WO2006090114A2 - Imaging of particles using evanescent radiation - Google Patents

Imaging of particles using evanescent radiation Download PDF

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Publication number
WO2006090114A2
WO2006090114A2 PCT/GB2006/000497 GB2006000497W WO2006090114A2 WO 2006090114 A2 WO2006090114 A2 WO 2006090114A2 GB 2006000497 W GB2006000497 W GB 2006000497W WO 2006090114 A2 WO2006090114 A2 WO 2006090114A2
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WO
WIPO (PCT)
Prior art keywords
particles
radiation
region
sample
substrate
Prior art date
Application number
PCT/GB2006/000497
Other languages
French (fr)
Other versions
WO2006090114A3 (en
Inventor
Sean Anthony Gillespie
Original Assignee
Smiths Detection-Watford Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Smiths Detection-Watford Limited filed Critical Smiths Detection-Watford Limited
Publication of WO2006090114A2 publication Critical patent/WO2006090114A2/en
Publication of WO2006090114A3 publication Critical patent/WO2006090114A3/en

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/55—Specular reflectivity
    • G01N21/552—Attenuated total reflection

Definitions

  • This invention relates to optical particle detector apparatus of the kind including a transparent substrate having a sample surface and a source of monochromatic optical radiation arranged to direct a beam of radiation into the substrate to be incident on a region of the underside of the sample surface.
  • WO03/093801 There are various ways in which particles can be detected optically. For example, high magnification microscopy or other microscopy techniques as described in WO03/093801 can be used. Another technique, such as described in EP938661 and WOO 1/42768 involves the surface plasmon effect, which is dependent on the presence of a thin metal film of a particular kind, such as gold, on the surface. WO03/093801 describes apparatus that does not employ the surface plasmon effect but relies on an opaque metal layer on the surface.
  • optical particle detector apparatus of the above-specified kind, characterised in that the beam of radiation is incident on the underside of the sample surface at an angle close to the angle of total internal reflection such that the major part of the radiation is reflected away from the region, that the region of the surface is transparent and arranged to receive sample particles, and that the apparatus includes a viewer arranged above the surface to view the region such as to view the sample particles in the region by the effect the particles have on radiation passing through the surface.
  • the region of the sample surface may be arranged such that particles bind to the surface. Preferably selected particles bind only to a part of the region such that particles are visible by contrast with other parts of the region.
  • the region preferably has a plurality of areas arranged such that different particles bind to different ones of the areas.
  • the particles may be biological particles and the region may be arranged to bind with biological particles by means of one or more biorecognition elements, such as an antibody or peptide binding ligand.
  • the viewer may include a magnifier for viewing by the eye or it may include an imaging device.
  • the substrate may be in the form of a prism. The substrate may have a side through which the radiation emerges after reflection from the underside of the sample surface, the side having attached therewith a radiation sink arranged to reduce the amount of radiation reflected back into the substrate.
  • Figure 1 is a side elevation view of the apparatus.
  • Figure 2 is a plan view of a part of the apparatus.
  • the apparatus includes a transparent substrate in the form of a glass prism 1 having angles 90°, 60° and 30°.
  • the prism has an upper sample surface 10 and two lower side surfaces 11 and 12 inclined respectively at 60° and 30° to the upper surface.
  • the upper surface 10 supports a flow cell 13 having an inlet 14 and an outlet 15 by which liquid to be analysed flows through the cell and over a part of the sample surface 10. That part of the sample surface 10 bounded by the flow cell 13 provides a sample region 16 and is transparent to radiation being used in the apparatus because it is not coated with any opaque material.
  • the sample region 16 has three parallel stripes 17, 18 and 19 of different antibody materials deposited on the sample surface 10.
  • the three antibody materials are chosen to be ones to which different particles of interest, such as specific viruses or bacteria, will bind.
  • the apparatus also includes a diode laser 30 emitting monochromatic radiation with a wavelength of 532nm located to the right of the right-hand face 11 of the prism 1.
  • the wavelength is not believed to be critical and could be anywhere within the visible range. It could also extend beyond the visible range if the apparatus is used with an ultraviolet or infrared imaging device.
  • the beam of light from the laser 30 is directed onto the right-hand face 11 of the prism 1 at an angle close to the normal to the face.
  • the radiation is directed upwardly to be imaged on the underside of the sample region 16.
  • the angle ⁇ at which the beam of radiation is incident on the underside of the sample region 16 is selected to be slightly less than the critical angle so that the beam undergoes total internal reflection.
  • the beam is not totally reflected and a small amount of the radiation is refracted to emerge from the upper surface 10.
  • the angle could be smaller such that the beam is refracted to travel closely parallel to the surface of the 10 of the prism.
  • the critical angle is dependent on the refractive index both of the glass or other material of the prism 1 and of any liquid or other material in contact with the upper surface.
  • the reflected part of the beam is directed downwardly towards the left-hand face 12 of the prism 1.
  • the left-hand face 12 of the prism 1 is coated or otherwise bonded to a black radiation sink 32 in the form of a material that is highly absorptive of the radiation being used and that is in intimate optical contact with the surface of the prism. In this way, substantially no radiation is reflected back into the prism 1 from the face 12.
  • the apparatus is completed by a viewer in the form of a low power (typically around x4 magnification, and preferably between about x3 and xlO) microscope objective 40.
  • the objective 40 is mounted vertically above the flow cell 13 in order to view the sample region 16.
  • the objective 40 has a shallow depth of field with the focal plane being located at the surface of the sample region 16.
  • the apparatus need not rely on the eye and a magnifier to provide a viewer for visible detection, instead, the viewed could include a camera or other imaging device such as a far-field photo-detector, which may be arranged to identify the presence of the particles automatically.
  • the particles being detected are viruses or bacteria that bind to one of the three antibody stripes 17, 18 or 19. It is readily apparent, by looking through the objective 40 whether the particles of interest are present since, the presence of the particles will cause the antibody stripe for that kind of particle to have a more pronounced speckled appearance than the other stripes. This is represented in Figure 2 by the lowest stripe 17. Background noise may cause some speckled appearance even, when no particles are present but, by confining the binding of the particles to a localised region their presence is more apparent because of the contrast with other regions where particles are not present. It is not essential for particles to be bound to the sample surface since particles that simply lie loose on the surface can also be detected in the same way.
  • the present invention enables small particles, especially particles of a biological nature, such as biological spores and viruses, to be detected readily visibly and in real time.
  • the relatively simple construction of the optical substrate, without any metal coating, enables the substrate to be provided at low cost, making it particularly suitable as a disposable component in a detector.

Landscapes

  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating Or Analysing Materials By Optical Means (AREA)

Abstract

An optical detector for particles, such as biological particles, has a transparent prism (1) with an upper surface (10) treated differently, such as with different antibodies, in several areas (17, 18, 19) so that different particles bind to different ones of the areas. A source (30) of monochromatic radiation directs a beam through a second face (11) so that it is incident on the underside of the upper surface (10) at an angle close to the angle of total internal reflection. Most of the radiation is reflected away from the upper surface and is absorbed in a radiation sink (32) on the third face (12) of the prism (1). Some of the radiation, however, is scattered by any particles bound to the antibody-treated areas. A magnifying viewer (40) mounted above the upper surface (10) enables identification of particles because of the different appearance of the area (17) to which the particles are bound.

Description

PARTICLE DETECTION
This invention relates to optical particle detector apparatus of the kind including a transparent substrate having a sample surface and a source of monochromatic optical radiation arranged to direct a beam of radiation into the substrate to be incident on a region of the underside of the sample surface.
There are various ways in which particles can be detected optically. For example, high magnification microscopy or other microscopy techniques as described in WO03/093801 can be used. Another technique, such as described in EP938661 and WOO 1/42768 involves the surface plasmon effect, which is dependent on the presence of a thin metal film of a particular kind, such as gold, on the surface. WO03/093801 describes apparatus that does not employ the surface plasmon effect but relies on an opaque metal layer on the surface.
It is an object of the present invention to provide alternative particle detection apparatus and methods.
According to the present invention there is provided optical particle detector apparatus of the above-specified kind, characterised in that the beam of radiation is incident on the underside of the sample surface at an angle close to the angle of total internal reflection such that the major part of the radiation is reflected away from the region, that the region of the surface is transparent and arranged to receive sample particles, and that the apparatus includes a viewer arranged above the surface to view the region such as to view the sample particles in the region by the effect the particles have on radiation passing through the surface.
The region of the sample surface may be arranged such that particles bind to the surface. Preferably selected particles bind only to a part of the region such that particles are visible by contrast with other parts of the region. The region preferably has a plurality of areas arranged such that different particles bind to different ones of the areas. The particles may be biological particles and the region may be arranged to bind with biological particles by means of one or more biorecognition elements, such as an antibody or peptide binding ligand. The viewer may include a magnifier for viewing by the eye or it may include an imaging device. The substrate may be in the form of a prism. The substrate may have a side through which the radiation emerges after reflection from the underside of the sample surface, the side having attached therewith a radiation sink arranged to reduce the amount of radiation reflected back into the substrate.
Particle detection apparatus and its method of use will now be described, by way of example, with reference to the accompanying drawing, in which:
Figure 1 is a side elevation view of the apparatus; and
Figure 2 is a plan view of a part of the apparatus.
The apparatus includes a transparent substrate in the form of a glass prism 1 having angles 90°, 60° and 30°. The prism has an upper sample surface 10 and two lower side surfaces 11 and 12 inclined respectively at 60° and 30° to the upper surface. The upper surface 10 supports a flow cell 13 having an inlet 14 and an outlet 15 by which liquid to be analysed flows through the cell and over a part of the sample surface 10. That part of the sample surface 10 bounded by the flow cell 13 provides a sample region 16 and is transparent to radiation being used in the apparatus because it is not coated with any opaque material. The sample region 16 has three parallel stripes 17, 18 and 19 of different antibody materials deposited on the sample surface 10. The three antibody materials are chosen to be ones to which different particles of interest, such as specific viruses or bacteria, will bind.
The apparatus also includes a diode laser 30 emitting monochromatic radiation with a wavelength of 532nm located to the right of the right-hand face 11 of the prism 1. The wavelength is not believed to be critical and could be anywhere within the visible range. It could also extend beyond the visible range if the apparatus is used with an ultraviolet or infrared imaging device. The beam of light from the laser 30 is directed onto the right-hand face 11 of the prism 1 at an angle close to the normal to the face. The radiation is directed upwardly to be imaged on the underside of the sample region 16. The angle θ at which the beam of radiation is incident on the underside of the sample region 16 is selected to be slightly less than the critical angle so that the beam undergoes total internal reflection. In practice, however, the beam is not totally reflected and a small amount of the radiation is refracted to emerge from the upper surface 10. Alternatively, the angle could be smaller such that the beam is refracted to travel closely parallel to the surface of the 10 of the prism. It will be appreciated that the critical angle is dependent on the refractive index both of the glass or other material of the prism 1 and of any liquid or other material in contact with the upper surface. The reflected part of the beam is directed downwardly towards the left-hand face 12 of the prism 1. The left-hand face 12 of the prism 1 is coated or otherwise bonded to a black radiation sink 32 in the form of a material that is highly absorptive of the radiation being used and that is in intimate optical contact with the surface of the prism. In this way, substantially no radiation is reflected back into the prism 1 from the face 12.
The apparatus is completed by a viewer in the form of a low power (typically around x4 magnification, and preferably between about x3 and xlO) microscope objective 40. The objective 40 is mounted vertically above the flow cell 13 in order to view the sample region 16. The objective 40 has a shallow depth of field with the focal plane being located at the surface of the sample region 16.
In operation, it has been found that relatively small particles in the sample region, around 20nm in diameter, that is, smaller that the wavelength of the illuminating radiation, can be seen by the eye through the objective 40. It is thought that the particles cause scattering of the relatively small amount of radiation that emerges through the sample surface, which may be evanescent radiation. The scattered radiation is sufficient to be discerned through the low power microscope objective and makes very small particles detectable. The apparatus need not rely on the eye and a magnifier to provide a viewer for visible detection, instead, the viewed could include a camera or other imaging device such as a far-field photo-detector, which may be arranged to identify the presence of the particles automatically.
In the present example, the particles being detected are viruses or bacteria that bind to one of the three antibody stripes 17, 18 or 19. It is readily apparent, by looking through the objective 40 whether the particles of interest are present since, the presence of the particles will cause the antibody stripe for that kind of particle to have a more pronounced speckled appearance than the other stripes. This is represented in Figure 2 by the lowest stripe 17. Background noise may cause some speckled appearance even, when no particles are present but, by confining the binding of the particles to a localised region their presence is more apparent because of the contrast with other regions where particles are not present. It is not essential for particles to be bound to the sample surface since particles that simply lie loose on the surface can also be detected in the same way.
The present invention enables small particles, especially particles of a biological nature, such as biological spores and viruses, to be detected readily visibly and in real time. The relatively simple construction of the optical substrate, without any metal coating, enables the substrate to be provided at low cost, making it particularly suitable as a disposable component in a detector.

Claims

1. Optical particle detector apparatus including a transparent substrate (1) having a sample surface (10) and a source of monochromatic optical radiation (30) arranged to direct a beam of radiation into the substrate (1) to be incident on a region (16, 17, 18, 19) of the underside of the sample surface, characterised in that the beam of radiation is incident on the underside of the sample surface (10) at an angle θ close to the angle of total internal reflection such that the major part of the radiation is reflected away from the region, that the region (16, 17, 18, 19) of the surface (10) is transparent and arranged to receive sample particles, and that the apparatus includes a viewer (40) arranged above the surface (10) to view the region (16, 17, 18, 19) such as to view the sample particles in the region by the effect the particles have on radiation passing through the surface.
2. Apparatus according to Claim 1, characterised in that the region (16, 17, 18, 19) of the sample surface (10) is arranged such that particles bind to the surface.
3. Apparatus according to Claim 2, characterised in that selected particles bind only to a part (17, 18, 19) of the region (16) such that particles are visible by contrast with other parts of the region.
4. Apparatus according to Claim 2 or 3, characterised in that the region (16) has a plurality of areas (17, 18 and 19) arranged such that different particles bind to different ones of the areas.
5. Apparatus according to any one of Claims 2 to 4, characterised in that the particles are biological particles, and that the region (16, 17, 18, 19) is arranged to bind with the biological particles by means of one or more biorecognition elements, such as an antibody or peptide binding ligand.
6. Apparatus according to any one of the preceding claims, characterised in that the apparatus includes a flow cell (13) attached with the sample surface (10), and that the region (16, 17, 18, 19) is within the flow cell.
7. Apparatus according to any one of the preceding claims, characterised in that the viewer includes a magnifier (40) for viewing by the eye.
8. Apparatus according to any one of Claims 1 to 6, characterised in that the viewer includes an imaging device.
9. Apparatus according to any one of the preceding claims, characterised in that the substrate is in the form of a prism (1).
10. Apparatus according to any one of the preceding claims, characterised in that the substrate (1) has a side (12) through which the radiation emerges after reflection from the underside of the sample surface (10), and that the side (12) has attached therewith a radiation sink (32) arranged to reduce the amount of radiation reflected back into the substrate (1).
PCT/GB2006/000497 2005-02-24 2006-02-13 Imaging of particles using evanescent radiation WO2006090114A2 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB0503767.6 2005-02-24
GBGB0503767.6A GB0503767D0 (en) 2005-02-24 2005-02-24 Particle detection

Publications (2)

Publication Number Publication Date
WO2006090114A2 true WO2006090114A2 (en) 2006-08-31
WO2006090114A3 WO2006090114A3 (en) 2006-12-07

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PCT/GB2006/000497 WO2006090114A2 (en) 2005-02-24 2006-02-13 Imaging of particles using evanescent radiation

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GB (1) GB0503767D0 (en)
WO (1) WO2006090114A2 (en)

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6110749A (en) * 1996-03-01 2000-08-29 Beckman Coulter, Inc. System for simultaneously conducting multiple ligand binding assays
WO2001042768A1 (en) * 1999-12-07 2001-06-14 The Secretary Of State For Defence Surface plasmon resonance
US6280960B1 (en) * 1997-06-13 2001-08-28 Robert Carr Optical detection and analysis of sub-micron particles
US6569383B1 (en) * 2000-03-11 2003-05-27 Intrinsic Bioprobes, Inc. Bioactive chip mass spectrometry

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6110749A (en) * 1996-03-01 2000-08-29 Beckman Coulter, Inc. System for simultaneously conducting multiple ligand binding assays
US6280960B1 (en) * 1997-06-13 2001-08-28 Robert Carr Optical detection and analysis of sub-micron particles
WO2001042768A1 (en) * 1999-12-07 2001-06-14 The Secretary Of State For Defence Surface plasmon resonance
US6569383B1 (en) * 2000-03-11 2003-05-27 Intrinsic Bioprobes, Inc. Bioactive chip mass spectrometry

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Publication number Publication date
WO2006090114A3 (en) 2006-12-07
GB0503767D0 (en) 2005-03-30

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