BIOLOGICAL SENSOR AND A METHOD OF THE PRODUCTION OF BIOLOGICAL SENSOR

Abstract

The invention is related to the field of biotechnology, specifically to the investigation of biomolecular interactions and sensing of biomolecules using a surface plasmon resonance. The biological sensor and a method of its production based on the thin films of graphene, graphene oxide, or single-walled or multi-walled carbon nanotubes are described.

The technical results of the invention are a high sensitivity of the biosensor in combination with a high biospecificity; an expansion of the range of device applications; the protection of the metal film from an environmental exposure; the possibility to detect large biological objects.

The proposed device and method of its production can be used for monitoring and recording of the concentration of chemical and biochemical substances and for the definition of parameters of biomolecular reactions in different industrial processes using biological materials, the invention can be also used in the pharmaceutical industry for the investigation of pharmacological properties and for the determination of a chemical composition of developing drugs, and also it can be used in processes of quality control of food products.

Claims

1-27. (canceled)

28. A method for producing a biological sensor, the method comprising the steps of: a) depositing a gold film onto a first surface of a substrate, the gold film having a thickness in a first range of from 10 nm to 150 nm and comprising an outer surface opposite to the substrate, b) depositing an intermediate binding layer onto the outer surface of the gold film, c) depositing a biospecific layer onto a second surface of the intermediate binding layer, the second surface being opposite to the substrate, wherein the intermediate binding layer consists of a thin film of graphene oxide having a thickness in a second range of from 0.7 nm to 2000 nm, and wherein the biospecific layer is adsorbed conformally and homogeneously on the second surface of the intermediate binding layer due to first chemical interaction forces between the intermediate binding layer and the biospecific layer, wherein the biospecific layer fills between 15% and 100% of the second surface of the intermediate binding layer, wherein the biospecific layer is adapted for a specific second chemical interaction with a certain type of biological molecules of an analyte.

29. The method for producing according to claim 28, wherein the step of depositing the gold film onto the first surface of the substrate is conducted in a vacuum chamber by an electron beam deposition.

30. The method for producing according to claim 29, wherein it comprises a step of controlling the thickness of the gold film by means of ellipsometric measurements.

31. The method for producing according to claim 30, wherein it comprises a step of controlling optical properties of the gold film by means of ellipsometric measurements.

32. The method for producing according to claim 31, wherein the step of depositing the intermediate binding layer onto the outer surface of the gold film comprises following subsequent stages of: a) preparing a graphene oxide solution, b) after said preparing, filtering the graphene oxide solution by a cellulose membrane, c) after said filtering, placing the cellulose membrane onto the outer surface of the gold film, d) after said placing, dissolving the cellulose membrane in acetone in view to leave the intermediate binding layer consisting of the thin film of graphene oxide onto the outer surface of the gold film.

33. The method for producing according to claim 32, wherein it comprises a step of checking a quality of the biospecific layer by means of a test sample, said quality being representative of a predetermined level of negligibility of nonspecific interactions of the biospecific layer.

34. The method for producing according to claim 33, wherein the step of depositing the biospecific layer onto the second surface of the intermediate binding layer comprises following subsequent stages of: preparing a biospecific solution of first molecules of a binding partner of the analyte, after said preparing, bringing the biospecific solution in a contact with the second surface of the intermediate binding layer using a flow cell.

35. The method for producing according to claim 34, wherein the biospecific solution further comprises: (i) second molecules having an affinity to the first molecules of the binding partner of the analyte, said second molecules being adapted to form a chemical bond with the first molecules of the binding partner of the analyte; or (ii) a first hydrogel comprising immobilized therein the first molecules of the binding partner of the analyte; or (iii) a second hydrogel comprising immobilized therein both the first molecules of the binding partner of the analyte and the second molecules having an affinity to the first molecules of the binding partner of the analyte, said second molecules being adapted to form a chemical bond with the first molecules of the binding partner of the analyte.

36. The method for producing according to claim 34, wherein the biospecific solution further comprises: a first hydrogel comprising immobilized therein the first molecules of the binding partner of the analyte, or a second hydrogel comprising immobilized therein both the first molecules of the binding partner of the analyte and second molecules having an affinity to the first molecules of the binding partner of the analyte, said second molecules being adapted to form a chemical bond with the first molecules of the binding partner of the analyte, wherein each hydrogel chosen between: (a) the first hydrogel, (b) the second hydrogel, comprises polysaccharides.

37. The method for producing according to claim 36, wherein the polysaccharides in the biospecific solution comprise agarose, alginic acid, dextran, carrageenan, starch, cellulose or derivatives thereof.

38. The method for producing according to claim 37, wherein the derivatives of dextran in the biospecific solution comprise carboxymethylated dextran.

39. The method for producing according to claim 34, wherein the biospecific solution further comprises: second molecules having an affinity to the first molecules of the binding partner of the analyte, said second molecules being adapted to form a chemical bond with the first molecules of the binding partner of the analyte; or a second hydrogel comprising immobilized therein both the first molecules of the binding partner of the analyte and the second molecules having an affinity to the first molecules of the binding partner of the analyte, said second molecules being adapted to form a chemical bond with the first molecules of the binding partner of the analyte, wherein said first molecules of the binding partner of the analyte are biotinylated, and wherein said second molecules are chosen from the following molecules: (a) molecules of avidin, (b) molecules of streptavidin, (c) molecules of deglycosylated avidin.

40. The method for producing according to claim 34, wherein the binding partner of the analyte is an antibody or a fragment of the antibody to the analyte, or wherein the binding partner of the analyte is a receptor of the analyte, or wherein the binding partner of the analyte is a binding partner of proteins, lipids, DNAs, RNAs, viruses, cells, bacteria, or toxins, or chemical modifications of these substances.

41. A method for producing a biological sensor, the method comprising the steps of: a) depositing a copper film onto a first surface of a substrate, the copper film having a thickness in a first range of from 10 nm to 150 nm and comprising an outer surface opposite to the substrate, b) depositing an intermediate binding layer onto the outer surface of the copper film, c) depositing a biospecific layer onto a second surface of the intermediate binding layer, the second surface being opposite to the substrate, wherein the intermediate binding layer consists of a thin film of graphene oxide having a thickness in a second range of from 0.7 nm to 2000 nm, and wherein the biospecific layer is adsorbed conformally and homogeneously on the second surface of the intermediate binding layer due to first chemical interaction forces between the intermediate binding layer and the biospecific layer, wherein the biospecific layer fills between 15% and 100% of the second surface of the intermediate binding layer, wherein the biospecific layer is adapted for a specific second chemical interaction with a certain type of biological molecules of an analyte.

42. The method for producing according to claim 41, wherein the step of depositing the copper film onto the first surface of the substrate is conducted in a vacuum chamber by an electron beam deposition.

43. The method for producing according to claim 41, wherein it comprises a step of controlling the thickness of the copper film by means of ellipsometric measurements.

44. The method for producing according to claim 41, wherein it comprises a step of controlling optical properties of the copper film by means of ellipsometric measurements.

45. The method for producing according to claim 41, wherein the step of depositing the intermediate binding layer onto the outer surface of the copper film comprises following subsequent stages of: a) preparing a graphene oxide solution, b) after said preparing, filtering the graphene oxide solution by a cellulose membrane, c) after said filtering, placing the cellulose membrane onto the outer surface of the copper film, d) after said placing, dissolving the cellulose membrane in acetone in view to leave the intermediate binding layer consisting of the thin film of graphene oxide onto the outer surface of the copper film.

46. The method for producing according to claim 41, wherein it comprises a step of checking a quality of the biospecific layer by means of a test sample, said quality being representative of a predetermined level of negligibility of nonspecific interactions of the biospecific layer.

47. The method for producing according to claim 41, wherein the step of depositing the biospecific layer onto the second surface of the intermediate binding layer comprises following subsequent stages of: preparing a biospecific solution of first molecules of a binding partner of the analyte, after said preparing, bringing the biospecific solution in a contact with the second surface of the intermediate binding layer using a flow cell.

Description

LIST OF FIGURES

[0026] On FIG. 1 the general view if the biological sensor (side flew) is shown.

[0027] On FIG. 2 the biological sensor with the biospecific layer (4) containing the molecules of a binding partner of an analyte (5) is shown.

[0028] On FIG. 3 the biological sensor with the biospecific layer (4) containing the molecules of a binding partner of an analyte (5) and the molecules capable of forming a chemical bond with the molecules of a binding partner (6) is shown.

[0029] On FIG. 4 the biological sensor with the biospecific layer (4) containing the hydrogel with the immobilized molecules of a binding partner of an analyte (5) and the molecules capable of forming chemical a bond with the molecules of a binding partner (6) is shown.

[0030] On FIG. 5 the kinetic curve of adsorption of the biotinylated oligonucleotide molecules adsorption on the surface of the thin film of graphene oxide and on the surface of biological sensor comprising of three layers: the substrate, the metal film, and the carboxymethylated dextran with the immobilized molecules of streptavidin is shown.

[0031] On FIG. 6 the kinetic curve of adsorption of the molecules capable of forming a chemical bond with the molecules of a binding partner of an analyte on the biological sensor based on the thin film of graphene oxide is shown.

[0032] On FIG. 7 the kinetic curve of adsorption of the oligonucleotides on the surface of the biospesific layer with the immobilized molecules of streptavidin is shown.

[0033] On FIG. 8 the raster electronic microscopy image of the thin film of graphene oxide deposited on the surface of the metal film is shown.

[0034] On FIG. 9 the comparative table of experimental data obtained by the biological sensors containing as the intermediate binding layer thin film of the hydrogel and the thin film of graphene oxide is shown.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] The biological sensor (FIG. 1) consists of a substrate (1), a metal film (2), which is covered by the intermediate binding layer (3) made of the thin film of graphene, the thin film of graphene oxide, or the thin film of carbon nanotubes. The biospecific layer (4) is conformally and homogeneously adsorbed on the surface of layer (3). The layer of the molecules of a binding partner of an analyte (5) (FIG. 2) or the layer of the complex of the molecules capable chemically bind with the molecules of a binding partner of an analyte and chemically bond with them (FIG. 3) can be used as the biospecific layer. Also the hydrogel (7) (FIG. 4) with the immobilised molecules of the molecules of a binding partner of an analyte (5) and/or the complex of the molecules of a binding partner of an analyte and the molecules capable of chemically bind with them (6) can be used as the biospecific layer. FIG. 5 shows the kinetic curve of adsorption of the biotinylated oligonucleotides on the surface of the intermediate binding laayer of the biosensor based on the thin film of graphene oxide (curve 8) and on the surface of biological sensor consisting the following layers: the substrate, the metal film, and the biospecific layer with the hydrogel (carboxymethylated dextran) and streptavidin molecules (curve 9). The horizontal axis is time, the vertical axis is the change of the refractive index of the medium near the adsorption surface, which is proportional to the mass of molecules adsorbed on the surface. Therefore, we can conclude that the film based on graphene oxide has better adsorption properties than the layers containing hydrogel. FIG. 6 shows the graph of streptavidin molecule adsorption on the biological sensor based on the thin film of graphene oxide.

[0036] FIG. 7 shows the graph of oligonucleotide adsorption on the biological sensor comprising the substrate made of the borosilicate glass with the thickness of 0.4 nm which surface is covered by the titan film with the thickness of 2 nm. The substrate is covered by the gold film with the thickness of 40 nm. The intermediate binding layer of graphene oxide with the thickness of 20 nm and the biospecific layer are deposited on the gold film. The biospecific layer consists of streptavidin moilecules, which form a stable complex with the molecules having a biotin residue. Streptavidin was adsorbed during 10 minutes from the solution with the concentration of 50 ug/ml on the surface of the intermediate binding layer in the flow cell. Three peaks on graph correspond to the adsorption of oligonucleotides: 11, 13—without biotin residue, 12—with biotin residue. Oligonucleotides used in the cases 11, 13 and in the case 12 are complimentary and can form a bind with each other. Smallness of the peak 11 indicates a high specificity of the obtained biological sensor, which means that the biological sensor interacts only with certain types of molecules. FIG. 8 shows the image of the graphene oxide layer on the surface of the metal film, obtained using raster electron microscopy. The data in table (FIG. 9) are based on the experimental results and compares biological sensors comprising the thin layer of hydrogel with the thickness of 150 nm and the thin layer of graphene oxide with the thickness of 20 nm as intermediate binding layers. The signal of the biological sensor comprising film of the hydrogel obtained during the sensing of biotinylated DNA and which is proportional to the change of the refractive index of the media near the surface of the biological sensor is 409 arbitrary units. In the case of the biological sensor comprising the film of graphene oxide the signal is 570 arbitrary units. Thus, the response and, therefore, the sensitivity of the biological sensor comprising the thin film of graphene oxide as the intermediate binding layer is 40% higher.

[0037] The device operates as follows. The solution of an analyte is supplied to the biospecific layer (4) of the biological sensor by means of a flow cell or a cuvette. Wherein, the chemical reaction is carried out between an analyte and the molecules of the biospecific layer (4) represented by the molecules of a binding partner of an analyte (5) attached to the surface of the intermediate binding layer directly or using the biological molecules (6) capable to form a chemical bond with the molecules of a binding partner of an analyte and/or the hydrogel (7) deposited on the surface of the biological sensor. Further, required parameters of this reaction are obtained using the method of biosensing based on a surface plasmon resonance. The essence of the method is to detect in various ways the changes of the resonant conditions of the surface plasmon excitation in the metal layer (2) caused by the changes of the effective refractive index of the media near the surface due to attaching of biomolecules. The most popular in commercial devices way of the surface plasmon excitation is proposed by Kretschmann [6]. According to this, a laser beam is falling under certain angle on the metal film (1) from the substrate side (1) and excites surface plasmons on the border of the metal film (2) and the media containing analyte. Wherein the optimal thickness of metal film (2) is in the range of 10-150 nm. The upper border is explained by the fact, that at higher values of the film thickness the failure in reflection is small, which greatly affects the sensitivity of the method. At the thicknesses of the film (2) less than 10 nm the form of the resonant curve corresponding to the surface plasmon resonance changes due to the change of the waveguide mode of the surface plasmon. Further, the information about the refractive index change of the media near the metal film is obtained basing on the value of the resonant angle, phase shift of the reflected beam, or the changes of the intensity of the reflected beam. It does not make sense to deposit the intermediate binding layer (3) with the thickness greater than 2000 nm on the surface of the metal film (2) because of the penetration depth of the electromagnetic field of the surface plasmon is about 500 nm, therefore, molecules located at a distance greater than 2000 nm have little effect on conditions of a surface plasmon excitation and hence it cannot be detected. The intermediate binding layer (3) with the thickness greater than 2000 nm, in turn, hinders the access of the analyte in the region, where it can be detected. The minimal thickness of the intermediate binding layer comprising graphene corresponds to the monomolecular layer which the thickness is assumed to be equal 0.3 nm [7]. For the intermediate binding layer (3) comprising graphene oxide the minimum possible thickness corresponded to the monomolecular layer equals 0.7 nm [8]. For the intermediate binding layer (3) comprising carbon nanotubes the minimum possible thickness equals the diameter of carbon nanotubes which can be equal to 0.4 nm [9]. Molecules of proteins, lipids, DNA, RNA, viruses, cells, bacterias, and toxins can be used as analytes for the biological sensor.

[0038] The method of production of the biological sensor is realized as following:

[0039] The metal film (2) is deposited on the substrate (1) using for example electron beam deposition. So, for example, to deposit gold film with the thickness of 40 nm as a substrate the plate of borosilicate glass with the deposited titan film with the thickness of 2 nm is used. Further deposition of gold on the substrate is conducted in the vacuum chamber at the pressure of 10.sup.−7 Torr, the accelerating voltage of electrons of 4 kV, and the temperature of 150 degrees Celsius. The thickness and optical properties of the gold film are controlled by means of ellipsometric measurements.

[0040] Further the intermediate binding layer (3) in the form of the thin film of graphene, graphene oxide, or single-walled or multi-walled carbon nanotubes is deposited on the surface of the metal film (the image of the graphene oxide film obtained using rater electron microscopy is shown on FIG. 8). A thin film of graphene, graphene oxide, or single-walled or multi-walled carbon nanotubes are deposited using the solution of the respective substance, which is further filtrated by the cellulose membrane. After the filtration process the membrane is placed on the surface of the metal film and dissolved in acetone leaving the thin film of graphene, graphene oxide, or carbon nanotubes. So for example for the deposition of the intermediate binding layer containing the thin film of graphene oxide with the thickness of 20 nm 1 ml of graphene oxide solution in water with the concentration of 5 ug/ml is used.

[0041] The next step of the biological sensor creation is the stage of biospecific layer (4) deposition on the intermediate binding layer in which such molecules comprising the biospecific layer as molecules of the partner of an analyte (5), the molecules capable chemically bind with the molecules of the partner of an analyte (6), or the hydrogel are deposited directly from the solution. The solution with biomolecules is brought in a contact with for example a flow cell or a cuvette. FIG. 6 shows the adsorption of the streptavidin molecules which are the binding partner of the molecules with the biotin residue using a flow cell. At the same moment a time of adsorption is selected so that biological molecules occupy large number of adsorption centers on the surface of graphene, graphene oxide, or carbon nanotubes eliminating in further nonspecific binding of analyte molecules with the surface of the biological sensor. Wherein usage of special substances except molecules themselves are not required for manufacturing of such films. So for example for adsorption of the biospecific layer containing streptavidin molecules on the surface of graphene oxide film these molecules are adsorpted from the solution with the concentration of 10 ug/ml using the flow cell during 10 minutes. Subsequently the quality can be checked by using a test sample, which is known that molecules from its structure should not interact with the obtained biological layer. The kinetic curve (12) of biotinylated DNA deposition on the obtained biosensor comprising streptavidin molecules is shown on the FIG. 7. The smallness of the peak (11) reflecting the interaction of the nonbiotinylated molecules with the streptavidin layer shows a sufficient level of negligibility of nonspecific interactions.

[0042] The proposed device and method of its production provide in comparison with the known level of technique the following results: a high sensitivity of biosensor in combination with a high biospecificity; the protection of metal film from an environmental exposure that allows to use in the biosensing reagents that may damage the metal surface, and also to use such plasmonic materials as silver easily degrading under an environmental exposure; the possibility to detect large biological objects.

[0043] Thus the new relationship of known properties and a set of distinctive properties of the proposed biosensor and method of its creation allows creation of a highly sensitive and universal biological sensor for the biosensing based on the surface plasmon resonance.

[0044] The proposed device and a method of its production can be used for monitoring and recording of the concentration of chemical and biochemical substances and for the definition of parameters of biomolecular reactions in different industrial processes using biological materials.

[0045] The proposed invention can be also used in the pharmaceutical industry for the investigation of pharmacological properties and for the determination of a chemical composition of developing drugs.

[0046] Moreover, the developed device and a method of its production can be used in processes of a quality control of food products.

REFERENCES CITED

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