1. Follicular delivery of nanoparticles and microcontainers ex vivo and in vivo Sergey Zaitsev 1, Natalia Ksenofontova 1, Yulia I. Svenskaya 1, Olga Guslyakova 1, Elina A. Genina 1,2, Vsevolod Atkin 1, Georgy S. Terentyuk 1, Alexey N. Bashkatov 1,2, Dmitry A. Gorin 1, Valery V. Tuchin 1,2, and Gleb B. Sukhorukov 1,3 1 Saratov State University, Russia; 2 Tomsk State University, Russia; 3 Queen Mary University of London, UK Motivation Motivation The successful loading of nanoparticles with drugs and their triggered release inside the hair follicle can present an ideal method for localized drug delivery. Depending on the particle size, such a method would permit targeting specific structures in the hair follicles such as stem cells or immune cells or blood vessels found in the vicinity of the hair follicles. The goal of the study is development of the method of follicular delivery of particle and creation of depot in skin. Methods and Materials Methods and Materials  Rat skin ex vivo and in vivo  TiO 2 particles with the sizes 25 nm, 100 nm, and 5 μm (ex vivo experiments)  CaCO 3 submicron containers loaded with photodynamic dye Indocyanine Green (in vivo experiments)  Ultrasonic (US) low-frequency therapeutical device as enhancer of particle penetration (with power 0.5Wt and treatment time 2 min) and damage of submicron containers (power 2Wt and treatment time 2-4 min)  OCT-monitoring of particle penetration in skin was carried out every 2-4 min during US treatment and after 3 days  Biopsy and SEM were used for visualization of submicrocontainers inside follicles Results of ex vivo experiments (a) (b) Fig. 4 – SEM images of (a) follicle without submicrocontainers and (b) follicle wall Fig 5. – OCT-image of rat skin with submicrocontainers penetrated into hair follicles after 4 min of US treatment Fig. 6 – SEM images of (a) follicle wall with the penetrated submicrocontainers after 2-min no-damaging US treatment (just post- treatment) (b) follicle wall with the penetrated submicrocontainers after 4-min damaging US treatment (just post-treatment) (a)(b) (a) (b) Fig. 7 - SEM images of (a) follicle with the penetrated submicrocontainers after 2-min no-damaging US treatment (after 3 days) (b) CaCO 3 submicrocontainers inside the follicle Fig. 8 - SEM images of (a) follicle wall with the penetrated submicrocontainers after 4-min damaging US treatment (after 3 days) (b) CaCO 3 submicrocontainers inside the follicle (a) (b) Results of in vivo experiments Fig. 3 - Histogram of temporal dependence of penetration depth of particles with various sizes Fig. 1 ­ OCT-image of rat skin with 25-nm TiO 2 particles penetrated into hair follicle Fig. 2 - Histological section of rat skin with 25-nm TiO 2 particles penetrated into hair follicle Follicle filled with nanoparticles Conclusion  The rate of follicular penetration of particles depends on their sizes: 25-nm particles penetrated faster than 5-μm ones  2-min US treatment allowed for deep penetration of submicrocontainers into follicles without damaging  4-min US treatment led to recrystallization of CaCO 3 containers inside follicles and release of contents The work was carried out under the support by Russian Federation Governmental No. 14.Z50.31.0004 designed to support scientific research projects implemented under the supervision of leading scientists at Russian institutions of higher education Follicular transport Living epidermis Stratum corneum Dermis Follicle Recrystallization of particles