Vrednotenje vpliva lamelarnih tekočih kristalov na barierno funkcijo kože

Založnik, Neža (author), Gosenca Matjaž, Mirjam (mentor)

Tekoči kristali predstavljajo vmesno stanje med tekočinami in trdnimi snovmi. S trdnimi snovmi jih povezujemo zaradi anizotropnosti, dvolomnosti, urejenosti in mehanske stabilnosti, tok pa odraža lastnost tekočin. Glede na njihov nastanek jih delimo na termotropne in liotropne. Liotropni obstajajo v več oblikah: lamelarni, kubični in heksagonalni. Lamelarni tekoči kristali predstavljajo aktualen dermalni dostavni sistem, predvsem zaradi podobnosti njihove strukturne urejenosti z medceličnimi lipidi rožene plasti kože. V okviru diplomskega dela smo na modelu in vitro na prašičji koži vpeti v Franz-ove difuzijske celice vrednotili vpliv lamelarnih tekočih kristalov na osnovi lecitina na barierno funkcijo kože, natančneje na transepidermalno izgubo vode in hidratacijo. Izdelali smo osem sistemov tekočih kristalov z različno kvantitativno sestavo (razmerje med oljno fazo in emulgatorsko zmesjo je bilo konstantno ob naraščajočem deležu vodne faze) in ugotavljali vpliv na vrednosti proučevanih parametrov. Najprej smo v sklopu preliminarnih testov določili čas predhodne hidratacije kože v Franz-ovih difuzijskih celicah za določitev bazalnih vrednosti, čas delovanja tekočih kristalov na koži in časovne točke za oceno učinka tekočih kristalov po odstranitvi s kože. Transepidermalno izgubo vode smo določali s Tewametrom® TM 300 in nato v enakih časovnih točkah še hidratacijo s Corneometrom® CM 825. Vrednosti, ki smo jih izmerili pred nanosom tekočih kristalov (bazalne vrednosti), smo primerjali s končnimi vrednostmi, tj. 30 min in 90 min po odstranitvi. Vsi sistemi tekočih kristalov so izboljšali barierno funkcijo, kar se je izražalo v znižanju transepidermalne izgube vode in zvišanju hidratacije. Največje znižanje TEWL je 30 min po odstranitvi TK s kože znašalo 18,6 %, po 90 min pa 22,3 %, medtem ko je bilo največje zvišanje hidratacije po 30 min za 158,3 %, po 90 min pa za 165,5 %. Izboljšanje barierne funkcije kože, zlasti hidratacije, je bilo odvisno od kvantitativno sestave tekočih kristalov, in sicer deleža oljne faza in emulgatorske zmesi, ki vplivata na nastanek semipermeabilnega filma na površini kože, prav tako je bil učinek časovno odvisen.

• Language: Slovenian
• Keywords: barierna funkcija, transepidermalna izguba vode, hidratacija, lamelarni tekoči kristali, Franz-ova difuzijska celica
• Work type: Bachelor thesis/paper
• Organization: FFA - Faculty of Pharmacy
• Year: 2021
• PID: 20.500.12556/RUL-129913
• Publication date in RUL: 09.09.2021

Secondary language

• Language: English
• Title: Evaluation of lamellar liquid crystals' impact on skin barrier function

Abstract

Liquid crystals are considered to be an intermediate state between liquids and solids. They are associated with solids because of their anisotropy, birefringence, structure and mechanical stability, while their flowability correlate them with liquids. According to their origin, they are divided into thermotropic and lyotropic liquid crystals. Lyotropic ones exist in several forms: lamellar, cubic and hexagonal Lamellar liquid crystals represent the innovative dermal delivery system, mainly because of their structure, which is similar to that of the intercellular lipids of the stratum corneum of the skin. For the purposes of this thesis, the influence of lecithin-based lamellar liquid crystals on the skin’s barrier function, more precisely on transepidermal water loss and hydration, was evaluated in vitro on a porcine skin model embedded in Franz diffusion cells. Influence of eight liquid crystal systems with different quantitative compositions (while the proportion of the aqueous phase was rising, the ratio of the oil phase to the emulsifiers was constant) on the studied parameters was determined. First, as a part of the preliminary tests, we determined the time of the skin’s pre-hydration in Franz diffusion cells to determine basal values, the amount of time the liquid crystals were exposed to the skin, and time points to assess the effect of liquid crystals after removal from the skin. Transepidermal water loss was determined using the Tewameter® TM 300. Afterwards, the hydration was determined at the same time points using the Corneometer® CM 825. The values measured before the application of the liquid crystals (basal values) were compared with the final values, i.e. 30 minutes and 90 minutes after the liquid crystals had been removed. Following skin application, the liquid crystals improved the barrier function as seen in decreased transepidermal water loss and increased hydration. The maximum decrease in TEWL was 18,6 %, 30 minutes after, and 22,3 %, 90 min after the liquid crystal system had been removed from the skin. The maximum increase in hydration was 158,3 %, 30 minutes after, and 165,5 %, 90 min after the liquid crystal had been removed from the skin. The improvement of skin barrier function, especially hydration, correlates with quantitative composition of liquid crystals, namely the proportion of oil phase and emulsifier mixture, contributing to formation of semipermeable film on the skin surface. Moreover, the effect was time dependent.

• Keywords: barrier function, transepidermal water loss, skin hydration, lamellar liquid crystals, Franz diffusion cell