-CoV infection is an attractive means to control the spread of viruses in public. In this study, we employed a DNA vaccine technology with the levamisole, our newly discovered chemical adjuvant, to generate Th1 type of response. To avoid the enhancement antibody issue, genes encoding the nucleocapsid, membrane, and envelope protein of SARS-CoV were cloned and their expressions in mammalian cells were determined. After the intramuscular introduction into animals, we observed that the constructs of the E, M, and N genes could induce high levels of specific antibodies, T cell proliferations, IFN-gamma, DTH responses, and in vivo cytotoxic T cells activities specifically against SARS-CoV antigens. The highest immune responses were generated by the construct encoding the nucleocapsid protein. The results suggest that the N, M, and E genes could be used as the targets to prevent SARS-CoV infection in the DNA vaccine development.