| Method for measuring skin absorbability -> Monitor Keywords |
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Method for measuring skin absorbabilityRelated Patent Categories: Drug, Bio-affecting And Body Treating Compositions, In Vivo Diagnosis Or In Vivo TestingMethod for measuring skin absorbability description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060034762, Method for measuring skin absorbability. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a method for screening an ingredient which is to be applied to the hair; a kit for carrying out the screening; and a composition comprising an ingredient exhibiting effects to accelerate absorption of an active ingredient through skin pores (hereinafter the absorption will be referred to as "skin-pore absorption") and transfer of the active ingredient to sebum, the effects being confirmed by means of the screening method. [0003] 2. Background Art [0004] An important step in the development of a hair-growing agent is to confirm that an active ingredient exhibits excellent hair-growing effect and has penetrability so as to reliably reach a target site. Whether or not the active ingredient reliably reaches the target site greatly depends on the properties of the active ingredient or the base ingredient of the hair-growing agent. [0005] The mechanism of absorption of a drug or an active agent through hair follicles has become of interest, since hair follicles are considered to be an effective route through which a hair-growing agent as well as a vaccine or a gene can be administered. [0006] The degree of transfer of a drug to sebum (hereinafter the degree will be referred to as "sebum transferability") has been reported to influence whether the drug easily reaches a target site in the skin (e.g., hair follicles or sebaceous gland) (Critical Reviews, 14 (3): 207 219 (1997)). [0007] The penetrability of a drug through the hair follicles has been studied, for example, by the following methods: [0008] (1) a method for observing tissue sections by means of fluorescence labeling or radioisotopes (Suzuki, M., et al., J. Soc. Cosmet. Chem. (1978), Nicholau, G., et al., Xenobiolica (1987), Lieb, L. M., et al., J. Invest. Dermatol. (1995)) and [0009] (2) a method for comparing hairy skin and hairless skin with respect to the transdermal permeability of a drug (e.g. comparison of hairless rat and hairy rat: Illel, B., et al., J. Pherm. Sci. (1991); comparison of normal human skin and skin which has received burns and has subsequently healed: Hueber, F., et al., J. skin Pharmacol. (1994)). [0010] However, method (1) is qualitative rather than quantitative, and the method involves the time-consuming preparation of tissue sections. In method (2), absorption of a drug is studied only from the viewpoint of transdermal absorption, and "skin-pore absorption" and "sebum transferability," which are important properties of a hair-growing agent, cannot be confirmed directly. [0011] Therefore, the aforementioned conventional methods encounter difficulty in directly confirming that a drug reaches a target site in the skin and exerts the intended effects. SUMMARY OF THE INVENTION [0012] In view of the foregoing, an object of the present invention is to provide means for conveniently and reliably determining the degree of skin-pore absorption (hereinafter the degree will be referred to as "skin-pore absorbability") and sebum transferability of a substance such as a drug, the skin-pore absorbability and sebum transferability being indexes for directly confirming that the substance reaches a target site in the skin and exerts the desired effects. Another object of the present invention is to provide a composition for the scalp and hair which exhibits excellent skin-pore absorbability and sebum transferability and which enables a drug contained in the composition to reliably reach a target site in the skin, the skin-pore absorbability and the sebum transferability being determined through the means of the present invention. [0013] The sebum transferability of a drug is considered a useful index to evaluate whether or not the drug easily reaches a specific target site in the skin, but can not be easily evaluated in vivo. Therefore, a specific object of the present invention is to provide means for accurately and conveniently evaluating the sebum transferability of a drug in vitro. [0014] The present inventors have performed extensive studies, and have found that, when the amount of a substance which is penetrated into hair follicles, the amount being determined in vitro or in vivo, is employed as an index of the amount of the substance which is absorbed through skin pores, the skin-pore absorbability of the substance can be conveniently and reliably determined, to thereby measure the skin absorbability of the substance. [0015] As used herein, the term "skin-pore absorption" refers to absorption through skin pores, although the term "transdermal absorption" refers to absorption through any portion of the skin (i.e., over the entire skin area). Therefore, as described below, a drug which exhibits transdermal absorbability does not necessarily exhibit skin-pore absorbability. In addition, because a hair-growing agent exerts its actions in the vicinity of the hair follicle, evaluating the "skin-pore absorbability" of the agent is very important. [0016] The present invention provides a method for the measurement of skin absorbability of a substance (hereinafter the method will be referred to as "measurement method 1"), which comprises measuring the amount of a substance which is penetrated into the hair follicles; and using the resultant data as an index representing the amount of the substance which is absorbed through the skin pores, to thereby determine the skin-pore absorbability of the substance. [0017] If the phenomenon of "skin-pore absorption" is considered from the function of absorption, penetration of a substance into hair follicles substantially occurs through skin pores. Therefore, in the present invention, "absorption through skin pores" or "skin-pore absorption" and "absorption through hair follicles" or "transfollicular absorption" are used as terms having the substantially same meaning. [0018] Accordingly, measurement method 1 is also provided as a method for the measurement of skin absorbability of a substance, which comprises measuring the amount of a substance which is penetrated into the hair follicles; and using the resultant data as an index representing the amount of the substance which is absorbed through the hair follicles, to thereby determine the transfollicular absorbability of the substance. [0019] Measurement method 1 is classified into the following two methods: [0020] (1) an in vitro quantification method (hereinafter referred to as "measurement method 1-1") in which the amount of a substance (e.g., a drug) which is penetrated into the hair follicle or skin tissue is determined by applying the substance to a model skin having a pseudo-biological state, removing the hair follicle from the dermis or skin tissue of the skin model, and measuring the concentration of substance which is delivered to the hair follicle or skin tissue; and [0021] (2) an in vivo quantification method (hereinafter referred to as "measurement method 1-2") in which the amount of a substance (e.g., a drug) which is penetrated into the hair follicle is determined by applying the substance to the human scalp, removing the hair follicle from the scalp, and measuring the concentration of the substance which is delivered to the hair follicle. [0022] The present inventors have also found that the sebum transferability of a substance can be easily evaluated in vitro by use of a skin model comprising artificial sebum. [0023] The present invention also provides a method for the measurement of skin absorbability of a substance (hereinafter the method will be referred to as "measurement method 2"), which comprises bringing a substance into contact with a first surface of a film that mimics the skin surface layer, a second surface of the film being brought into contact with artificial sebum; and using the degree of transfer of the substance to the artificial sebum as an index, to thereby evaluate the sebum transferability of the substance. [0024] The present inventors have also found that, by means of measurement methods 1 and 2, an oily ingredient having an I.O.B. value of 0.06-4.0 exhibits excellent effects of accelerating skin-pore absorption and sebum transfer of extensive polar substances from water-soluble substances to fat-soluble substances. [0025] The present invention also provides a composition for the scalp and hair comprising an oily ingredient having an I.O.B. value of 0.06-4.0 (hereinafter the composition may be referred to as "the composition of the present invention"). [0026] As used herein, I.O.B. (Inorganic/Organic Balance) value refers to an index representing the polarity of an oily ingredient (hereinafter the term "oily ingredient" includes fats and oils, waxes, hydrocarbon oils, higher fatty acids, higher alcohols, esters, general alcohols, and fatty acids). The I.O.B. value represents the ratio of an inorganic value of the oily ingredient to an organic value of the oily ingredient (note: the ratio is calculated as follows: an organic value of 20 is assigned for each carbon atom in the molecule of the oily ingredient, and an inorganic value of 100 is assigned per hydroxyl group in the molecule of the oily ingredient, and these values are used as yardsticks for calculating an inorganic value for another substituent (inorganic group); see (1) "Organic Analysis" authored by Fujita (1930), published by Kaniya Shoten, (2). "Prediction of Organic Compounds and Organic Conceptual Diagram ("Kagaku-no-Ryoiki 11-10" (1957), pp. 719-725, authored by Fujita, (3) "Systematic Organic Qualitative Analysis (Book of Purified Substances)" (1970), p 487, authored by Fujita and Akatsuka, published by Kazama Shoten, (4) "Organic Conceptual Diagram, Its Fundamentals and Applications" (1984), p 227, authored by Koda, published by Sankyo Shuppan, (5) "Design of Emulsion Formulations by use of Organic Conceptual Diagram" (1985), p 98, authored by Yaguchi, published by Nippon Emulsion K.K., and (6) R. H. Ewell, J. M. Harrison, L. Berg.: Ind Eng. Chem. 36, 871 (1944)), and is expressed by: I.O.B.=inorganic value of the oily ingredient/organic value of the oily ingredient. Continue reading about Method for measuring skin absorbability... 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