Abstract:
A system and method for measurement and analysis of a sample by absorption spectrophotometry is taught by the present invention. According to various embodiments, the invention utilizes a novel receptacle comprising of at plurality of layers including a transparent layer, a channel layer, and a reflective layer coupled to one another and allowing for fluid communication within and among the layers to allow for illumination by a light source and interrogation and analysis by a light measuring device. Examples of the light source and light measuring devices that could be used with the present invention include reflectance and/or fluorescence spectroscopy and a spectrometer, respectively. Measurement and analysis of a sample is compared to known values of constituents for comparison.

Description:
CROSS REFERENCE OF RELATED APPLICATIONS  
       [0001]    This application claims priority to U.S. provisional application 60/272,112 filed on Feb. 28, 2001, the entirety of which is incorporated herein by reference. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0002]    [0002]FIG. 1 shows a schematic diagram of an aspect of the method of the invention according to an embodiment.  
           [0003]    [0003]FIGS. 2A and 2B show top/bottom view and a staggered side view, respectively, of an aspect of a device of the invention according to an embodiment of the invention.  
           [0004]    [0004]FIG. 3 is an illustrative graph of absorbance wavelengths of characteristics of a blood sample.  
           [0005]    [0005]FIG. 4 shows the components of one aspect of the invention according to another embodiment.  
           [0006]    [0006]FIG. 5A shows a side view of an aspect of the invention according to an embodiment; FIG. 5B shows a top view of the aspect of the invention shown in FIG. 5A.  
           [0007]    [0007]FIG. 6 shows another aspect of the invention according to an embodiment.  
           [0008]    [0008]FIG. 7 shows another embodiment of the invention.  
         SUMMARY OF THE INVENTION  
         [0009]    A system and method for measurement and analysis of a sample by absorption spectrophotometry is taught by the present invention. According to various embodiments, the invention utilizes a novel receptacle comprising of at plurality of layers including a transparent layer, a channel layer, and a reflective layer coupled to one another and allowing for fluid communication within and among the layers to allow for illumination by a light source and interrogation and analysis by a light measuring device. Examples of the light source and light measuring devices that could be used with the present invention include reflectance and/or fluorescence spectroscopy and a spectrometer, respectively. Measurement and analysis of a sample is compared to known values of constituents for comparison. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0010]    The present invention may be understood more readily by reference to the following detailed description of the various embodiments of the invention and the Figures.  
         [0011]    Before the present articles and methods are disclosed and described, it is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. It must be noted that, as used in the specification and the appended claims, the singular forms “a”, “an” and “the” include plural referents unless the context clearly dictates otherwise.  
         [0012]    According to its various embodiments, the present invention comprises of a method and a device for measuring a characteristic of a sample by measuring the sample&#39;s reflective and/or fluorescent properties. The method comprises the steps of illuminating a sample, interrogating a sample with a light measuring device, collecting the reflected and/or fluoresced light, measuring the reflected light, and determining the characteristic of a sample by comparing the property or properties of the collected light to those of properties of known characteristics. For example, where the sample is blood and the particular characteristic is an analyte, specifically bilirubin, measurements of light absorption at the absorption peak wavelength of bilirubin can yield quantitative information about the concentration of bilirubin in a sample. FIG. 1 shows a schematic example of this measurement and determination of a characteristic in a sample according to various embodiments of the present invention.  
         [0013]    Furthermore, the device of the present invention performs the functions/steps taught by the method of the present invention. The device comprises a light source, a light measuring device, and a sample receptacle. The receptacle  100  comprises a reflective surface adjacent to a housing/chamber to store the sample of interest to be measured as the light source interrogates the sample at a first wavelength(s) either directly or through a transparent cover depending on the embodiment. As the light causes the sample to reflect and/or fluoresce at a second wavelength(s), the reflected and/or fluoresced light is collected and measured by a light measuring device, e.g. a spectrometer. In embodiments where the absorbance/fluorescence properties are being measured, the reflective surface comprises of a uniform or otherwise known spectral reflectance. Furthermore, the surface has sufficient backscatter, i.e. a high scattering coefficient and/or low scattering anisotropy so that minimal or no light passes through the layer and vice versa. The measuring device then compares the properties of the collected light to properties of known characteristics, such as particular analytes and/or subcomponents thereof. And depending on the embodiment, the device may, but not necessarily, be powered by a portable energy source such as a battery or a fuel cell. Based on this comparison, the present invention is able to measure and determine a characteristic of a sample.  
         [0014]    According to an embodiment of the invention, the receptacle  100  may take the shape of a multilayer “sandwich”. As shown by the embodiment in the top view of FIG. 2A and a staggered view as shown in FIG. 2B, the invention comprises of at least three layers. The receptacle  100  may comprise an access layer  210 , a channel layer  220 , and a base layer  230 . The access layer  210  comprises of an opaque reflective surface to serve as the reflective background for the invention. In one embodiment, this reflective access layer is white, however, other colors producing possessing similar reflective or desired reflective properties may be used. Application of various different colors to produce the desired results are common to those skilled in the art. Other colors may be used if the spectrum is known and such that the reflectance may be subject to normalization and produce a “spectrally flat” property.  
         [0015]    The layers are coupled in a manner so as operate in a synergistic and cooperative approach. The access layer  210  further comprises of at least a first reflective access opening  211  and at least a second reflective access opening  212 . The first reflective access opening  211  allows for the delivery of the sample whereas the second reflective access opening  212  provides a view for visualizing the sample in the layer below. Next, the receptacle  100  comprises of a channel layer  220  coupled to the other layers. The channel layer  220  comprises a channel  221  that may further, but not necessarily, comprise of at least one channel layer opening  222  coupled in fluid and/or gaseous communication with one another such that the liquid traverses via the channel  221  (and thereby the channel layer  220 ) either by capillary action via a capillary action escape port  223  or some other fluid dynamic means commonly known to those skilled in the art. The channel opening(s) comprise a channel access opening  222  that is in alignment with the first reflective access opening  212  which receives the sample deposited thereinabove and a channel layer view opening  223  that is in alignment with the second reflective access opening  212 . The third or base layer  230  serves as the protective layer of the receptacle  100  such that the sample does not escape the channel layer  220  after receipt from the access layer  210 . The base layer  230  is transparent to allow for light to penetrate through the receptacle  100  to allow for light interrogation of the sample contained in the channel layer  220  of the receptacle  100 . Although it is not shown by the diagrams, it is foreseeable that the aspects and/or qualities of each layer could be combined and merged such that this aspect of the invention comprises of a bilayer or a monolayer.  
         [0016]    Using the example above, the present invention utilizes a source of polychromatic light of a known intensity and directs it to a sample deposited in the receptacle  100 . In one embodiment [not shown], the light is delivered via a fiber optic probe. As the light passes through the transparent base layer  230  to the sample in the channel layer  220  and hits the reflective access layer  210 , a portion of the light reflects, scatters, and/or fluoresces to the source of the light where it is then collected by at least on separate fiber in communication with a spectrometer [not shown].  
         [0017]    Once the various wavelengths of the light are collected, they are separated and quantified. FIG. 3 shows an illustrative graph where the sample is blood and the characteristics are oxygen-bound hemoglobin, bilirubin, red blood cells, oxygen-bound hemoglobin attached to red blood cells, and a combination of all measured characteristics of the sample. Based on the known light absorption, scattering and/or fluorescent properties of the blood sample constituents, the absorption spectrum is quantified, analyzed and established to identify the contribution made by the characteristics measured within the sample. Once interfering constituents/characteristics are removed, the concentration of a particular characteristic can be determined by, for example, the known molar extinction coefficient of the particular characteristic.  
         [0018]    According to another embodiment of the invention as shown in FIG. 4, the receptacle  100  may comprise of a solid inert medium with known light absorption/reflectance/fluorescent properties rather than the “sandwich” approach shown in FIGS. 2A and 2B. The receptacle  100  as shown in FIGS. 4 and 5 show embodiments of the receptacle  100  of the present invention where the receptacle  100  comprises of a first layer  410  capable of being connected or otherwise coupled to a second layer  420 . Examples of such connection  300  may include, without limitation, a hinge, adhesives, or mating elements with complementary male and female counterparts. Furthermore, the first  410  and second layer  420  may engage with an attachment  400  of a light interrogating source pathway [not shown] and/or collection pathway [also not shown] as in FIG. 4. In this embodiment, the first layer  410  comprises a reflective section  415  whereas the second layer  420 , comprises a second layer chamber  425 . The reflective section  415  and the second layer chamber  425  are positioned such that when the first  410  and second layer  420  are brought in contact, they are in alignment and in communication with respect to one another. The chamber  425  contains the inert medium and houses the sample to be analyzed. Furthermore, the chamber comprises of an opening [not shown] or at least a first transparent side [also not shown] and also a second transparent side [also not shown]. In embodiments where the chamber  425  has an opening, the opening allows the reflective surface  415  of the first layer  410  to act as the cover of the chamber  425 . In embodiments where the chamber  425  comprises of at least a first transparent side [not shown], the first transparent side can be placed such that it also serves as the cover of the chamber without compromising the reflective characteristics of the first layer  410 . The second side of the chamber  425  also provides for the containment of the sample while also providing for a window for a light to pass through to interrogate the sample. Interrogation, collection, measurement, quantification and other analysis utilizing this embodiment is the same as described above with the “sandwich” embodiment.  
         [0019]    In embodiments according to FIG. 5A and FIG. 5B, the receptacle  100  comprises of at least two layers connected at at least one end  300 . The connection  300  may, for example, comprise of a hinge such that the two layers can attach and separate via this connection. According to this embodiment, the two layers comprise a first layer  510  and a second layer  520 . A side view and a top view of each layer is shown in FIG. 5A and FIG. 5B, respectively. As shown in FIG. 5B, the first layer  510  comprises of an application area  511 , a capillary channel  512 , and a recessed chamber  513  whereas the second layer  520  comprises an indicator membrane  521  and a protrusion  522 . Furthermore, the application area  511 , channel  512  and the recessed chamber  513  are shaped such that they are recessed areas within the surface of the first layer  510  with the top surface of the application area  511 , the capillary channel  512  and sample recessed chamber  513  exposed. With respect to this exposed top surface, a seal is created when the first layer  510  and bottom layer  520  are brought together in proper attachment. Also, the indicator membrane  521  is positioned such that when the first layer  510  and the second layer  520  are brought together in contact with one another, the indicator membrane  521  is aligned with the recessed chamber  513 . Similarly, the protrusion  522  is also aligned such that once the first layer  510  and second layer  520  are properly attached, the protrusion  522  enters into a complementary receptor  523  within the channel  512 . In further embodiments, there exists a fastener [not shown] to hold the first layer  510  and second layer  520  together in attachment.  
         [0020]    According to this embodiment, the sample, e.g. blood, is deposited in the application area  511 . The sample then travels via the channel  512  to the chamber  513 . When the measurement and analysis is ready to be performed, the first layer  510  and second layer  520  are brought together such that a seal exists between the two layers. The protrusion  522  then engages the receptor  523  thereby interrupting the channel  512  and thereby further interrupting the flow of the sample from the application area  511  into the chamber  513 . In further embodiments, the first layer  510  and second layer  520  may be securely attached by a fastener [not shown] or an equivalent thereof to maintain the seal and/or interruption within the channel  512  during measurement and analysis. Once the first layer  510  and second layer  520  are brought together, the indicator membrane  521  is now also properly aligned with the chamber  513 . The indicator membrane  521  is analogous to the reflective layer of the previous embodiments of the present invention already disclosed hereinabove. Accordingly, measurement and analysis methods are performed in a similar manner.  
         [0021]    In another embodiment, the sample may be placed on an inert medium  610  such as silica fibers that are in contact with a semipermeable membrane  620  and which is in contact with the sample chamber  600 . The chamber  600  may be filled with air or with an inert fluid medium  610  as shown in FIG. 6. When the sample is added to the medium  610 , the aqueous portion of the sample along with its constituents/characteristics move across the semipermeable membrane  615  via capillary flow or by osmotic pressure into the measuring and interrogation region  620 . Examples of such surfaces include without limitation cellulose, nitrocellulose, PVDF or other similar hydrophilic membranes used for filtration. The characteristics are then filtered and ready to be interrogated, collected, measured, quantified and otherwised analyzed by directing a light source [not shown] and the light collection device [also not shown] at the interrogation aperture  630  upon which light enters and relflects against a reflective aspect  640  and then is collected again through the aperture  630 .  
         [0022]    In embodiments as shown according to FIG. 7, the receptacle  100  comprises of an integrated layer  700  for filtering and analysis. According to this embodiment, the integrated layer  700  comprises an application port  710 , a separation zone  720 , a transport and detection zone  730 , a reflective aspect  740 , a transparent aspect  750 , and an optical filter  760 . In further embodiments, reagents [not shown] may be used also. As shown in FIG. 7, the sample is deposited into the integrated layer  700  via the application port  710 . The sample then enters the separation zone  720  wherein the certain components may be filtered and separated from the sample. For example, where the sample is plasma, red blood cells may be separated via use of specific binders within the separation zone that binds/separates other interfering substances. Furthermore, indicators may employed to specifically detect and/or amplify presence of a particular characteristic, such as the existence of an analyte.  
         [0023]    The filtered/separated sample then proceeds to the transport and detection zone  730 . This zone may be generally more dense, in the case of capillary action, or more hydrophobic, in the case of surface tension, to aid the transport of the separated sample. Non-woven or mesh or other similar material commonly known and used by those skilled in the art may be used to draw the fluid from the separation zone  720  as well. Each of the above methods, either separately or in various combinations with one another, may be used to facilitate transport of the separated sample. In further embodiments, reagents may be used to quench interferents or specify and amplify the desired analyte.  
         [0024]    The reflective  740  and the transparent  750  aspects may each be adjacent to the application port  710 . These aspects serve similar function to those analogous aspects disclosed in other embodiments of the present invention and previously disclosed hereinabove. The optical filter  760  comprises at least one filter to limit the wavelength entering and exiting the integrated layer  700  and is used in conjunction with the interrogating light source to produce measurement and/or other analysis results. The reflective aspect  740  is opposite of the at least one optical filter  760  as shown in FIG. 7. The optical filter  760  can either be coupled to the integrated layer  700  or separate from it.  
         [0025]    The foregoing embodiments and advantages are merely exemplary and are not to be construed as limiting the present invention. The present teaching can be readily applied to other types of devices and applications that may be common to those of ordinary skill in the art. The description of the present invention is intended to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art.