Environmental Diagnostic Applications Research Articles

Incorporation of quantum carbon dots into a PVP/ZnO hydrogel for use as an effective hexavalent chromium sensing platform

Hydrogels offer a unique medium for sensing applications as they can draw upon the benefits of both solid and liquid sensing platforms. Incorporation of functionalised fluorescent nanoparticles within the hydrogel matrix results in a three-dimensional nanocomposite capable of interacting with water-soluble analytes, facilitating quantitative sensing applications. Here, we report the solvothermal synthesis of a novel Polyvinylpyrrolidone assembled hydrogel stabilised with zinc oxide quantum dots which does not require additional organic crosslinkers. Functionalization of these hydrogel with novel, brightly photoluminescent 2-amino-2-methyl-1-propanol quantum carbon dots (quantum yield of 62.5%) results in a composite capable of specific interaction with hexavalent chromium. Quantitative fluorescence quenching measurements of the hydrogel composite in the presence of hexavalent chromium shows a limit of detection of 1.2μM Cr6+ which is below maximum allowable concentrations for drinking water. The hydrogel composite is cheap to manufacture and can be injected into 96 well plates for high throughput analysis of environmental water samples. These results are encouraging for the development of hydrogels and polymetric films to be used as novel fluorescent sensing platforms for environmental diagnostic applications.

Green synthesis and physiochemical characterization of nickel oxide nanoparticles: Interaction studies with Calf thymus DNA.

One of the most promising applications of nanomaterials is that of nanobiosensors, using biomolecules such as nucleic acids as receptors. This study aimed to synthesize nickel oxide nanoparticles (NiO NPs) by an environmentally friendly green synthesis, using the extract of the herb Coriandrum sativum (coriander). The synthesized NPs were characterized using UV-Visible spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photon spectroscopy, field emission scanning electron microscopy coupled with energy dispersive spectroscopy, dynamic light scattering, zeta potential and transmission electron microscopy. All results confirmed the synthesis of pure, spherical, positively charged NiO NPs of around 95nm in diameter with prominent hydroxyl groups attached to the surface. Furthermore, interaction studies of synthesized NiO NPs with calf thymus DNA (CT DNA) were performed using UV-Visible spectroscopy, UV-thermal melting, circular dichroism, and fluorescence spectroscopy. CT DNA served as a substitute for nucleic acid biosensors. All experimental studies indicated that the NiO NPs bound electrostatically with CT DNA. These studies may facilitate exploring the potential of NiO NP-nucleic acid conjugated materials to be used as nanobiosensors for various applications, especially in pharmacological, epidemiological, and environmental diagnostic applications, and in detection.

Nanomaterial based aptasensors for clinical and environmental diagnostic applications.

Nanomaterials have been exploited extensively to fabricate various biosensors for clinical diagnostics and food & environmental monitoring. These materials in conjugation with highly specific aptamers (next-gen antibody mimics) have enhanced the selectivity, sensitivity and rapidness of the developed aptasensors for numerous targets ranging from small molecules such as heavy metal ions to complex matrices containing large entities like cells. In this review, we highlight the recent advancements in nanomaterial based aptasensors from the past five years also including the basics of conventionally used detection methodologies that paved the way for futuristic sensing techniques. The aptasensors have been categorised based upon these detection techniques and their modifications viz., colorimetric, fluorometric, Raman spectroscopy, electro-chemiluminescence, voltammetric, impedimetric and mechanical force-based sensing of a multitude of targets are discussed in detail. The bio-interaction of these numerous nanomaterials with the aptameric component and that of the complete aptasensor with the target have been studied in great depth. This review thus acts as a compendium for nanomaterial based aptasensors and their applications in the field of clinical and environmental diagnosis.

Comparative endpoint sensitivity of in vitro estrogen agonist assays

Environmental and human health implications of endocrine disrupting chemicals (EDCs), particularly xenoestrogens, have received extensive study. In vitro assays are increasingly employed as diagnostic tools to comparatively evaluate chemicals, whole effluent toxicity and surface water quality, and to identify causative EDCs during toxicity identification evaluations. Recently, the U.S. Environmental Protection Agency (USEPA) initiated ToxCast under the Tox21 program to generate novel bioactivity data through high throughput screening. This information is useful for prioritizing chemicals requiring additional hazard information, including endocrine active chemicals. Though multiple in vitro and in vivo techniques have been developed to assess estrogen agonist activity, the relative endpoint sensitivity of these approaches and agreement of their conclusions remain unclear during environmental diagnostic applications. Probabilistic hazard assessment (PHA) approaches, including chemical toxicity distributions (CTD), are useful for understanding the relative sensitivity of endpoints associated with in vitro and in vivo toxicity assays by predicting the likelihood of chemicals eliciting undesirable outcomes at or above environmentally relevant concentrations. In the present study, PHAs were employed to examine the comparative endpoint sensitivity of 16 in vitro assays for estrogen agonist activity using a diverse group of compounds from the USEPA ToxCast dataset. Reporter gene assays were generally observed to possess greater endpoint sensitivity than other assay types, and the Tox21 ERa LUC BG1 Agonist assay was identified as the most sensitive in vitro endpoint for detecting an estrogenic response. When the sensitivity of this most sensitive ToxCast in vitro endpoint was compared to the human MCF-7 cell proliferation assay, a common in vitro model for biomedical and environmental monitoring applications, the ERa LUC BG1 assay was several orders of magnitude less sensitive than MCF-7. These observations highlight the importance of employing multiple assays with various molecular initiation and signaling events to inform selection, application, and interpretation of in vitro endpoint responses during future environmental diagnostic applications.

Development of a species-specific probe for Pythium insidiosum and the diagnosis of pythiosis.

Pythium insidiosum, the only species in the genus that infects mammals, is the etiological agent of pythiosis, a granulomatous disease characterized by cutaneous and subcutaneous lesions and vascular diseases. Accurate diagnosis of pythiosis and identification of its causal agent are often inconsistent with current immunological diagnostic methods. A species-specific DNA probe was constructed by using a 530-bp HinfI fragment from the ribosomal DNA intergenic spacer of P. insidiosum. When the probe was incubated with dot blots of genomic DNA from 104 Pythium species, it hybridized only to the DNA of P. insidiosum and P. destruens-two species that have been considered conspecific. The probe also hybridized to DNA from 22 P. insidiosum isolates in this study, regardless of their geographic origin or animal host. When tested against genomic DNA from other pathogenic organisms (Aspergillus fumigatus, Basidiobolus ranarum, Conidiobolus coronatus, Lagenidium giganteum, Paracoccidioides brasiliensis, and Prototheca wickerhamii), no cross-hybridization of the probe was detected. The specificity of the probe to hybridize to genomic DNA from all isolates of P. insidiosum and not cross-react with DNA from other Pythium species or pathogens that cause symptoms similar to pythiosis in their hosts makes it a powerful tool for the accurate diagnosis of pythiosis. In addition, the probe has the potential for pathological and environmental diagnostic applications.