BEGIN:VCALENDAR VERSION:2.0 PRODID:icalendar-ruby CALSCALE:GREGORIAN X-WR-CALNAME:Performing Electrochemical Reactions in a Droplet Hydrogel Ele ctrochemical Cell X-WR-TIMEZONE:Pacific Time (US & Canada) BEGIN:VEVENT DTSTAMP:20261013T101916Z UID:tag:localist.com\,2008:EventInstance_46561001680621 DTSTART:20240607T160000Z DTEND:20240607T170000Z DESCRIPTION:A Chemistry Department Thesis Defense by Bronson Samel-Garloff (Koley Group)\n\n \n\nSocial Media:\n\n \n\nHerein we explore the characte rization and application of micro-volume hydrogel based electrochemical an alysis for monitoring the metabolic output of bacteria in complex multi-sp ecies biofilms. The main analytical challenges this method aims to address are quantification of very low amounts of analyte\, direct analysis of th e raw untreated sample after collection\, and real-time monitoring of meta bolic output by bacteria at biological temperature. This novel method is c urrently equipped to coulometrically measure the hydrogen peroxide and lac tic acid produced by oral bacteria in dental plaque samples\, which has po tential application as a point-of-care screening device for early detectio n of dysbiosis within the oral microbiome. Thus\, this method can facilita te prevention of oral diseases by providing patients and dentists with per tinent information on the balance of pathogenic and non-pathogenic species in the oral microbiome. The fundamental electrochemistry principles that govern this method will be explained\, followed by the electrochemical cel l design rationale. Other analytical methods used for studying the human m icrobiome\, and biofilms in general\, will also be discussed in terms of t heir respective advantages and limitations\, and how the presented method can fill gaps in knowledge. The first study presented focused on the chara cterization of platinum black\, an electrodeposited high surface area plat inum catalytic towards the oxidation of hydrogen peroxide\, for measuring from populations of hydrogen peroxide producing bacteria (green fluorescen t protein labeled S. sanguinis) of less than one hundred cells on a 50 μL pH buffered hydrogel. The average number of cells added was quantified us ing confocal microscopy. The buffering characteristics of the hydrogel wer e measured using a novel method for quantifying the buffering capacity thr ough monitoring the redox behavior of pyocyanin as it depended on the prot on concentration within the hydrogel as it was titrated with acid. Coulome tric quantification of hydrogen peroxide was achieved by integration of am perometric data after glucose feeding of the sample at 37 ℃. Sensor inte grity and electrochemical cell connection was maintained at higher tempera ture in the presence of organic acid production based on the size-exclusiv e nature of the hydrogel polymer\, the unique pH buffering nature of a mor pholine type monomer within the hydrogel structure\, and the relatively sl ow evaporation rate of water from within the hydrogel. Coulometric data yi elding the moles of analyte measured were normalized by the average number of bacteria added to each experiment. In the second study presented\, the working electrode material was composed of conductive carbon mixed into p olydimethylsiloxane (PDMS)\, and the sensing material consisted of an elec trodeposited layering of Prussian blue and nickel hexacyanoferrate crystal which is reduced to Prussian white in the presence of hydrogen peroxide. The electrochemical cell hydrogel medium was also augmented from a single buffering hydrogel to a layering of two unbuffered hydrogels for encapsula ting the bacteria and a smaller buffered hydrogel between the encapsulated sample and the working electrode. Lactate sensing was also incorporated i nto the method by adding lactose oxidase enzymes to the buffering hydrogel where its activity was maintained by the high buffering capacity of the h ydrogel. The hydrogen peroxide and lactate produced from dental plaque sam ples was measured in the same manner as in the first study\, and the resul ting data was normalized by the mass of dental plaque added. The mole frac tion of hydrogen peroxide produced was found by dividing the moles of hydr ogen peroxide from experiments without lactate oxidase by the moles of hyd rogen peroxide and lactate from experiments with lactate oxidase\, which w as used as the primary metric for evaluating the state of the dental plaqu e sample. This method was validated using quantitative polymerase chain re action experiments on genomic DNA extracted from the remaining dental plaq ue sample coupled with the respective electrochemical experiments. The gen es quantified were spxB\, gtfB and 16s which served as genetic markers for peroxide producing species\, pathogenic species\, and total bacteria resp ectively. Further normalization of electrochemical data by the genetic dat a was conducted to discern random error from actual fluctuations in dental plaque species composition. The limitations of this method\, and potentia l means of further optimization with regards to the experiment enclosure\, sensor design and hydrogel composition will be discussed. It is foreseeab le that this method can be adapted with sensors for other analytes pertine nt to a wider variety of complex biological samples such as soil\, urine\, and feces\, which will be discussed as an avenue for future research with this method. GEO:44.566532;-123.283691 LOCATION:Linus Pauling Science Center\, 402 SUMMARY:Performing Electrochemical Reactions in a Droplet Hydrogel Electroc hemical Cell URL;VALUE=URI:https://events.oregonstate.edu/event/performing-electrochemic al-reactions-in-a-droplet-hydrogel-electrochemical-cell CATEGORIES:Lecture or Presentation END:VEVENT END:VCALENDAR