Application Of Bioassay Research Articles

The usefulness of ecotoxicological tools to improve the assessment of water bodies in a climate change reality

This study aimed to analyse the added value of using ecotoxicological tools to complement and improve the assessment of natural water bodies status, in situations of climate change, with a higher frequency of extreme events as floods or droughts.Four water bodies of streams in the Guadiana Basin (Álamos, Amieira, Lucefécit, Zebro) were studied in 2017 and 2018 and classified based on the Water Framework Directive (WFD) parameters: Biological Quality Element – Phytobenthos (diatoms), General chemical and physicochemical elements, Specific pollutants, and Priority Substances. Complementarily, bioassays (including lethal and sublethal parameters) were carried out with organisms of different trophic levels: (i) the bacteria Aliivibrio fischeri; (ii) the microalgae Pseudokirchneriella subcapitata; (iii) the crustaceans Daphnia magna, Thamnocephalus platyurus and Heterocypris incongruens. A classification system with 5 scores was developed, permitting to classify water bodies from non-toxic (EC50 > 100 %; growth and feeding rate > 80 %; blue) to highly toxic (EC50 < 10 %; growth and feeding rate < 10 %; red). The comparison between the classification based on the WFD parameters and on ecotoxicological endpoints showed similar results for 71 % of the samples, and significant positive Pearson correlations were detected between the diatom-based Specific Polluosensitivity Index (SPI) and EC50V.fisheri, the algae growth rate and Shannon diversity index. These results indicate that when the biological quality elements cannot be used (namely under drought or flooding conditions) the application of ecotoxicological bioassays may be a good alternative. Further, when ecotoxicological parameters were included, an increase of worse classifications (Bad and Poor) was observed, revealing an improvement in the sensitivity of the classification, mainly in presence of specific and priority substances. So, the ecotoxicological analysis appears to provide useful information regarding the potential presence of both known and unknown contaminants at concentrations that cause biological effects (even within the WFD limits), in agreement with several authors that have already suggested its use in biomonitoring.

Electrochemiluminescent determination of sphingomyelin in milk based on polyaniline hydrogel coupled with enzyme-functionalized Au nanoparticles

In this paper, sphingomyelin (SM) is detected by a polyaniline hydrogel and Au nanoparticles with enzyme modified electrode (GCE/PAniH/AuNPs@enzyme). After a battery of enzymic degradation, SM can generate H2O2 and enhance the electrochemiluminescence (ECL) response of luminol, which endows the sensor with good sensitivity, specifiity and repeatability. Additionally, the proposed ECL biosensor displays good analytical performances with a wide range from 10.0 μg·mL−1 to 250.0 μg·mL−1 as well as a low detection limit of 3.50 μg·mL−1 (S/N = 3). When the ECL biosensor is used in the detection of SM in milk samples, satisfactory results are obtained, indicating that PAniH/AuNPs@enzyme will serve as a promising ECL material in the applications of H2O2-related bioassay in the future.

Immobilization-free dual-aptamer-based photoelectrochemical platform for ultrasensitive exosome assay

Exosomes, involved in cancer-specific biological processes, are promising noninvasive biomarkers for early diagnosis of cancer. Herein, an immobilization-free dual-aptamer-based photoelectrochemical (PEC) biosensor was proposed for the enrichment and quantification of cancer exosome based on photoactive bismuch oxyiodide/gold/cadmium sulfide (BiOI/Au/CdS) composites, nucleic acid-based recognition and signal amplification. In this biosensor, the recognition of exosome by two aptamers would trigger the deoxyribonucleotidyl transferase (TdT) enzyme-aided polymerization, leading to the enrichment of alkaline phosphatase (ALP) on Fe3O4 surface. After magnetic separation, ALP could catalyze the generation of ascorbic acid (AA) as electron donor and initiate the following redox cycle reaction for further signal amplification. Furthermore, all the above processes were performed in solution, the recognition and signal amplification efficiency would be superior than the heterogeneous strategy owing to the avoidance of steric hindrance effect. As a result, the proposed PEC biosensor was capable of enriching and detecting of cancer exosomes with high sensitivity and selectivity. The linear range of the biosensor was from 1.0 × 102 particles·μL−1 to 1.0 × 106 particles·μL−1 and the detection limit was estimated to be 21 particles·μL−1. Therefore, the proposed PEC biosensor holds great promise in quantifying tumor exosome for nondestructive early clinical cancer diagnosis and various other bioassay applications.

A test battery approach for ecotoxicological evaluation of disinfectants prepared on the basis of sodium hypochlorite

Abstract The research is related to the assessment of the overall sensitivity and applicability of many bioassays representing different trophic levels for the preliminary ecotoxicological testing of commercial disinfectants marked as SA (SAVO, Bochemie a.s., Czech Republic) and DoAm (Dom Amor, BOOS – Biologické substancie, Slovak Republic). Disinfectants were prepared based on sodium hypochlorite (NaOCl). SA contains only NaOCl while earthworm enzymes enrich DoAm. In both commercial products, the NaOCl content did not exceed 5%; pure NaOCl was used as a 10% solution as well. For bioassay, water organisms (Vibrio fischeri, Desmodesmus subspicatus, Daphnia magna and Tubifex tubifex) situated in various trophic levels were used. All the tests were confirmed as suitable for the determination of chlorine’s adverse effects. Because the organisms’ reactions to the tested disinfectants varied, they can be arranged in the following rank order of sensitivity: V. fischeri ≥ D. subspicatus &gt;&gt; D. magna &gt;&gt; T. tubifex. The toxicity of the tested substances (NaOCl, SA, DoAm) depends on the length of exposure, the species of the organism and FAC (free available chlorine) content. The effective concentrations of the tested products ranged from 0.13 to 8.18 μL L–1, i.e., 0.014 to 0.26 mg L–1 of FAC. However, in the tests with T. tubifex and V. fischeri the toxic effect of NaOCl was the weakest; the tests with other two organisms confirmed this compound as the most toxic. Only for T. tubifex (96 hrs) did SA have a more adverse effect than DoAm.

A high performance dual-mode biosensor based on Nd-MOF nanosheets functionalized with ionic liquid and gold nanoparticles for sensing of ctDNA.

A dual-mode biosensor constructed based on photoelectrochemical (PEC) and electrochemical (EC) property was developed for assaying circulating tumor DNA (ctDNA), which is commonly used for triple-negative breast cancer diagnosis. Ionic liquid functionalized two-dimensional Nd-MOF nanosheets were successfully synthesized through a template-assisted reagent substituting reaction. Nd-MOF nanosheets integrated with gold nanoparticles (AuNPs) were able to improve photocurrent response and supply active sites for assembling sensing elements. To achieve selective detection of ctDNA, thiol-functionalized capture probes (CPs) were immobilized on the Nd-MOF@AuNPs modified glassy carbon electrode surface, thereby generating a "signal-off" photoelectrochemical biosensor for ctDNA under visible light irradiation. After the recognition of ctDNA, ferrocene-labeled signaling probes (Fc-SPs) were introduced into the biosensing interface. After hybridization between ctDNA and Fc-SPs, the oxidation peak current of Fc-SPs generated from square wave voltammetry can be employed as a "signal-on" electrochemical signal for ctDNA quantification. Under the optimized conditions, a linear relationship was obtained to the logarithm of ctDNA concentration in between 1.0fmolL-1 to 10nmolL-1 for the PEC model and 1.0fmolL-1 to 1.0nmolL-1 for the EC model. The dual-mode biosensor can provide accurate results for ctDNA assays, effectively eliminating the probable occurrence of false-positive or false-negative results in single-model assays. By switching DNA probe sequences, the proposed dual-mode biosensing platform can serve as a strategy for detecting other DNAs and possesses broad applications in bioassay and early disease diagnosis.

A Versatile PdRu Bimetallic Nanoenzyme-Integrated Enzyme-Linked Immunosorbent Assay for Highly Sensitive Escherichia coli O157:H7 Detection.

Nanozymes have drawn much attention as an enzyme mimetic with low cost and stability in enhancing analytical performance. Herein, a peroxidase-mimicking nanozyme-improved enzyme-linked immunosorbent assay (ELISA) was developed employing the bimetallic PdRu nanozyme to replace the natural enzymes as a catalytic carrier for the sensing of Escherichia coli O157:H7 (E. coli O157:H7). The PdRu nanozyme displayed ultrahigh catalytic activity, possessing a catalytic rate that was 5-fold higher than horseradish peroxidase (HRP). In addition, PdRu exhibited great biological affinity with antibody (affinity constant was about 6.75 × 1012 M) and high stability. All those advantages ensure the successful establishment and the construction of a novel colorimetric biosensor for E. coli O157:H7 detection. PdRu-based ELISA not only achieved an ultrasensitive detection sensitivity (8.7 × 102 CFU/mL) by approximately 288-fold as compared to the traditional HRP-based ELISA and also possessed satisfactory specificity and reproducibility (relative standard deviation (RSD) < 10%). Furthermore, the feasibility of PdRu-ELISA was further evaluated by detecting E. coli O157:H7 in actual samples with satisfactory recoveries, indicating its potential for applications in bioassays and clinical diagnostics.

Application of Luminescent Bacteria Bioassay in the Detection of Pollutants in Soil

The luminescent bacteria bioassay has been commonly used in the detection of environmental pollutants. Compared with traditional chemical and other biological detection methods, the luminescent bacteria bioassay has many demonstrated advantages such as a sensitive response, low cost, high efficiency, and environmental friendliness. The traditional luminescent bacteria bioassay has poor reproducibility and cannot achieve undisturbed soil testing, and the use of leach liquor also affects the results. This paper reviews the research progress and existing issues for the traditional luminescent bacteria bioassay used in the detection of soil pollutants. The luminescence mechanisms and detection principles of three commonly used luminescent bacteria, i.e., Vibrio fischeri, Photobacterium phosphoreum, and Vibrio qinghaiensis, are discussed and compared. In addition, two new luminescent bacteria bioassays are introduced to detect soil pollutants. One method is based on recombinant luminescent bacteria obtained with a gene-modification technique. This method can realize specific detection and enhance sensitivity, but it still cannot achieve undisturbed soil detection. The other method involves using magnetic nanoparticle (MNP)-based biosensors made from luminescent bacteria and MNPs. It can realize the accurate detection of the biological toxicity of the combined pollutants in soil without disturbing the soil’s integrity. This study shows that MNP-based biosensors have good application prospects in soil pollution detection, but the mechanism behind their utility still needs to be investigated to realize their popularization and application.

Design and Development of a Traveling Wave Ferro-Microfluidic Device and System Rig for Potential Magnetophoretic Cell Separation and Sorting in a Water-Based Ferrofluid.

The timely detection and diagnosis of diseases and accurate monitoring of specific genetic conditions require rapid and accurate separation, sorting, and direction of target cell types toward a sensor device surface. In that regard, cellular manipulation, separation, and sorting are progressively finding application potential within various bioassay applications such as medical disease diagnosis, pathogen detection, and medical testing. The aim of this paper is to present the design and development of a simple traveling wave ferro-microfluidic device and system rig purposed for the potential manipulation and magnetophoretic separation of cells in water-based ferrofluids. This paper details in full: (1) a method for tailoring cobalt ferrite nanoparticles for specific diameter size ranges (10-20 nm), (2) the development of a ferro-microfluidic device for potentially separating cells and magnetic nanoparticles, (3) the development of a water-based ferrofluid with magnetic nanoparticles and non-magnetic microparticles, and (4) the design and development of a system rig for producing the electric field within the ferro-microfluidic channel device for magnetizing and manipulating nonmagnetic particles in the ferro-microfluidic channel. The results reported in this work demonstrate a proof of concept for magnetophoretic manipulation and separation of magnetic and non-magnetic particles in a simple ferro-microfluidic device. This work is a design and proof-of-concept study. The design reported in this model is an improvement over existing magnetic excitation microfluidic system designs in that heat is efficiently removed from the circuit board to allow a range of input currents and frequencies to manipulate non-magnetic particles. Although this work did not analyze the separation of cells from magnetic particles, the results demonstrate that non-magnetic (surrogates for cellular materials) and magnetic entities can be separated and, in some cases, continuously pushed through the channel based on amperage, size, frequency, and electrode spacing. The results reported in this work establish that the developed ferro-microfluidic device may potentially be used as an effective platform for microparticle and cellular manipulation and sorting.

Deciphering the origin of total estrogenic activity of complex mixtures.

Identifying compounds with endocrine properties in food is getting increasingly important. Current chemical analysis methodology is mainly focused on the identification of known substances without bringing insight for biological activity. Recently, the application of bioassays has been promoted for their potential to detect unknown bioactive substances and to provide information on possible interactions between molecules. From the toxicological perspective, measuring endocrine activity cannot inform on endocrine disruption and/or health risks without sufficient knowledge on the nature of the responsible factors. The present study addresses a promising approach using High Performance Thin-Layer Chromatography (HPTLC) coupled to bioassays were analyzed using the Liquid Chromatography Mass-Spectrometry (LC-MS). The estrogen receptor activation was assessed using the transcription activation Estrogen Receptor Alpha Chemical Activated LUciferase gene eXpression assay (ERα- CALUX) and the HPTLC coupled to the Estrogen Screen Yeast assay (p-YES). Seven isoflavones were identified in the soy isolates. Estrogen receptor activation was assessed for both, the identified isoflavones and the soy isolates with ERα-CALUX test. Correlation between the soy isolates extracts and the identified isoflavones was shown. Moreover, p-YES revealed the presence of an estrogenic bioactive zone. Analysis of the bioactive zone through LCHRMS highlighted signals corresponding to several isoflavones already detected in the isolates as well as two additional ones. For all detected isoflavones, an estrogenic activity dose-response was established in both bioassays. Finally, genistein, daidzein, and naringenin were found as the most active substances. A concordance analysis integrating the analytical and bioassay data indicated that genistein and daidzein were the drivers of the estrogenic activity of these soy protein isolates. Altogether, these data suggest that the integration of HPTLC-bioassay together with chemical analysis is a powerful approach to characterize the endocrine activity of complex mixtures.

Zn2+-Modified Nonmetal Porphyrin-Based Metal–Organic Frameworks with Improved Electrochemiluminescence for Nanoscale Exosome Detection

Exploring effective and robust strategies for enhancing electrochemiluminescence (ECL) emissions of porphyrin-based metal–organic frameworks (MOFs) is of great importance for expanding their applications in bioassays. Herein, a simple, convenient, and effective endogenous strategy of post-synthesis-modified Zn2+ was proposed to enhance ECL of nonmetal porphyrin-based MOFs. The ECL emissions of porphyrin-cobuilt UiO-66-NH2 (TCPP/UiO-66-NH2), PCN-224, PCN-222, and Ce–TCPP–LMOF could be enhanced 31.9, 47.1, 49.9, and 19.2 times, respectively. By studying TCPP/UiO-66-NH2 nanoluminophores as a model, Zn2+ was incorporated into TCPP/UiO-66-NH2 through the coordination of Zn and pyrrolic N of TCPP. The ECL enhancement was attributed to the conversion of TCPP to ZnTCPP with high emission efficiency and MOFs could enrich co-reactants, shorten the ion/electron-transfer distance, and render electrochemical activation of porphyrin luminophores. On this basis, a simple ECL biosensor for detecting nanoscale exosomes was developed based on the boosted ECL signal of Zn–TCPP/UiO-66-NH2 nanoluminophores without additional recognition and amplification elements. The ECL biosensor exhibited good sensitivity with a detection range from 1.00 × 104 to 3.16 × 106 particles/μL and a detection limit of 9.08 × 103 particles/μL (S/N = 3). The linear range and detection limit of the proposed label-free ECL biosensor are better than most of the existing label-free methods for detecting exosomes, indicating its good performance as a powerful tool for accurate and sensitive detection of HepG2-derived exosomes. As a result, this work provides inspiration for exploring strategies to enhance ECL efficiencies of porphyrin-based MOFs, which has important application prospects in sensitive bioassays.

Mosquito Adult Bioassays.

Topical application and bottle bioassays measure the responses of adult mosquitoes to specific doses of an insecticide (dose-response). Topical application bioassays are generally used to measure the dose-response of adult mosquitoes to insecticides in which the amount (dose) of insecticides the mosquitoes receive is known in the laboratory. Here, a 0.5-µL drop of the insecticide dissolved in a relatively nontoxic solvent, such as acetone, is applied to the thorax of insects, and the insects' susceptibility to the insecticide is determined in terms of either the median lethal dose (LD50) or 90% of the mortality lethal dose (LD90). Bottle bioassays measure the dose-responses in which the exact amount of insecticide in a bottle is known while the exact amount of insecticide that mosquitoes (field-collected or laboratory-susceptible) receive is not known. Bottle bioassays can be either single dose tests or multiple dose applications. The bottle bioassay described in this protocol is a modified form of the World Health Organization (WHO) and U.S. Centers for Disease Control (CDC) bottle bioassays. For the single bottle assay, a detailed protocol with the amount (dose/bottle) of each insecticide and threshold times is provided by the CDC; here we provide protocols for topical and bottle bioassay applications with multiple doses.

Pt-anchored MoS2 nanotubes with enzyme reaction for photoelectrochemical biosensing of miRNA-155

The development of photoactive materials based on single-atom catalysts is essential to improve the performance of photoelectrochemical (PEC) biosensors. Herein, we have designed Pt atoms-anchored MoS2 nanotubes (Pt-MoS2NT) as photoactive materials. Catalytic kinetics of Pt-MoS2NT can enable efficient separation of photogenerated electron-hole pairs and extend the charge carrier lifetime, which makes Pt-MoS2NT possess a significantly enhanced photocurrent response compared to MoS2NT. During the detection of miRNA-155, horseradish peroxidase-catalyzed reaction produces a solid precipitate (benzo-4-chlorohexadienone), which can block the electron transport pathway between the electrolyte solution and Pt-MoS2NT, resulting in a significant reduction of the PEC signal. Based on a dual strategy of single-atoms Pt enhanced photocurrent response and enzymatic reaction, the constructed PEC biosensor achieves ultra-sensitive detection of miRNA-155 (detection limit up to 3.1 aM). The present work confirms the advantages of single-atom catalysts for bioassay applications.

Applicability of Different Methods for Quantifying Virucidal Efficacy Using MENNO Florades and Tomato Brown Rugose Fruit Virus as an Example

After entry of a quarantine/regulated pathogen, infected plants shall be destroyed, and the cultivated area (e.g., greenhouse) shall be disinfected. Therefore, the selection of an effective disinfectant plays an important role. With the availability of different methods for virus quantification, we investigated the application of quantitative ELISA (qELISA), RT-qPCR (reverse transcription-quantitative polymerase chain reaction), and bioassays for the quantification of disinfectant efficacy. Therefore, we estimated the titer reduction in tomato brown rugose fruit virus (ToBRFV), a regulated pathogen, in plant sap and on germ carriers after treatment with MENNO Florades 4% for 16 h. The virus load before and after the treatment was measured with the mentioned methods. The RT-qPCR and qELISA methods showed very low efficacy in the presence of the disinfectant. Although bioassays are time-consuming, need purified particles for establishing the quantification models, and are less sensitive than RT-qPCR, they were able to quantify the differences in virus titer in the presence/absence of disinfectant. Interestingly, the bioassays reached at least the lower limit sensitivity of a qELISA. By being less sensitive to the presence of the disinfectant, bioassays proved to be the only technique for the determination of the disinfectant efficacy against ToBRFV on different germ carriers as well as on virus-infected plant sap.

Are the ecotoxicological tools viable to evaluate the effectiveness of wastewater treatment plant effluents?

Ecotoxicological tools have proved to be sensitive and appropriate for the evaluation of the effectiveness of treatments used in wastewater treatment plants (WWTP). The objective of this study was to assess the applicability of bioassays and biomarkers to evaluate the efficiency of different treatments throughout WWTP samples[A—raw influent, B—preliminary effluent, C—final effluent, and D—receiving stream], seasonally over 1 year, through a multispecies approach: i) bacterial cell viability [Escherichia coli, Rhodopirellulla rubra, Arthrobacter sp., and Pseudomonas putida]; ii) microalgae Raphidocelis subcapitata and the macrophyte Lemna minor growth inhibition; and iii) microcrustacean Daphnia magna acute and feeding rate assays. Total chlorophyll, malondialdehyde, and proline levels were evaluated in L. minor, and catalase, glutathione-S-transferase activities, and thiobarbituric acid reactive substances levels were quantified in D. magna, after exposure to wastewater samples. Overall, the tested species showed different sensitivities, P. putida = Arthrobacter sp. = R. rubra < R. subcapitata < E. coli = D. magna = L. minor, to the collected samples. The results obtained in D. magna and L. minor assays demonstrated that these organisms can be used in programs for monitoring and environmental assessment of wastewater effluents. The present study demonstrates the usefulness of ecotoxicological tools, with multispecies and different endpoints, to assess the effectiveness of WWTPs. Moreover, it is important to ensure that WWTP implements a monitoring program to minimize the discharge of effluents that compromise the environment in order to guarantee the good ecological quality of the environmental ecosystems.

AC-electric-field-controlled multi-component droplet coalescence at microscale.

Droplet coalescence with fast response, high controllability and monodispersity has been widely investigated in industrial production and bioengineering. Especially for droplets with multiple components, programmable manipulation of such droplets is crucial for practical applications. However, precise control of the dynamics can be challenging, owing to the complex boundaries and the interfacial and fluidic properties. AC electric fields, with their fast response and high flexibility, have attracted our interest. We design and fabricate an improved flow-focusing microchannel configuration together with a non-contact type of electrode featuring asymmetric geometries, based on which we conduct systematic investigations of the AC-electric-field-controlled coalescence of multi-component droplets at the microscale. Parameters such as flow rates, component ratio, surface tension, electric permittivity and conductivity were given our attention. The results show that droplet coalescence in different flow parameters can be achieved in milliseconds by adjusting the electrical conditions, which shows high controllability. Specifically, both the coalescence region and reaction time can be adjusted by a combination of applied voltage and frequency, and unique merging phenomena have appeared. One is contact coalescence with the approach of paired droplets, while the other is squeezing coalescence, which occurs in the start position and promotes the merging process. The fluid properties, such as the electric permittivity, conductivity and surface tension, present a significant influence on merging behavior. The increasing relative dielectric constant leads to a dramatic reduction of the start merging voltage from the original 250 V to 30 V. The range of effective voltage for coalescence decreases with the addition of surfactant, offering a stricter and yet higher selectivity on electrical conditions, about 1500 V. The conductivity presents a negative correlation with the start merging voltage due to the reduction of the dielectric stress, from 400 V to 1500 V. Finally, we achieve the precise fabrication process of the Janus droplet via implementation of the proposed method, where the components of the droplets and the coalescence conditions are well controlled. Our results can serve as a potent methodology to decipher the physics of multi-component droplet electro-coalescence and contribute to applications in chemical synthesis, bioassay and material synthesis.

BODIPY-based near-infrared semiconducting polymer dot for selective yellow laser-excited cell imaging.

Semiconducting polymer dots (Pdots) with both narrow-band absorption and emission are desirable for multiplexed bioassay applications, but such Pdots with absorption peaks beyond 400 nm are difficult to achieve. Here we describe a donor-energy transfer unit-acceptor (D-ETU-A) design strategy to produce a BODIPY-based Pdot that exhibits simultaneously narrow absorption and emission bands. A green BODIPY (GBDP) unit was employed as the main building block of the polymer backbone, conferring a strong, narrow-band absorption around 551 nm. An NIR720 acceptor provides narrow-band NIR emission. The small Stokes shift of the GBDP donor allows introduction of a benzofurazan-based ETU, resulting in a ternary Pdot with a fluorescence quantum yield of 23.2%, the most efficient yellow-laser excitable Pdot. Due to the strong absorbance band centered at 551 nm and weak absorbance at 405 nm and 488 nm, the Pdot showed high single-particle brightness when excited by a 561 nm (yellow) laser, and selective yellow laser excitation when used to label MCF cells, with much greater brightness when excited at 561 nm than at 405 nm or 488 nm.

Frequency and Amplitude Optimizations for Magnetic Particle Spectroscopy Applications

Nowadays, there is a growing interest in the field of magnetic particle spectroscopy (MPS)-based bioassays. MPS monitors the dynamic magnetic response of surface-functionalized magnetic nanoparticles (MNPs) upon excitation by an alternating magnetic field (AMF) to detect various target analytes. This technology has flourished in the past decade due to its low cost, low background magnetic noise interference from the biomatrix, and fast response time. A large number of MPS variants have been reported by different groups around the world, with applications ranging from disease diagnosis to foodborne pathogen detection and virus detection. However, there is an urgent need for guidance on how to optimize the sensitivity of MPS detection by choosing different types of MNPs, AMF modalities, and MPS assay strategies (i.e., volume- and surface-based assays). In this work, we systematically study the effect of AMF frequencies and amplitudes on the responses of single- and multicore MNPs under two extreme conditions, namely, the bound and unbound states. Our results show that some modalities such as dual-frequency MPS utilizing multicore MNPs are more suitable for surface-based bioassay applications, whereas single-frequency MPS systems using single- or multicore MNPs are better suited for volumetric bioassay applications. Furthermore, the bioassay sensitivities for these modalities can be further improved by a careful selection of AMF frequencies and amplitudes.

Influence of Plant Resistance in Certain Genotypes of Green Gram on Insecticide Tolerance on Spotted Pod Borer, Maruca vitrata (Geyer)

Ten genotypes of green gram viz., WGG-42, LGG-407, PM-115, MGG-360, PM-110, LGG-410, PM-112, TM-962, LGG-450 and LGG-460 were screened for their susceptibility to Spotted pod borer, Maruca vitrata (Geyer) infestation at wetland farm, S.V.Agricultural College, Tirupati in a randomized block design (RBD) during the late Kharif season of 2014. Two crops were raised one at during last week of August-2014 and second was raised durin second week of September-2014. Readings on the number of Maruca webbings per plant, total number of caterpillars per plant and per cent infestation were taken at weekly intervals. Field screening experiments which were conducted on green gram genotypes against M. vitrata infestation revealed that WGG-42, TM-962 and MGG-360 were observed resistant, moderately resistant and susceptible reaction based on number of webbings per plant and number of caterpillars per plant. Further investigation on feeding preference of Maruca by free-choice and no-choice techniques on selected genotypes of green gram in the laboratory to confirm the resistance ranking observed in the field screening have yielded similar resistance reaction to Maruca infestation. Larvae of the first instar were allowed to feed on the susceptible and resistant genotypes of green gram upto third instar. At the third instar stage, they were allowed for topical bioassay application with Chlorpyriphos insecticide after taking the larval weights. The larvae which fed on the WGG-42 (resistant) gave LC50 (Lethal Concentration) and LD50 (Lethal Dose) values of 1.39 µL/ml and 36.98 µg/g and the larvae which fed on the MGG-360 (susceptible) gave LC50 and LD50 values of 1.63 µL/ml and 36.85 µg/g.

2D MXene-Based Biosensing: A Review.

MXene emerged as decent 2D material and has been exploited for numerous applications in the last decade. The remunerations of the ideal metallic conductivity, optical absorbance, mechanical stability, higher heterogeneous electron transfer rate, and good redox capability have made MXene a potential candidate for biosensing applications. The hydrophilic nature, biocompatibility, antifouling, and anti-toxicity properties have opened avenues for MXene to perform in vitro and in vivo analysis. In this review, the concept, operating principle, detailed mechanism, and characteristic properties are comprehensively assessed and compiled along with breakthroughs in MXene fabrication and conjugation strategies for the development of unique electrochemical and optical biosensors. Further, the current challenges are summarized and suggested future aspects. This review article is believed to shed some light on the development of MXene for biosensing and will open new opportunities for the future advanced translational application of MXene bioassays.

Self-coordinated nanozyme on Cu3BiS3 nanorods for high-performance aptasensing.

Anovel strategy is reportedto access high-performance nanozymes via the self-coordination of ferrocyanides ([Fe(CN)6]4-) onto the surface of the Cu3BiS3 (CBS) nanorods. Notably, the in situ formed nanozymes had high catalytic activity, good stability, low cost, and easy mass production. The formed nanozyme catalyzed the oxidation of the typical chromogenic substrate of 3,3',5,5'-tetramethylbenzidine (TMB) with a distinctive absorption peak at 652nm, accompanied by a blue color development. Moreover, the attachment of deoxyribonucleoside 5'-monophosphates (dNMP) beforehand onto the surface of CBS prevented coordination of ferrocyanides and resulted in the tunable formation of the nanozyme, thereby enabling the construction of an exquisite biosensing platform. Taking the aptasensing of chloramphenicol (CAP) as an example, the engineered nanozyme allowed the construction of a homogenous, label-free, and high-performance bioassay in terms of its convenience and high sensitivity. Under the optimal conditions, changes in the absorption intensity at 652nm for the oxidized TMB provides a good linear correlation with the logarithm of CAP concentrations in the range 0.1pM to 100nM, and the limit of detection was 0.033pM (calculated from 3σ/s). Considering a vast number of bioreactions can be connected to dNMP production, we expect the engineerable nanozyme as a universal signal transduction scaffold for versatile applications in bioassays. Through the attachment of deoxyribonucleoside 5'-monophosphate (dNMP) on the surface of CBS to regulate the generation of self-coordinated nanozyme CBS/BiHCF, a homogeneous, label-free, and high-performance universal aptasensing platform was constructed.