A. James Clark School of Engineering

Permanent URI for this communityhttp://hdl.handle.net/1903/1654

The collections in this community comprise faculty research works, as well as graduate theses and dissertations.

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Author: search.filters.author.Beardslee, Luke A.

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Now showing 1 - 4 of 4
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    Miniaturized Capsule System Toward Real-Time Electrochemical Detection of H2S in the Gastrointestinal Tract
    (Wiley, 2023-11-20) Stine, Justin M.; Ruland, Katie L.; Beardslee, Luke A.; Levy, Joshua A.; Abianeh, Hossein; Botasini, Santiago; Pasricha, Pankaj J.; Ghodssi, Reza
    Hydrogen sulfide (H2S) is a gaseous inflammatory mediator and important signaling molecule for maintaining gastrointestinal (GI) homeostasis. Excess intraluminal H2S in the GI tract has been implicated in inflammatory bowel disease and neurodegenerative disorders; however, the role of H2S in disease pathogenesis and progression is unclear. Herein, an electrochemical gas-sensing ingestible capsule is developed to enable real-time, wireless amperometric measurement of H2S in GI conditions. A gold (Au) three-electrode sensor is modified with a Nafion solid-polymer electrolyte (Nafion-Au) to enhance selectivity toward H2S in humid environments. The Nafion-Au sensor-integrated capsule shows a linear current response in H2S concentration ranging from 0.21 to 4.5 ppm (R2 = 0.954) with a normalized sensitivity of 12.4% ppm−1 when evaluated in a benchtop setting. The sensor proves highly selective toward H2S in the presence of known interferent gases, such as hydrogen (H2), with a selectivity ratio of H2S:H2 = 1340, as well as toward methane (CH4) and carbon dioxide (CO2). The packaged capsule demonstrates reliable wireless communication through abdominal tissue analogues, comparable to GI dielectric properties. Also, an assessment of sensor drift and threshold-based notification is investigated, showing potential for in vivo application. Thus, the developed H2S capsule platform provides an analytical tool to uncover the complex biology-modulating effects of intraluminal H2S.
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    Gelatin-Enabled Microsensor for Pancreatic Trypsin Sensing
    (MDPI, 2018-01-31) Banis, George; Beardslee, Luke A.; Ghodssi, Reza
    Digestive health is critically dependent on the secretion of enzymes from the exocrine pancreas to the duodenum via the pancreatic duct. Specifically, pancreatic trypsin is a major protease responsible for breaking down proteins for absorption in the small intestine. Gelatin-based hydrogels, deposited in the form of thin films, have been studied as potential sensor substrates that hydrolyze in the presence of trypsin. In this work, we (1) investigate gelatin as a sensing material; (2) develop a fabrication strategy for coating sensor surfaces; and (3) implement a miniaturized impedance platform for measuring activity levels of pancreatic trypsin. Using impedance spectroscopy, we evaluate gelatin’s specificity and rate of degradation when exposed to a combination of pancreatic enzymes in neutral solution representative of the macromolecular heterogeneity present in the duodenal environment. Our findings suggest gelatin’s preferential degradation to trypsin compared to enzymes such as lipase and amylase. We further observe their interference with trypsin behavior in equivalent concentrations, reducing film digestion by as much as 83% and 77%, respectively. We achieve film patterns in thicknesses ranging from 300–700 nm, which we coat over interdigitated finger electrode sensors. Finally, we test our sensors over several concentrations to emulate the range of pancreatic secretions. Ultimately, our microsensor will serve as the foundation for developing in situ sensors toward diagnosing pancreatic pathologies.
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    Thermomechanical Soft Actuator for Targeted Delivery of Anchoring Drug Deposits to the GI Tract
    (Wiley, 2022-12-04) Levy, Joshua A.; Straker, Michael A.; Stine, Justin M.; Beardslee, Luke A.; Borbash, Vivian; Ghodssi, Reza
    Current systemic therapies for inflammatory gastrointestinal (GI) disorders are unable to locally target lesions and have substantial systemic side effects. Here, a compact mesoscale spring actuator capable of delivering an anchoring drug deposit to point locations in the GI tract is demonstrated. The mechanism demonstrated here is intended to complement existing ingestible capsule-based sensing and communication technologies, enabling treatment based on criteria such as detected GI biomarkers or external commands. The 3D-printed actuator has shown on command deployment in 14.1 ± 3.0 s, and a spring constant of 25.4 ± 1.4 mN mm−1, sufficient to insert a spiny microneedle anchoring drug deposit (SMAD) into GI tissue. The complementary SMAD showed a 22-fold increase in anchoring force over traditional molded microneedles, enabling reliable removal from the actuator and robust prolonged tissue attachment. The SMAD also showed comparable drug release characteristics (R2 = 0.9773) to penetrating molded microneedles in agarose phantom tissue with a drug spread radius of 25 mm in 168 h. The demonstrated system has the potential to enable on command delivery and anchoring of drug-loaded deposits to the GI mucosa for sustained treatment of GI inflammation while mitigating side effects and enabling new options for treatment.
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    Gelatin-Enabled Microsensor for Pancreatic Trypsin Sensing
    (MDPI, 2018-01-31) Banis, George; Beardslee, Luke A.; Ghodssi, Reza
    Digestive health is critically dependent on the secretion of enzymes from the exocrine pancreas to the duodenum via the pancreatic duct. Specifically, pancreatic trypsin is a major protease responsible for breaking down proteins for absorption in the small intestine. Gelatin-based hydrogels, deposited in the form of thin films, have been studied as potential sensor substrates that hydrolyze in the presence of trypsin. In this work, we (1) investigate gelatin as a sensing material; (2) develop a fabrication strategy for coating sensor surfaces; and (3) implement a miniaturized impedance platform for measuring activity levels of pancreatic trypsin. Using impedance spectroscopy, we evaluate gelatin’s specificity and rate of degradation when exposed to a combination of pancreatic enzymes in neutral solution representative of the macromolecular heterogeneity present in the duodenal environment. Our findings suggest gelatin’s preferential degradation to trypsin compared to enzymes such as lipase and amylase. We further observe their interference with trypsin behavior in equivalent concentrations, reducing film digestion by as much as 83% and 77%, respectively. We achieve film patterns in thicknesses ranging from 300–700 nm, which we coat over interdigitated finger electrode sensors. Finally, we test our sensors over several concentrations to emulate the range of pancreatic secretions. Ultimately, our microsensor will serve as the foundation for developing in situ sensors toward diagnosing pancreatic pathologies.