Fiber optic analyte sensor

A fiber optic analyte sensing needle 10 with a photoluminescent analyte-sensitive probe 70 nonadherently entrapped within the lumen 29 of the needle 20 between the distal tip 51 of a fiber optic filament 50 and the distal tip 21 of the needle 20. The probe 70 has unimpeded fluid communication with the external environment through a port 28 in the needle 20.

BACKGROUND

Photoluminescent sensors or probes are a widely employed method of measuring analyte concentration, typically oxygen, within a defined space, typically an enclosed space such as the headspace of a package or container. See, for example United States Published Patent Applications 2009/0029402, 2008/8242870, 2008/215254, 2008/199360, 2008/190172, 2008/148817, 2008/146460, 2008/117418, 2008/0051646, and 2006/0002822, and U.S. Pat. Nos. 7,569,395, 7,534,615, 7,368,153, 7,138,270, 6,689,438, 5,718,842, 4,810,655, and 4,476,870.

Briefly, analyte concentration within a package or container can be measured by placing an analyte-sensitive photoluminescent probe within the package or container, allowing the probe to equilibrate within the package or container, exciting the probe with radiant energy, and measuring the extent to which radiant energy emitted by the excited probe is quenched by the presence of the target analyte. Such optical sensors are available from a number of suppliers, including PreSens Precision Sensing, GmbH of Regensburg, Germany, Oxysense of Dallas, Tex., United States, and Luxcel Biosciences, Ltd of Cork, Ireland.

In order to permit impromptu testing of a defined space, the photoluminescent probe can be provided as a coating on the distal tip of a fiber optic filament which is threaded into the lumen of a needle and protectively retained in a fixed position within the lumen by a target analyte permeable encapsulant. One example of such a fiber optic sensing needle for use in measuring the concentration of oxygen within living tissue is described in United States Patent Application Publication US 2009/0075321, the entire disclosure of which is hereby incorporated by reference.

While fiber optic sensing needles, such as that described in US 2009/0075321, are effective for impromptu measurement of analyte concentration within a defined space, they are difficult to assemble and slow to respond after being placed into fluid communication with a defined space to be tested.

Hence, a need exists for a fast response fiber optic sensing needle that is easy to assemble.

SUMMARY OF THE INVENTION

The invention is a fiber optic analyte sensing needle. The sensing needle includes a needle, at least one fiber optic filament and a photoluminescent analyte-sensitive probe. The needle has a longitudinal lumen with at least one lateral side port proximate the distal tip. The at least one fiber optic filament has a distal end portion sealingly jacketed within the lumen of the needle. The photoluminescent analyte-sensitive probe is nonadherently entrapped within the lumen between the distal tip of the at least one fiber optic filament and the distal tip of the needle. The probe has unimpeded fluid communication with the external environment through the at least one lateral side port in the needle.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

Nomenclature

Description

Construction

Referring generally toFIG. 1, the invention is a fiber optic analyte sensing needle10. The sensing needle10includes a needle20, at least one fiber optic filament50and a photoluminescent analyte-sensitive probe70.

Referring generally toFIGS. 2A and 2B, the needle20has a longitudinal lumen29with at least one port28proximate the distal tip21of the needle20. The port28is preferably a lateral side port28, most preferably at least two diametrically opposed lateral side ports28.

The needle20is preferably attached to a collar30via a Luer taper fitting40, such as a Luer-Lok or Luer-Slip fitting.

The at least one fiber optic filament50has a distal end portion sealingly jacketed within the lumen29of the needle20. The fiber optic filament50is preferably sealingly adhered to the inner wall (not separately numbered) of the needle20by a suitable target-analyte impermeable sealant60, such as an epoxy, to secure the at least one fiber optic filament50within the lumen29and prevent target-analyte located outside a container or package being tested from reaching and contaminating the photoluminescent analyte-sensitive probe70through the annular interface between the inner wall (not separately numbered) of the needle20and the outer wall (not separately numbered) of the fiber optic filament50.

The photoluminescent analyte-sensitive probe70is nonadherently entrapped within the lumen29between the distal tip51of the at least one fiber optic filament50and the distal tip21of the needle20, and has unimpeded fluid communication with the external environment through the at least one port28in the needle20.

Referring toFIG. 3, the probe70includes a carrier substrate71coated with an analyte-sensitive photoluminescent dye73. The analyte-sensitive photoluminescent dye73is preferably embedded within an analyte-permeable polymer matrix72.

The carrier substrate71may be selected from any material possessing sufficient structural integrity to physically support the analyte-sensitive photoluminescent dye73and capable of withstanding extended exposure to the environment into which the probe70is to be used (e.g., high humidity, low humidity, submerged in water, submerged in an acidic solution, etc). Materials suitable for use as the carrier substrate71, dependent of course upon the environment into which the probe10is to be used, include specifically but not exclusively, cellulosics such as paper, wax paper, cardstock, cardboard, wood and wood laminates; plastics such polyethylene, polypropylene and polyethylene terephthalate; metals such as aluminum sheets, aluminum foil, steel and tin; woven and unwoven fabrics; glass; and various combinations and composites thereof such a mylar. A preferred carrier substrate71is nonwoven glass fiber fabric. Without intending to be unduly limited thereby, it is believed that the compounded photoluminescent dye73and analyte-permeable polymer matrix72penetrate into the interstitial void volume of the glass fiber carrier substrate71and coat the individual fibrils (not shown) of the carrier substrate71. Suitable glass fiber filter discs are widely available from a number of sources including specifically, but not exclusively, Millipore Corporation of Bedford, Mass. under the designations (APFA, APFB, APFC, APFD, APFF and AP40 for binder-free filters and AP15, AP20 AP25 for binder-containing filters), Zefon International, Inc. of Oscala, Fla. (IW-AH2100, IW-A2100, IW-AE2100, IW-B2100, IW-C2100, IW-D2100, IW-E2100 and IW-F2100 for binder-free filters) and Pall Corporation of Port Washington, N.Y. (A/B, A/C A/D and A/E for binder-free filters and Metrigard™ for binder-containing filters). The glass fiber carrier substrate71preferably has a thickness of between 100 μm and 5,000 μm, most preferably between 200 μm and 2,000 μm.

The analyte-sensitive photoluminescent dye73may be selected from any of the well-known analyte-sensitive photoluminescent dyes73. One of routine skill in the art is capable of selecting a suitable dye73based upon the intended use of the fiber optic analyte-sensing needle10. For example, a nonexhaustive list of suitable oxygen-sensitive photoluminescent dyes73includes specifically, but not exclusively, ruthenium(II)-bipyridyl and ruthenium(II)-diphenylphenanothroline complexes, porphyrin-ketones such as platinum(II)-octaethylporphine-ketone, platinum(II)-porphyrin such as platinum(II)-tetrakis(pentafluorophenyl)porphine, palladium(II)-porphyrin such as palladium(II)-tetrakis(pentafluorophenyl)porphine, phosphorescent metallocomplexes of tetrabenzoporphyrins, chlorins, azaporphyrins, and long-decay luminescent complexes of iridium(III) or osmium(II).

Typically, the analyte-sensitive photoluminescent dye73is compounded with a suitable analyte-permeable polymer matrix72. Again, one of routine skill in the art is capable of selecting a suitable analyte-permeable polymer matrix72based upon the intended use of the fiber optic analyte-sensing needle10. For example, a nonexhaustive list of suitable polymers for use as an oxygen-permeable polymer matrix72includes specifically, but not exclusively, polystryrene, polycarbonate, polysulfone, polyvinyl chloride and some co-polymers.

Manufacture

The photoluminescent analyte-sensitive probe70can be manufactured by the traditional methods employed for manufacturing such elements. Briefly, the probe70can be conveniently manufactured by (A) preparing a coating cocktail (not shown) which contains the photoluminescent analyte-sensitive dye73and the analyte-permeable polymer matrix72in an organic solvent (not shown) such as ethylacetate, (B) applying the cocktail to at least one major surface (unnumbered) of a carrier substrate71, such as by dunking the carrier substrate71in the cocktail (not shown), and (C) allowing the cocktail (not shown) to dry, whereby a solid-state, thin film coating is formed on the carrier substrate71to form the probe70.

Generally, the concentration of the polymer matrix72in the organic solvent (not shown) should be in the range of 0.1 to 20% w/w, with the ratio of dye73to polymer matrix72in the range of 1:20 to 1:10,000 w/w, preferably 1:50 to 1:5,000 w/w.

The fiber optic analyte sensing needle10can be assembled by (a) attaching the needle20to a collar30with a suitable fitting40such as a Luer-Lok fitting, (b) obtaining a probe70small enough to fit within the lumen29of the needle20but large enough not to fall out through a port28in the needle20, (c) inserting the probe70into the open end (not separately numbered) of the collar30and tamping the probe70into the lumen29of the needle20until it is positioned proximate the distal tip21of the needle20, (d) coating a distal end portion of the at least one fiber optic filament50, excluding the distal tip51, with uncured sealant60, (e) threading the coated distal end portion of the fiber optic filament50through the collar30and into the lumen29of the needle20until the distal tip51of the coated fiber optic filament50is positioned proximate the probe70, and (f) allowing the sealant60to cure.

The proximal end (not shown) of the fiber optic filament50can then be connected to the necessary electronics.

The fiber optic analyte sensing needle10can be used to quickly, easily, accurately and reliably measure analyte concentration within a defined space, typically an enclosed spaced, (not shown). Briefly, the fiber optic analyte sensing needle10can be used to measure analyte concentration within a defined space (not shown) by (A) placing the distal end portion of the needle20into fluid communication with a defined space to be tested (not shown), such as by placing the distal end portion of the needle20proximate the sealing mechanism (not shown) of a modified atmosphere packaging form, fill and seal machine (not shown), or sealingly penetrating a heremtically sealed package (not shown) with the distal end portion of the needle20, and (B) ascertaining the analyte concentration within the defined space (not shown) by (i) repeatedly exposing the probe70to excitation radiation transmitted down the at least one fiber optic filament50over time, (ii) measuring radiation emitted by the excited probe70and transmitted up the at least one fiber optic filament50after at least some of the exposures, (iii) measuring passage of time during the repeated excitation exposures and emission measurements, and (iv) converting at least some of the measured emissions to an analyte concentration based upon a known conversion algorithm. Such conversion algorithms are well know to and readily developable by those with routine skill in the art.

In a similar fashion, the fiber optic analyte sensing needle10can be used to quickly, easily, accurately and reliably monitor changes in analyte concentration within a defined space, typically an enclosed spaced, (not shown). Briefly, the fiber optic analyte sensing needle10can be used to measure analyte concentration within a defined space (not shown) by (A) placing the distal end portion of the needle20into fluid communication with a defined space to be tested (not shown), such as by placing the distal end portion of the needle20proximate the sealing mechanism (not shown) of a modified atmosphere packaging form, fill and seal machine (not shown), or sealingly penetrating a heremtically sealed package (not shown) with the distal end portion of the needle20, (B) ascertaining the analyte concentration within the defined space (not shown) by (i) repeatedly exposing the probe70to excitation radiation transmitted down the at least one fiber optic filament50over time, (ii) measuring radiation emitted by the excited probe70and transmitted up the at least one fiber optic filament50after at least some of the exposures, (iii) measuring passage of time during the repeated excitation exposures and emission measurements, and (iv) converting at least some of the measured emissions to an analyte concentration based upon a known conversion algorithm, and (C) reporting at least one of (i) at least two ascertained analyte concentrations and the time interval between those reported concentrations, and (ii) a rate of change in analyte concentration within the defined space calculated from data obtained in step (B). Conversion algorithms used to convert the measured emissions to an analyte concentration are well know to and readily developable by those with routine skill in the art.

The radiation emitted by the excited probe70can be measured in terms of intensity and/or lifetime (rate of decay, phase shift or anisotropy), with measurement of lifetime generally preferred as a more accurate and reliable measurement technique when seeking to establish analyte concentration via measurement of the extent to which the dye21has been quenched by the analyte.