| 1. |
- Beal, Jacob, et al.
(författare)
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Robust estimation of bacterial cell count from optical density
- 2020
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Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.
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| 2. |
- Han, Yuanyuan
(författare)
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Biosensing platforms using graphene based bioreactive nanostructures with various dimensions
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Nanomaterials have brought new aspects and improvements to the biosensing field due to their unique physical and chemical properties that are not shown in the bulk state. This thesis focuses on concepting, developing and testing of biosensors where nanomaterials including graphene gold nanoparticles (AuNPs) and magnetic nanoparticles (MNPs) constitute the biosensors. The motivation is to improve the properties of biosensors for protein and nucleic acids by using the nanomaterials’ high surface volume ratio, their unique electrical properties, their good stability and biocompatibility.The synthesis of well controlled hybrid materials was essential to obtain well performing nucleic acids sensors, whereas a protein sensor contained mainly graphene and organic molecules. The nanomechanical measurements were applied on pyrene-maltose functionalized graphene surfaces after incubating them with the protein. When the Concanavalin A was captured by the pyrene-maltose, the adhesion force of biosensor surface increased significantly. This detection principle was employed to quantify the Concanavalin A attachment to the surface sensitively.In the development of the eletrocatalytic microRNA sensor, AuNPs were packaged into graphene oxide (GO) sheets to form three-dimensional network structures that both guide the electrical current and increase the surface area of the electrodes. Prior to the assembly of these GO-AuNPs hybrid materials, a duplex-specific nuclease-assisted target recycling reaction was employed for opening the surface of the DNA functionalized AuNPs. The electrocatalytical water splitting activity increased with the fraction of the AuNP surface and thus with the activity of the nuclease-assisted target recycling reaction.Owing to the high shape anisotropy of graphene, a two-dimensional optomagnetic label GO-MNP nanohybrid was investigated for DNA detection. The DNA coils that were generated through rolling circle amplification absorbed on GO-MNP nanohybrid, leading to a hydrodynamic size increase or aggregation of the proposed nanolabels that can be detected by an optomagnetic sensor. An MNP assembly-based microRNA biosensing strategy is also included in the thesis. DNA scaffolds of the MNP assemblies contain DNAzyme substrate and thus can form cleavage catalytic structures in the presence of microRNA, leading to the disintegration of assemblies. The proposed nanomaterials based biosensing platforms show great potential in the clinical and biomedical applications.
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| 3. |
- Han, Yuanyuan, et al.
(författare)
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Flexible conductive silk-PPy hydrogel toward wearable electronic strain sensors
- 2022
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Ingår i: Biomedical Materials. - : IOP Publishing Ltd. - 1748-6041 .- 1748-605X. ; 17:2
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Tidskriftsartikel (refereegranskat)abstract
- Conductive hydrogels have been studied as promising materials for the flexible and wearable bioelectronics, because of their unique electrical and mechanical properties. Addition of conducting polymers in biomaterial-based hydrogel matrix is a simple yet effective way to construct hydrogels with good conductivity and flexibility. In this work, a conductive hydrogel composed by a silk hydrogel and a conducting polymer, polypyrrole (PPy), is developed via in situ polymerization of pyrrole into the silk fibroin network. The silk-PPy hydrogel shows high conductivity (26 S m(-1)), as well as sensitive and fast responses to corresponding conformation changes. Taking advantages of these properties, flexible and wearable strain sensors are proposed for the monitoring of various body movements, which can detect both the large and subtle human motions with good sensitivity, reproducibility and stability. The hybridization of biomaterials and conducting polymers endows the multifunctions of the conductive hydrogels, thus showing considerable potentials in the advancement of the wearable electronics.
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| 4. |
- Han, Yuanyuan, et al.
(författare)
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Graphene Based Mechanical Biosensor by Employing Non-covalent Stacking Functionalization
- 2019
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Herein we demonstrate a novel methodology to achieve mechanical biosensor by employing the distinguished interaction forces between the atomic force microscope (AFM) probe and sensor surfaces as the response signal. This mechanical biosensor is fabricated by utilizing the non-covalent π-π stacking of pyrene-maltose onto graphene surfaces with Concanavalin A (Con A) as a target protein. The atomic resolution scanning tunneling microscopy (STM) images indicate the successful formation of the self-assembled and densely packed pyrene-maltose layer on the sensor surface, which gives distinct atomic lattice structure as compared to pristine graphene. This mechanical biosensor exhibits detection of Con A with the sensitivity down to nanomolar level. Therefore, this proposed mechanical biosensor has the potential to be employed in a variety of bio-sensing applications.
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| 5. |
- Han, Yuanyuan, et al.
(författare)
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MicroRNA detection based on duplex-specific nuclease-assisted target recycling and gold nanoparticle/graphene oxide nanocomposite-mediated electrocatalytic amplification
- 2019
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Ingår i: Biosensors & bioelectronics. - : Elsevier BV. - 0956-5663 .- 1873-4235. ; 127, s. 188-193
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Tidskriftsartikel (refereegranskat)abstract
- DNA technology based bio-responsive nanomaterials have been widely studied as promising tools for biomedical applications. Gold nanoparticles (AuNPs) and graphene oxide (GO) sheets are representative zero- and two-dimensional nanomaterials that have long been combined with DNA technology for point-of-care diagnostics. Herein, a cascade amplification system based on duplex-specific nuclease (DSN)-assisted target recycling and electrocatalytic water-splitting is demonstrated for the detection of microRNA. Target microRNAs can form DNA: RNA heteroduplexes with DNA probes on the surface of AuNPs, which can be hydrolyzed by DSN. MicroRNAs are preserved during the reaction and released into the suspension for the digestion of multiple DNA probes. After the DSN-based reaction, AuNPs are collected and mixed with GO to form AuNP/GO nanocomposite on an electrode for the following electrocatalytic amplification. The utilization of AuNP/GO nanocomposite offers large surface area, exceptional affinity to water molecules, and facilitated mass diffusion for the water-splitting reaction. For let-7b detection, the proposed biosensor achieved a limit detection of 1.5 fM in 80 min with a linear detection range of approximately four orders of magnitude. Moreover, it has the capability of discriminating non-target microRNAs containing even single-nucleotide mismatches, thus holding considerable potential for clinical diagnostics.
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| 6. |
- Han, Yuanyuan, et al.
(författare)
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Optimization and analysis of pyrene-maltose functionalized graphene surfaces for Con A detection
- 2020
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Ingår i: Applied Surface Science. - : ELSEVIER. - 0169-4332 .- 1873-5584. ; 510
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Tidskriftsartikel (refereegranskat)abstract
- Utilizing the non-covalent pi-pi stacking of pyrene functionalized molecules onto graphene surfaces has achieved great success in the detection of various bio-objects, while the fundamental investigations on surface modifications stills remain rarely exploited. Here, we report the nano and atomic scale analysis of the pi-pi stacking functionalized graphene surface regarding to its surface topography, molecular self-assembly as well as process optimizations. The 'amphipathic' molecule, pyrene-maltose, is used for the non-covalent functionalization of graphene and systematical analysis is performed to understand the influence of different solvents on the molecular surface arrangement. Atomic force microscopy (AFM) and spectroscopy analysis indicate the successful formation of pyrene-maltose layer on graphene surface and it is further confirmed by scanning tunneling microscopy, depicting the self-assembled and densely packed pyrene-maltose layer that give distinguished and ordered diamond-shape lattice as compared to triangular lattice in pristine graphene. We also demonstrated that the interfacial adhesion forces between the AFM probe and the functionalized surfaces allow the detection of the lectin protein Concavalin A through selective absorption. This work provides essential evidence of the pi-pi interactions between pyrene molecules and graphene, and the AFM based adhesion measurement also has the potential to be employed in a variety of bio-detection applications.
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| 7. |
- Johansson, Fredrik, et al.
(författare)
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Tailoring ultra-fast charge transfer in MoS2
- 2020
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 22:18, s. 10335-10342
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Tidskriftsartikel (refereegranskat)abstract
- Charge transfer dynamics are of importance in functional materials used in devices ranging from transistors to photovoltaics. The understanding of charge transfer in particular of how fast electrons tunnel away from an excited state and where they end up, is necessary to tailor materials used in devices. We have investigated charge transfer dynamics in different forms of the layered two-dimensional material molybdenum disulphide (MoS2, in single crystal, nanocrystalline particles and crystallites in a reduced graphene oxide network) using core-hole clock spectroscopy. By recording the electrons in the sulphur KLL Auger electron kinetic energy range we have measured the prevalence of localised and delocalised decays from a state created by core excitation using X-rays. We show that breaking the crystal symmetry of the single crystal into either particles or sheets causes the charge transfer from the excited state to occur faster, even more so when incorporating it in a graphene oxide network. The interface between the MoS2 and the reduced graphene oxide forms a Schottky barrier which changes the ratio between local and delocalised decays creating two distinct regions in the charge transfer dependent on the energy of the excited electron. Thereby we show that ultra-fast charge transfer in MoS2 can be tailored, a result which can be used in the design of emergent devices.
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| 8. |
- Li, Hu, et al.
(författare)
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Dyes as Labels in Biosensing
- 2021
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Ingår i: Dyes and Pigments. - London : IntechOpen. - 9781839686153
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Bokkapitel (refereegranskat)abstract
- Investigation and evaluation of dyes play a vital role in the process of introduction novel labels and their corresponding sensing methods, which signify opportunities for the development of biosensors. This chapter introduces applications of various dyes as labels in biosensing. Bio-recognition molecules with dyes transduce biological information into measurable optical, electrochemical, magnetic or other kinds of signals for quantification. The dyes used in this field were summarized and reviewed according to their signal types, namely colorimetric, fluorescent and electrochemical. Some dyes can transduce signals between multiple physical signals. For some most important dyes, detailed descriptions were given focused on their unique properties, labeling methods and sensing mechanisms.
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| 9. |
- Li, Hu, 1986-, et al.
(författare)
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Enhanced gas sensing performance of graphene/ZnS-CdS hetero-nanowires gas sensor synthesized by Langmuir-Blodgett self-assembly method
- 2017
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Ingår i: Journal of Physics Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 922
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Tidskriftsartikel (refereegranskat)abstract
- Graphene is a promising material in the field of solid-state gas sensors due to the unique two-dimensional structure. Here, we have shown by fabricating graphene/ZnS-CdS hetero-nanowire structure, the gas sensor sensitivity has a two-fold increase to 20% under 15 ppm gaseous concentration compared to a 10% response in pristine graphene. Spectroscopy and microscopy analysis indicate that the semi-conducting ZnS-CdS hetero-nanowires are 2 nm wide and densely packed on top of graphene. By combining UV illumination, the device approaches a fast response/recovery and high gas sensitivity, thus has a potential to be used in a detection of wide range of gases.
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| 10. |
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