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
  • G01N21/75—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated
  • G01N21/76—Chemiluminescence; Bioluminescence
• • C—CHEMISTRY; METALLURGY
  • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
  • C12Q—MEASURING OR TESTING PROCESSES INVOLVING ENZYMES, NUCLEIC ACIDS OR MICROORGANISMS; COMPOSITIONS OR TEST PAPERS THEREFOR; PROCESSES OF PREPARING SUCH COMPOSITIONS; CONDITION-RESPONSIVE CONTROL IN MICROBIOLOGICAL OR ENZYMOLOGICAL PROCESSES
  • C12Q1/00—Measuring or testing processes involving enzymes, nucleic acids or microorganisms; Compositions therefor; Processes of preparing such compositions
  • C12Q1/66—Measuring or testing processes involving enzymes, nucleic acids or microorganisms; Compositions therefor; Processes of preparing such compositions involving luciferase
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
  • G01N33/48—Biological material, e.g. blood, urine; Haemocytometers
  • G01N33/50—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing
  • G01N33/58—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing involving labelled substances
  • G01N33/582—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing involving labelled substances with fluorescent label

Definitions

• the present invention relates to environmentally friendly, degradable cationic surfactants for enhancing the chemiluminescence of acridinium compounds.
• Related methods and kits are also provided.
• Chemiluminescent acridinium dimethylphenyl esters are highly sensitive labels ( Figure IB) that are used for the measurement of a wide range of clinically important analytes in automated immunoassays such as Siemens Healthcare Diagnostics' AD VIA: Centaur ® systems.
• Figure IB highly sensitive labels
• An initial treatment with 0.3 mL of 0.1 M nitric acid (also containing 0.5% hydrogen peroxide) converts the non-chemiluminescent pseudobase of the acridinium ester ( Figure 1A) to the chemiluminescent acridinium form of the label.
• CTAC cetyltrimethylammonium chloride
• Cationic surfactants such as CTAC are considered to be quite toxic to aquatic life when they are discharged into the environment (Nal ⁇ cz-Jawecki et al, Ecotoxicology and Environmental Safety, 2003, 54, 87-91; Pantani et al, Bull. Environ. Contamin.
• chemiluminescence of chemiluminescent acridinium compounds are enhanced by incorporating degradable surfactants into light triggering reagents, to a degree that is at least comparable to that of conventional surfactants such as CTAC.
• degradable surfactants such as CTAC.
• the use of these environmentally friendly surfactants in light triggering reagents for widely used acridinium labels is a green and in some embodiments, unexpectedly more effective alternative to the conventional cationic surfactant CTAC.
• a method of enhancing chemiluminescence from a chemiluminescent label comprising contacting a chemiluminescent label with an acid and hydrogen peroxide in the presence of a degradable cationic surfactant having formula I:
• X is nitrogen or phosphorus
• R 1 , R 2 and R 3 are each independently selected from hydrogen and an alkyl, alkenyl, alkynyl, cycloalkyl or aralkyl group optionally having one or more heteroatoms;
• R 4 and R 5 are each independently selected from an alkyl, alkenyl, alkynyl, cycloalkyl or aralkyl group optionally having one or more heteroatoms;
• Y is a cleavable linkage
• a " is an anionic counterion to X + .
• the chemiluminescent label can be an acridinium dimethylphenyl ester, an acridinium sulfonamide, or a derivative or conjugate thereof.
• the acid can be nitric acid.
• the method can further include compressing light emission time of said chemiluminescent label, thereby providing a compressed emission time than a standard emission time without surfactants, wherein said compressed emission time is comparable to that of cetyltrimethylammonium chloride.
• the compressed emission time may be shorter (e.g., about 20%, about 30% or about 50% shorter) than that of cetyltrimethylammonium chloride.
• the surfactant of the present invention is as effective as cetyltrimethylammonium chloride in enhancing total light yield of the chemiluminescent label.
• the method can further include increasing chemiluminescence of said chemiluminescent label, thereby providing an increased light emission than a standard light emission without surfactants, wherein said increased light emission is comparable to that of cetyltrimethylammonium chloride.
• said increased light emission may be at least about 2.5 fold enhancement compared to the standard light emission without surfactants.
• said enhancement can be at least about 70%, at least about 80% or at least about 90% that of cetyltrimethylammonium chloride.
• the surfactant of the present invention is at least as effective as cetyltrimethylammonium chloride in compressing emission time of the chemiluminescent label.
• R 1 , R 2 and R 3 can be each independently a C 1-10 alkyl, C2-10 alkenyl, C 2-10 alkynyl, C 3-10 cycloalkyl or C4-10 aralkyl group optionally having one or more heteroatoms.
• R 4 can be a Ci_ 2 o alkyl, C2-20 alkenyl, C2-20 alkynyl, C3-20 cycloalkyl or C 4- 20 aralkyl group optionally having one or more heteroatoms.
• R 5 can be a Ci_ 3 o alkyl, C 2 _ 3 o alkenyl, C 2 _ 3 o alkynyl, C 3 _ 3 o cycloalkyl or C 4 - 3 o aralkyl group optionally having one or more heteroatoms.
• Y can be degradable under hydrolytic conditions.
• Y can be selected from a carbonate linkage, an amide linkage, an ester linkage, or any combination thereof.
• a " can be chloride, bromide, iodide, sulfate, sulfonate or hydroxide ion.
• the surfactant of the present invention can be compound 1 or 2 or a mixture thereof:
• an immunoassay kit comprising:
• a chemiluminescent label having an acridinium dimethylphenyl ester, an acridinium sulfonamide, or a derivative or conjugate thereof;
• an acidifying reagent comprising an acid, hydrogen peroxide and a degradable cationic surfactant having formula I:
• the chemiluminescent label can be an acridinium dimethylphenyl ester, an acridinium sulfonamide, or a derivative or conjugate thereof.
• the surfactant of the present invention when in use, can provide a compressed emission time of the chemiluminescent label than a standard emission time without surfactants, wherein said compressed emission time is comparable to (e.g., about the same as, or about 20%, about 30% or about 50% shorter than) that of cetyltrimethylammonium chloride.
• the surfactant of the present invention when in use, can exhibit an increased light emission of the chemiluminescent label compared to a standard light emission without surfactants, wherein said increased light emission is comparable to (e.g., at least about 70%>, at least about 80%> or at least about 90%>) that of cetyltrimethylammonium chloride.
• the acid can be nitric acid.
• the alkaline hydroxide may be sodium hydroxide.
• Figure 1A Acridinium-pseudobase equilibrium of an N-sulfopropyl acridinium dimethylphenyl ester.
• Figure IB Structures of chemiluminescent acridinium dimethylphenyl ester labels containing N-sulfopropyl groups in the acridinium ring that are used in automated immunoassays in Siemens Healthcare Diagnostics' ADVIA:Centaur ® systems.
• Figure 3 Exemplary synthetic scheme for cationic surfactant 1 with cleavable amide linkage.
• Figure 4 Exemplary synthetic scheme for cationic surfactant 2 with cleavable carbonate linkage.
• Figure 6 Chemiluminescence emission profiles of anti-TSH antibody conjugate of acridinium ester 3b in the absence and presence of cationic surfactants.
• Figure 7 Chemiluminescence emission profiles of anti-TSH antibody conjugate of acridinium ester 3c in the absence and presence of cationic surfactants.
• the present invention relates to methods of enhancing chemiluminescence from a chemiluminescent label comprising contacting a chemiluminescent label with an acid and hydrogen peroxide in the presence of a degradable cationic surfactant.
• Related kits containing such degradable cationic surfactant are also provided.
• the degradable cationic surfactant can compress light emission time of the chemiluminescent label to an extent that is comparable to or shorter than conventional surfactants.
• the degradable cationic surfactant can also increase chemiluminescence of the chemiluminescent label, providing increased light emission that is comparable to conventional surfactants.
• the present invention introduces cleavable linkages between the quaternary head group and the alkyl chain of cationic surfactants.
• cationic surfactants containing cleavable linkages e.g., carbonate or amide
• CTAC chemiluminescence from acridinium esters.
• the use of these environmentally friendly surfactants in light triggering reagents for widely used acridinium labels is a green alternative to the conventional cationic surfactant CTAC.
• the term "about” means within 20%, within 10% or within 5%.
• the term "comparable” as used herein, means that a property of a first compound (e.g., a first surfactant) is about the same, or similar or equivalent to that of a second compound (e.g., a second surfactant).
• a property e.g., compressed emission time or increased light emission
• cetyltrimethylammonium chloride it is meant that such property is about the same as cetyltrimethylammonium chloride, the difference being within 20%, within 10% or within 5%.
• the green surfactant of the present invention may exhibit better properties in light emission than cetyltrimethylammonium chloride.
• surfactant refers to compounds that lower the surface tension of a liquid, the interfacial tension between two liquids, or that between a liquid and a solid.
• Surfactants typically are chemicals that are amphipathic, which means that they contain both hydrophobic "head” and hydrophilic "tail” groups. Most commonly, surfactants are classified according to polar head group.
• a non-ionic surfactant has no charge groups in its head. The head of an ionic surfactant carries a net charge. If the charge is negative, the surfactant is more specifically called anionic; if the charge is positive, it is called cationic. If a surfactant contains a head with two oppositely charged groups, it is termed zwitterionic.
• a "micelle” is an aggregate of surfactant molecules dispersed in a liquid colloid.
• a typical micelle in aqueous solution forms an aggregate with the hydrophilic head regions in contact with surrounding solvent, sequestering the hydrophobic tail regions in the micelle center.
• This type of micelle is known as a normal phase micelle (oil-in- water micelle).
• Inverse micelles have the head groups at the center with the tails extending out (water-in-oil micelle).
• Micelles may form when the concentration of surfactant is greater than the critical micelle concentration (CMC).
• CMC critical micelle concentration
• Micelles can exist in different shapes, including spherical, cylindrical, and discoidal.
• the main objective of the present invention is the elimination of the cationic surfactant CTAC and its replacement with more environmentally friendly, cationic surfactants in light triggering reagents for chemiluminescent acridinium labels.
• the structure of a degradable cationic surfactant for enhancing the chemilummescence of acridinium ester labels can be represented by the following formula (I):
• X is nitrogen or phosphorus
• R 1 , R 2 and R 3 are each independently selected from hydrogen and an alkyl, alkenyl, alkynyl, cycloalkyl or aralkyl group optionally having one or more heteroatoms
• R 4 and R 5 are each independently selected from an alkyl, alkenyl, alkynyl, cycloalkyl or aralkyl group optionally having one or more heteroatoms
• Y is a cleavable linkage
• a " is an anionic counterion.
• the structure of a degradable cationic surfactant for enhancing the chemilummescence of acridinium ester labels can be represented by the following formula (II):
• R , R and R can be the same or different.
• R , R and R can be each independently a Ci_io alkyl, C2-10 alkenyl, C 2 _io alkynyl, C3-10 cycloalkyl or C4_io aralkyl group optionally having one or more heteroatoms (e.g., methyl, ethyl, propyl or butyl);
• R 4 can be a Ci_ 2 o alkyl, C 2 _ 2 o alkenyl, C 2 _ 2 o alkynyl, C 3 _ 2 o cycloalkyl or C 4 _ 2 o aralkyl group optionally having one or more heteroatoms.
• R 4 can be an alkyl chain comprising 2-4 carbons;
• R 5 can be a Ci_ 30 alkyl, C 2 _ 30 alkenyl, C 2 _ 30 alkynyl, C 3 _ 30 cycloalkyl or C 4 _ 30 aralkyl group optionally having one or more heteroatoms.
• R 5 can be straight or branched alkyl chain (e.g., 10-16 carbons);
• a " can be an anion selected from chloride, bromide, iodide, sulfate, sulfonate or hydroxide ions.
• he structure of a degradable cationic surfactant for enhancing the chemiluminescence of acridinium ester labels can be represented by the following formula (III):
• R 1 , R 2 , R 3 , R 4 , R 5 and A can have the same definitions as above.
• the acridinium esters whose chemiluminescence can be enhanced by the degradable cationic surfactants can be represented by the following formula:
• R 6 , R 7 , Rs and R9 can be alkyl, alkenyl, alkynyl or aralkyl groups containing 0-20 heteroatoms; Rio and Rn can be hydrogen, alkyl, alkenyl, alkynyl or aralkyl groups containing 0-20 heteroatoms.
• Other suitable acridinium compounds include those described in U.S. Patent Nos. 8,293,908; 8,119,422; 7,875,467; 7,785,904; 7,611,909; and 7,459,284; and U.S. Pub. Nos. 2012/0225497, 2010/0256380 and 2010/0099077; all of which are hereby incorporated herein by reference in their entirety.
• cationic surfactants such as cetyltrimethylammonium chloride (CTAC)
• CCTAC cetyltrimethylammonium chloride
• degradable cationic surfactants are advantageous because they are rapidly degraded under both aerobic and anaerobic conditions and therefore pose a significantly lower risk when discharged into the environment.
• These cationic surfactants are also useful for enhancing the chemiluminescence of other labels such as acridinium sulfonamides whose light emission pathway is identical to that of acridinium esters.
• one aspect of the present invention relates to a method of enhancing chemiluminescence from a chemiluminescent label comprising contacting a chemiluminescent label with an acid and hydrogen peroxide in the presence of a degradable cationic surfactant described herein.
• the method can further include compressing light emission time of the chemiluminescent label, thereby providing a compressed emission time than a standard emission time without surfactants.
• Such compressed emission time can be comparable to that of cetyltrimethylammonium chloride.
• the compressed emission time may be shorter (e.g., about 20%, about 30%> or about 50% shorter) than that of cetyltrimethylammonium chloride.
• the surfactant of the present invention can be as effective as cetyltrimethylammonium chloride in enhancing total light yield of the chemiluminescent label.
• the method can further include enhancing chemiluminescence of said chemiluminescent label, thereby providing an increased light emission than a standard light emission without surfactants.
• Such increased light emission can be comparable to that of cetyltrimethylammonium chloride.
• said increased light emission may be at least about 2.5 fold enhancement compared to the standard light emission without surfactants.
• such enhancement can be at least about 70%, at least about 80% or at least about 90% that of cetyltrimethylammonium chloride.
• the surfactant of the present invention can be at least as effective as cetyltrimethylammonium chloride in compressing emission time of the chemiluminescent label.
• an immunoassay kit comprising:
• a chemiluminescent label having an acridinium dimethylphenyl ester, an acridinium sulfonamide, or a derivative or conjugate thereof;
• an acidifying reagent comprising an acid and a degradable cationic surfactant described herein;
• an oxidizing reagent comprising alkaline hydrogen peroxide.
• the surfactant of the present invention when in use, can provide a compressed emission time of the chemiluminescent label than a standard emission time without surfactants. Such compressed emission time may be comparable to (e.g., about the same as, or about 20%, about 30% or about 50% shorter than) that of cetyltrimethylammonium chloride.
• the surfactant of the present invention when in use, can alternatively or additionally exhibit an increased light emission of the chemiluminescent label compared to a standard light emission without surfactants, such that the increased light emission may be comparable to (e.g., at least about 70%, at least about 80% or at least about 90%) that of cetyltrimethylammonium chloride.
• degradable cationic surfactants such as those containing cleavable amide and carbonate linkages are at least as effective as conventional cationic surfactants such as CTAC in enhancing the chemiluminescence of widely used acridinium ester labels. It was also surprisingly discovered that degradable cationic surfactants can be more effective in accelerating light emission than CTAC.
• the degradable surfactants show excellent stability in acidic solution and are environmentally friendly alternatives to CTAC. These surfactants are also useful in enhancing the luminescence of other labels such as acridinium sulfonamides. Because perturbations of chemical reactions rely on the ability of surfactants to increase the local concentrations of reactants and/or alter the polarity of the reaction medium, degradable surfactants can serve as benign alternatives to conventional surfactants for such applications.
• Palmitic acid i, 2.564 g, 10.00 mmoles
• toluene 100 mL
• N,N- dimethylethylenediamine 1.147 mL, 10.50 mmoles
• the reaction mixture was concentrated to dryness which gave 3.21 g of a slightly yellow solid.
• the crude solid was re-crystallized from dry acetone (75 mL).
• the desired product ii (1.83g) was obtained as white, needle-like crystals.
• the conjugates were stored at 4°C in buffer and chemilummescence from each conjugate was measured in the absence of surfactant and in the presence of CTAC as well as cationic surfactants 1 and 2 (Tables 1-3, Figures 5-7).
• the ability of each surfactant to (a) increase total light output and (b) accelerate emission kinetics was evaluated over a period of 80 days.
• Each chemilummescence flash curve was measured in 240 intervals of 0.5 second (120 seconds total time). Each chemilummescence reaction was carried out a minimum of three times, averaged and converted to a percentage of the chemilummescence accumulated up to each time interval. The output from the luminometer instrument was expressed as R.L.U.s (Relative Light Units).
• Table la shows that surfactant 2 is as effective as CTAC within at least the first 10 days in enhancing chemiluminescence (i.e., the fold of increased light emission by surfactant 2 is the same as CTAC). Even at day 80, the fold of increased light emission using surfactant 2 remains to be about 80% (2.8/3.5) of CTAC. Similarly, the fold of increased light emission using Surfactant 1 is about 89% (3.1/3.5) on day 1, and 74% (2.6/3.5) on day 80 compared to CTAC. Thus, both surfactants 1 and 2 are comparable to CTAC in enhancing chemiluminescence.
• the two cationic surfactants 1 and 2 proved to be quite stable in Reagent 1 (0.5 % peroxide in 0.1 M nitric acid) as evidenced by little loss in their ability to enhance chemiluminescence from the acridinium ester antibody conjugates even after 80 days at room temperature.
• both surfactants 1 and 2 were very effective in accelerating light emission from the acridinium ester antibody conjugates (Tables lb, 2b and 3b, Figures 5-7). In the absence of surfactant, times for emission of > 90% light from the conjugates of 3a, 3b and 3c were observed to be 57.5 seconds, 49.5 seconds and 62.5 seconds respectively. In the presence of CTAC or the two cationic surfactants 1 and 2, emission times were compressed to ⁇ 3 seconds for the conjugates of all three acridinium ester labels. Surprisingly, surfactants 1 and 2 are more effective than CTAC in accelerating light emission.
• both surfactants 1 and 2 accelerated emission kinetics of acridinium ester 3a from 57.5 seconds to 1.0 second, while CTAC was 1.5 seconds.
• the ability of the two cationic surfactants 1 and 2 to accelerate light emission did not diminish even after 80 days of storage at room temperature as also illustrated in the chemiluminescence emission profiles of the conjugates ( Figures 5-7).
• the present invention provides among other things green surfactants and their use in enhancing chemiluminescence. While specific embodiments of the subject invention have been discussed, the above specification is illustrative and not restrictive. Many variations of the invention will become apparent to those skilled in the art upon review of this specification. The full scope of the invention should be determined by reference to the claims, along with their full scope of equivalents, and the specification, along with such variations.

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