Biosensors

Nuisance odors from landfills have more impact than just being an annoyance to nearby residents. With an ever-increasing population, a larger number of communities are located in closer proximity to landfills than ever before. This has brought along with it, more regular conflicts with landfill authorities surrounding the issue of odors, resulting in complaints, lawsuits, fines, and even re-siting operations. The absence of an objective method of quantifying nuisance odors makes the task of creating regulations and setting standards even more complicated. The current research focuses on a method to objectively quantify landfill odors. The human odorant binding protein 2A (hOBPIIa) can be produced using published recombinant gene technology and can be used as a biosensor to quantify odorants through spectrofluorometric measurements. The current work is a continuation of the previous work by Rahman (2020). In this work, the spent biosensor after it reacts with an odorant is shown to be regenerated by applying additional fluorophore following La Chateliers’ principle, so that the same batch of protein can be used to run multiple experiments with odorants. An important part of the work miniaturized the earlier version of the experimental setup and incorporates a much more efficient flow-through system. This setup is capable of collecting real-time readings, increasing the overall accuracy and shortening the duration of each set of the experiment. The current work also explores the response of the biosensor with an expanded group of pure odorants, including hydrogen sulfide, ammonia, toluene, formaldehyde, tert-butyl mercaptan, and methyl mercaptan as well as their mixtures, thus expanding the list of odorants tested under this principle. The results show that the protein shows a concentration-dependent response differing on the hydrophobicity of the target compound.

Nuisance odor levels produced by solid waste management operations are subject to regulatory standards due to their impacts on the quality of life of the residents living nearby the facility. Failure to meet regulatory standards may result in fines, litigation, inability to acquire permits, mitigation, and re-siting operations. Since measurement of environmental nuisance odors is currently limited to subjective techniques, monitoring odor levels to meet such standards is often problematic. This is becoming more acute as increasing residential populations begin to encroach on properties adjacent to landfills. In order to ensure that nuisance odor issues are minimized, it is necessary to provide an objective measurement. The objective of the current research is to develop a biosensor for providing an objective, standard measurement of odors. The approach is to modify the human odorant binding protein (hOBPIIa), isolated using published biomolecular techniques, by fluorescently tagging it with a chromophore functional group. When this protein is tagged with a fluorophore marker and excited in a spectrofluorometer, it emits light of a certain wavelength that can be detected and quantified. Once odorant molecules are exposed to this complex, they start replacing the fluorophore, and as a result, the emitted light intensity decreases in proportion to the number of odorant molecules. Since the protein response depends on odorant concentration, following an inverse Beer’s Law relationship, the odorants can be quantified accurately and rapidly using fluorometric measurements. The results establish quantitation ranges for different pure and mixture of odorant gases as well as the amount of gas that can be quantified across various flow rates.

This study explores the application of two methods of spectroscopy; Near Infrared
spectroscopy (NIR) and Fourier transform spectroscopy (FTIR) as alternative approaches
for measuring glucocorticoid metabolites in chimpanzee feces. The goals of this study
were twofold: The first was to determine if cortisol can be identified within the NIR
and/or FTIR spectra of chimpanzee fecal hormone extract in ethanol solution. The second
objective was to determine the capability of NIR and FTIR to predict FGM
concentrations obtained using standard laboratory methods. Fecal glucocorticoid
concentrations measured by Enzyme Immunoassay were used as the reference data of
partial least square (PLS) regression of fecal extract NIR spectra and FTIR spectra. Low
accuracies (NIR: R2 = 0.152; FTIR: R2 = 0.199) were obtained from regression models
using data from both methods. Though this study did not successfully demonstrate the feasibility of using NIR and FTIR to qualify and quantify FGMs, it is likely not a
reflection of the capabilities of the technology, but rather of appropriate sample types and
preparation methods.

Microcystin-LR (MCLR) is hepatotoxic to animals and humans with disruption of liver structure causing cytoskeletal damage, necrosis and pooling of blood in the liver, leading to large increase in liver weight. It is also a strong liver tumor promoter and protein phosphatase inhibitor. Microcysin-LR binds protein phosphatases 1 and 2A, and influences regulation of cellular protein phosphorylation. In the present study, a colloidal gold based immunoassay test strip was developed for Microcystin-LR detection. The detection limit was found to be 1 ng/mL. 5 nm colloidal gold test strips exhibits more efficient for detection, compared with 20 nm colloidal gold test strips. The interaction between Microcystin-LR antibody (immunoglobulin G) and colloidal gold nanoparticles was investigated by various analytical methods, including Ultraviolet/Visible (UV/VIS), Fourier Transform Infrared (FTIR) and Fluorescence spectroscopy as well as transmission electron microscopy (TEM).