Vpliv izbranih kozmetično aktivnih sestavin na mikrostrukturo liotropnih tekočih kristalov

Jereb, Sara (author), Gosenca Matjaž, Mirjam (mentor), Mravljak, Janez (comentor)

Liotropni tekoči kristali z lamelarno strukturo so zaradi svoje termodinamske stabilnosti, enostavne izdelave, velike solubilizacijske kapacitete in hkrati strukturne podobnosti z roženo plastjo kože ter ugodnih učinkov na njeno hidratacijo vedno bolj proučevani kot dermalni nosilni sistemi ter zagotovo premalo zastopani na trgu, kjer prevladujejo klasične emulzije, geli itd.. Da lahko v polni meri izkoristimo učinke kozmetično aktivnih sestavin, jih moramo namreč vgraditi v ustrezno podlago, da zagotovimo optimalno stabilnost in dermalno absorpcijo ter tako dosežemo željen učinek. Pri načrtovanju nosilnega sistema na osnovi tekočih kristalov moramo zagotoviti, da vgrajene kozmetično aktivne sestavine ne spremenijo ali podrejo mikrostrukture, slednja je namreč ključna za njihove prednosti pri nanosu na kožo. Na podlagi tega nas je v okviru diplomske naloge zanimalo, kako vgradnja izbranih kozmetično aktivnih sestavin vpliva na mikrostrukturo tekočih kristalov. Slednjo smo ovrednotili z metodo elektronske paramagnetne resonance. V izbran sistem tekočih kristalov z lamelarno strukturo smo želeli vgraditi tri različne kozmetično aktivne sestavine, ki se med seboj razlikujejo v topnosti, ter v različnih deležih (m/m %). V sistem smo uspeli vgraditi dekspantenol, ki je analog pantotenske kisline (vitamina B5) ter tokoferil acetat, ki deluje kot antioksidant. Dekspantenol smo vgradili v različnih deležih, in sicer 0%, 1%, 2%, 5%, 7,5%, 10%, 15% ali 30%, tokoferil acetat pa v 5% deležu. Alantoina pa nismo uspeli vgraditi, ker se ni raztapljal v izbranem sistemu. Nadalje smo jih označili z izbranimi spinskimi označevalci, kar je ključen korak pri meritvah z elektronsko paramagnetno resonanco, saj preko spinskih označevalcev dobimo informacije o mikrostrukturi tekočih kristalov. Ugotovili smo, da različni deleži dekspantenola ne spremenijo značilno mikrostrukture tekočih kristalov. Razlika je bila očitna le pri višjih koncentracijah, saj je imel maksimalni hiperfini razcep večjo vrednost, kar nakazuje na bolj urejeno strukturo. Čeprav bi bilo optimalno vgraditi različne deleže tokoferil acetata v tekoče kristale, so rezultati pri 5% deležu spodbudni, saj večjega odstopanja v primerjavi s kontrolnim vzorcem nismo zaznali. Dekspantenol in tokoferil acetat torej na strukturo tekočih kristalov ne delujeta destruktivno, prav tako pa ne izzoveta faznih prehodov pri spremembi temperature, kar je za razvoj kozmetičnega izdelka ugodno.

• Language: Slovenian
• Keywords: elektronska paramagnetna resonanca, tekoči kristali, dekspantenol, spinski označevalec
• Work type: Bachelor thesis/paper
• Organization: FFA - Faculty of Pharmacy
• Year: 2019
• PID: 20.500.12556/RUL-109742
• Publication date in RUL: 07.09.2019

Secondary language

• Language: English
• Title: Influence of selected cosmetically active ingredients on lyotropic liquid crystals' microstructure

Abstract

Liotropic liquid crystals with lamellar structure have been, due to their thermodynamic stability, ease of manufacture, high solubilization capacity as well as structural similarity to the corneal skin layer and their beneficial effects on hydration, increasingly studied as dermal carrier systems and certainly underrepresented in the market, dominated by classic emulsions, gels, etc. In order to take full advantage of the effects of cosmetically active ingredients, they must be incorporated into a suitable vehicle to ensure optimal stability and dermal absorption, and thus achieve the desired effect. When designing a carrier system based on liquid crystals, we have to ensure that the incorporated cosmetically active ingredient(s) do not alter or disrupt their microstructure, the latter being crucial for their advantages in applying it to the skin. On this basis within this diploma thesis, we were interested in how the incorporation of the selected cosmetically active ingredients affects the microstructure of liquid crystals. The latter was evaluated by the electron paramagnetic resonance method. Three different cosmetically active ingredients with different solubility and in different ratios (w/w %) were incorporated into the selected system of liquid crystals with lamellar structure. Into the system, we also managed to incorporate dexpanthenol, which is an analogue of pantothenic acid (vitamin B5) and tocopherol acetate, which acts as an antioxidant. The dexpanthenol was then incorporated in shares of 0 %, 1 %, 2 %, 5 %, 7.5 %, 10 %, 15 % or 30 %, and tocopherol in share of 5 %. However, we could not incorporate allantoin because it did not dissolve in the selected system. We further labelled them with selected spin labels, which is a key step in electron paramagnetic resonance measurements, as the information on the microstructure of liquid crystals is obtained through spin labels. Different ratios of dexpanthenol did not significantly alter the microstructure of the liquid crystals. The structural differences were only observed at higher ratios due to the observed higher value of maximum hyperfine splitting, suggesting a more orderly structure. Although it would be optimal to incorporate different proportions of tocopherol acetate in liquid crystals, the results are encouraging, at 5 %, since no significant deviation from the sample without cosmetically active ingredient was detected. Dexpanthenol and tocopherol acetate, therefore, do not have a destructive effect on the liquid crystal structure nor do they cause phase transitions, which is advantageous for the development of cosmetic products.

• Keywords: electron paramagnetic resonance, liquid crystals, dexpanthenol, spin labels