title: In vivo penetration of bare and lipid-coated silica nanoparticles across the human stratum corneum.
abstract: Skin penetration of silica nanoparticles (NP) currently used in pharmaceutical and cosmetic products is a topic of interest not only to evaluate their possible toxicity, but also to understand their behaviour upon contact with the skin and to exploit their potential positive effects in drug or cosmetic delivery field. Therefore, the present work aimed to elucidate the in vivo mechanism by which amorphous hydrophilic silica NP enter human stratum corneum (SC) through the evaluation of the role played by the nanoparticle surface polarity and the human hair follicle density. Two silica samples, bare hydrophilic silica (B-silica, 162±51nm in size) and hydrophobic lipid-coated silica (LC-silica, 363±74nm in size) were applied on both the volar and dorsal side of volunteer forearms. Twelve repetitive stripped tapes were removed from the human skin and evaluated for elemental composition by Energy Dispersive X-ray (EDX) analysis and for silicon content by Inductively Coupled Plasma quadrupole Mass Spectrometry (ICP-MS). All the stripped tapes revealed nanosized structures generally located in the broad spaces between corneocytes and characterized by the same elemental composition (relative weight percentage of silicon and silicon to oxygen weight ratio) than that of the applied samples. However, only about 10% B-silica permeated until the deepest SC layers considered in the study indicating a silica retention in the upper layers of SC, regardless of the hair follicle density. Otherwise, the exposure to LC-silica led to a greater silica skin penetration extent into the deeper SC layers (about 42% and 18% silica following volar and dorsal forearm application, respectively) indicating that the NP surface polarity played a predominant role on that of their size in determining the route and the extent of penetration.
authors.affiliation: Department of Life Sciences, University of Modena and Reggio Emilia, via G. Campi 183, 41125 Modena, Italy. Electronic address: valentina.iannuccelli@unimore.it.
authors.forename: Valentina
authors.initials: V
authors.lastname: Iannuccelli
authors.affiliation: Department of Life Sciences, University of Modena and Reggio Emilia, via G. Campi 183, 41125 Modena, Italy. Electronic address: davide.bertelli@unimore.it.
authors.forename: Davide
authors.initials: D
authors.lastname: Bertelli
authors.affiliation: Department of Engineering Enzo Ferrari, University of Modena and Reggio Emilia, Strada Vignolese 905, 41125 Modena, Italy. Electronic address: marcello.romagnoli@unimore.it.
authors.forename: Marcello
authors.initials: M
authors.lastname: Romagnoli
authors.affiliation: Department of Chemical and Pharmaceutical Sciences, University of Ferrara, via Fossato di Mortara 17, 44121 Ferrara, Italy. Electronic address: sls@unife.it.
authors.forename: Santo
authors.initials: S
authors.lastname: Scalia
authors.affiliation: Department of Life Sciences, University of Modena and Reggio Emilia, via G. Campi 183, 41125 Modena, Italy. Electronic address: ele.maretti@hotmail.it.
authors.forename: Eleonora
authors.initials: E
authors.lastname: Maretti
authors.affiliation: Department of Life Sciences, University of Modena and Reggio Emilia, via G. Campi 183, 41125 Modena, Italy. Electronic address: francesca.sacchetti@unimore.it.
authors.forename: Francesca
authors.initials: F
authors.lastname: Sacchetti
authors.affiliation: Department of Life Sciences, University of Modena and Reggio Emilia, via G. Campi 183, 41125 Modena, Italy. Electronic address: eliana.leo@unimore.it.
authors.forename: Eliana
authors.initials: E
authors.lastname: Leo
mesh_terms: D006801:Humans; D008055:Lipids / Q000493:pharmacokinetics*; D053758:Nanoparticles; D012822:Silicon Dioxide / Q000493:pharmacokinetics*; D012867:Skin / Q000378:metabolism*
chemical_list: D008055:Lipids; D012822:Silicon Dioxide
keywords: Hair follicles; In vivo skin penetration; Lipid-coated silica; Nanoparticles; Silica; Tape stripping test