HK1112963A - Holographic sensor - Google Patents

Description

Holographic sensor

Technical Field

The present invention relates to holographic sensors.

Background

WO-A-95/26499 describes A holographic sensor. The sensor includes a holographic support medium and a hologram distributed throughout its volume. The support medium interacts with the analyte to cause a change in a physical property of the medium. This change causes a change in the optical properties of the holographic element, such as its polarisability, reflectance, refractance or absorbance. If any change occurs in the hologram reconstruction (e.g. using incident broadband, non-ionic electromagnetic radiation), then a change in colour, for example, can be observed using an optical detector. The optical detector may be a spectrometer or simply the human eye.

WO-A-99/63408 describes an alternative method of producing A holographic sensor. A continuous process is used in which a polymer film is first produced and photosensitive silver halide particles are subsequently added. These particles are introduced into the polymeric medium by diffusion of a soluble salt and react with the halide ion and the photosensitive dye to form an insoluble photosensitive precipitate. The holographic image is then recorded.

PCT/GB04/00976 describes how holographic sensors can be made using a technique known as "silver free double polymerization".

Holographic sensors have been proposed for subcutaneous use, for example to detect glucose. However, the hologram will not typically reflect light of sufficient intensity to penetrate the skin to be detected and be detected. This is mainly due to the problem of light scattering.

The support medium of conventional holographic sensors may include a crosslinking agent such as N, N' -Methylenebisacrylamide (MBA).

In Analytical Biochemistry (1988), volume 173, page 412-423, Hochstrasser et al report the use of several different cross-linking agents in acrylamide gels to limit the binding of silver to the background of the gel when silver staining of the gel is performed. They found that any cross-linking agent with a free amide, such as Methylene Bis Acrylamide (MBA), tends to cause a significant background coloration.

They thought that the free amide on MBA interacts mainly with silver and binds it to the polymer. They found that Bisacryloylpiperazine (BAP), which is a tertiary amide (unlike MBA and most other bisacrylamide crosslinkers, which are secondary amides), did not show such random binding and high silver background upon silver staining. This is believed to be due to the nitrogen in BAP which is unable to interact with silver.

Disclosure of Invention

The present invention is based on the realization that the brightness and sensitivity of a holographic sensor is increased by reducing the degree of detrimental ("background") silver binding.

According to a first aspect of the present invention, there is disclosed a sensor comprising a medium and a hologram disposed therein, wherein an optical characteristic of the medium changes as a result of a change in a physical property of the medium, wherein silver particles form fringes of the hologram, and wherein the medium comprises a material that inhibits detrimental silver binding. Preferably, the medium is an acrylamide-based material crosslinked with a bis (tertiary amide), such as 1, 4-bis (acryloyl) piperazine.

A second aspect of the invention is a subcutaneous implant comprising a sensor of the invention.

The sensors of the present invention can be much higher in brightness and sensitivity than conventional sensors, and the light they reflect can be highly monochromatic, and therefore have better resolution. It follows that the sensor of the invention is particularly suitable for subcutaneous use, for example in the detection of glucose or lactate. The sensor may also be used in security/authentication.

Detailed Description

In a preferred embodiment of the invention, for illustrative purposes, the holographic support medium is a material crosslinked with 1, 4-bis (acryloyl) piperazine (BAP) and having the structure:

without wishing to be bound by theory, it is believed that the presence of a cross-linking agent such as BAP inhibits random (or non-specific) binding of silver to the support medium, thus minimizing background noise generated during holographic recording.

Holographic sensors of the type used in the present invention typically comprise a medium and a hologram disposed throughout the volume of the medium. The support medium may interact with the analyte, resulting in a change in a physical property of the medium. This change causes a change in the optical properties of the holographic element, such as its polarisability, reflectance, refractance or absorbance. If any change occurs when the hologram is reproduced by using incident broadband, non-ionic electromagnetic radiation, a change such as color or brightness can be observed.

There are many basic ways to change the physical properties and thus the optical properties. The physical property that is varied is preferably the volume of the support medium and thus the spacing of the holographic fringes of the holographic element. Such changes may be achieved by incorporating specific groups into the support medium in which they interact with the analyte to change conformation, charge or degree of cross-linking, and cause the support medium to expand or contract. Such a group is preferably a specific binding conjugate of an analyte species.

Holographic sensors can be used to perform a variety of detection analytes by simply changing the composition of the support medium. The support medium preferably comprises a polymeric medium whose composition must be optimized to obtain a high quality film, i.e. a film having a homogeneous medium in which holographic fringes can be formed. Preferably, the medium is obtained by (co) polymerizing monomers having an acrylamide-based monomer.

Other examples of holographic support media are gel, K-carageenan, agar, agarose, polyvinyl alcohol (PVA), sol gel (broadly classified), hydrogel (broadly classified), and acrylates. Other materials are polysaccharides, proteins and proteinaceous materials, oligonucleotides, RNA, DNA, cellulose acetate, polyamides and polyacrylamides. Gels are standard dielectric materials for carrying photosensitive substances such as silver halide particles. Gels can also be crosslinked by chromium (III) particles between carboxyl groups on gel strips (gelstrands).

The sensor may be prepared according to the methods disclosed in WO-A-95/26499, WO-A-99/63408 and WO-A-03/087789. The contents of the specification of these applications are incorporated into this specification by reference.

The hologram in the sensor of the present invention can be generated by light diffraction. The hologram may be visible under magnification only, or under white light, UV light or infrared radiation, under specific temperature, magnetism or pressure conditions, under light focused in a specific manner or under laser light of a specific frequency or wavelength. The holographic image is preferably an object or has a two-dimensional or three-dimensional effect.

The sensor may further comprise means for generating an interference effect when illuminated with laser light, preferably the means comprises a depolarizing layer.

The sensor may have a layer of material covering all or part of it that changes the properties of the light passing through itself or acts as a filter. The material may be transparent and have a specific refractive index or may act as a color filter. Such materials are advantageous and serve to ensure that analysis of any particular holographic response can be performed easily and unambiguously.

The invention also relates to a method of detecting an analyte in a sample, the method comprising contacting the sample with the medium of a sensor according to the invention and detecting any change in its optical properties. The analyte is preferably of a chemical, biochemical or biological type. The change in the optical characteristic can be detected by the naked eye or by using a device. A device may also be used to store, transmit or process data relating to the optical change. The device is preferably selected from the group consisting of an optical reader, a mobile phone, a computer, a digital camera, etc. It is contemplated that any type of computer may be used, such as a laptop computer, a desktop computer, or a handheld device such as a Personal Digital Assistant (PDA) that is a personal organizer device.

Articles comprising sensors according to the invention may be used in various fields. Such an article may be a transaction card, banknote, passport, identification card, smart card, driving license, share certificate, bond, cheque card, tax banderole, gift voucher, postage stamp, train or air ticket, telephone card, lottery card, event ticket (event ticket), credit or debit card, business card, or an article used in consumer, brand or product protection for the purpose of distinguishing genuine products from counterfeit products or for identifying stolen products.

Alternatively, the item may be a smart packaged item. The "smart packaged item" is a system that includes a portion of a container, package, or enclosure, or an accessory thereof, to monitor, indicate, or test product information or quality, or environmental conditions that can affect product quality, shelf life, or safety. Common applications include, for example, indicators that show time-temperature, freshness, humidity, alcohol, gas, object damage, and the like.

The invention may be used with industrial or handicraft articles including decorative elements selected from jewelry, articles of clothing including footwear, textiles, furniture, toys, gifts, household items including crockery and glassware, buildings including glass, tile, paints, metals, bricks, ceramics, wood, plastics and other internal and external installations, art including pictures, sculptures, ceramics and lighting installations, stationery including greetings cards, letterheads and promotional material, and sporting goods, or the articles may be products or devices used in agricultural research, environmental research, human or veterinary prognostics, theranostics, diagnostics, therapy or chemical analysis, more preferably test strips, chips, cartridge containers (cards), swabs (swabs), tubes, disposable articles, a pipette, contact lens, subconjunctival implant, subcutaneous implant, breathalyzer, catheter, or fluid sampling or analysis device.

The sensor of the present invention may be included on a transferable holographic film. The film is preferably present on a hot stamping belt (stamping tape). The security of the article can be improved by transferring the sensor from the film to the article.

The invention also relates to products comprising the inventive sensors capable of generating data and systems for data read storage, control, transmission, reporting and/or modeling using data generated by such products.

The following examples serve to illustrate the invention.

Example 1

The support medium is formed by copolymerizing 12 mol% of 3-aminophenylboronic acid, 86.5 mol% of acrylamide and 1.5 mol% of BAP as a crosslinking agent. A similar medium was then formed using 1.5 mol% MBA as the crosslinker. Silver halide was then fixed in each medium using a 2-pulse laser and a hologram was recorded. Another medium was formed by a "silver-free double polymerization" mode of 12 mol% 3-aminophenylboronic acid and acrylamide using 1.5 mol% MBA as a cross-linking agent. Also, a hologram is recorded in the medium.

The hologram of the sensor of the present invention is believed to be significantly brighter (by a factor of about 10-100) than conventional sensors even with only 2 pulses of laser light in its construction. In fact, the hologram of the present invention is so bright that it can be viewed even under a strip light. The present invention also compares the responses of the various sensors, which are shown to be virtually identical. The diffraction peaks of the sensor of the present invention are highly monochromatic relative to the diffraction peaks of the other two.

Example 2

The support medium is formed by copolymerizing 5 mol% of acrylic acid, 90 mol% of acrylamide to methacrylamide (ratio 2: 1) and 5 mol% of BAP as a crosslinking agent. Silver halide is then immobilized within the medium and the hologram recorded. The sensor showed similar characteristics as the sensor of example 1.

Claims (33)

1. A sensor comprising a medium and a hologram disposed in the medium, wherein an optical characteristic of the medium changes as a result of a change in a physical property of the medium, wherein silver particles form fringes of the hologram, and wherein the medium comprises a material that inhibits silver binding.

2. The sensor according to claim 1, wherein the medium is a cross-linked material.

3. A sensor according to claim 1 or claim 2, wherein the material is obtainable by polymerising monomers comprising acrylamide-based monomers.

4. A sensor according to claim 3, wherein the monomer comprises acrylamide and/or methacrylamide.

5. A sensor according to claim 3 or claim 4, wherein the material is cross-linked with a bis (tertiary amide).

6. The sensor according to claim 5, wherein the material is crosslinked with 1, 4-bis (acryloyl) piperazine.

7. A sensor according to any preceding claim, for use in detecting an analyte.

8. The sensor according to claim 6, for detecting glucose or lactate.

9. A sensor according to any preceding claim, wherein the hologram is generated by diffraction of light.

10. A sensor according to any preceding claim, wherein the hologram is only visible under magnification or under laser illumination.

11. A sensor according to any preceding claim, wherein the holographic image is an object or has a two or three dimensional effect.

12. A sensor according to any preceding claim, further comprising means for generating an interference effect when illuminated with laser light.

13. The sensor of claim 12, wherein the means comprises a depolarizing layer.

14. The sensor according to any of the preceding claims, wherein the hologram is visible under white light, UV light or infrared radiation.

15. A sensor according to any one of claims 1 to 13 wherein the hologram is visible under specific temperature, magnetic force or pressure conditions.

16. A sensor according to any preceding claim, wherein the sensor has a layer of material covering all or part of it, the material being transparent or acting as a colour filter.

17. A subcutaneous implant comprising a sensor according to any of the preceding claims.

18. A method of detecting an analyte in a sample comprising contacting the sample with the medium of a sensor according to any preceding claim and detecting any change in an optical property.

19. The method of claim 18, wherein the analyte is of a chemical, biochemical or biological type.

20. The method according to claim 18 or 19, wherein any change in the optical characteristic is detected using a device selected from the group consisting of an optical reader, a mobile phone, a computer and a digital camera, or data related to the optical change is stored, transmitted or processed.

21. An article comprising a sensor according to any one of claims 1 to 16.

22. An article according to claim 21, which is a transaction card, banknote, passport, identification card, smart card, driver's license, share certificate, bond, cheque card, tax banderole, gift voucher, postage stamp, rail or air ticket, telephone card, lottery card, event ticket, credit or debit card, business card or an article used in consumer, brand or product protection for the purpose of distinguishing genuine products from counterfeit products or for identifying stolen products.

23. An article according to claim 21, which is an intelligent packaging article as defined herein.

24. An article according to claim 21, which is an industrial or handicraft article, including decorative elements selected from jewellery, items of clothing (including footwear), textiles, furniture, toys, gifts, household items (including crockery and glassware), buildings (including glass, tiles, paints, metals, bricks, ceramics, wood, plastics and other internal and external installations), art (including pictures, sculpture, ceramics and lighting installations), stationery (including greeting cards, letterheads and promotional material) and sporting goods.

25. An article according to claim 21, which is a product or device for use in agricultural research, environmental research, human or veterinary predictive diagnostics, theranostics, diagnostics, therapy or chemical analysis.

26. An article according to claim 25, which is a test strip, chip, cartridge, swab, tube, pipette, contact lens, subconjunctival implant, subcutaneous implant, breathalyzer, catheter or fluid sampling or analysis device.

27. A transferable holographic film comprising the sensor of any of claims 1-16.

28. A film according to claim 27, which is present on a hot-stamped strip.

29. A method of improving the security of an article comprising transferring a sensor from a film according to claim 27 or claim 28 to the article.

30. A product comprising a sensor according to any one of claims 1 to 16, capable of generating data from said sensor.

31. A system for data storage, control, transmission, reporting and/or modeling using data generated by the product of claim 30.

32. A method of manufacturing a holographic sensor, comprising the steps of:

recording a hologram on a medium, wherein fringes of the hologram are formed by silver particles, wherein the medium comprises a material that inhibits silver binding.

33. A method according to claim 32, wherein the sensor further comprises any of the features of claims 2 to 16.