WO2023242869A1

WO2023242869A1 - Non-enzymatic biodegradable electrochemical cathode from biomolecules of natural origin and biodegradable electrochemical cell

Info

Publication number: WO2023242869A1
Application number: PCT/IN2023/050561
Authority: WO
Inventors: Kaushik Palicha; Harinipriya Seshadri
Original assignee: Kaushik Palicha; Harinipriya Seshadri
Priority date: 2022-06-14
Filing date: 2023-06-14
Publication date: 2023-12-21

Abstract

The present disclosure provides a non-enzymatic biodegradable electrochemical cathode comprising Microtubules (MTs) isolated from natural sources, preferably from plant sources, and a process for fabricating the cathode. In an aspect of the present disclosure, there is provided a biodegradable electrochemical cell using the biodegradable electrochemical cathode, wherein the anode material includes a carbon rich material such as Carbon Black (CB), graphite or graphene, or the anode includes a biopolymer such as ethyl cellulose.

Description

TITLE

NON-ENZYMATIC BIODEGRADABLE ELECTROCHEMICAL CATHODE FROM BIOMOLECULES OF NATURAL ORIGIN AND BIODEGRADABLE ELECTROCHEMICAL CELL

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is based upon and claims priority to India complete patent application number 202241033885 filed on March 27, 2023, which claims priority to India provisional patent application number 202241033885 filed on June 14, 2022. The entire contents of all are herein incorporated by reference.

FIELD

The present disclosure relates to electrochemical cells, more particularly relates to a biodegradable electrochemical cathode comprising microtubules (MTs) isolated from natural sources, process of fabrication of the cathode, and biodegradable electrochemical cell using the biodegradable electrochemical cathode.

BACKGROUND

Microtubules (MTs) are self-assembled polymeric tubules made of a and tubulin dimers. MTs are the major constituent of cytoskeleton involved in variety of functions such as cell division, intracellular transport of organelles and prominently neuronal signal transmission due to their high ionic conductivity, unique structure and ordered arrangement. Living cells are known to possess intrinsic electric fields and are sensitive to external electric fields. MTs are affected by the external electric fields and thereby affect their major role in cell division. As cancer being an uncontrolled cell division, MTs’ mechanism of action in treating various cancer types is also affected by electrical perturbations. It is found in the literature that protein monomers and their polymeric forms differ largely in their conductivity. Hence proteins in the cells can be regarded as semiconducting in nature. In the ionic medium, inside the cell, counterion condensation effect compensates these unbalanced charges in polymeric forms of protein. Hence studying the effects of electric field on the monomers and polymer ensembles of tubulin will provide insights in to the role of MTs in signal transmission. A single Microtubule (MT) is an intracellular cytoskeletal cylindrical protein polymer made of a tubulin dimer that self-assemble in to MTs under appropriate conditions and rapidly depolymerize. These proto filaments form hollow MTs of 15-25 nm diameters and lengths up to a few mm, with almost 900 amino acid residues and measures 4x5x8 nm³' They are involved in many critical cellular functions such as cell division, intracellular transport and signal transduction. MTs are associated with many proteins to perform various functions. Motor proteins such as kinesin and dynein use MTs as track to carry cargo such as neurotransmitters and deliver them.

MTs are also known to play an important role in the functioning of neurons and the brain and are said to be responsible for cognition, memory and consciousness. Consciousness is thought to be the emergent phenomena of highly complicated nested complex of neurons within the brain, however if we look closer, it is indeed due to the quantum effects of the MTs present in the neuronal cells as said in Orchestrated objective reduction (Orch. OR) theory. The unit of information processing in brain is the tubulin protein and change in their conformational state. They are known to increase the conductivity of electrolyte solutions by 23%. This high conductivity can be attributed to the counterion polarization effect where the positive ions such as K⁺ and Ca²⁺ adsorb on the highly localized negatively charged surface of MTs and due to the mobility of these ions along the length of the MTs, the conductivity increases. They also transmit signals received from the external environment into the cell through the initiation of signal transduction cascade. Transmission of signal in terms of passage of charged particles such as electron and ions through them is possible because of the nanopores and defects present in their wall. Cytoskeletal proteins transmit signals in the form of ionic solitons. Bunch of MTs form bundles in neuronal cells acting as bio-electrical transistor that generate electrical signals similar to action potential.

US2010171081A1 discloses an energy storage device having electrodes containing mineral microtubules. The electrodes may be formed, for example, from a paste containing microtubules, a conductive polymer containing mineral microtubules, or an aerogel containing the mineral microtubules. The mineral microtubules may be filled with carbon, a pseudocapacitance material, or a magnetoresistive material. The mineral microtubules may also be coated with a photoconductive material.

KR102202773B1 discloses a positive electrode slurry containing a biomolecule- carbon composite in which a biomolecule and a nano-carbon material are complexed; the biomolecule includes a phosphoric acid group in the main chain, and a lithium secondary battery including the positive electrode slurry. According to one aspect, the biomolecule is from the group consisting of DNA, RNA, ATP (adenosine triphosphate), ADP (adenosine diphosphate), AMP (adenosine monophosphate), NADPH (nicotine amide adenine dinucleotide phosphate), and pyrophosphate. It may include at least one selected biomolecule, a similar biomolecule including sodium dodecyl phosphate (SDP), or a combination thereof.

US7410709B2 discloses a bio-battery including a first cell having a biomolecular energy source and a first electrode, a second cell having a reducible substrate and a second electrode. The biomolecular energy is in ionic communication with the reducible substrate. The first electrode is in oxidizing contact with the biomolecular energy source. The second electrode is in reducing contact with the reducible substrate. The first electrode is in electrically conductive communication with the second electrode. The biomolecular energy source is any suitable electrolytically oxidizable biomolecule. The biomolecular energy source may be selected from the group consisting of Nicotinamide Adenine Dinucleotide (NADH), Nicotinamide Adenine Dinucleotide Phosphate (NADPH) and 5,10-Methylenetetrahydrofolate Reductase (FADH), however other biomolecular energy sources may also be used.

While some researchers have used artificial MTs as anode, they have the following disadvantages: Major disadvantages due to the artificial nature of the MTs (Not natural MTs) in the existing art:

- Relatively low speed (low diffusion),

- Low dispersal in complex and dynamic flow environments,

- Requires high-resolution spatiotemporal tracking with limited capability to compensate for environmental disturbances,

- Not easily miniaturized to the micro-meter scale.

Major disadvantages due to the MTs used in the anode (not in the cathode) in the existing art:

- Electrical conductivity is very low, need to be mixed with conducting carbon.

- Conducting carbon loading goes up to 35 - 40% thereby making MTs to lose its inherent property of ionic conductivity as trade off.

- Due to different interfaces formed such as MT-Carbon, carbon-carbon, the longevity and functionality as anode active material drastically reduces.

Hence there is a need to study the potential of natural MTs used in the cathode of an electrochemical cell.

And also, due to growing environmental concerns, and batteries being increasingly ubiquitous as a portable power source across the globe, there is a need to devise a biodegradable battery.

SUMMARY

The present disclosure provides a non-enzymatic biodegradable electrochemical cathode comprising Microtubules (MTs) isolated from natural sources, preferably from plant sources, wherein the cathode is prepared by crystallising the isolated MTs, making a slurry of the crystallised MTs with a suitable solvent such as ethanol, acetone or isopropanol, and coating the slurry on a metallic current collector. In an aspect of the present disclosure, there is provided a biodegradable electrochemical cell using the biodegradable electrochemical cathode, wherein the electrochemical cell is SS/MT//PP-1M KC1//CB/A1, wherein Stainless Steel (SS) and Aluminium (Al) are used as current collectors for cathode and anode respectively, Polypropylene (PP) membrane soaked in IM KC1 as electrolyte and carbon rich material such as Carbon Black (CB), graphite or graphene is the anode material.

In another aspect of the disclosure, the anode includes a biopolymer such as ethyl cellulose, wherein the electrochemical cell is SS/MT/PP-1M KC1/EC/A1).

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

Fig. 1 is an illustration of the electrode/electrolyte interface and the interaction between the protein units and the metal surface.

Fig. 2 illustrates the configuration of non-enzymatic biodegradable electrochemical half-cell.

Fig. 3 illustrates a flow chart of the methodology of the experimental work.

Fig. 4 illustrates cyclic voltammetry (CV) of MTs eluent in 0.4M KC1 at different scan rates, wherein the arrows indicate the direction of scan rates.

Fig. 5A illustrates the phase transition in MTs due to charge perturbations - showing variation of peak current with increasing Load.

Fig. 5B illustrates the phase transition in MTs due to charge perturbations - showing variation of free energy of adsorption (AG) with increasing Load. Fig. 6 is an illustration of dynamic stability of MTs on Au surface.

Fig. 7 is an illustration of Tubulin dimer of 4 nm x 5 nm x 8 nm.

Fig. 8 A shows the load dependency of Energy of Adsorption (E_a< ) of the MTs - variation of Diffusion coefficient with Load.

Fig. 8B shows the load dependency of Energy of Adsorption (E_ad^ of the MTs - variation of mobility with Load.

Fig. 8C illustrates Variation of E_ad of MTs with Load. Fig. 9A illustrates the Specific Capacity profile of non-enzymatic biodegradable electrochemical cell of configuration SS/MT//PP-1M KC1//CB/A1 with 10000 cycles @ 0.1 C rate.

Fig. 9B illustrates the Specific Capacitance profile of non-enzymatic biodegradable electrochemical cell of configuration SS/MT//PP-1M KC1//CB/A1 with 10000 cycles @ 0.1 C rate.

Fig. 10 illustrates the Galvanostatic Charge/Discharge profile of the fabricated 2032-coin cell of the non-enzymatic biodegradable electrochemical cell.

Fig. 11A illustrates the Specific Capacity profile of non-enzymatic biodegradable electrochemical cell of configuration SS/MT//PP-1M KC1//EC/A1 with 334 cycles @ 0.1 C rate.

Fig. 11B illustrates the Specific Capacitance profile of non-enzymatic biodegradable electrochemical cell of configuration SS/MT//PP-1M KC1//EC/A1 with 334 cycles @ 0.1 C rate.

Fig. 12 shows the UV-vis, spectra of eluted MTs.

Fig. 13 represents the FTIR analysis of eluted MTs.

Fig. 14(a) shows the SEM spectra of bare MWCNTs.

Fig. 14(b) shows the SEM spectra of MTs soaked in MWCNTs.

DETAILED DESCRIPTION

The preferred embodiments of the present disclosure will be described in detail with the following disclosure and examples. The foregoing general description and the following detailed description are provided to illustrate only some embodiments of the present disclosure and not to limit the scope of the present disclosure. The disclosure is capable of other embodiments and can be carried out or practiced in various other ways.

Unless otherwise specified, all the technical and scientific terms used herein have the same meaning as is generally understood by a person skilled in the art pertaining to the present disclosure.

Headings are used solely for organizational purposes, and are not intended to limit the disclosure in any way.

The use of the singular includes the plural unless specifically stated otherwise. As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well. The use of “or” means “and/or” unless stated otherwise.

As used herein, the terms “comprises” and/or “comprising” specify the presence of the stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. Furthermore, to the extent that the terms “includes,” “having,” “has,” “with,” “composed,” “comprised” or variants thereof are used in either the detailed description or the claims, such terms are intended to be inclusive in a manner similar to the term “comprising.”

As used herein, ranges and amounts can be expressed as “about” a particular value or range. “About” is intended to also include the exact amount. Hence “about 5 percent” means “about 5 percent” and also “5 percent.” “About” means within typical experimental error for the application or purpose intended.

It is to be understood that wherein a numerical range is recited, it includes all values within that range, and all narrower ranges within that range, whether specifically recited or not.

Reference throughout this specification to “one embodiment,” “an embodiment,” “one example,” or “an example” means that a particular feature, structure, or characteristic described in connection with the embodiment or example is included in at least one embodiment of the present disclosure. Thus, appearances of the phrases “in one embodiment,” “in an embodiment,” “one example,” or “an example” in various places throughout this specification are not necessarily all referring to the same embodiment or example. Furthermore, the particular features, structures, or characteristics may be combined in any suitable combinations and/or sub-combinations in one or more embodiments or examples. In addition, it should be appreciated that if any figures are provided herewith, they are for explanation purposes to persons ordinarily skilled in the art and that the drawings of them are not necessarily drawn to scale.

In this specification, certain aspects of one embodiment include process steps and/or operations and/or instructions described herein for illustrative purposes in a particular order and/or grouping. However, the particular order and/or grouping shown and discussed herein are illustrative only and not limiting. Those of skill in the art will recognise that other orders and/or grouping of the process steps and/or operations and/or instructions are possible and, in some embodiments, one or more of the process steps and/or operations and/or instructions discussed above can be combined and/or deleted. In addition, portions of one or more of the process steps and/or operations and/or instructions can be re-grouped as portions of one or more other of the process steps and/or operations and/or instructions discussed herein. Consequently, the particular order and/or grouping of the process steps and/or operations and/or instructions discussed herein do not limit the scope of the disclosure.

The present disclosure provides a non-enzymatic biodegradable electrochemical cathode comprising Microtubules (MTs) isolated from natural sources, preferably from plant sources, wherein the cathode is prepared by crystallising the isolated MTs, making a slurry of the crystallised MTs with ethanol or acetone or isopropanol, and coating the slurry on a Stainless Steel (SS) Current Collector.

In an aspect of the present disclosure, there is provided a non-enzymatic biodegradable electrochemical cell using the non-enzymatic biodegradable electrochemical cathode.

The anode for the non-enzymatic biodegradable electrochemical cell of the present disclosure can include a carbon rich material such as Carbon Black (CB), graphite, or graphene; In an aspect of the present disclosure, the anode can include a biopolymer, wherein the biopolymer is ethyl cellulose.

In an aspect of the present disclosure, the electrochemical cell is SS/MT//PP-1M KC1//CB/A1, wherein Stainless Steel (SS) and Aluminium (Al) are used as current collectors for cathode and anode respectively, Polypropylene (PP) membrane soaked in IM KC1 as electrolyte and carbon rich material such as Carbon Black (CB), graphite or graphene is the anode material.

In another aspect of the disclosure, the anode includes a biopolymer such as ethyl cellulose, wherein the electrochemical cell is SS/MT/PP-1M KC1/EC/A1.

In yet another aspect of the disclosure, a process of fabrication of the non-enzymatic biodegradable electrochemical cathode is provided.

In a further aspect of the disclosure, a process of fabrication of a biodegradable electrochemical cell is provided using the biodegradable electrochemical cathode.

MTs were isolated from plant source Arachis Hypogea. Then, the isolated MTs were purified using Column chromatography. The column chromatography eluent is used in KC1 electrolyte for electrochemical studies. All experiments are carried out in Standard Temperature and Pressure (STP) conditions.

Detailed Process of isolation of MTs

All the chemicals were procured from Sigma Aldrich.

The procedure employed is as given below:

- To 0.05 rnM HC1, 1 g of Sephadex A25 is added and the buffer pH is maintained at 8.3.

- The buffer solution is boiled at 100°C for 2 h. - The callus from a plant source (the plant in the present disclosure used was Arachis Hypogaed) is homogenised (0.0482 g @ 4°C for 30 min) in a 6 ml of PM buffer (50 mM PIPES in KOH at pH 6.9, 1 mM EGTA, 0.5 mM MgCl₂, 1 rnM dithio-threitol).

- The Sephadex beads were poured in the column and equilibrated with PM buffer.

- The supernatant of the homogenate is poured into the column (chromatography) .

- The entire mixture is taken from the column and placed at 4°C for 1 h.

- The mixture is then stacked in the column and elution is carried out directly to yield FRACTION A as first elute.

- Three bed volumes of PM buffer containing 0.4 M KC1 and 0.5 M GTP were poured to yield FRACTION B as second elute.

- Three bed volumes of PM buffer containing 0.8 M KC1 and 0.5 M GTP were poured to yield FRACTION C as third elute.

An eliquot of elute is employed in recording the UV-Vis, FUR and SEM studies to understand the presence of functional groups and the surface morphology of the elute.

The elute is recrystallized as MTs and dissolved in ethanol or acetone or isopropanol and made into a slurry. The slurry is doctor blade coated on SS sheet and vacuum dried at 60°C.

In an embodiment of the present disclosure, a method of manufacturing the non- enzymatic biodegradable electrochemical cathode is provided, which comprises the following steps.

- Extracting the Microtubules (MTs) from a natural source;

- purifying the extracted MTs using column chromatography;

- drying the purified MTs at 60°C for 24 h;

- MT crystal formation; - MT crystals dissolved in ethanol or acetone or isopropanol to form a slurry;

- making a slurry of the Microtubules (MTs) isolated from natural sources;

- coating the slurry on a metallic current collector via doctor blade coating;

- Vacuum dry the MT coated metallic sheet at 60°C.

The natural source for obtaining the MTs can be a plant source or animal source. While, in the present disclosure, the MTs were sourced from a plant source, and all the experimentation, the fabrication of the non-enzymatic biodegradable electrochemical cathode, and the biodegradable cell using the cathode were done using the MTs derived from plant sources, a person skilled in the art may use MTs of animal origin for fabricating the biodegradable cathode and the biodegradable cell defined in the present disclosure.

The coating of the slurry on the metallic current collector can be done by using any suitable method known in the art including using a doctor blade.

Experiments to evaluate the Isolated MTs

Fig. 3 illustrates a flow chart of the methodology of the experimental work. The methodology is to understand the dynamic behaviour of MTs under wide range of conditions like charge perturbations by Cyclic voltammetry (CV) experiments. From CV, using Randle Sevcik’s equation, the diffusion coefficient of K⁺ ions in the MTs is evaluated. Employing Butler - Volmer equation, the free energy of dynamic instability of microtubules is obtained. The exchange current density is written as in equation 1.

and the heterogeneous rate constant is written via free energy of activation using Arrhenius equation as in equation 2.

Cyclic Voltammetry (CV) studies of the MTs

The CV studies were performed for the microtubules (MTs) fraction obtained from the column chromatography in 0.4 M KC1 electrolyte solution in a half-cell as shown in Fig. 2, where the electrodes used were (i) Au - working electrode, (ii) Pt wire - counter electrode and (iii) Ag/AgCl - reference electrode employing Zahner- Zennium workstation (Germany). The area of each electrode exposed to the electrolyte is 0.0005 m². CV is recorded at a scan rate of 10, 20, 50, 100, 150 and 200 mV/s in the potential window of -1 to IV.

Fig. 4 illustrates cyclic voltammetry (CV) of MTs eluent in 0.4M KC1 at different scan rates, wherein the arrows indicate the direction of scan rates. From Fig 4, it is inferred that at all the scan rates (or load applied), forward scan involved a small peak at 0.3V triggered by the adsorption of MT from the solution on Au surface. In the reverse scan, peaks at 0.05 and -0.3 V were noticed. The former peak could be attributed to the Hydrogen Evolution Reaction (HER), whereas, the latter peak is due to desorption of MT dimers from the Au surface to the electrolyte solution as illustrated in Fig. 1. The reversible nature of 0.3V peak indicates that the adsorbed MTs comes back to the electrolyte without any degradation on Au surface. As the applied load increases, the tubulin adsorption process becomes more facile because of the decrease in activation energy. It is known in the art that, as sulphur has natural affinity towards Au, sulphur containing amino acids such as cysetine & methionine present in tubulin interacts with the Au electrode via Au-S bond.

Free energy of adsorption of MTs on Au surface (AG ) calculated from CV

The Free energy of adsorption of MT on Au surface (AG ) can be calculated via Butler-Volmer kinetics. AG is related to i_p via the following equations 3, and 4.

Wherein i_o denotes exchange current density in Amps/cm² i_p denotes peak current from CV in Amps, A is the area of electrode in cm², h represents planks constant (Js ¹), kn depicts Boltzmann constant in JK ¹, T is the temperature (298K),

C is the concentration of MTs in mol/cm³, and R represents the gas constant (Jk^mol ¹).

F is Faraday’s constant n is number of electrons involved in the reaction

From CV, i_p at different load is utilized to evaluate the corresponding AG as provided in Table 1.

As shown in Fig. 5A and Fig. 5B, as the load increases, i_p increases by 5 times and AG decreases by 40meV. This energy is nearly equivalent to free energy of tubulin immobilization (50 meV) on MT, which indicates the incorporation of tubulin (monomers) in MT (polymer) with application of load. Thus, it could be inferred that with increased charge perturbation, the feasibility of MT being adsorbed on the Au surface increases. Since there is no degradation seen in CV analysis, AG shows very minimal variation with the load applied (40meV).

Table 1

Conductivity of MTs from CV studies The charge-transfer resistance (R_ct) and electronic conductivity of tubulin dimers were calculated using the following equations 5, 6, and 7, and the values are as given in Table 1.

As shown in Fig. 5A, it is found that with increase in applied load, i_p increases indicating a linear proportionality between the load and the intensity of peak current. Fig. 5B indicates the decrease in the Free energy of adsorption of MT with increase in applied load by 40meV. From the data in Table 1, it is observed that the resistivity (p) of the dimers decreased linearly with increasing load. The electronic conductivity (o) showed an exponential increase with increasing load. Hence it is evident that as the magnitude of the voltage applied increases, the resistance, and the free energy of interaction of the dimers decreases, thus they become more reactive to their surroundings by taking up the charged particles around them and conducting the positive ions such as K⁺ from bulk to the Au surface.

Dynamic stability of MTs on Au surface

Fig. 6 shows the evolution of AG during the transfer of tubulin monomers to Au surface from the bulk of the solution. Steps (I-V) indicate processes by which the tubulin units diffuse towards the Au surface. As observed, upon experiencing higher load in M , a decreasing trend in the AG with applied load indicates facile dimerization of a & |3 tubulin monomers into MTs. Initially the monomer units coexisted without strong interaction between them (I). As the load applied per second increases, AG slowly decreases with the a and -tubulin interacting to form dimers (II) via electrostatic interaction, H-bond formation and Vander-Waals forces. These dimers adsorb on Au surface due to the interaction between amino acid residues in tubulin such as cysteine, methionine, tyrosine and Au surface. The interaction between Au and tyrosine, tryptophan is through conjugated 71- electrons and in the case of cysteine and methionine via hetero sulphur atoms as represented in Scheme 1. Many such dimers start covering the electrode (Au) surface (IV) and due to the crowding of dimer units, they associate themselves as self-assembly to form linear polymer filaments (V) and attain stability. As the applied load increases, decrease in Resistivity (p) (i.e. increase in conductivity G) with simultaneous decrease in AG had been noticed. This could be attributed to the self-assembly of monomers forming dimers and the dimers interacting with Au surface. Free monomers in the solution have high energy and when they assemble into ensembles this energy reduces. In the case of free monomers, the electronic band gap between the conduction and valence band is large and when they start aggregating in an orderly manner, this gap decreases, making the conductivity (o) to increase as supported by decrease in resistivity (p) in Fig 5A. Conductivity (o) measurements of several proteins under various conditions indicated a band gap or activation energy of the order of 3 eV. Thus, as shown in Fig. 5A, which represents the phase transition in MT due to charge perturbations, the maximum limit of AG is found to be 1.22 eV and is in satisfactory agreement with the dimerization energy (1.10 eV) of tubulin monomers as in the literature. The difference in AG with respect to the difference in load is nearly 40meV, such small variation may be due to the conformational change of independent a and P tubulin subunits to a, -dimer and their incorporation into MT. Thus, Fig. 4 clearly indicates the dimerization of tubulin monomers, its self-assembly into linear proto filaments and adsorbing on Au surface with increase in load applied. It could also be inferred that electronic conductivity (o) of tubulin monomers (dimerizing and self-assembling) increased upon transfer from bulk to Au/electrolyte interface. The electronic conductivity (o) evaluated from CV studies is of the order of 0.86 to 3.89 mSm ¹ demonstrating the increase in electrical conductivity (o) by 4.58 times for 20 times increase in the load.

In addition, Fig. 6, explicitly depicts the dynamic nature of the MTs formed on Au surface to the self-assembly of tubulin monomers in bulk of the electrolyte upon charge perturbations. Fig. 7 represents the nanopores formed by the dimerization of tubulins which forms the nanochannel for ionic conductivity in the MTs.

Diffusion coefficient of the electrolyte from CV studies

Using Randle Sevcik’s equation (Equation 8) for quasi-reversible system the diffusion coefficient was calculated from i_p

The mobility of a species in electrolyte, K⁺ is directly proportional to the diffusion coefficient of that particular species and is given by Einstein-smoluchowski equation (Equation 9).

Diffusion coefficient (D) from Randle Sevcik’s equation tells us about the extent of diffusion of analyte (tubulin) and its dependency on applied load. D is linearly proportional to the load in a diffusion limited process. Diffusion coefficient of MTs in the electrolyte for varying load along with their mobility are given in Table 2.

Table 2

From Fig. 8A and Fig. 8B, it is inferred that with increase in load, diffusion coefficient and mobility follow drastic pattern, increases, and decreases with every load application, forming three spikes indicating the increased mobility of monomers in the electrolyte, followed by sudden drop, the reason behind this kind of variation is due to the shift in equilibrium between aggregated monomers (oligomers, dimers) and free monomer forms of tubulin (cf. Fig. 8C). The aggregated tubulin has less mobility and less D value, whereas the free forms are able to move freely hence, showing a spike in the values of mobility and D, leading to a conclusion that they are constantly associating and dissociating among themselves leading to dynamic instability. The average value of D is obtained as 1.95 x 10’⁷ cm²/s in agreement with the literature value of (4.5 ± 0.2) x 10^-7 cm²/s for labelled tubulin at nano molar concentration. The calculated average value of mobility for tubulin is 7.73 x 10^-6cm²/Vs. Hence the electrochemical perturbations are clearly making the tubulin units associate and dissociate causing the rise and fall of Diffusion coefficient and mobility values with load.

Examples:

The present disclosure will now be explained in further detail by the following examples. These examples are illustrative of certain embodiments of the disclosure without limiting the scope of the present disclosure.

Example 1

A biodegradable coin cell-2032 was prepared with the following architecture:

S S/MT//PP- 1 MKC1//CB/A1

Cathode was prepared by crystallising the isolated MTs, making a slurry of the crystallised MTs with ethanol, and coating the slurry with a doctor blade on a Stainless Steel (SS) Current Collector, wherein the SS current collector was having a circular shape with a thickness of 4 mm, and a diameter of 20 mm.

An Aluminium (Al) circular sheet having a thickness of 4 mm, and a diameter of 20 mm was used as current collector for the anode, Polypropylene (PP) membrane soaked in IM KC1 was used as electrolyte, and Carbon Black (CB) was used the anode material.

And, the fabricated coin cell had a thickness of 4 mm, and a diameter of 20 mm, having a weight of 5gms.

Example 2

A biodegradable coin cell-2032 was prepared with the following architecture:

S S/MT//PP- 1 MKC1//EC/A1 The components, and the dimensions of the components to fabricate the coin cell- 2032, the dimensions and the weight of the fabricated coin cell-2032 were the same as the coin cell in Example 1, and the process of preparing the coin cell was the same as given in Example 1, with the exception that in this Example 2, Ethyl cellulose (EC) was used the anode material.

Evaluation of Example 1

Galvanostatic Charge/Discharge Profile of non-enzymatic biodegradable coin cell- 2032

The specific capacity of the non-enzymatic biodegradable electrochemical cell is calculated at every At (s) for the discharge current of I (Amps) from the GCD profile for the electroactive mass m (gms) as follows:

Specific Capacity = lAt/m

Analogously,

Specific Capacitance = lAt/mAV

As shown in Fig. 9A and Fig. 9B, at 0.1C rate of discharge, the initial specific capacity and specific capacitance of 63.2 mAh/g and 173.65 F/g respectively during discharge with At = 90s, I=1A, m=0.5g, AV = 0.214V. The subsequent cycles show slight variation in the capacity and capacitance showing steady decrement at every cycle and levelled at 36.35 mAh/g and 101.33 F/g after 10000 cycles. This corresponds to 42.48% capacity retention after 10000 cycles.

This demonstrates that the non-enzymatic biodegradable electrochemical cell fabricated in the present disclosure possess very long cycling stability upto 10000 cycles at 0.1 C rate and can be utilized in low power electronic devices and power bank applications. The fabricated full cell is shown in Fig. 10. The energy density of the biodegradable coin cell-2032 was calculated employing the following equation.

ED = Nominal Battery voltage * Rated Battery capacity/Battery weight = V*C/m

For 1kg battery, with nominal voltage of 0.214 V and rated battery capacity being 63.2 mAh/g, the gravimetric energy density is obtained as 13.53 Wh/kg attributed to the protein type Microtubules (MTs) cathode and Carbon Black anode with the full-cell configuration of SS/MT//PP-1MKC1//CB/A1 of Example 1.

Evaluation of Example 2

Whereas, the full-cell configuration of Example 2 SS/MT//PP-1MKC1//EC/A1 possessed much less performance with stability up to 334 cycles with lower specific capacity and gravimetric energy density. As seen in Fig. 11, the rated capacity is of the order of 54 mAh/g, the gravimetric energy density of 10.58 Wh/kg for nominal voltage of 0.2 V attributed to the protein cathode (MTs) and Ethyl Cellulose (EC) anode with the full cell configuration of SS/MT//PP-1M KC1/EC/A1 of Example 2

Hence of all configurations attempted, the one with carbon-based anode such as carbon black, graphite or graphene possessed good performance as biomolecules- based energy storge devices.

Figs. 12 & 13 demonstrate the optical spectroscopic characterization of the MTs eluent after extraction employing UV-Vis spectroscopy and FTIR analysis.

The UV-Visible spectra of c<,|3-tubulin dimer extracted from the plant source Arachis hypogea is shown in Fig. 12. In that, the peaks at 254nm and 280nm are concordant with the peaks of amide linkages of tubulin protein (cf. inset of Fig. 12). The FTIR spectra of tubulin dimers extracted from the plant source Arachis Hypogea is provided in Fig. 13 and compared with that of the reported tubulin extract of Silybum marianum (cf. inset in Fig. 13). It is seen that the fingerprint region is localized between 900 - 1500 cm'¹ and the stretching and bending vibrations of the functional groups present in MTs are discussed as follows.

The presence of peak less than 1000 cm'¹ region is due to the C-H bending vibrations. The peaks in the range 997-1130 cm'¹ correspond to the stretching vibrations of C-0 bonds, with signals at 1030, 1054, 1104, and 1130 cm'¹ whereas the peaks from 1150 to 1270 cm'¹ represents the stretching vibrations of carbonyl C-0 or O-H bending vibrations. The peaks due to the stretching vibrations of C - O (amide) and C - C (phenyl) groups are seen in the range of 1300 - 1450 cm'¹ while the peaks of aromatic ring and N - H bending vibrations are in the region of 1500 - 1600 cm ¹. Peaks appeared in the range of 1600 - 1760 cm'¹ indicate the N - H bending vibrations of amino acids, C=O stretching vibrations (aldehydes and acetones, esters), presence of free fatty acids (at 1710 cm'¹) and glycerides (at 1740 cm'¹). The peaks in the range of 2800-2900 cm ¹, corresponds to C-H stretching vibrations specific to CH3 and CH2 from lipids, methoxy derivatives, C-H (aldehydes), including cis double bonds. The peaks in the region 3500-3600 cm'¹ corresponds to stretching vibrations of OH groups (from water, alcohols, phenols, carbohydrates, peroxides) and from amides (at 3650 cm'¹).

From Fig 14, the surface morphology studies of bare MWCNTs and MTs soaked in MWCNTs and dried, it is obvious that MTs form aggregates on MWCNTs when soaked in MWCNTs and dried. Fig 14(a) denotes the SEM spectra of bare MWCNTs at 10 pm, and Fig 14(b) indicates the SEM spectra of MTs soaked in MWCNTs and dried. From Fig 14(b) it is evident that MTs form aggregates on the MWCNT support. The aggregates are identical in morphology to the MTs represented in Fig 7. Thus, SEM images of MTs demonstrate the formation of aggregates on any conducting surface (in the present disclosure, MTs on Au surface). Advantages:

The non-enzymatic biodegradable electrochemical cell of the present disclosure has the following non-limiting advantages.

- 0.1C rate of discharge, the initial specific capacity and specific capacitance of 63.2 mAh/g and 173.65 F/g respectively during discharge with At = 90s, 1=1 A, m=0.5g, AV = 0.214V.

- 42.48% capacity retention after 10000 cycles.

- Biodegradable, contributes towards environmental wellness.

- Utilization of non-toxic and plant source derived biodegradable cathode active material.

- No need of carbon coating of the cathode for electronic conductivity as the MT itself is semiconducting in nature.

Applications:

The non-enzymatic biodegradable electrochemical cell of the present disclosure has the following non-limiting industrial applications.

- Low power electronic device charging.

- Power banks.

- Powering Bio-medical devices such as pace makers and glucose meter etc.

- Powering Toys.

Source And Geographical Origin of Biological Materials:

The source and geographical origin of biological materials used in the present disclosure are as mentioned below:

Common name of Plant: Peanut

Scientific name of Plant: Arachis hypogaea

Family: Fabaceae

Subfamily: Faboideae

Genus: Arachis Species: Arachis hypogaea

Other Common names of the plant: Groundnut

- Goober (US) Pindar (US) Monkey nut (UK)

Nativity and Availability of the plants:

Arachis hypogaea L., commonly known as peanut, groundnut, monkey nut, goober, or earth nut because the seed develop underground, is in the division Papiolionaceae of the family Leguminosae. The peanut is only one of a few hundred species of legumes that produces flowers above ground but develops the fruit below ground. Peanuts are native to South America and were cultivated in pre-Columbian native societies of Peru as early as 3000 be. Peanuts probably originated in the region of eastern South America, where a large number of species are found growing wild. A Bolivian origin is suggested by the wide range in seed and pod morphology documented there. It has been suggested that A. hypogaea originated from a hybrid between A. cardenasii (nn) and A. batizocoi (K. & G.), as both parents occurred in reasonable proximity in Bolivia. Peanuts were widely distributed throughout South and Central America and the Caribbean region during the time of Columbus. Peanuts were probably brought to West Africa from Brazil in the sixteenth century and then to the African east coast and to India. Peanuts from widely separated regions of the world were brought to Africa and it is regarded as a center of genetic diversity.

According to a report, in 2020, China contributes to 34% of global production of peanuts, followed by India (19%). Other significant producers were Nigeria, the United States, and Sudan. According to a report of Ministry of Agriculture, major state wise distribution of Indian Production of Peanut (Groundnut) in the year 2019-2020 are as given below.

(URL: https://agriexchange.apeda.gov.in/india%20production/AgriIndia_Productions.asp x?productcode= 1007)

Average Size and Appearance of the Plants:

The peanut is an annual herbaceous plant growing 30 to 50 cm (12 to 20 in) tall. As a legume, it belongs to the botanical family Fabaceae, also known as Leguminosae, and commonly known as the legume, bean, or pea family. Like most other legumes, peanuts harbor symbiotic nitrogen-fixing bacteria in their root nodules.

The leaves are opposite and pinnate with four leaflets (two opposite pairs; no terminal leaflet); each leaflet is 1 to 7 centimetres (1/2 to 2+3/4 in) long and 1 to 3 cm (FT to 1+1/4 in) across. Like those of many other legumes, the leaves are nyctinastic; that is, they have "sleep" movements, closing at night.

The flowers are 1 to 1.5 cm (341 to 5/8 in) across, and yellowish orange with reddish veining. They are borne in axillary clusters on the stems above ground and last for just one day. The ovary is located at the base of what appears to be the flower stem but is a highly elongated floral cup.

Peanut fruits develop underground, an unusual feature known as geocarpy. After fertilization, a short stalk at the base of the ovary — often termed a gynophore, but which appears to be part of the ovary — elongates to form a thread-like structure known as a "peg". This peg grows into the soil, allowing the fruit to develop underground. These pods, technically called legumes, are 3 to 7 centimetres (1 to 3 in) long, normally containing one to four seeds. The shell of the peanut fruit consists primarily of a mesocarp with several large veins traversing its length.

Although the present disclosure is described in terms of certain preferred embodiments, it is to be understood that they have been presented by way of example, and not limitation. Thus, the present disclosure should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

Claims

1. A non-enzymatic biodegradable electrochemical cathode comprising Microtubules (MTs) isolated from natural sources, wherein the MTs are coated on a metallic current collector to form the cathode.

2. The non-enzymatic biodegradable electrochemical cathode as claimed in claim 1, wherein the MTs are purified crystallised MTs.

3. The non-enzymatic biodegradable electrochemical cathode as claimed in claim 1, wherein the metallic current collector is selected from stainless steel (SS) or Gold (Au).

4. The non-enzymatic biodegradable electrochemical cathode as claimed in claim 1, wherein the cathode at 0.1 C rate of discharge has an initial specific capacity of 63.2 mAh/g during discharge with At = 90s, I=1A, m=0.5g, AV = 0.214V.

5. The non-enzymatic biodegradable electrochemical cathode as claimed in claim 1, wherein the cathode at 0.1 C rate of discharge has a specific capacitance of 173.65 F/g during discharge with At = 90s, I=1A, m=0.5g, AV = 0.214V.

6. The non-enzymatic biodegradable electrochemical cathode as claimed in claim 1, wherein the cathode has 42.48% capacity retention after 10000 cycles.

7. A method of manufacturing a non-enzymatic biodegradable electrochemical cathode comprising the steps of:

- extracting the Microtubules (MTs) from a natural source;

- purifying the extracted MTs using column chromatography;

- drying the purified MTs at 60°C, for 24 hours duration to obtain crystallised MTs;

- dissolving the crystallized MTs in a solvent selected from ethanol, acetone or isopropanol to form a slurry;

- coating the slurry on a metallic current collector; and - drying the coated slurry under vacuum at 60°C to form cathode active material on the current collector.

8. A non-enzymatic biodegradable electrochemical cell comprising: - the non-enzymatic biodegradable electrochemical cathode as claimed in claims 1-6;

- an anode; and

- an electrolyte.

9. The non-enzymatic biodegradable electrochemical cell as claimed in claim 8, wherein the anode includes a carbon rich material, wherein the carbon rich material is selected from Carbon Black (CB), graphite, or graphene.

10. The non-enzymatic biodegradable electrochemical cell as claimed in claim 8, wherein the anode includes a biopolymer, wherein the biopolymer is ethyl cellulose.