ИСТИНА

Respirable dust is one of the sources of pathogenic bacteria and toxic compounds. As reported [1], one of the main sources of dust in occupied rooms is shed human skin. Human skin flasks are often responsible for contamination and infection spreading because of microorganisms attached to them. On the other hand, human skin flasks are digested by fungi and dust mites that may be a cause of allergy and asthma [2]. So, monitoring of skin cell content in house dust is a necessary step in ecology control of dwellings and health care. Skin cells consist of more than 80% keratins cross linked to other cornified proteins. Keratin from human skin cells is the major protein component of indoor airborne dust [3]. So, keratin concentration in dust can be used as an indicator of indoor bacterial contamination. The main goal of the current research was to develop a rapid express method for the determination of keratin content in house dust for detection of bacterial or allergen indoor contamination or dust state in occupied rooms. From the numerous works which deal with fluorescence of human skin, it is known that keratin exhibits fluorescence when excited in the UV region of spectrum (at ca 350 nm). However, this fluorescence is different from the tryptophan fluorescence and is due to the presence of specific fluorophores, e.g., fluorescent cross-linkings in the protein structure. Here, we made an attempt to separate the contribution of keratin fluorescence to the overall signal of house dust. Dust from volunteers’ Moscow homes and office rooms was used for the investigation. Water extracts of sieved fine dust were used to measure fluorescence signal and protein concentration. Dust extract fluorescence spectra obtained upon 275 nm excitation exhibited two major peaks with its maxima near 350 nm and 420 nm, neither of which correlated with total protein concentration in the samples determined using Lowry assay. At the same time, we observed that the spectral band shape of fluorescence emission of house dust obtained at 350 nm excitation was similar for all the samples under investigation. Further investigation showed that this band shape was typical for keratins from different sources. Moreover, the fluorescence intensity obtained upon 350 nm excitation exhibited linear correlation with the total protein content in dust. As for keratin is an insoluble fibrillar protein, in order to increase its concentration in dust extract proteinase K was used. When dust samples and human keratin were treated with proteinase K with mercaptoethanol, the increase of fluorescence intensity of extracts was found, while the spectral band shape remained similar. It was also shown the that peak of dust fluorescence fluorescence at 275 nm excitation was due to the impacts of raw keratin and hydrolyzed keratin. As a result, it was shown that dust fluorescence may be used to measure keratin content, hence, it could be a promising indicator of indoor microbial and allergen exposure. [1] A. Fox, W. Harley, C. Feigley, D. Salzberg, C. Toole, A. Sebastian, & L. Larsson, Large particles are responsible for elevated bacterial marker levels in school air upon occupation. Journal of Environmental Monitoring, 7(5), 450-456, (2005). [2] Colloff, Matthew J. "Dust mites." (2009). [3] K. Fox, E. Castanha, A. Fox, C. Feigley, & D. Salzberg, Human K10 epithelial keratin is the most abundant protein in airborne dust of both occupied and unoccupied school rooms. Journal of Environmental Monitoring, 10(1), 55-59, (2008).