The present invention relates to the field of diagnosis or prognosis. In particular, it relates to compositions useful in the implementation of immunoassays, including as a stabilizer and / or blocking.

STATE OF THE ART

Immunoassays are commonly used in the fields of clinical analysis, food, pharmaceutical and chemical. Thus, they are intended to determine the presence of one or more analytes in samples which may contain them. The immunoassay is a widely known test the Expert involving specific interactions between the analyte to be detected and one or more partner (s) link to this analyte. Examples of such immunoassays include methods such as ELISA (Enzyme Linked Immuno Sorbent Assay), ELFA (Enzyme Linked Florescent Assay) and RIA (radioimmunoassay) that can operate on the principle of "sandwich" , or according to the principle of "competition", and immunodetection methods such as immunohistochemistry, immunocytochemistry, immunofluorescence, Western blotting and Dot blotting. The methods in "competition" are usually used for small molecules such as haptens, "sandwich" methods being used for other analytes.

Immunoassays include contacting the sample device that is capable of containing an analyte with at least one labeled binding partner or a competitive reagent to the labeled analyte. Said binding partner or competition reagent is for example formed of an antibody conjugated to a label capable of providing a signal. These reagents can be placed in solution and kept in a diluent before the implementation of the immunoassay.

Whatever type of interactions detected, adsorption on the solid matrix, the binding partner or the competition reagent, reagents which are not directly attached to it, can help generate background noise . It is therefore essential to reduce the non-specific interactions to reduce as much as possible the noise.

This is done using a blocking agent or saturating agent whose function is to saturate the sites after the adsorption.

Reactive diluents for immunoassay may thus comprise blocking agents and / or stabilizers on the one hand to stabilize the reagents (conjugates markers) and secondly to reduce non-specific interactions of the reagent, for example with the solid matrix, the binding partners and / or competition reagent.

These blocking agents are preferably selected from animal or human proteins, including animal serum, skim milk, including powder, caseins hydrolysed or not, the bovine albumin, human and gelatins.

These bio-based products, and in particular animal or human, have the drawback of having a variable composition depending on the batch. Indeed, for animal sera, their composition may vary depending on the species, breed, sex, and diet (seasonal variation). For purified proteins such as bovine albumin for example, depending on the purification method used is dependent on the provider, the quality of these proteins is variable. Contaminations, such as the presence of proteases, bovine immunoglobulins or other molecules in amounts more or less important, are the cause of changes in the background noise. These raw materials of human or animal origin retain their stabilizing power but the power blocking is variable from one batch to the other. In addition, their implementation must follow safety standards for biological hazards and also have constraints in terms of supply, source storage products and handling. Therefore, to overcome these drawbacks, it would be advantageous to use stabilizers and / or synthetic blocking agents useful in compositions for immunoassays, especially in reactive diluents to immunoassays, such as labeled antibodies.

Amphoteric copolymers of 2-methacryloyloxyethyl phosphorylcholine, are described as stabilizers and / or blocking agents in ELISA-type immunoassays (Sakaki et al, 1999 J.Biomed.Mater.Res, 47, 523;. Sakaki et al, 2000, Polymer Journal, Vol 32, No. 8, pp 637-641). Copolymers of 2-methacryloyloxyethyl phosphorylcholine are marketed by NOF Corporation under the name

Commercial Biolipidure ™ or Lipidure®. They are presented as an alternative to bovine albumin in particular to reduce the non-specific interactions and / or stabilize -marqués antibodies (EP1314982 A).

Patent applications WO 98/27434 and WO2008 / 058963 disclose the use of amphiphilic polymers as solvent and stabilizing agent of membrane proteins or in targeting of applications. The use of these compounds, the family amphipols, as stabilizer of therapeutic antibodies has also been described in the application WO2010 / 073119.

The Applicant has now demonstrated that a composition comprising the combination of a combined amphipol and an amphoteric copolymer of (meth) acrylate comprising at least one phosphorylcholine group can be advantageously used as a stabilizing agent and / or blocking reagents including replacing some stabilizers and / or blocking animal conventionally used.

Further, and most surprisingly, the Applicant has demonstrated that the use of these compositions according to the invention in an immunoassay test is used to substantially reduce background noise signal thereby contributing to increase the sensitivity test, while maintaining the stability of the reagents over time.

RESUME

Thus, the present invention relates to a composition for immunoassay, comprising at least (i) a amphipol and (ii) an amphoteric copolymer based on monomers of (meth) acrylate, a portion of these monomers having a phosphorylcholine group.

In particular, Γ amphipol can be an amphiphilic polymer comprising a homopolymer or copolymer of maleic anhydride or acrylate onto which are grafted at least one hydrophobic group and a hydrophilic group, and an average molecular weight between 1000 and 100 000 , preferably between 4 000 and 70 000 g mol "1 .

In a specific embodiment, amphipol is selected from poly (anhydride-alt-1-octadecene maleic), poly (anhydride-alt-maleic l-tetradecene), poly (anhydride-alt- 1-decene maleic) being substituted by a hydrophilic group, for example an alkyl ammonium, and in particular the 3- (dimethylamino) -l-propylamine.

In another specific embodiment, optionally combined with the previous specific embodiments, the composition according to the invention is characterized in that the amphoteric copolymer is an amphoteric-based monomer 2-methacryloyloxyethyl phosphorylcholine (MPC) and another methacrylate monomer functionalized with a hydrophobic group, an anionic group, a cationic group or a group for forming one or more hydrogen bonds.

In a specific embodiment, the amphoteric copolymer is an amphoteric-based MPC and methacrylate functionalized with a hydrophobic group selected from

the linear or branched C 4 to C 30;

linear or branched C 4 to C 30 comprising at least one cycloalkyl; - hydro carbon chains of C 4 to C 30 comprising at least one double bond; hydro carbon chains of C 4 to C 30 comprising at least one triple bond; or, hydro carbon chains of C 4 to C 30 comprising at least one aromatic ring.

For example, these are the ™ or Lipidure® Biolipidures, eg Biolipidure ™ 206 sold especially by NOF Corporation.

The invention also provides an aqueous solution comprising the compositions according to the invention and at least one reactive immunoassay. In particular, in a preferred embodiment, the aqueous solution according to the invention is characterized in that it does not comprise a stabilizing agent and / or blocking of human or animal origin agent, for example selected from animal sera, skim milk, in particular skimmed milk powder, caseins hydro lysed or not, bovine or human albumin and gelatins.

The invention further kits immunoassay comprising at least one aqueous solution according to the invention and at least one binding partner to an analyte to be detected or quantified by immunoassay and, if appropriate, the compounds required to set detection of a specific interaction or binding partners and the analyte.

The aqueous compositions and solutions of the invention are useful in particular to reduce non-specific interaction between

i. at least one binding partner for detecting or quantifying an analyte in a biological sample liable to contain it, for example, a labeled binding partner, and

ii. a solid phase.

Or they are useful in reducing the non-specific interaction between

i. a positive control for the immunoassay, a standard immunoassay and / or an adjuster of the immunoassay, and

ii. a solid phase.

Finally, the invention provides a method of immunoassay by determining the presence or quantification of a target analyte in a biological sample liable to contain it, comprising contacting said sample with at least two binding partners to said analyte, PI and P2, sequentially or simultaneously, one of the two partners being labeled P2 to reveal the presence of said analyte, if present, the other IP partner is preferably immobilized on a solid phase, and said labeled P2 partner being contained in at least one composition or aqueous solution according to the invention, to form optionally a Pl / analyte complex / P2, the revelation of the presence of said complex formed to conclude to the presence or amount of analyte in the 'sample.

It also relates to a method of immunoassay by determining the presence or quantification of a target analyte in a biological sample liable to contain it, comprising contacting said sample with at least one analyte to said binding partner and a reagent PI RI competition to the analyte, said PI binding partner is preferably immobilized on a solid phase, said reagent being labeled IR for indirectly revealing the presence of said analyte, and said RI reagent being contained in at least one composition or aqueous solution according to the invention, to form a Pl / Rl complex, revealing the presence of said complex formed to indirectly enter the absence or quantity of analyte in the sample.

DETAILED DESCRIPTION

The Applicant has therefore developed against all odds compositions for immunoassay to replace animal macromolecules conventionally used in the reactive diluents for immunoassay.

The compositions for immunoassay according to the invention include (i) a amphipol and (ii) an amphoteric copolymer based on monomers of (meth) acrylate, a portion of these monomers having a phosphorylcholine group or more generally a group of formula (III) described later, for example a part of this monomer is the monomer of MPC (2-Méthacryloyloxyléthyl-phosphorylcholine).

amphipols

For the purposes of the invention, the term "amphipol" refers to the family courts and flexible amphiphilic polymers and described in particular in magazines and Zoonens Popot, 2014 (J. Membrane Biol 2014, 247 (0). 759- 796) and Zoonens et al, 2014 (I. Mus-Veteau (ed.), Membrane proteins Production for Structural Analysis, © Springer Science + business Media New York 2014, "Chapter 7 Amphipols: A General Introduction and Some Protocols" on page 173 -203).

In a particular embodiment, the amphipols used in the compositions according to the invention are chosen from amphiphilic polymers comprising a homopolymer or copolymer of maleic anhydride or polyacrylate, onto which are grafted at least one hydrophobic group and a hydrophilic group, and an average molecular weight between 1000 and 100 000 g / mol, preferably between 4000 and 70 000 g / mol.

The first amphipols described in the prior art are polyacrylate polymers where some carboxylate functional groups are functionalized with octylamine, or isopropyl lamine.

In a particular embodiment, the amphipols used in the compositions of the invention are amphiphilic polymers, as described in WO 98/27434, and in particular amphipol of formula (I):

(I)

in which

- R4, R5, 5 identical or different are a hydrogen atom or the methyl radical, - R13, R14 are identical or different linear alkyl or alkenyl or branched of 6 to 12 carbon atoms, and further the one of the two can correspond to a hydrogen atom,

- Ri6, R17 is a radical (Ci -C 5 ) alkyl, and most one of the two can correspond to a hydrogen atom,

x, y, z correspond to the respective percentages of the units,

- x being between 20 and 90%

- y being between 10 and 80%

- z being between 0 and 60%,

the average molecular weight being between 500 and 100 000 g / mol, preferably less than or equal to 50 000 g / mol, preferably between 1000 and 50 000 g / mol.

All molecular weights are given by weight.

Among the alkyl radicals R 13 to R 14, mention is made especially the radicals n-hexyl, -n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, the radicals C 6 -C 2 having a secondary carbon or a tertiary carbon.

Among the alkenyl radicals R 3 to R 4, mention is made especially linear radicals C 6 -Ci2 mentioned above having one or two double bonds or the same groups having a secondary carbon or a tertiary carbon.

Among the alkyl radicals R 6 to Rn, mention is made especially ethyl, isopropyl, n-propyl, n-butyl, isobutyl, sec-butyl, t-butyl, n-pentyl, sec-pentyl, t-pentyl, isopentyl.

The acrylic polymers of amphiphilic nature of formula (I) are obtained in known manner from precursors acrylic polymers, may be available commercially or synthesized by polymerizing monomers of acrylic acid or methacrylic acid or a mixture of these monomers.

In the latter case, the copolymer is obtained which, by extension, are included in the generic term "polymer".

The acrylic polymers of amphiphilic nature of formula (I) result from the reaction of compounds R13R14NH and optionally R16R17NH with an acrylic polymer, which leads to a random distribution of the amide throughout the chain. The polymer is previously or in a subsequent step, placed in the salified form. Such a synthesis method is described for example in March, J. (1985 Advanced Organic Chemistry: Reactions, Mechanisms and Structure, pp 372-374 (Wiley, New York); Wang, TK, Iliopoulos, 1. Audebert & R. . (1988) Polym. Bull 20, 577-582.) and also described in WO 98/27434 which is incorporated by reference.

The following indicates embodiments of amphipols of formula (I) above:

- In a first variant, R13, R14 correspond to a hydrogen atom or a linear alkyl radical of 6 to 12 carbon atoms, R13, R14 can not be simultaneously hydrogen, R13 or R14 preferably is an n-octyl radical, the other radical R14 or R13 being a hydrogen atom.

- According to a second alternative, R 6 , R 17 correspond to an alkyl radical selected from a group consisting of isopropyl, isobutyl or a hydrogen atom, R 6 , R 17 can not simultaneously correspond to a hydrogen atom ,

- According to a third variant

x is between 30 and 80%

y is between 20 and 70%

z is between 0 and 50%,

- According to a fourth variant, the acrylic polymer of amphiphilic nature is chosen from the group consisting of polymers in which

M + is Na + or K +

R1 is n-octyl, R 14 is H

x is between 70 and 80%

y is between 20 and 30%

z is 0%

The average molecular weight is between 2000 and 50000 g / mol.

- According to a fifth variant, the acrylic polymer of amphiphilic nature is chosen from the group consisting of polymers in which

M + is Na + or +

R13 is n-octyl, R 14 is H

Ri6 is isopropyl, R is H

x is between 30 and 40%

y is between 20 and 30%

z is between 30 and 50%

The average molecular weight is between 2000 and 50000 g / mol.

In a particular embodiment, the polymer is amphipol A8-35 of formula (Ia) below:

x, y, z correspond to the respective percentages of the units,

- x being between 34 and 36%, preferably about 35%,

- y being between 24 and 26%, preferably about 25%,

- z is between 38 and 42%, preferably about 40%,

the average molecular weight being between 4000 and 4600 g / mol, preferably about 4300 g / mol.

In another specific embodiment, amphipol used in the compositions according to the invention is chosen from poly (maleic anhydride) onto which are grafted at least one hydrophobic alkyl chain and at least one hydrophilic group.

Preferably, it is a polymer of formula (II)

(H)

wherein Z is a divalent radical, preferably O, S or NH, R 7 is a hydrophilic group, preferably an alkyl ammonium, and R 8 a hydrophobic group, for example a linear carbon chain.

In a particular embodiment, the hydrophilic group R 7 is selected from functional groups such as amines, alcohols or ketones.

The average molecular weight of these poly (maleic anhydride) is preferably between 1 000 and 70 000 g / mol, more preferably between 10 000 and 20 000 g / mol.

In another specific embodiment, the hydrophilic group is a carboxylate group or a positively charged group, preferably an ammonium, for example an alkyl ammonium having the following formula: - (CH 2 ) n -NH (CH 3 ) 2 with n being between 2 and 6, for example 3- (dimethylamino) -l-propylamine.

Ammonium alkyl is preferably attached to maleic anhydride by an amide, ester or thioester, preferably an amide function.

The hydrophobic alkyl chain is selected preferably from linear chains of formula - (CH 2 ) n - with n greater than or equal to 4, preferably greater than or equal to 6, preferably greater than or equal to 8, and for example including between 4 and 16, preferably between 8 and 12.

These maleic anhydride polymers may be chosen in particular from the poly (anhydride-alt-maleic l-octadecene), poly (anhydride-alt-maleic l-tetradecene) and poly (anhydride-alt-maleic l-decene) substituted with a hydrophilic group, preferably a positively charged group as defined above, including alkylated ammonium, such as 3- (dimethylamino) -l-propylamine.

In a specific embodiment, amphipol used according to the invention is the poly (anhydride-a / t-maleic tetradecene) substituted of formula (IIa) below:

(Lia)

and average molecular weight between 10 000 and 14 000 g / mol, for example about 12 000 g / mol.

In another specific embodiment, amphipol used according to the invention is the poly (anhydride-a / t-decene maleic) substituted of formula (IIb) below:

and average molecular weight between 16 000 and 20 000 g / mol, for example about 18 500 g / mol.

In another specific embodiment, amphipol used according to the invention is the poly (anhydride-a / t-octadecene) substituted of formula (IIc) below:

and average molecular weight between 39 000 and 65 000 g / mol.

In a preferred embodiment, amphipol is selected from C12 PMAL (CAS: [869857-14-7]), the PMAL C8 (CAS: [869856-84-8]) and the PMAL C16 (n CAS RN: [869857-16-9]).

Some of these polymers amphipols including the PMAL series (e.g. PMAL Cl 2, PMAL PMAL C8 and Cl 6) are manufactured and marketed by the company Anatrace.

Amphoteric polymers

The compositions according to the invention comprise a amphipol as described above, in combination with an amphoteric copolymer based on monomers of (meth) acrylate, one part comprising a group of formula (III):

and wherein n is an integer from 1 to 6 (preferably 2),

Ri, Pv 2 , P 3, identical or different, independently represent hydrogen or alkyl of 1 to 6 carbons, substituted or unsubstituted, preferably Ri, R 2 and R 3 are methyl.

For example, Ri, R 2 and R 3 according to formula (IV) may be methyl, ethyl, propyl, butyl, isobutyl, pentyl, hexyl. The number of alkyl substituents is 1 to 3 and the substituents include hydroxy or aryl. The aryl includes benzyl or naphthyl.

The average molecular weight of the amphoteric copolymers used according to the invention is preferably between 100 and 1 000 000 g / mol, for example between 1 000 and 500 000 g / mol.

In addition, the amphoteric copolymers include a polymer prepared by polymerizing a monomer comprising a group of formula (III) with another polymerizable monomer.

In a specific embodiment, the monomer comprising a group of formula (III) is a monomer comprising phosphorylcholme and a vinyl group include 2-acryloyloxyethyl phosphorylcholme, 2-methacryloyloxyethyl phosphorylcholme (described below under the abbreviation MPC ), 2- (meth) acryloyloxyéthoxyéthyl phosphorylcholme, 6-meth (acryloyloxyhexyl phosphorylcholme, 10- (meth) acryloyloxyéthoxynonyl phosphorylcholme, allyl phosphorylcholme, the butenyl phosphorylcholme the phosphorylcholme hexenyl, octenyl phosphorylcholme, the decenyl phosphorylcholme . These monomers may be prepared according to known methods described in particular in Japanese patent application No.6325 / 79 and No. 154591/83.

The other polymerizable monomer includes (meth) acrylate such as methyl (meth) acrylate, (meth) acrylate, (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, tridecyl méthacrylate2-d'hydroxyéthyle; a styrene monomer such as styrene, alpha-methyl styrene, styrene having a phenyl group substituted with the (or several) group (s) methyl group (s) and styrene having a phenyl group substituted by chlorine; preferably it is functionalized methacrylate.

These polymers and their synthesis are described in the patent application EP 1314982 Al.

In particular, in a specific embodiment, use of amphoteric polymers based on monomers of (meth) acrylate, a portion of such monomers comprising a group phosphorylcholme.

The percentage of the monomers comprising phosphorylcholme group is preferably between 1 and 100%, for example between 1 and 50% or between 5 and 10%.

Preferably, it is an amphoteric copolymer based on 2-methacryloyloxyethyl phosphorylcholme (MPC), in particular a methacrylate monomer comprising a phosphorylcholme group and another methacrylate monomer having a hydrophobic group, an anionic group, a cationic group and / or a group permitting the formation of hydrogen bonds.

A hydrophobic group is selected from

the linear or branched C 4 to C 30;

linear or branched C 4 to C 30 comprising at least one cycloalkyl; hydro carbon chains of C 4 to C 30 comprising at least one double bond; - hydro carbon chains of C 4 to C 30 comprising at least one triple bond; or, hydro carbon chains of C 4 to C 30 comprising at least one aromatic ring.

Preferably, the hydrophobic group is selected from linear alkyl chains of the formula - (CH 2 ) n - with n greater than or equal to 4, preferably greater than or equal to 6, preferably greater than or equal to 8, and for example including between 4 and 16, preferably between 8 and 12.

An anionic group can be chosen in particular from those comprising a carboxylate radical, especially alkyl carboxylates (C 1 -C 5 ), those comprising a sulfonate radical, especially alkyl sulfonates (C 1 -C 5 ), and those comprising a phosphonate radical, and in particular alkylphosphonates (C 1 -C 5 ).

A cationic group can be chosen in particular from a (CH 2 ) n -NR 9 RioRn, n being an integer from 1 to 5 and R 9 , Rio and R, identical or different, being hydrogen or an alkyl chain ( Ci-C 4 ).

The compounds used to form hydrogen bonds are widely known to the Expert. An example of a group for hydrogen bond formation includes amines, alcohols, thiols, aldehydes, acids or ketones.

MPC preferred copolymers are marketed in particular by NOF Corporation under the trade name of Lipidure® or Biolipidure® and particularly of general formula (IV):

wherein R is a hydrophobic group as defined above, with m and n corresponding to the respective percentages of the two monomers, and m is between 1 and 99%, for example between 1 and 50% or between 1 and 10%>, and n is between 1 and 99%, for example between 50 and 99% or between 90 and 99%.

In a more specific embodiment, the amphoteric polymer of 2-methacryloyloxyethyl phosphorylcholine (MPC) is an amphoteric copolymer of MPC and methacrylate functionalized with a linear alkyl chain of formula (CH 2 ) n - with n greater than or equal to 4, or greater than or equal to 6, or greater than or equal to 8, and for example between 4 and 16, for example between 8 and 12.

CLAIMS

A composition for immunoassay, comprising at least (i) a amphipol selected from

- poly (maleic anhydride) onto which are grafted at least one hydrophobic alkyl chain and at least one hydrophilic group of average molecular weight between 1 000 and 100 000 g / mol, preferably between 4000 and 70 000 g / mol , or,

- amphipols of formula (I):

(I)

in which

- R4, R5, 5 identical or different are hydrogen or methyl,

- R13, R14 are identical or different linear alkyl or alkenyl or branched of 6 to 12 carbon atoms, and in addition one of the two can correspond to a hydrogen atom,

- Ri6, R17 is a radical (Ci -C 5 ) alkyl, and most one of the two can correspond to a hydrogen atom,

x, y, z correspond to the respective percentages of the units,

- x being between 20 and 90%

- y being between 10 and 80%

- z being between 0 and 60%,

the average molecular weight being between 500 and 100 000 g / mol, preferably less than or equal to 50 000 g / mol, preferably between 1000 and 50 000 g / mol,

and (ii) an amphoteric copolymer based on monomers of (meth) acrylate, a portion of these monomers having a phosphorylcholine group.

2. Composition according to claim 1, characterized in that said hydrophobic alkyl chain is a linear alkyl chain of formula (CH2) n - where n is an integer greater than or equal to 4, preferably greater than or equal to 6, preferably greater than or equal to 8, and for example between 4 and 16, preferably between 8 and 12.

3. Composition according to one of the preceding claims, characterized in that the hydrophilic group is a carboxylate group or a positively charged group, particularly an alkyl ammonium, e.g., 3- (dimethylamino) -l-propylamine.

4. Composition according to any one of claims 1 to 3, characterized in that the amphipol is selected from poly (anhydride-alt-maleic l-octadecene), poly (anhydride-alt- 1 -tétradécène maleate), poly (anhydride-alt- 1-decene maleic), substituted by a hydrophilic group, especially alkyl-substituted ammonium, e.g., 3- (dimethylamino) -l-propylamine.

5. Composition according to any one of claims 1 to 4, characterized in that the amphipol is selected from

the amphiphilic polymer of the following formula (Ia)

(the)

x, y, z correspond to the respective percentages of the units, x being between 34 and 36%, preferably about 35%, y being between 24 and 26%, preferably about 25%, z is between 38 and 42% >, preferably about 40%, mean molecular weight being between 4000 and 4600 g / mol, preferably about 4300 g / mol,

poly (anhydride-a / t-maleic tetradecene) substituted of formula (IIa) below:

and average molecular weight between 10 000 and 14 000 g / mol, xample about 12 000 g / mol,

poly (anhydride-a / t-decene maleic) substituted of formula (IIb) below

and average molecular weight between 16 000 and 20 000 g / mol, for example about 18 500 g / mol, and

poly (anhydride-a / t-maleic octadecene) substituted following formula:

and average molecular weight between 39 000 and 65 000 g / mol.

Composition according to one of claims 1 to 5, characterized in that the amphoteric copolymer is an amphoteric-based monomer 2-methacryloyloxyethyl phosphorylcholine (MPC) and another methacrylate monomer functionalized with a hydrophobic group, an anionic group, a cationic group or a group which allow the formation of hydrogen bonds.

Composition according to one of claims 1 to 6, characterized in that the amphoteric copolymer is an amphoteric-based MPC and methacrylate functionalized with a hydrophobic group selected from

the linear or branched C 4 to C 30;

linear or branched C 4 to C 30 comprising at least one cycloalkyl; the hydrocarbon chains of C 4 to C 30 comprising at least one double bond; the hydrocarbon chains of C 4 to C 30 comprising at least one triple bond; and the hydrocarbon chains of C 4 to C 30 comprising at least one aromatic ring.

Composition according to one of claims 1 to 7, characterized in that the amphoteric copolymer is Biolipidure ™ 206 sold by the company NOF CORPORATION.

An aqueous solution comprising the composition according to any one of claims 1 to 8 and at least one reactive immunoassay.

Aqueous solution according to claim 9, wherein the immunoassay reagent is selected from a binding partner for detecting or quantifying an analyte in a biological sample liable to contain it, said partner being labeled or not, a positive control, standard and an adjuster of an immunoassay.

Aqueous solution according to claim 9 or 10, characterized in that it does not comprise a stabilizing agent and / or blocking of human or animal origin agent, for example selected from animal sera, skimmed milk, caseins hydrolysed or not, bovine or human albumin, and gelatin.

Immunoassay kit comprising at least one aqueous solution according to one of claims 9 to 11, and at least one binding partner to an analyte to be detected or quantified by immunoassay and, where applicable, the compounds necessary for the detection of a specific interaction or binding and Γ analyte partners.

13. Use of a composition as defined in one of claims 1 to 8 or an aqueous solution as defined in one of claims 9 to 11, in a method by immunoassay, as a stabilizing agent and / or blocker.

14. Use according to claim 13, to reduce non-specific interaction between (i) at least one binding partner for detecting or quantifying an analyte in a biological sample liable to contain it, for example, a labeled binding partner, and, (ii) a solid phase.

15. Use according to claim 13 or 14, to reduce non-specific interaction between (i) a positive control for the immunoassay, a standard immunoassay and / or an adjuster of the immunoassay, and (ii ) a solid phase.

16. A method for immunoassay for determining the presence or quantification of a target analyte in a biological sample liable to contain it, comprising contacting said sample with at least two binding partners to said analyte, PI and P2, sequentially or concurrently, one of the two partners being labeled P2 to reveal the presence of said analyte, if present, the other IP partner is preferably immobilized on a solid phase, and said labeled P2 partner being contained in at least one composition as defined in one of claims 1 to 8 or at least an aqueous solution as defined in one of claims 9 to 11, to form optionally a Pl / analyte complex / P2,the revelation of the presence of said complex formed to conclude to the presence or amount of analyte in the sample.

17. A method for immunoassay for determining the presence or quantification of a target analyte in a biological sample liable to contain it, comprising contacting said sample with at least one analyte to said binding partner and a PI RI reagent competition to the analyte, said PI binding partner is preferably immobilized on a solid phase, said reagent being labeled IR for indirectly revealing the presence of said analyte, and said RI reagent being contained in at least one composition as defined in the one of claims 1 to 8 or at least an aqueous solution as defined in one of claims 9 to 11, to form a Pl / Rl complex, revealing the presence of said complex formed indirectly to conclude to the absence or the amount ofanalyte in the sample.