Prenatal gender prediction test

Details Prenatal gender prediction test Prenatal gender prediction test

1999-06-17

2002-07-16

Warden, Jill (Department: 1743)

Chemistry: analytical and immunological testing

Including titration or ph determination

C436S164000, C436S814000, C436S183000, C436S065000, C600S309000

Reexamination Certificate

active

06420182

ABSTRACT:

BACKGROUND
Prospective parents are often very interested in knowing the sex of their unborn child. While there are many methods for attempting to determine the gender of an unborn child, many of the methods are based on folklore rather than scientific principles. The accuracy of such techniques is doubtful. Scientifically based techniques are also available for attempting to determine the gender of an unborn child. However, many of the scientific techniques for determining the gender of an unborn baby are either invasive of the mother, the womb or the fetus or require expensive equipment. Amniocentesis involves insertion of a cannula or needle into the amniotic sac. Ultrasonographic examination of the fetal perineal can be used to attempt to detect external genitalia of a male fetus. However, ultrasound requires expensive equipment and has not proven to be completely reliable. Several approaches based on changes in the mother's endocrinology have been explored. For example, attempts to examine hormone levels in pregnant mothers have not resulted in any statistically reliable methods for distinguishing between mothers carrying a male fetus versus mothers carrying a female fetus. Other tests, such as polymerase chain reaction (PCR) amplification of Y-specific DNA sequences in maternal blood, require a sample of maternal blood and expensive equipment.
It would accordingly be very desirable to have a simple, reliable non-invasive method for determining the gender of an unborn baby.
SUMMARY
The present invention provides a gender-indicating composition, and a method and kit for determining the gender of an unborn child. The gender-indicating composition includes thymol blue and may include one or more additional indicators as discussed below. The gender-indicating composition can be provided in any of a number of common forms. For example, gender-indicating composition may be in the form of a powder or a solution which includes a water miscible organic solvent. One particularly suitable form of the gender-indicating composition is an aqueous solution that includes a water-miscible organic solvent, such as a water-miscible alcohol. Suitable examples of water-miscible alcohols include ethanol and methanol. The gender-indicating composition optionally may also include non-interfering indicators such as bromthymol blue, phenolphthalin or methyl red.
The present invention also provides a non-invasive colorimetric assay of a pregnant woman's urine to determine the sex of the fetus. According to the present method, the gender-indicating composition is combined with a urine sample from a pregnant woman. The resulting treated urine solution is generally compared to a color standard.
The present invention also provides a kit for assaying a pregnant woman's urine to determine the sex of the fetus. The kit includes a dosage unit of the gender-indicating composition. The kit may also includes a color standard to which the color of the treated urine solution is compared. Typically, the color standard includes a male child color standard and/or a female child color standard. Optionally, the kit can include instructions for performing the colorimetric assay and/or a reaction vessel in which the assay can be performed.
DETAILED DESCRIPTION
The present invention provides a gender-indicating composition, method and kit for determining the gender of an unborn child.
Gender-Indicating Composition
One aspect of the invention provides a gender-indicating composition. According to the invention, the gender-indicating composition includes thymol blue. Optionally, the gender-indicating composition can include non-interfering indicators such as bromthymol blue, phenolphthalin, methyl red or mixtures thereof. As used herein, the term “non-interfering” indicators refers to colorimetric indicators which do not affect the color of the treated urine solution under the test conditions. Suitable “non-interfering” indicators are preferably uncolored or yellow in their acid form (e.g., at a pH of about 1-7) and uncolored or yellow in their base form (e.g., at a pH of 7-14). The color response of a number of common pH indicators are shown in Table 1, below.
In some instances the presence of the optional non-interfering indicator(s) can have an advantageous effect. For example, the presence of bromthymol blue and phenolphthalin can enhance the stability of test solutions containing thymol blue. Although the bromthymol blue and phenolphthalin are not necessary components of the indicator solution, their action can occupy varying pH levels of the buffer offering color consistency for the indicators. Weak acid and weak bases are often found in urine, which regularly has high concentrations of both. The levels can vary depending on a person's diet. Adding an equal number of moles (for example, equal volumes of solutions of the same molarity) of each will result in a neutral solution. Adding more acid will result in an acidic solution. Conversely, adding more base will result in a basic solution. The bromthymol blue and phenolphthalin occupy the pH around neutrality, thus providing a more suitable buffer to conduct the present gender test.
TABLE 1
Known pH Indicators
Indicator
pH range
pKa
Acid Form
Base Form
thymol blue
1.2-2.8
1.6
red
yellow
methyl red
4.2-6.2
5.0
red
yellow
bromthymol blue
6.0-7.6
7.1
yellow
blue
thymol blue
8.0-9.6
8.9
yellow
blue
phenolphthalin
8.0-9.8
9.7
colorless
red
The present gender-indicating composition can be in the form of a solid, e.g., crystals or a powder. Alternatively, the gender-indicating composition combined with a neutral water miscible organic solvent to form a gender-indicating solution. The gender-indicating solution may be a relatively dilute form of the gender-indicating composition such that 1 to 10 mL of the solution are combined with a urine sample (e.g., circa 50-100 mL of urine) during the test. Alternatively, the gender-indicating solution may be a relatively concentrated solution of the gender-indicating composition such that only a few drops of the solution are needed to conduct the test on an urine sample of 50 mL or larger. The amount of polypeptide byproduct to be detected which is dissolved in the test solution may be of a very low concentration, and the thymol blue, a necessary component, indicates specific to the gender test.
As discussed above, gender-indicating composition includes thymol blue and may include one or more additional indicators. Thymol blue (4,4′-(3H-2, 1-Benzoxathiol-3-ylidene)bis[5-methyl-2-(1-methylethyl)phenol] S,S-dioxide) is a known acid-base indicator. Thymol blue reported to be a brown/green powder or crystalline material that is soluble in alcohol or dilute alkali. As indicated in Table 1, at a pH of 1.2 thymol blue is red; at a pH between 2.8 and 8.0, thymol blue is yellow; and at a pH of 9.6 or above, this indcator is blue.
The present gender-indicating composition commonly also includes bromthymol blue in addition to the thymol blue. Bromthymol blue is 4,4′-(3H-2,1-Benzoxathiol-3-ylidene)bis[2-bromo-3-methyl-6-(1-methylethyl)phenol] S,S-dioxide. Bromthymol blue is reported to exist as cream colored crystals and be sparingly soluble in water, soluble is alcohol or ether and aqueous solutions of alkali. As indicated in Table 1, at a pH of 6.0 bromthymol blue is yellow and at a pH of 7.6 bromthymol is blue.
Other indicators which may be present gender-indicating composition include methyl red and/or phenolphthalin. Methyl red (2-[[4-(Dimethylamino)phenyl]azo]-benzoic acid) is a known acid-base indicator. Methyl red is a dark-red powder or a violet crystalline material. It is reported to be soluble in alcohol, ether, and glacial acetic acid. Typically, methyl red is prepared in an alcoholic solution, for example, a 0.1% aqueous alcoholic solution. At a pH of 4.4 or below, methyl red is red. At a pH of 6.2 methyl red is yellow.
In test solutions, the function of methyl red can be defined as having the capacity to minimize changes in the sought after pH, 2.5. The methyl

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