Use of spray-drying method for the preparation of microcapsules with salicylic acid

Salicilna kislina je kozmetično aktivna spojina, ki se pod določenimi omejitvami, navedenimi v Uredbi (ES) št. 1223/2009 o kozmetičnih izdelkih že dolgo časa uporablja kot aktivna sestavina predvsem v izdelkih za nego mastne kože, nagnjene k nastanku aken ter v šamponih proti prhljaju. V boju proti komedonom ima pred drugimi keratolitiki to prednost, da je lipofilna, ima pa tudi slabe strani - ker je molekula salicilne kisline majhna, zlahka penetrira v globlje plasti kože, kar v tem primeru ni zaželeno, saj se tako le majhen čas po aplikaciji zadrži na roženi plasti. Poleg tega lahko na bolj občutljivi koži povzroča draženje. To sta bila tudi glavna vzroka, ki sta nas pripeljala do ideje, da to kozmetično aktivno spojino vgradimo v mikrokapsule. V okviru diplomske naloge smo pripravljali disperzije ogrodnih materialov arabskega gumija in maltodekstrina v različnih razmerjih. V prvem primeru smo salicilno kislino raztopili v etanolu, v drugem pa v olju. Emulzijo smo pred sušenjem z razprševanjem stabilizirali s Tween-om 20. Iz formulacij, ki so vsebovale etanol, smo dobili delce, velike 27 µm, v katere se salicilna kislina ni vgradila, kar smo ugotovili s pomočjo profila raztapljanja. Ko smo raztopini arabskega gumija z dodano površinsko aktivno snovjo dodali salicilno kislino, predhodno raztopljeno v sončničnem olju, ter nastalo emulzijo posušili s postopkom sušenja z razprševanjem nam je uspelo narediti mikrokapsule z visoko vsebnostjo učinkovine. Profil sproščanja učinkovine v vodi je pokazal, da je sproščanje preveč podaljšano. Sprememba medija iz nevtralnega v kisel pH (4 in 5) ni pokazala razlik. V alkalnem mediju (pH 8) se je sprostilo nekaj več učinkovine, vendar v predolgem časovnem okvirju, da bi bila vgradnja naših mikrokapsul v kozmetični izdelek smiselna. V prihodnosti bi bilo smiselno optimizirati pogoje sušenja, predvsem pa formulacijo – na primer z dodatkom hidroksipropil metil celuloze ali katerega drugega vodotopnega polimera.Salicylic acid is a cosmetically active ingredient, which has long been used as an active ingredient, especially in products for oily skin prone to acne and in anti-dandruff shampoos. It is used under certain restrictions, listed in the Regulation (EC) No. 1223/2009 on cosmetic products. In the fight against comedones, it has the advantage over other keratolytics because of its lipophilic nature. Nonetheless, it has some disadvantages as well - the molecule of the salicylic acid is small, so it can easily penetrate into deeper layers of the skin, which is not desirable in this case, as the active ingredient is retained on the corneal layer only for a short period of time. In addition, it can cause irritation on sensitive skin. These were also the main reasons that led us to the idea of incorporating this cosmetically active compound into microcapsules. Within the frame of the diploma thesis, dispersions of arabic gum and maltodextrin were prepared in various proportions. In the first case, the salicylic acid was dissolved in ethanol, and in the second case, it was dissolved in oil. The emulsion was stabilized before spray-drying with Tween 20. The formulations containing ethanol yielded 27-µm large particles in which the salicylic acid was not incorporated - this was determined by the dissolution profile. When the salicylic acid, previously dissolved in sunflower oil, was added to a solution of arabic gum with a surfactant, and the resulting emulsion was dried by a spray-drying, we were able to make microcapsules with a high content of the active substance. The release profile of the active substance in water showed that the release was too prolonged. Changing the medium from neutral to acidic (pH 4 and 5) showed no difference. A little more substance was released in the alkaline medium (pH 8), but it was still not enough to make sense of incorporating our microcapsules into a cosmetic product. In the future, it would be wise to optimize the drying conditions and the formulation, for example, by adding hydroxypropyl methyl cellulose or any other water-soluble polymer