Science Hub
Appan's new paper (2023, DILI biosensor, Screen-printed gold electrodes, PNA, miR-122)
''POCT compatible biosensors are promising alternatives to PCR and other traditional methods because of their low complexity, low cost, ease of operation, and scalability for mass production''
'' electrochemical impedance spectroscopy (EIS), which is particularly well-suited for developing rapid and sensitive assays for nucleic acid hybridisation-based detection without the need of labelling of targets''
''Biosensors often rely on diffusion of targets from the bulk solution to the surface-immobilised probes. This purely diffusion-controlled binding results in lengthy procedures with slow binding kinetics and reduced binding efficiency (Liu et al., 2003; Tavallaie et al., 2018). However, POCT requires shorter time to results which could be achieved by faster transport of target molecules to their binders on the sensor surface. Several attempts have been made to improve hybridisation kinetics by facilitating mass transfer, such as by using direct electric field (Edman et al., 1997; Sosnowski et al., 1997), magnetic actuation (Tavallaie et al., 2018), acoustic micromixer (Liu et al., 2003) and pumping of target solution (Kim et al., 2006; Wang et al., 2011). In the present work, we used a microfluidic system with a continuous flow of target solution for enhanced transport of miR-122 targets to immobilised PNA probes. ''
Highlight: Great specificity (can tell the difference between compl target, non-compl, nearly-compl, common isoforms, and single nucleotide mismatch.
miniaturisation小型
Inspiring me of the keywords of my study:
early detection
easy-to-use biosensor to enable point-of-care tests
The ability to identify emerging pathogens.
Graphene sensor company:
dentifysensors: Check4® (printed graphene, phone reader, disposable test cartridge, saliva sample, multiple viruses and bacteria)
IdentifySensors develops novel technologies based on rapidly detecting harmful materials from graphene — a carbon-based film that is the strongest, thinnest and most conductive material known. The company’s patented technology can instantly identify a wide range of dangers, such as viruses and bacteria, foodborne pathogens and explosives.
gripmolecular
At-home diagnostics can empower individuals with actionable information about their infection status so that they can self-isolate, which can help reduce community transmission, and seek medical care and treatment early in the course of any infection. Developing rapid and affordable home-based diagnostics, along with the technologies that support them, is essential to enabling widespread adoption of COVID-19 at-home testing.
Accelerating the capabilities of COVID-19 tests can propel these new diagnostic platforms for future use against other pathogens.
Check4
''There are numerous issues yet to be resolved, associated with DNA biosensing at the fundamental level. Much of this stems from the inherent variability in the manufacture of uniform DNA layers (for me, the inherent variability of electrode itself...), self-assembled monolayer (SAM) instability, required optimization of receptor molecule packing densities, availability of binding sites for target hybridization, and the determination of appropriate electrochemical parameters for maximum signal gain. '' Signal Amplification in Electrochemical DNA Biosensors Using Target-Capturing DNA Origami Tiles | ACS Sensors
Questions to ChatGPT:
Q:
what kind of information does OCP provide in electrochemical measurement?
A:
OCP, or Open Circuit Potential, provides information about the thermodynamic stability of an electrochemical system. It is the potential difference between an electrode and its electrolyte solution when there is no current flowing between them.
In electrochemical measurements, OCP is often used as a reference point to measure the potential difference between two electrodes, or between an electrode and a reference electrode, to determine the direction and magnitude of a reaction. OCP can also provide information about the electrochemical properties of the system, such as the presence of electron transfer reactions or the potential for corrosion.
In summary, OCP provides information about the thermodynamic stability and electrochemical properties of a system, making it a useful tool for understanding electrochemical reactions and processes.
Q:
What does it mean if the OCPs between two electrodes are different?
A:
If the OCP (Open Circuit Potential) between two electrodes is different, it means that there is a potential difference or voltage difference between the two electrodes in their respective electrolyte solutions when they are not connected by an external circuit. This potential difference arises due to differences in the chemical and electrochemical properties of the electrodes and their surrounding electrolyte solutions.
In an electrochemical system, the OCP between two electrodes can provide information about the direction and magnitude of any electrochemical reactions occurring between them. A higher OCP for one electrode compared to another may indicate a greater tendency for that electrode to undergo oxidation, reduction or corrosion, whereas a lower OCP may indicate a greater tendency for the other electrode to undergo these reactions.
The difference in OCP between two electrodes can also be used to determine the feasibility and direction of electrochemical reactions, as well as the potential for material degradation or corrosion. Therefore, it is important to measure and monitor the OCP of an electrochemical system to ensure its stability and performance over time.
de Levie, R. On porous electrodes in electrolyte solutions: I. Capacitance effects. Electrochim. Acta 8, 751–780 (1963).
de Levie, R. On porous electrodes in electrolyte solutions — IV. Electrochim. Acta 9, 1231–1245 (1964).
de Levie, R. in Advances in Electrochemistry and Electrochemical Engineering Vol. 6 (eds Delahay, P. & Tobias, C.W.) 329–397 (Wiley, 1967). This pioneering work develops an EIS model for a porous electrode.
Barcia, O. E. et al. Further to the paper “Application of the impedance model of de Levie for the characterization of porous electrodes” by Barcia et al. [Electrochim. Acta 47 (2002) 2109]. Electrochim. Acta 51, 2096–2097 (2006).
Lasia, A. in Electrochemical Impedance Spectroscopy and its Applications 1–367 (Springer, 2014).
https://www.nature.com/articles/s43586-021-00039-w/figures/4 Similar to the data I obtained....
EIS Bible 2.0: https://pubs.acs.org/doi/10.1021/acsmeasuresciau.2c00070
(A) The semi-infinite regime of an electrochemical cell, (B) the transmission line (TL) depiction of the semi-infinite regime, (C) finite boundary diffusion at t < td spans, (D) transmissive, and (E) reflective boundary at t > td.
Warburg impedance is a complex element which represents the mass transfer of redox species to the electrode surface and is depicted as a 45° line over the low frequency range of the Nyquist plot. This behavior refers to the time dependent (not-steady state) semi-infinite diffusion of the chemical species, in which, there is a single boundary at the electrode/electrolyte interface, at a distance x = 0. Toward to the bulk solution, and under quiescent conditions, the diffusion layer is extended to infinite length (x → ∞) delimited by the dimensions of the electrochemical cell, while the concentration gradient is decreased with time.
Important to read mentioned by Till
Binder of graphene...
non-commercialised but self-synthesied large molecule...
If I cannot have an application (which is all I want) in the end, at least I can better know the property of this material and may find a better way to probe it, patent it. Then the company will be happy.
I'm the one who suffered... Damn it..........................................
Stable ways to have stable pi-pi stacking on graphene
1. Mann et al. revealed that molecules consisting of a single pyrene unit were unstable in organic solution, which prompted the design of compounds consisting of three pyrene “feet” in order to form stable films. https://pubs.acs.org/doi/10.1021/ja208239v
2. An alternative method to ensure stability of pyrene on graphene was implemented by Singh et al., who demonstrated electropolymerized pyrene films on graphene for a graphene-based SPR (surface plasmon resonance) sensor https://pubs.acs.org/doi/10.1021/ja511512m
3. Perylene bisimide derivatives https://pubs.rsc.org/en/content/articlelanding/2015/cc/c5cc06433c#cit11
https://www.chemistrysteps.com/solubility-of-organic-compounds/
the stronger the interactions between the solute and the solvent the higher the solubility of the solute. And this observation is formulated in the golden rule of solubility: “like dissolves like”.
This means polar compounds dissolve in polar solvents, and nonpolar compounds dissolve in nonpolar solvents.
Organic liquids, on the other hand, are mostly nonpolar since the hydrocarbon part of them consists of C-H bonds which are nonpolar and only interact via London dispersion forces.
The overall polarity of the compound comes from the imbalance of the nonpolar hydrocarbon chain (carbon skeleton) and the presence of polar bonds. For example, methanol, ethanol, and isopropanol are water soluble while butanol is a lot less soluble than the former. (large carbon skeleton reduces the solubility)
the carbonyl group is polar because of the polarity of the C=O bond. This can be seen by the fact that acetone, having three carbon atoms, is still miscible with water. The C=O group serves as an acceptor of hydrogen bonding with water. This does not however, make the molecule as polar as the OH group does since the latter is capable of being both a donor and an acceptor in hydrogen bonding.
Hexane is the most common nonpolar solvent
As a rough estimate, remember that water soluble organic compounds must have an oxygen or nitrogen containing functional groups (O, N, S). In any case, if the molecule has more than 3-4 carbon atoms, its solubility is going to significantly decrease.
To be an “average” molecule in terms of solubility, the solute should have one polar group for roughly 6-7 carbon atoms
If the carbon skeleton largely predominates in the mass of the solute, consider nonpolar solvents such as diethyl ether, toluene and lastly hexanes and cyclohexane. Some examples of such molecules commonly used in organic laboratories are porphyrins, pyrenes, perylene and other chromophores. These molecules are extremely hydrophobic unless other functional groups are connected to them.
New binder candidate:PTCDA https://www.sigmaaldrich.com/GB/en/product/aldrich/p11255
It provides a high electron mobility due to its low intermolecular distance which results in π-π conjugation
The difference between (single) t test and multiple t tests
single t-test: in one test, only one pair of data was compared
multiple t-tests: run many tests to compare two groups of data at once
Graphene biosensor (graphene oxide)
Highlight:
use transcript activator-like effectors (TALEs) as a new diagnostic probe. It is a class of programmable DNA-binding domains. TALE can identify sequence-specific double-strand DNA (ssDNA). Therefore, no need for denaturation and renaturation of dsDNA.
Utilise the fluorescence quench effect of GO and QC-labeled TALEs to develop a turn-on strategy.
After dsDNA binds to TALEs, the conformation change happens on TALEs. Fluorescence energy stores back.
