A Study of Biomedical Sensors Based on Layered Semiconductors: From Characteristics to Nanofabrication Approaches

Among other layered two-dimensional (2D) materials, transition metal dichalcogenides (TMDCs) have revealed their importance in developing novel electronic devices such as field-effect transistors (FETs), optoelectronics, and biomedical sensors. The superior electrical, mechanical, and optoelectronic characteristics, in combination with naturally formed sizable and tunable bandgap of TMDCs, have turned out to be promising for making new biomedical sensors. Despite such a bright prospect, there remain critical scientific and technical gaps that should be filled to enable advanced and practical biomedical sensor applications. Specifically, such gaps include (i) loss of operation stability of MoS2 FET biosensors under wet conditions, (ii) lack of reusability of the electronic biosensors made of TMDCs, and (iii) absence of scalable nanofabrication methods capable of producing well-defined TMDC device patterns. A series of studies presented in this thesis leveraged scientific and technical knowledge to deal with the aforementioned urgent demands and was categorized into three main topics: (i) devise a cycle-wise method for operating MoS2 FET biosensors integrated with a microfluidic channel, which alleviates the liquid-solution-induced issues; (ii) design a new biosensor structure consisting of a bio-tunable nanoplasmonic window and a low-noise few-layer MoS2 photodetector, which can enable highly sensitive, fast, and reusable biosensing processes; (iii) invent scalable nanofabrication and nanomanufacturing approaches capable of producing orderly-arranged TMDCs device channel patterns at designated locations on a target substrate. The presented works have engineered layered semiconductors and device structures based on the scientific knowledge and device physics to realize practical and functional TMDC-based biomedical devices. Additionally, the nanofabrication methods invented in this thesis work could be further developed into cost-efficient and scalable nanomanufacturing techniques that will speed up the development of a wide variety of new device applications made of layered semiconductors.PHDMechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/163205/1/bhryu_1.pd

An Integrated Plasmo‐Photoelectronic Nanostructure Biosensor Detects an Infection Biomarker Accompanying Cell Death in Neutrophils

Bacterial infections leading to sepsis are a major cause of deaths in the intensive care unit. Unfortunately, no effective methods are available to capture the early onset of infectious sepsis near the patient with both speed and sensitivity required for timely clinical treatment. To fill the gap, the authors develop a highly miniaturized (2.5 × 2.5 µm2) plasmo‐photoelectronic nanostructure device that detected citrullinated histone H3 (CitH3), a biomarker released to the blood circulatory system by neutrophils. Rapidly detecting CitH3 with high sensitivity has the great potential to prevent infections from developing life‐threatening septic shock. To this end, the author’s device incorporates structurally engineered arrayed hemispherical gold nanoparticles that are functionalized with high‐affinity antibodies. A nanoplasmonic resonance shift induces a photoconduction increase in a few‐layer molybdenum disulfide (MoS2) channel, and it provides the sensor signal. The device achieves label‐free detection of serum CitH3 with a 5‐log dynamic range from 10−4 to 101 ng mL and a sample‐to‐answer time <20 min. Using this biosensor, the authors longitudinally measure the dynamic CitH3 profiles of individual living mice in a sepsis model at high resolution over 12 hours. The developed biosensor may be poised for future translation to personalized management of systemic bacterial infections.The lack of an appropriate biosensing technology to detect the early onset of bacterial infections has prohibited timely clinical treatment of sepitc shock. This article presents a highly miniaturized plasmo‐photoelectronic device incorporating high‐affinity antibody‐conjugated hemispherical gold nanoparticles and a few‐layer molybdenum disulfide (MoS2) photoconductive channel to detect a blood biomarker released by neutrophils with high speed and sensitivity.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/152883/1/smll201905611-sup-0001-SuppMat.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/152883/2/smll201905611_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/152883/3/smll201905611.pd

Regulation of BRCA1 stability through the tandem UBX domains of isoleucyl-tRNA synthetase 1

Aminoacyl-tRNA synthetases possess unique domains. In this study the structure of the vertebrate IARS1 and EARS1 complex reveals that vertebrate IARS1 protects the DNA repair factor BRCA1 from proteolytic degradation via its UBX-fold domain. Aminoacyl-tRNA synthetases (ARSs) have evolved to acquire various additional domains. These domains allow ARSs to communicate with other cellular proteins in order to promote non-translational functions. Vertebrate cytoplasmic isoleucyl-tRNA synthetases (IARS1s) have an uncharacterized unique domain, UNE-I. Here, we present the crystal structure of the chicken IARS1 UNE-I complexed with glutamyl-tRNA synthetase 1 (EARS1). UNE-I consists of tandem ubiquitin regulatory X (UBX) domains that interact with a distinct hairpin loop on EARS1 and protect its neighboring proteins in the multi-synthetase complex from degradation. Phosphomimetic mutation of the two serine residues in the hairpin loop releases IARS1 from the complex. IARS1 interacts with BRCA1 in the nucleus, regulates its stability by inhibiting ubiquitylation via the UBX domains, and controls DNA repair function

Near‐Infrared Multilayer MoS2 Photoconductivity‐Enabled Ultrasensitive Homogeneous Plasmonic Colorimetric Biosensing (Adv. Mater. Interfaces 24/2021)

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/171208/1/admi202170145.pd

Near‐Infrared Multilayer MoS2 Photoconductivity‐Enabled Ultrasensitive Homogeneous Plasmonic Colorimetric Biosensing

The ability to detect low‐abundance proteins in human body fluids plays a critical role in proteomic research to achieve a comprehensive understanding of protein functions and early‐stage disease diagnosis to reduce mortality rates. Ultrasensitive (sub‐fM), rapid, simple “mix‐and‐read” plasmonic colorimetric biosensing of large‐size (≈180 kDa) proteins in biofluids using an ultralow‐noise multilayer molybdenum disulfide (MoS2) photoconducting channel is reported here. With its out‐of‐plane structure optimized to minimize carrier scattering, the multilayer MoS2 channel operated under near‐infrared illumination enables the detection of a subtle plasmonic extinction shift caused by antigen‐induced nanoprobe aggregation. The demonstrated biosensing strategy allows quantifying carcinoembryonic antigen in unprocessed whole blood with a dynamic range of 106, a sample‐to‐answer time of 10 min, and a limit of detection of 0.1–3 pg mL−1, which is ≈100‐fold more sensitive than the clinical‐standard enzyme‐linked immunosorbent assays. The biosensing methodology can be broadly used to realize timely personalized diagnostics and physiological monitoring of diseases in point‐of‐care settings.A plasmonic colorimetric biosensing platform for rapid and ultrasensitive detection of cancer biomarkers in biofluids is developed using an ultralow‐noise multilayer molybdenum disulfide (MoS2) photoconducting channel. Near‐infrared operation of the multilayer MoS2 channel coupled with a nanoparticle aggregation‐based assay enables user‐friendly homogeneous on‐chip immunosensing that is poised for point‐of‐care testing.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/171210/1/admi202101291_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/171210/2/admi202101291.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/171210/3/admi202101291-sup-0001-SuppMat.pd

Enhancing Electrochemical Sensing through Molecular Engineering of Reduced Graphene Oxide–Solution Interfaces and Remote Floating-Gate FET Analysis

Two-dimensional nanomaterials such as reduced graphene oxide (rGO) have captured significant attention in the realm of field-effect transistor (FET) sensors due to their inherent high sensitivity and cost-effective manufacturing. Despite their attraction, a comprehensive understanding of rGO–solution interfaces (specifically, electrochemical interfacial properties influenced by linker molecules and surface chemistry) remains challenging, given the limited capability of analytical tools to directly measure intricate solution interface properties. In this study, we introduce an analytical tool designed to directly measure the surface charge density of the rGO–solution interface leveraging the remote floating-gate FET (RFGFET) platform. Our methodology involves characterizing the electrochemical properties of rGO, which are influenced by adhesion layers between SiO2 and rGO, such as (3-aminopropyl)trimethoxysilane (APTMS) and hexamethyldisilazane (HMDS). The hydrophilic nature of APTMS facilitates the acceptance of oxygen-rich rGO, resulting in a noteworthy pH sensitivity of 56.8 mV/pH at the rGO–solution interface. Conversely, hydrophobic HMDS significantly suppresses the pH sensitivity from the rGO–solution interface, attributed to the graphitic carbon-rich surface of rGO. Consequently, the carbon-rich surface facilitates a denser arrangement of 1-pyrenebutyric acid N-hydroxysuccinimide ester linkers for functionalizing capturing probes on rGO, resulting in an enhanced sensitivity of lead ions by 32% in our proof-of-concept test

Biosensors: An Integrated Plasmo‐Photoelectronic Nanostructure Biosensor Detects an Infection Biomarker Accompanying Cell Death in Neutrophils (Small 1/2020)

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/153219/1/smll202070004.pd

Remote Floating-Gate Field-Effect Transistor with 2-Dimensional Reduced Graphene Oxide Sensing Layer for Reliable Detection of SARS-CoV-2 Spike Proteins

Despite intensive research of nanomaterials-based field-effect transistors (FETs) as a rapid diagnostic tool, it remains to be seen for FET sensors to be used for clinical applications due to a lack of stability, reliability, reproducibility, and scalability for mass production. Herein, we propose a remote floating-gate (RFG) FET configuration to eliminate device-to-device variations of two-dimensional reduced graphene oxide (rGO) sensing surfaces and most of the instability at the solution interface. Also, critical mechanistic factors behind the electrochemical instability of rGO such as severe drift and hysteresis were identified through extensive studies on rGO–solution interfaces varied by rGO thickness, coverage, and reduction temperature. rGO surfaces in our RFGFET structure displayed a Nernstian response of 54 mV/pH (from pH 2 to 11) with a 90% yield (9 samples out of total 10), coefficient of variation (CV) \u3c 3%, and a low drift rate of 2%, all of which were calculated from the absolute measurement values. As proof-of-concept, we demonstrated highly reliable, reproducible, and label-free detection of spike proteins of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in a saliva-relevant media with concentrations ranging from 500 fg/mL to 5 μg/mL, with an R2 value of 0.984 and CV \u3c 3%, and a guaranteed limit of detection at a few pg/mL. Taken together, this new platform may have an immense effect on positioning FET bioelectronics in a clinical setting for detecting SARS-CoV-2

Cyclewise Operation of Printed MoS₂ Transistor Biosensors for Rapid Biomolecule Quantification at Femtomolar Levels

Field-effect transistors made from MoS₂ and other emerging layered semiconductors have been demonstrated to be able to serve as ultrasensitive biosensors. However, such nanoelectronic sensors still suffer seriously from a series of challenges associated with the poor compatibility between electronic structures and liquid analytes. These challenges hinder the practical biosensing applications that demand rapid, low-noise, highly specific biomolecule quantification at femtomolar levels. To address such challenges, we study a cyclewise process for operating MoS₂ transistor biosensors, in which a series of reagent fluids are delivered to the sensor in a time-sequenced manner and periodically set the sensor into four assay-cycle stages, including incubation, flushing, drying, and electrical measurement. Running multiple cycles of such an assay can acquire a time-dependent sensor response signal quantifying the reaction kinetics of analyte-receptor binding. This cyclewise detection approach can avoid the liquid-solution-induced electrochemical damage, screening, and nonspecific adsorption to the sensor and therefore improves the transistor sensor’s durability, sensitivity, specificity, and signal-to-noise ratio. These advantages in combination with the inherent high sensitivity of MoS₂ biosensors allow for rapid biomolecule quantification at femtomolar levels. We have demonstrated the cyclewise quantification of Interleukin-1β in pure and complex solutions (e.g., serum and saliva) with a detection limit of ∼1 fM and a total detection time ∼23 min. This work leverages the superior properties of layered semiconductors for biosensing applications and advances the techniques toward realizing fast real-time immunoassay for low-abundance biomolecule detection