Maximizing Electrochemical Information: A Perspective on Background-Inclusive Fast Voltammetry.

This perspective encompasses a focused review of the literature leading to a tipping point in electroanalytical chemistry. We tie together the threads of a "revolution" quietly in the making for years through the work of many authors. Long-held misconceptions about the use of background subtraction in fast voltammetry are addressed. We lay out future advantages that accompany background-inclusive voltammetry, particularly when paired with modern machine-learning algorithms for data analysis.

A functional group-guided approach to aptamers for small molecules.

Aptameric receptors are important biosensor components, yet our ability to identify them depends on the target structures. We analyzed the contributions of individual functional groups on small molecules to binding within 27 target-aptamer pairs, identifying potential hindrances to receptor isolation-for example, negative cooperativity between sterically hindered functional groups. To increase the probability of aptamer isolation for important targets, such as leucine and voriconazole, for which multiple previous selection attempts failed, we designed tailored strategies focused on overcoming individual structural barriers to successful selections. This approach enables us to move beyond standardized protocols into functional group-guided searches, relying on sequences common to receptors for targets and their analogs to serve as anchors in regions of vast oligonucleotide spaces wherein useful reagents are likely to be found.

Technology Roadmap for Flexible Sensors.

Humans rely increasingly on sensors to address grand challenges and to improve quality of life in the era of digitalization and big data. For ubiquitous sensing, flexible sensors are developed to overcome the limitations of conventional rigid counterparts. Despite rapid advancement in bench-side research over the last decade, the market adoption of flexible sensors remains limited. To ease and to expedite their deployment, here, we identify bottlenecks hindering the maturation of flexible sensors and propose promising solutions. We first analyze challenges in achieving satisfactory sensing performance for real-world applications and then summarize issues in compatible sensor-biology interfaces, followed by brief discussions on powering and connecting sensor networks. Issues en route to commercialization and for sustainable growth of the sector are also analyzed, highlighting environmental concerns and emphasizing nontechnical issues such as business, regulatory, and ethical considerations. Additionally, we look at future intelligent flexible sensors. In proposing a comprehensive roadmap, we hope to steer research efforts towards common goals and to guide coordinated development strategies from disparate communities. Through such collaborative efforts, scientific breakthroughs can be made sooner and capitalized for the betterment of humanity.

Males With Traumatic Lower Limb Loss Differ in Body Fat Distribution Compared to Those Without Limb Loss.

OBJECTIVES: The primary objective was to examine body fat composition in males with traumatic lower limb loss and a comparison group without limb loss. A secondary objective was to determine if there are differences in body fat composition by traumatic limb loss level. RESEARCH METHODS AND PROCEDURES: Cross-sectional analyses of baseline in-person intake data was completed at a large military medical center. Data were collected from 2011 to 2020, and analysis was conducted in 2020. Participants (n = 89) included males who sustained traumatic lower limb loss (n = 50) and an age-matched comparison group without limb loss (n = 39). Mean age of participants was 36.0 ± 13.2 years. Main outcomes measured included age, height, body mass index, weight, body fat mass and percent, android fat mass and percent, gynoid fat mass and percent, and android/gynoid percent fat ratio. Differences between groups were assessed using t-tests or Mann-Whitney U tests. Differences between limb loss levels were assessed using one-way ANOVA or Wilcoxon signed-rank test. RESULTS: Body fat percent (P = .001), gynoid fat percent (P = .010), android fat mass (P = .01), and percent (P = .02) were higher in the group with limb loss. There were no differences in body fat composition between limb loss levels (P > .05). CONCLUSION: Males with traumatic lower limb loss had a higher body fat percent compared to those without limb loss. Given higher body fat composition in individuals with limb loss and the relationship between body fat composition and cardiovascular disease risk, including body composition analysis with clinical screening could identify changes and allow for early intervention.

Flexible and Implantable Polyimide Aptamer-Field-Effect Transistor Biosensors.

Monitoring neurochemical signaling across time scales is critical to understanding how brains encode and store information. Flexible (vs stiff) devices have been shown to improve in vivo monitoring, particularly over longer times, by reducing tissue damage and immunological responses. Here, we report our initial steps toward developing flexible and implantable neuroprobes with aptamer-field-effect transistor (FET) biosensors for neurotransmitter monitoring. A high-throughput process was developed to fabricate thin, flexible polyimide probes using microelectromechanical-system (MEMS) technologies, where 150 flexible probes were fabricated on each 4 in. Si wafer. Probes were 150 µm wide and 7 µm thick with two FETs per tip. The bending stiffness was 1.2 × 10-11 N·m2. Semiconductor thin films (3 nm In2O3) were functionalized with DNA aptamers for target recognition, which produces aptamer conformational rearrangements detected via changes in FET conductance. Flexible aptamer-FET neuroprobes detected serotonin at femtomolar concentrations in high-ionic strength artificial cerebrospinal fluid. A straightforward implantation process was developed, where microfabricated Si carrier devices assisted with implantation such that flexible neuroprobes detected physiological relevant serotonin in a tissue-hydrogel brain mimic.

Optogenetic Stimulation of Midbrain Dopamine Neurons Produces Striatal Serotonin Release.

Targeting neurons with light-driven opsins is widely used to investigate cell-specific responses. We transfected midbrain dopamine neurons with the excitatory opsin Chrimson. Extracellular basal and stimulated neurotransmitter levels in the dorsal striatum were measured by microdialysis in awake mice. Optical activation of dopamine cell bodies evoked terminal dopamine release in the striatum. Multiplexed analysis of dialysate samples revealed that the evoked dopamine was accompanied by temporally coupled increases in striatal 3-methoxytyramine, an extracellular dopamine metabolite, and in serotonin. We investigated a mechanism for dopamine-serotonin interactions involving striatal dopamine receptors. However, the evoked serotonin associated with optical stimulation of dopamine neurons was not abolished by striatal D1- or D2-like receptor inhibition. Although the mechanisms underlying the coupling of striatal dopamine and serotonin remain unclear, these findings illustrate advantages of multiplexed measurements for uncovering functional interactions between neurotransmitter systems. Furthermore, they suggest that the output of optogenetic manipulations may extend beyond opsin-expressing neuronal populations.

Wearable aptamer-field-effect transistor sensing system for noninvasive cortisol monitoring.

Wearable technologies for personalized monitoring require sensors that track biomarkers often present at low levels. Cortisol­a key stress biomarker­is present in sweat at low nanomolar concentrations. Previous wearable sensing systems are limited to analytes in the micromolar-millimolar ranges. To overcome this and other limitations, we developed a flexible field-effect transistor (FET) biosensor array that exploits a previously unreported cortisol aptamer coupled to nanometer-thin-film In2O3 FETs. Cortisol levels were determined via molecular recognition by aptamers where binding was transduced to electrical signals on FETs. The physiological relevance of cortisol as a stress biomarker was demonstrated by tracking salivary cortisol levels in participants in a Trier Social Stress Test and establishing correlations between cortisol in diurnal saliva and sweat samples. These correlations motivated the development and on-body validation of an aptamer-FET array­based smartwatch equipped with a custom, multichannel, self-referencing, and autonomous source measurement unit enabling seamless, real-time cortisol sweat sensing.

Implantable aptamer-field-effect transistor neuroprobes for in vivo neurotransmitter monitoring.

While tools for monitoring in vivo electrophysiology have been extensively developed, neurochemical recording technologies remain limited. Nevertheless, chemical communication via neurotransmitters plays central roles in brain information processing. We developed implantable aptamer­field-effect transistor (FET) neuroprobes for monitoring neurotransmitters. Neuroprobes were fabricated using high-throughput microelectromechanical system (MEMS) technologies, where 150 probes with shanks of either 150- or 50-µm widths and thicknesses were fabricated on 4-inch Si wafers. Nanoscale FETs with ultrathin (~3 to 4 nm) In2O3 semiconductor films were prepared using sol-gel processing. The In2O3 surfaces were coupled with synthetic oligonucleotide receptors (aptamers) to recognize and to detect the neurotransmitter serotonin. Aptamer-FET neuroprobes enabled femtomolar serotonin detection limits in brain tissue with minimal biofouling. Stimulated serotonin release was detected in vivo. This study opens opportunities for integrated neural activity recordings at high spatiotemporal resolution by combining these aptamer-FET sensors with other types of Si-based implantable probes to advance our understanding of brain function.

Simultaneous serotonin and dopamine monitoring across timescales by rapid pulse voltammetry with partial least squares regression.

Many voltammetry methods have been developed to monitor brain extracellular dopamine levels. Fewer approaches have been successful in detecting serotonin in vivo. No voltammetric techniques are currently available to monitor both neurotransmitters simultaneously across timescales, even though they play integrated roles in modulating behavior. We provide proof-of-concept for rapid pulse voltammetry coupled with partial least squares regression (RPV-PLSR), an approach adapted from multi-electrode systems (i.e., electronic tongues) used to identify multiple components in complex environments. We exploited small differences in analyte redox profiles to select pulse steps for RPV waveforms. Using an intentionally designed pulse strategy combined with custom instrumentation and analysis software, we monitored basal and stimulated levels of dopamine and serotonin. In addition to faradaic currents, capacitive currents were important factors in analyte identification arguing against background subtraction. Compared to fast-scan cyclic voltammetry-principal components regression (FSCV-PCR), RPV-PLSR better differentiated and quantified basal and stimulated dopamine and serotonin associated with striatal recording electrode position, optical stimulation frequency, and serotonin reuptake inhibition. The RPV-PLSR approach can be generalized to other electrochemically active neurotransmitters and provides a feedback pipeline for future optimization of multi-analyte, fit-for-purpose waveforms and machine learning approaches to data analysis.

Getting Interdisciplinary Teams into the Field: Institutional Review Board Preapproval and Multi-Institution Authorization Agreements for Rapid Response Disaster Research.

This article describes an interdisciplinary community resilience research project and presents a case study that supports bringing researchers together before a disaster to develop plans, procedures, and preapproved Institutional Review Board (IRB) protocols. In addition, this article explains how researchers from various academic institutions and their federal agency partners can effectively collaborate by creating an IRB Authorization Agreement (IAA). Such preparations can support interdisciplinary rapid response disaster fieldwork that is timely, ethically informed, and scientifically rigorous. This fieldwork preplanning process can also advance interdisciplinary team formation and data collection efforts over the long term.

Circumference Method Estimates Percent Body Fat in Male US Service Members with Lower Limb Loss.

BACKGROUND: The Department of Defense circumference method (CM) is used to estimate percent body fat (%BF) in evaluation of health, physical fitness, appearance, and military readiness; however, the CM has not been validated in individuals with lower limb loss. OBJECTIVE: To evaluate the agreement between CM and dual-energy X-ray absorptiometry (DXA) for measuring %BF in individuals with lower limb loss. DESIGN: This study is part of a larger cross-sectional comparison study, and this analysis was included as a secondary objective. Two methods of measuring %BF included CM and DXA, with DXA as the reference standard for this study. PARTICIPANTS/SETTING: This study was conducted at Walter Reed Army Medical Center. Data were collected from summer 2010 to summer 2011. One hundred individuals, 50 with and 50 without lower limb loss, were screened for this study; three individuals with limb loss and two without limb loss had incomplete data, and one individual (female, without limb loss) lacked a comparison participant. All participants were recruited from a military medical center, and data were collected in a clinic research laboratory. MAIN OUTCOME MEASURES: Measurements of %BF were compared between methods for each group. STATISTICAL ANALYSES PERFORMED: Measurements of %BF were compared using paired t-tests and intraclass correlation coefficient. Agreement and bias were assessed with Bland-Altman analysis. Receiver operating characteristic analysis was used to determine the diagnostic accuracy of the CM to identify participants with %BF levels in the obese category (≥25%). RESULTS: A statistically significant difference was found between %BF methods in the group with limb loss (1.7%; P = 0.001) and the group without limb loss (1.4%; P = 0.005), with DXA consistently higher than CM. However, the intraclass correlation coefficient estimates for the agreement between %BF by CM and DXA were 0.848 (95% confidence interval [CI]: 0.683-0.922; P < 0.001) and 0.828 (CI: 0.679-0.906; P < 0.001), for the groups with and without limb loss, respectively, suggesting that CM has good to near excellent agreement with DXA for estimating %BF in these groups. Receiver operating characteristic analysis indicated that the area under the curve supported predictive ability to detect obesity-based %BF in males with and without limb loss. CONCLUSIONS: Although a statistically significant difference was found between methods for individuals with limb loss, there was also good agreement between the methods, suggesting that CM may be a useful tool for estimating %BF in individuals with lower limb loss. The CM may be a useful and field expedient method for assessing %BF in a clinical setting when DXA is not available.

Racial and Ethnic Disparities in Utilization of Tonsillectomy among Medicaid-Insured Children.

OBJECTIVE: To examine racial differences in tonsillectomy with or without adenoidectomy (T&A) for sleep-disordered breathing (SDB) among Medicaid-insured children. STUDY DESIGN: Retrospective analysis of the 2016 MarketScan Multistate Medicaid Database was performed for children ages 2 to <18 years with a diagnosis of SDB. Patients with medical complexity and infectious indications for surgery were excluded. Racial groups were categorized into non-Hispanic White, non-Hispanic Black, Hispanic, and other. Adjusted multivariate logistic regression was used to determine if race/ethnicity was a significant predictor of obtaining T&A, polysomnography, and time to intervention. RESULTS: There were 83 613 patients with a diagnosis of SDB that met inclusion criteria, of which 49.2% were female with a mean age of 7.9 ± 3.8 years. The cohort consisted of White (49.2%), Black (30.0%), Hispanic (8.0%), and other (13.2%) groups. Overall, 15.4% underwent T&A. Black (82.2%) and Hispanic (82.3%) children had significantly higher rates of no intervention and White patients had the lowest rate of no intervention (76.9%; P < .0001) and the highest rate of T&A (18.7%; P < .0001). Mean time to surgery was shortest in White compared with Black children (P < .0001). Logistic regression adjusting for age and sex showed that Black children had 45% reduced odds of surgery (95% CI 0.53-0.58), Hispanic 38% (95% CI 0.58-0.68), and other 35% (95% CI 0.61-0.70) compared with White children with Medicaid insurance. CONCLUSIONS: Racial and ethnic disparities exist in the utilization of T&A for children with SDB enrolled in Medicaid. Future studies that investigate possible sources for these differences and more equitable care are warranted.

Divalent Cation Dependence Enhances Dopamine Aptamer Biosensing.

Oligonucleotide receptors (aptamers), which change conformation upon target recognition, enable electronic biosensing under high ionic-strength conditions when coupled to field-effect transistors (FETs). Because highly negatively charged aptamer backbones are influenced by ion content and concentration, biosensor performance and target sensitivities were evaluated under application conditions. For a recently identified dopamine aptamer, physiological concentrations of Mg2+ and Ca2+ in artificial cerebrospinal fluid produced marked potentiation of dopamine FET-sensor responses. By comparison, divalent cation-associated signal amplification was not observed for FET sensors functionalized with a recently identified serotonin aptamer or a previously reported dopamine aptamer. Circular dichroism spectroscopy revealed Mg2+- and Ca2+-induced changes in target-associated secondary structure for the new dopamine aptamer, but not the serotonin aptamer nor the old dopamine aptamer. Thioflavin T displacement corroborated the Mg2+ dependence of the new dopamine aptamer for target detection. These findings imply allosteric binding interactions between divalent cations and dopamine for the new dopamine aptamer. Developing and testing sensors in ionic environments that reflect intended applications are best practices for identifying aptamer candidates with favorable attributes and elucidating sensing mechanisms.

Narrower Nanoribbon Biosensors Fabricated by Chemical Lift-off Lithography Show Higher Sensitivity.

Wafer-scale nanoribbon field-effect transistor (FET) biosensors fabricated by straightforward top-down processes are demonstrated as sensing platforms with high sensitivity to a broad range of biological targets. Nanoribbons with 350 nm widths (700 nm pitch) were patterned by chemical lift-off lithography using high-throughput, low-cost commercial digital versatile disks (DVDs) as masters. Lift-off lithography was also used to pattern ribbons with 2 µm or 20 µm widths (4 or 40 µm pitches, respectively) using masters fabricated by photolithography. For all widths, highly aligned, quasi-one-dimensional (1D) ribbon arrays were produced over centimeter length scales by sputtering to deposit 20 nm thin-film In2O3 as the semiconductor. Compared to 20 µm wide microribbons, FET sensors with 350 nm wide nanoribbons showed higher sensitivity to pH over a broad range (pH 5 to 10). Nanoribbon FETs functionalized with a serotonin-specific aptamer demonstrated larger responses to equimolar serotonin in high ionic strength buffer than those of microribbon FETs. Field-effect transistors with 350 nm wide nanoribbons functionalized with single-stranded DNA showed greater sensitivity to detecting complementary DNA hybridization vs 20 µm microribbon FETs. In all, we illustrate facile fabrication and use of large-area, uniform In2O3 nanoribbon FETs for ion, small-molecule, and oligonucleotide detection where higher surface-to-volume ratios translate to better detection sensitivities.

Racial Disparities in Pediatric Endoscopic Sinus Surgery.

OBJECTIVE: To determine the impact of race and ethnicity on 30-day complications following pediatric endoscopic sinus surgery (ESS). STUDY DESIGN: Cross-sectional cohort study. SUBJECTS AND METHODS: Patients ≤ 18 years of age undergoing ESS from 2015 to 2017 were identified in the Pediatric National Surgical Improvement Program-Pediatric database. Patient demographics, comorbidities, surgical indication, and postoperative complications were extracted. Patient race/ethnicity included non-Hispanic black, non-Hispanic white, Hispanic, and other. Multivariable logistic regression was performed to determine if race/ethnicity was a predictor of postoperative complications after ESS. RESULTS: A total of 4,337 patients were included in the study. The median age was 10.9 (interquartile range: 14.5-6.7) years. The cohort was comprised of 68.3% non-Hispanic white, 13.9% non-Hispanic black, 9.7% Hispanic, and 2.1% other. The 30-day complication rate was 3.2%, and the mortality rate was 0.3%. The rate of reoperation was 3.8%, and readmission was 4.1%. Black and Hispanic patients had higher rates of urgent operations (P = .003 and P < .001, respectively), and black patients had a higher incidence of emergent operations (P < .001) compared to their white peers. For elective ESS cases, multivariable analysis adjusting for sex, age, comorbidities, and surgical indication indicated that children of Hispanic ethnicity had increased postoperative complications (odds ratio: 1.57, 95% confidence interval: 1.04-2.37). CONCLUSION: This analysis demonstrated that black and Hispanic children disproportionately undergo more urgent and emergent ESS. Hispanic ethnicity was associated with increased 30-day complications following elective pediatric ESS. Further studies are needed to elucidate potential causes of these disparities and identify areas for improvement. LEVEL OF EVIDENCE: 3 Laryngoscope, 131:E1369-E1374, 2021.

Flexible Multiplexed In2O3 Nanoribbon Aptamer-Field-Effect Transistors for Biosensing.

Flexible sensors are essential for advancing implantable and wearable bioelectronics toward monitoring chemical signals within and on the body. Developing biosensors for monitoring multiple neurotransmitters in real time represents a key in vivo application that will increase understanding of information encoded in brain neurochemical fluxes. Here, arrays of devices having multiple In2O3 nanoribbon field-effect transistors (FETs) were fabricated on 1.4-µm-thick polyethylene terephthalate (PET) substrates using shadow mask patterning techniques. Thin PET-FET devices withstood crumpling and bending such that stable transistor performance with high mobility was maintained over >100 bending cycles. Real-time detection of the small-molecule neurotransmitters serotonin and dopamine was achieved by immobilizing recently identified high-affinity nucleic-acid aptamers on individual In2O3 nanoribbon devices. Limits of detection were 10 fM for serotonin and dopamine with detection ranges spanning eight orders of magnitude. Simultaneous sensing of temperature, pH, serotonin, and dopamine enabled integration of physiological and neurochemical data from individual bioelectronic devices.

Detecting DNA and RNA and Differentiating Single-Nucleotide Variations via Field-Effect Transistors.

We detect short oligonucleotides and distinguish between sequences that differ by a single base, using label-free, electronic field-effect transistors (FETs). Our sensing platform utilizes ultrathin-film indium oxide FETs chemically functionalized with single-stranded DNA (ssDNA). The ssDNA-functionalized semiconducting channels in FETs detect fully complementary DNA sequences and differentiate these sequences from those having different types and locations of single base-pair mismatches. Changes in charge associated with surface-bound ssDNA vs double-stranded DNA (dsDNA) alter FET channel conductance to enable detection due to differences in DNA duplex stability. We illustrate the capability of ssDNA-FETs to detect complementary RNA sequences and to distinguish from RNA sequences with single nucleotide variations. The development and implementation of electronic biosensors that rapidly and sensitively detect and differentiate oligonucleotides present new opportunities in the fields of disease diagnostics and precision medicine.

Chemical Lift-Off Lithography of Metal and Semiconductor Surfaces.

Chemical lift-off lithography (CLL) is a subtractive soft-lithographic technique that uses polydimethylsiloxane (PDMS) stamps to pattern self-assembled monolayers of functional molecules for applications ranging from biomolecule patterning to transistor fabrication. A hallmark of CLL is preferential cleavage of Au-Au bonds, as opposed to bonds connecting the molecular layer to the substrate, i.e., Au-S bonds. Herein, we show that CLL can be used more broadly as a technique to pattern a variety of substrates composed of coinage metals (Pt, Pd, Ag, Cu), transition and reactive metals (Ni, Ti, Al), and a semiconductor (Ge) using straightforward alkanethiolate self-assembly chemistry. We demonstrate high-fidelity patterning in terms of precise features over large areas on all surfaces investigated. We use patterned monolayers as chemical resists for wet etching to generate metal microstructures. Substrate atoms, along with alkanethiolates, were removed as a result of lift-off, as previously observed for Au. We demonstrate the formation of PDMS-stamp-supported bimetallic monolayers by performing CLL on two different metal surfaces using the same PDMS stamp. By expanding the scope of the surfaces compatible with CLL, we advance and generalize CLL as a method to pattern a wide range of substrates, as well as to produce supported metal monolayers, both with broad applications in surface and materials science.

Insurance type impacts bronchoscopy for foreign body aspiration: An analysis of the Kids' Inpatient Database.

OBJECTIVES: To ascertain whether insurance type is associated with postoperative adverse effects and hospital length of stay for inpatient airway foreign body removal. METHODS: Retrospective analysis of children <18 years of age that underwent inpatient bronchoscopy with removal of airway foreign body in the national Healthcare Cost and Utilization Project Kid's Inpatient Database (KID). Postoperative outcomes and length of stay were analyzed for racial disparities and insurance type using multivariable logistic regression and negative binomial regression. Models adjusted for race, insurance type, sex, age, and presence of pulmonary risk factors. RESULTS: A total of 5,850 children underwent bronchoscopy for foreign body removal. The median age was 2 (IQR: 4-1) years and 61.6% patients were male. Payer status included Medicaid (38.9%), private insurance (51.5%), self-pay (4.3%) and other (9.6%). The Medicaid cohort had a higher proportion of black (19.1%) and Hispanic patients (34.5%) (P < 0.001). Children covered under Medicaid had higher odds of postoperative complications (odds ratio [OR] 1.216; P = 0.031) and a greater length of stay (OR 1.533; P < 0.001) relative to the private insurance group when adjusting for sex, age, race and presence of pulmonary risk factors. The odds of having a greater length of stay was 33% higher for black (P < 0.001) and 37% higher for Hispanic (P < 0.001) children compared to white children. The average adjusted LOS under Medicaid was 8.37 days compared to 5.46 days for privately insured children. CONCLUSION: This study demonstrated that a difference in postoperative complications and LOS exist between public and privately insured children for foreign body removal via bronchoscopy. Further studies are warranted to investigate factors that drive these disparities.