CBEE seminar by Laura Walker and Kiranmayi Mangalgiri

Kiranmayi Mangalgiri (PhD student, Blaney Lab) 

Role of Poultry Litter Derived Dissolved Organic Matter on the Photodegradation of Antibiotics

Antibiotic pharmaceuticals are widely used as feed additives in concentrated animal feeding operations to prevent spread of disease among livestock. Land application of litter waste from poultry operations has introduced antibiotics in the environment, which has been associated with an increase in antibiotic resistance. This study examined the photolytic fate of multiple classes of antibiotics used in the poultry industry (i.e., fluoroquinolones, organoarsenicals, sulfonamides, and tetracyclines), for which the fluence-based, pseudo-first order rate constants in deionized water (buffered at pH 6.8) range from 1.8×10^-7 to 1.0×10^-3 cm²mJ^-1. To study the effect of dissolved organic matter (DOM) on the photolytic fate, antibiotic solutions containing poultry litter DOM at environmentally-relevant concentrations for agricultural wastewater (0 – 150 mg C/L), were irradiated at 310 – 410 nm. Suwannee River natural organic matter (SRN) was used as a surrogate DOM standard. DOM can serve as a source and sink of reactive species (e.g., HO*, ¹O₂, ³DOM*) during irradiation, and the reactivity of each antibiotic with reactive species played a significant role in the overall photodegradation trends. For example, the apparent rate constant for photodegradation of roxarsone, an organoarsenical compound, increased from 1.8×10^-7 cm²mJ^-1 to 6.0×10^-7 cm²mJ^-1 at higher DOM concentrations due to increased production of ¹O₂. These results demonstrate that photolysis of antibiotics in agricultural runoff occurs despite high concentrations of animal-derived DOM.

Laura Walker (PhD student, Leach Lab)

Design and Analysis of Bioengineered Models of Alzheimer’s Disease

Amyloids are native proteins that are misfolded due to genetic or environmental factors in such a way that aggregation is initiated, ultimately yielding insoluble fibrous protein deposits found in Alzheimer’s disease (AD), Parkinson’s disease, Huntington’s disease and prion diseases.  In AD, pathogenesis mechanisms of unstable intermediate β amyloid (Aβ) oligomers have been studied in detail: Aβ oligomers have a higher diffusibility, hydrophobicity and ability to interact with lipid membranes, as compared to mature Aβ fibrils.  When confined within a 3D environment such as the in vivo tissue or a tissue-like hydrogel, Aβ transport is altered vs in solution due to covalent and noncovalent binding events and hindered diffusion when confined in a 3D structure.  We hypothesize that 3D environment factors may stabilize unfolded oligomers and alter aggregation kinetics resulting in fewer toxic Aβ species formed.  Utilizing Thioflavin T (ThT) binding assays, Fluorescence Correlation Spectroscopy (FCS), and Transmission Electron Spectroscopy (TEM) we can depict Aβ aggregate sizes and general structures within 3D hydrogels over a period of time.  To determine the cytotoxicity of the Aβ aggregate species present, Live/Dead assays were used on SY5Y cells with and without Aβ present. Preliminary results identify a lack of a lag phase during aggregation in 3D hydrogels suggesting stabilization of β-sheet structures vs Aβ aggregation kinetics in media solutions including low molecular weight Aβ species detected during the lag phase.  SY5Y cells cultured on a surface are susceptible to Aβ toxicity while in 3D hydrogels there is minimal difference in cell viability with or without Aβ suggesting the 3D hydrogel environment promotes fewer toxic Aβ species.