Kamath Yash K, Ruetsch Sigrid B
TRI/Princeton, Princeton, NJ 08542, USA.
J Cosmet Sci. 2010 Jan-Feb;61(1):1-12.
A microfluorometric method has been developed to characterize lipid removal or "delipidation" of the human hair cuticula during light exposure and chemical grooming processes such as oxidation (bleaching) and reduction. In the case of photochemical and chemical oxidation, lipid removal ("delipidation" of the F-layer or lipid-layer) from the outer beta-layer of the exposed scale faces and generation of cysteic acid groups occurs. This "delipidation," which ultimately results in "acidification" of the scale faces, leading to a change in surface chemistry from hydrophobic to hydrophilic, can be detected and quantified by microfluorometry by tagging, e.g., with the cationic fluorochrome Rhodamine B. In the case of reduction, similar tagging of the acid sites on the scale faces is possible, but this time, Rhodamine B reacts with the mixed disulfide containing a carboxyl group that will be ionized above a pH of about 4. In addition to this, we have shown by microfluorometric scanning that the negative charges generated in the cuticle surface can be used to bind low-molecular-weight quaternary conditioners. This process can be considered as "relipidation" or "refatting" of the scale faces. We have shown in earlier studies (1) that this entire process of oxidation-induced "delipidation" and subsequent "relipidation" of the acidic scale faces with a cationic conditioning molecule can also be reliably quantified by X-ray photoelectron spectroscopy (XPS). Furthermore, single-fiber wettability scanning using the Wilhelmy technique, which is highly sensitive to any changes in surface chemistry, is well-suited to detect and characterize treatment-induced changes in the chemical nature of the hair surface from hydrophobic to hydrophilic.
已开发出一种显微荧光测定法，用于表征在光照以及氧化（漂白）和还原等化学梳理过程中人类毛发角质层的脂质去除或“脱脂”情况。在光化学氧化和化学氧化的情况下，暴露的鳞片表面外β层会发生脂质去除（F层或脂质层的“脱脂”）并生成半胱氨酸基团。这种“脱脂”最终会导致鳞片表面“酸化”，从而使表面化学性质从疏水变为亲水，通过用阳离子荧光染料罗丹明B等进行标记，可通过显微荧光测定法检测和量化这种变化。在还原的情况下，也可以对鳞片表面的酸性位点进行类似的标记，但此时，罗丹明B会与含有羧基的混合二硫化物反应，该羧基在pH约为4以上时会被离子化。除此之外，我们通过显微荧光扫描表明，角质层表面产生的负电荷可用于结合低分子量季铵调理剂。这个过程可被视为鳞片表面的“再脂质化”或“再脂肪化”。我们在早期研究（1）中表明，氧化诱导的酸性鳞片表面“脱脂”以及随后用阳离子调理分子进行“再脂质化”的整个过程，也可以通过X射线光电子能谱（XPS）可靠地量化。此外，使用威尔海姆技术进行的单纤维润湿性扫描对表面化学的任何变化都高度敏感，非常适合检测和表征处理引起的毛发表面化学性质从疏水到亲水的变化。
