Colorimetric sensors for detecting bacteria and / or viruses

Abstract

To provide a colorimetric sensor capable of accurately detecting a bacterium and a virus, such as a COVID-19 virus and having higher sensitivity.SOLUTION: A bacterium and / or virus detection colorimetric sensor includes a functional layer (4) superimposed on one or more layers (3', 3'', ...) having a photonic crystal structure and one or more layers (3', 3'', ...) including a nanomaterial capable of forming surface plasmon having bacterium and / or virus biological responsibility and having a photonic crystal structure. A protein or antibody acting as a virus receptor is injected into the nanomaterial having bacterium and / or virus biological responsibility in the functional layer (4); the functional layer (4) is superimposed on a receptor layer (5); and the colorimetric sensor (1) includes a plasmonic nano structure layer (7) superimposed on the one or more layers having a nano structure for forming plasmonic color and having a photonic crystal structure (3', 3'', ...).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a colorimetric sensor for detecting bacteria and / or viruses. [Background technology]

[0002] Colorimetric sensors for the detection of bacterial contaminants such as E. coli bacteria are known.

[0003] An example of a colorimetric sensor for detecting bacteria, such as E. coli, is described in G.M. Paterno, L. Moscardi, S. Donini, D. Ariodanti, I. Kriegel, M. Zani, E. Parisini, F. Scotognella, and G. Laznani, "Hybrid One-Dimensional Plasmonic Photonic Crystals for Optical Detection of Bacterial Contaminants," J. Phys. Chem. Lett. 2019, 10, 4980-4986. Such a sensor includes a layer of silver (a plasmonic metal) and a one-dimensional photonic crystal. The silver is characterized by a bioresponsiveness to E. coli bacteria, changing its optical response upon contact with the bacteria. In other words, when the presence of bacteria is detected, for example, by contacting a subject's secretions with the silver layer, a color change in the sensor is perceived.

[0004] However, to detect other pollutant bodies or even viruses, which generally have a size much smaller than that of bacteria, a higher sensitivity of the sensor is required. Summary of the Invention

[0005] It is therefore an object of the present invention to provide a colorimetric sensor with improved sensitivity that is capable of accurately detecting bacteria and also viruses, such as the COVID-19 virus.

[0006] This and other objects are achieved by a colorimetric sensor for detecting bacteria and / or viruses according to claim 1 and by a colorimetric sensor for detecting bacteria and / or viruses according to claim 18.

[0007] The dependent claims define possible advantageous embodiments of the invention. [Brief explanation of the drawings]

[0008] In order that the present invention may be better understood and its advantages appreciated, certain illustrative, non-limiting embodiments thereof will now be described with reference to the accompanying drawings, in which: [Figure 1] FIG. 1 is a cross-sectional schematic diagram of a colorimetric sensor according to a first possible embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional schematic diagram of a colorimetric sensor according to a second possible embodiment of the present invention. [Figure 3] FIG. 3 is a cross-sectional schematic diagram of a colorimetric sensor according to a third possible embodiment of the present invention. [Figure 4] FIG. 4 is a cross-sectional schematic diagram of a colorimetric sensor according to a fourth possible embodiment of the present invention. [Figure 5] FIG. 5 is a cross-sectional schematic diagram of a colorimetric sensor according to a fifth possible embodiment of the present invention. [Figure 6] FIG. 6 is a cross-sectional schematic diagram of a colorimetric sensor according to a sixth possible embodiment of the present invention. [Figure 7] FIG. 7 is a cross-sectional schematic diagram of a one-dimensional photonic crystal. [Figure 8] 8a to 8c are perspective views of a kit including a colorimetric sensor according to a possible embodiment of the present invention in different use conditions. [Figure 9] 9a to 9c are perspective views of a kit including a colorimetric sensor according to a further possible embodiment of the present invention in different conditions of use. [Figure 10] 10a to 10c are perspective views of a kit including a colorimetric sensor according to a further possible embodiment of the present invention in different conditions of use. [Figure 11]1 is a cross-sectional schematic view of a colorimetric sensor according to a further possible embodiment of the present invention; [Figure 12] 1 is a cross-sectional schematic view of a colorimetric sensor according to a further possible embodiment of the present invention; [Figure 13] 1 is a cross-sectional schematic view of a colorimetric sensor according to a further possible embodiment of the present invention; [Figure 14] 1 is a cross-sectional schematic view of a colorimetric sensor according to a further possible embodiment of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0009] With reference to the accompanying Figures 1 to 6, a colorimetric sensor for detecting bacteria and / or viruses is generally designated by the reference numeral 1. The sensor 1 may be applied, for example, as a label applied to one or more sheet- or roll-shaped supports, or, for example, on an instrument 200, as illustrated, for example, in Figures 8 to 10. Illustratively, the sensor 1 embodied by a label may be immersed, directly or indirectly, by the extraction device 201 of the instrument 200, in a container that receives a sample of secretions to be analyzed. Alternatively, the sensor 1 embodied by a label may be applied, directly or indirectly, by the extraction device 201 of the instrument 200, to, for example, the tongue of a subject whose infection it is desired to check.

[0010] For example, with reference to Figures 8a to 8c, an instrument 200 may include a spatula-shaped body 202 to which a sensor 1 is applied.

[0011] 9a to 9c, the instrument 200 may include a spatula-shaped body 202 to which the sensor 1 is applied and a second spatula-shaped body 203 to which the removal device 201 is applied. The second spatula body 203 rotates relative to the spatula body 202, causing the removal device 201 to contact the sensor 1. According to the illustrated embodiment, the relative rotation of the spatula bodies is about an axis perpendicular to the longitudinal axes of the aligned spatula bodies.

[0012] 10a to 10c, the instrument 200 may include a spatula-shaped body 202 to which the sensor 1 is applied, and a second spatula-shaped body 203 to which the removal device 201 is applied. The second spatula body 203 rotates relative to the spatula body 202, causing the removal device 201 to contact the sensor 1. According to the illustrated embodiment, the relative rotation of the spatula bodies is about an axis parallel to the longitudinal axes of the side-by-side, parallel spatula bodies.

[0013] Preferably, according to a possible embodiment, the colorimetric sensor 1 comprises a support layer 2 having the function of supporting further overlying layers. The support layer 2 can be made, in an exemplary and non-limiting manner, from polycarbonate, or PVC, or Teslin, or polyester, or similar materials, or from a paper material.

[0014] The colorimetric sensor 1 has a photonic crystal structure and preferably comprises one or more, preferably several, layers 3', 3'',... overlying a support layer 2. In optics and microphotonics, the term "photonic crystal" means a structure with a refractive index that has a periodic modulation on a scale comparable to the wavelength of light, or more generally, the wavelength of electromagnetic radiation. Based on the type of periodic modulation of the refractive index, photonic crystals are classified as follows: - One-dimensional photonic crystals (also known as Bragg mirrors), which have a periodic refractive index in only one direction; - two-dimensional photonic crystals with bidirectional refractive index periodicity; - Three-dimensional photonic crystal with periodic refractive index in three directions.

[0015] According to one embodiment, the layer having the photonic crystal structure 3, 3'',... comprises a one-dimensional photonic crystal structure. Referring to FIG. 7, the one-dimensional photonic crystal structure comprises multiple layers with respective refractive indices n1, n2, n3, n4. Given an incident light ray 101 at an incident angle α, total internal reflection is provided by a reflected light beam 102. By appropriately selecting the periodicity and refractive indices of the layers, it is possible to fabricate a mirror with a very high reflection coefficient within a defined wavelength range. As a result, by varying the incident angle α of the incident light ray 101, an observer, considered to be in a stationary position relative to the photonic crystal structure, will observe a change in color of the structure. Analogously, for the same incident angle of the incident light ray, an observer will see a change in color in the photonic crystal structure if he / she changes his / her position and / or orientation with respect to the photonic crystal structure and, consequently, with respect to the reflected light beam 102.

[0016] According to one embodiment, the layer having the photonic crystal structure 3, 3'',... comprises multiple alternating layers of silica (SiO2) and titanium dioxide (TiO2).

[0017] Furthermore, the colorimetric sensor 1 comprises a layer 4, which includes a nanomaterial capable of generating surface electron excitation, i.e., surface plasmons, under certain conditions, bioresponsive to bacteria and / or viruses, directly or indirectly overlapping one or more layers having a crystalline photonic structure 3', 3'',... In this specification and the appended claims, the term "bioresponsive" means that the considered material, when contacted with and stimulated by bacteria or virus molecules, changes its properties, in particular its plasmonic resonance energy, which depends on what is located between the material and the bacteria / virus interface. Thus, elements bonded to the surface of nanoparticles of the nanomaterial contribute to a change in plasmon energy, resulting in the observed color being different from that of the macroscopic material.

[0018] For example, the antibacterial properties of silver are known, as it binds to bacterial membranes and thereby alters their electrostatic surface properties. Furthermore, recent studies have shown how colloidal silver and gold are bioresponsive to certain viruses.

[0019] According to one embodiment, the nanomaterial of the functional layer 4 comprises silver or a silver-based material (such as colloidal silver), or gold or a gold-based material. Of course, further nanomaterials not expressly mentioned can be provided that are not plasmonic and not bioresponsive to specific viruses or bacteria.

[0020] Preferably, the functional layer 4 is characterized by a nanometer thickness, in other words in the nanometer range. According to a possible embodiment, the functional layer 4 has a thickness comprised between 4 and 20 nanometers. This very thin layer can be applied by different deposition techniques, such as, for example, vacuum deposition, sputtering, physical vapor deposition or other spray techniques.

[0021] In other words, when bacteria are detected, for example by contacting the secretions of a bacterially infected subject with the functional layer 4, this latter structural change, due to its bioresponsiveness as described above, alters the plasmon energy in the part of the nanomaterial that is in contact with the bacteria itself, causing this part to exhibit a color different from that of the macroscopic material. Such a color change is amplified by the overall coherent electro-optical structure of the photonic crystal 3', 3'',... layer of the sensor 1.

[0022] According to one embodiment, the functional layer 4 is selectively removed to form, for example, an alphanumeric string, an image, a symbol, a code, etc. For example, the functional layer 4 may be removed to reveal one or more writings indicative of a bacteria or virus (e.g., COVID-19) to be identified.

[0023] It is known that certain proteins or antibodies act as virus receptors. For example, in the case of COVID-19 and SARS-CoV, the ACE2 protein (angiotensin-converting system 2) has been observed to act as a membrane receptor.

[0024] The Applicant has surprisingly found that adding such proteins or antibodies to the functional layer 4 enables the sensor 1 to detect viruses, such as the COVID-19 virus, present in human or other subjects or liquid secretions, and contributes to a modification of the plasmon energy, which in this case also causes an interferometric electro-optical change in the sensor structure comprising a layer of photonic crystal structure 3,3'',... which in turn causes an optically perceived color change.

[0025] For this purpose, the bioresponsive plasmonic nanomaterial forming the functional layer 4 can be infused with the above-mentioned proteins or antibodies acting as viral receptors. Alternatively, the sensor 1 can comprise a receptor layer 5 containing the above-mentioned proteins or antibodies acting as viral receptors, where the functional layer 4 and the receptor layer 5 overlap each other and preferably are in contact with each other. The receptor layer 5 is also preferably characterized by a nanometer thickness. According to one embodiment, the sensor 1 further comprises a second functional layer 6, preferably containing the same nanomaterial as the one of the functional layers 4 and overlapping the receptor layer 5. The second functional layer 6 is also preferably characterized by a nanometer thickness, even more preferably comprised between 4 nanometers and 20 nanometers.

[0026] Alternatively, or in addition to what has been described above, in order to improve the sensitivity of sensor 1 so that it can better detect the presence of bacteria and viruses, which generally have a size much smaller than bacteria, sensor 1 may include a layer 7 of plasmonic nanostructures that overlaps the layer with the photonic crystal structures 3, 3'',... and that includes nanostructures capable of forming plasmonic colors.

[0027] The plasmonic nanostructured layer 7 is a nano-etched structure, i.e., it contains etched nanostructures shaped to enhance the intensity of the electromagnetic field generated by the photonic and plasmonic resonances inherent in the nanostructures, which in turn enhances the interaction between light and matter to obtain so-called plasmonic colors, also known as structural colors. Such plasmonic colors are obtained through the resonant interaction between light and the nanostructures of the plasmonic nanostructured layer 7 ("nanostructured grating") etched into a metal layer or a polymer layer coated with metal nanoparticles. The surface-localized plasmons generated by these nanostructures allow for nanometer-scale control of their morphology, thereby enabling the generation of polarized colors without dyes. The nanostructures can be fabricated, for example, by electron beam techniques.

[0028] The nanostructures of plasmonic nanostructured layer 7 can induce the phenomenon of surface plasmonic resonance, thus improving the sensitivity of sensor 1, i.e., increasing the aforementioned phenomenon of color change of the sensor upon detection of the presence of bacterial organisms or viruses, such as COVID-19 in particular.

[0029] According to one embodiment, the nanostructures of the plasmonic nanostructured layer 7 have zero diffraction order, in other words, they can only produce reflection and refraction of incident light waves, but not diffraction.

[0030] According to one embodiment, the nanostructures of the plasmonic nanostructured layer 7 are configured to produce a polarization optical effect.

[0031] With reference to the accompanying figures 1 to 6, possible alternative embodiments of the present invention will now be described.

[0032] First embodiment (Fig. 1) According to this embodiment, the colorimetric sensor 1 is configured to sequentially (from bottom to top in the direction of the drawing) Support group 2 and a plurality of layers having a structure of alternating photonic crystals 3', 3'', ... of, for example, SiO2 and TiO2; a receptor layer 5; and a functional layer 4 made of, for example, silver, Ag.

[0033] Second embodiment (Fig. 2) According to this embodiment, the colorimetric sensor 1 is configured to sequentially (from bottom to top in the direction of the drawing) Support group 2 and a plurality of layers having a structure of alternating photonic crystals 3', 3'', ... of, for example, SiO2 and TiO2; For example, a functional layer 4 of silver, Ag, and a receptor layer 5.

[0034] Third embodiment (Fig. 3) According to this embodiment, the colorimetric sensor 1 is configured to sequentially (from bottom to top in the direction of the drawing) Support group 2 and For example, a plurality of layers having a structure of alternating photonic crystals 3', 3'', ... of SiO2 and TiO2; 7. A layer of plasmonic nanostructures; and a functional layer 4 made of, for example, silver, Ag.

[0035] Fourth embodiment (Fig. 4) According to this embodiment, the colorimetric sensor 1 is configured to sequentially (from bottom to top in the direction of the drawing) Support group 2 and a plurality of layers having a structure of alternating photonic crystals 3', 3'', ... of, for example, SiO2 and TiO2; 7. A layer of plasmonic nanostructures; a receptor layer 5; and a functional layer 4 made of, for example, silver, Ag.

[0036] Fifth embodiment (Fig. 5) According to this embodiment, the colorimetric sensor 1 is configured to sequentially (from bottom to top in the direction of the drawing): Support group 2 and a plurality of layers having an alternating photonic crystal 3', 3'', ... structure, for example of SiO2 and TiO2; 7. A layer of plasmonic nanostructures; For example, a functional layer 4 of silver, Ag, and a receptor layer 5.

[0037] Sixth embodiment (Fig. 6) According to this embodiment, the colorimetric sensor 1 is sequentially (from bottom to top in the direction of the drawing): Support group 2 and a plurality of layers having an alternating photonic crystal 3', 3'', ... structure, for example of SiO2 and TiO2; 7. A layer of plasmonic nanostructures; For example, a functional layer 4 of silver, Ag, a receptor layer 5; and a second functional layer 6, for example of silver.

[0038] It is observed that in the above-described embodiments, the receptor layer 5, if provided, may alternatively be replaced by injecting the functional layer 4 and / or the second functional layer 6.

[0039] Furthermore, it is observed that, throughout this specification and the appended claims, the term "overlapping," when referring to layers of sensor 1, does not necessarily imply direct contact between the recited layers. Thus, such layers may be in direct contact with one another or may have one or more intermediate layers disposed therebetween, provided they still overlap. Furthermore, the term "overlapping" does not imply the order in which layers are shown to overlap one another.

[0040] According to another variant of the present invention, the colorimetric sensor 1 can lack the layers 3', 3'',... having a photonic crystal structure when it includes the layer 7 of plasmonic nanostructures. In fact, it has been observed that the presence of the layer 7 of plasmonic nanostructures is sufficient to ensure adequate sensitivity even in the absence of the layers 3', 3'',... having a photonic crystal structure. For example, all variants shown in Figures 3-6 can be realized without the layers 3', 3'',... if all other shown layers are maintained (Figures 11-14).

[0041] Seventh embodiment (Fig. 11) According to this embodiment, the colorimetric sensor 1 is configured to sequentially (from bottom to top in the direction of the drawing) Support group 2 and 7. A layer of plasmonic nanostructures; and a functional layer 4 made of, for example, silver, Ag.

[0042] Eighth embodiment (Fig. 12) According to this embodiment, the colorimetric sensor 1 is configured to sequentially (from bottom to top in the direction of the drawing): Support group 2 and 7. A layer of plasmonic nanostructures; a receptor layer 5; and a functional layer 4 made of, for example, silver, Ag.

[0043] Ninth embodiment (Fig. 13) According to this embodiment, the colorimetric sensor 1 is configured to sequentially (from bottom to top in the direction of the drawing) Support group 2 and 7. A layer of plasmonic nanostructures; For example, a functional layer 4 of silver, Ag, and a receptor layer 5.

[0044] Tenth embodiment (Fig. 14) According to this embodiment, the colorimetric sensor 1 is configured to sequentially (from bottom to top in the direction of the drawing) Support group 2 and 7. A layer of plasmonic nanostructures; For example, a functional layer 4 of silver, Ag, a receptor layer 5; and a second functional layer 6, for example of silver.

[0045] It is observed that even in the above embodiment, the receptor layer 5, if provided, may alternatively be replaced by injecting the functional layer 4 and / or the second functional layer 6.

[0046] To meet specific contingency needs, those skilled in the art can introduce many additions, modifications or substitutions of other operationally equivalent elements into the above description of the colorimetric sensor without departing from the scope of the appended claims.

Claims

1. A colorimetric sensor (1) for detecting viruses, comprising: a functional layer (4) comprising a nanomaterial capable of generating viral bioresponsive surface plasmons and having a uniform thickness comprised between 4 nanometers and 20 nanometers; a receptor layer (5) containing a protein or antibody that acts as a virus receptor, wherein the functional layer (4) and the receptor layer (5) overlap and are in direct contact with each other; Including, The colorimetric sensor (1) further comprises a plasmonic nanostructured layer (7) that is different from the functional layer (4) and includes nanostructures etched to generate plasmonic colors, and the functional layer (4) overlaps the plasmonic nanostructured layer (7). Colorimetric sensor (1).

2. The colorimetric sensor (1) according to claim 1, wherein the nanomaterial of the functional layer (4) comprises silver or a silver-based material, or gold or a gold-based material.

3. The colorimetric sensor (1) according to claim 1 or 2, wherein said protein or antibody acting as a viral receptor comprises the ACE2 protein (angiotensin converting enzyme 2).

4. 4. The colorimetric sensor (1) according to claim 1, further comprising a second functional layer (6) comprising a nanomaterial capable of generating viral bioresponsive surface plasmons, the second functional layer (6) overlapping the receptor layer (5) and facing the functional layer (4).

5. The colorimetric sensor (1) according to claim 4, wherein the second functional layer (6) comprises the same nanomaterial as one of the functional layers (4).

6. The colorimetric sensor (1) according to claim 4 or 5, wherein the second functional layer (6) and the receptor layer (5) are in direct contact with each other.

7. The colorimetric sensor (1) according to any one of claims 4 to 6, wherein the second functional layer (6) has a thickness comprised between 4 nanometers and 20 nanometers.

8. The colorimetric sensor (1) of any one of claims 1 to 7, wherein the etched nanostructures of the plasmonic nanostructured layer (7) are shaped to induce surface plasmonic resonance.

9. The colorimetric sensor (1) according to any one of claims 1 to 8, wherein the diffraction order of the etched nanostructures of the nanostructured plasmonic layer (7) is zero.

10. The colorimetric sensor (1) according to any one of claims 1 to 9, wherein the etched nanostructures of the nanostructured plasmonic layer (7) are configured to produce a polarization optical effect.

11. The colorimetric sensor (1) according to any one of claims 1 to 10, further comprising a support layer (2).

12. A colorimetric sensor (1) according to any one of claims 1 to 11, adapted as a label.

13. A colorimetric sensor (1) according to any one of claims 1 to 12, applied to a support in sheet or roll form in an instrument (200).

14. The colorimetric sensor (1) according to any one of claims 1 to 13, wherein the functional layer (4) is selectively deposited to form an alphanumeric string, or an image, or a symbol, or a code.

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