For more information visit: https://bese.kaust.edu.sa/study/bioengineering
Inkjet-printed Ti3C2Tx MXene electrodes for multimodal cutaneous biosensing(Journal of Physics: Materials, IOP Publishing, 2020-08-28) [Article]Among the existing 2D materials, MXenes, i.e., transition metal carbides, nitrides and/or carbonitrides, stand out for their excellent electrochemical properties. On account of their high charge storage capacity, metal-like conductivity, biocompatibility as well as hydrophilicity, Ti3C2Tx MXene-based inks hold great potential for scalable production of skin conformable electronics via direct printing methods. Herein, we develop an aqueous MXene ink and inkjet-print MXene films on freestanding, flexible conducting polymer-based substrates. These skin-adherent MXene electrodes detect electrocardiography signals with high signal-to-noise ratio while exhibiting preserved electrical performance after 1000 cycles of bending with a 50 day-long shelf life in ambient conditions. We show that printed MXene films can further be functionalized to perform as multifunctional biosensing units. When integrated with a sodium (Na+) ion-selective membrane, MXene electrodes detect Na+ in artificial sweat with a sensitivity of 40 mV per decade. When the films are functionalized with antibodies, they generate an electrical signal in response to a pro-inflammatory cytokine protein (interferon gamma) with a sensitivity of 3.9 mV per decade. Our findings demonstrate how inkjet-printed MXene films simplify the fabrication of next-generation wearable electronic platforms that comprise multimodal sensors.
A Self-standing Organic Supercapacitor to Power Bioelectronic Devices(ACS Applied Energy Materials, American Chemical Society (ACS), 2020-07-27) [Article]The last decade has witnessed rapid progress in the development of implantable and wearable bio(chemical) sensors, which allow for real-time, continuous health monitoring. Among different device configurations, organic electrochemical transistors (OECTs) have shown great potential in transducing weak biological signals with on-site amplification and as components of complex circuits with low power requirements. Yet, a significant technological challenge remains in the way these devices are integrated with power sources that are conventionally bulky and rigid. Here, we present a simple process to assemble a supercapacitor (SC) that is self-standing, lightweight, and biocompatible and made of two identical conducting polymer (poly(3,4-ethylenedioxythiophene) electrodes and an agarose hydrogel comprising alkali metal halides. This SC is distinguished by its high energy and power density (20 Wh kg-1 and 105 W kg-1, respectively), moderate gravimetric specific capacitance (70 F g-1), excellent stability (charge retention of 75% after 12,000 cycles), operational flexibility (can accommodate various types of aqueous electrolytes), long-lasting self-discharge (>10 h), and fast response time (between 0.1 and 30 s). We use the SC to power a micron-scale OECT, which selectively detects sodium ions in aqueous media. When miniaturized, the SC maintains its high performance and delivers a volumetric capacitance of 240 F cm-3, highlighting the possibility of fabrication in nonstandard form factors to couple with various bioelectronic devices. This low-cost and portable power source instigates the development of robust and biocompatible onboard power sources to be implemented alongside biosensors.
A Computational Analysis of Cell Fate Dynamics during Zebrafish Embryonic Development using Single Cell Transcriptomics(2020-07) [Thesis]
Advisor: Tegner, Jesper
Committee members: Li, Mo; Gao, XinDevelopment and the associated cellular differentiation are some of the most fundamental processes in biology. Since the early conception of the Waddington landscape, with cells portrayed as rolling down a landscape, understanding these processes has been at the forefront of biology. Progress in tissue regeneration, organoid culture, and cellular reprogramming relies on our ability to unfold cellular decision making and its dynamics. In this thesis, we ask to what extent development follows such landscape. Secondly, we address whether cellular branching points are discrete events. Given the recent surge in single-cell genomics data, we can now address these fundamental questions. To this end, we analyzed two large-scale single-cell RNAseq time course datasets from vertebrate embryogenesis in zebrafish. From the Waddington analogy, we expect the cell-to-cell correlation to increase across development as cells specialize. Our analysis does not show a linear trend, but rather, that cell-to-cell variability is lowest during gastrulation. Interestingly, the two different datasets from two different laboratories display a qualitatively similar trend, providing internal consistency of our analysis. To uncover the branchpoint dynamics, we extended our analysis to include computations of gene-to-gene correlations. It has been shown, using PCR data, that the transition index, the ratio between cell-to-cell and gene-to-gene correlations, displays a peak during such branchpoints, suggesting discrete transitions. To this end, we tracked individual developmental trajectories, and characterized both correlations, enabling computation of the transition index. However, the cell-to-cell correlation and gene-to-gene correlation did not follow a generic inverse relationship, as previously suggested. No unique signal corresponding to the branchpoints could, thus, be detected. Therefore, our analysis does not support the view that branchpoints during vertebrate embryogenesis are discrete, well-defined transition events. In conclusion, this first large-scale single-cell based analysis of time-resolved developmental data does not support a downhill rolling ball notion where cells decide their fate at discrete transition points. The temporal organization of an undulating developmental landscape appears to be more complex than initially conceptualized by Waddington. Therefore, it is of paramount interest to extend this type of analysis to other systems and to develop techniques to compute such landscape in a data-driven manner.