Unexploited potential of polyelectrolytes for the development of advanced delivery systems of drugs and probiotics : doctoral dissertation

Mirtič, Janja (author), Kristl, Julijana (mentor)

Polyelectrolytes are polymers whose repeating units carry groups that can be ionized, making the polymers charged. The main objective of this doctoral dissertation was to resolve the challenges of utilising polyelectrolytes, in the development of advanced delivery systems for drugs and probiotic bacteria. The focus was on polyelectrolytes that originate from nature (i.e., polysaccharides: alginate, chitosan) that are biocompatible and biodegradable, with a primary objective of periodontal disease treatment. Periodontal disease is an inflammatory disease primarily caused by the microbial imbalance. Current therapeutic approaches lead only to short-term recovery, thus there is a need for the development of novel treatments that would reduce the periodontal plaques, reestablish oral microbial balance, modulate the immune response, and regenerate the periodontal tissues. In the first part, polyelectrolyte complexation of alginate with different crosslinkers as a method of nanoparticle formation is thoroughly investigated and described. We showed that nanoparticle formation is spontaneous, led by entropy, even when different classes of crosslinkers are used. The class of crosslinker is affecting the molar ratio of the components at which nanoparticles are formed as well as their characteristics. Completely novel surfactant-polyelectrolyte-complex nanoparticles were investigated further, where the cooperative interaction between the surfactant - cetylpyridinium chloride, and polyelectrolyte - alginate, was proven. These cetylpyridinium-alginate nanoparticles were further utilised for increasing water solubility of ibuprofen, where distinct nanoparticle substructures were shown for the first time. In the second part, nanofibers with a high proportion of alginate in composition were successfully electrospun. With the addition of high molecular weight poly(ethylene oxide), blend solutions of appropriate rheological and conductometric properties were made, that enabled electrospinning. Using multivariate analysis and by varying different solution parameters the nanofiber diameter could be finely tuned to produce scaffolds useful in regenerative medicine. The last section focused on bacterial cell entrapment, as single cells with a layer-by-layer deposition method, or as the incorporation of probiotics into alginate microcapsules. In the first case, different polyelectrolytes were tested, and stimulated emission depletion microscopy was utilized for the first time to visualize the effects of polyelectrolyte layering on bacteria. These were, contrary to the expectation, mainly dependent on the bacterial strain used, and not on the polyelectrolyte properties. Alginate microcapsules for probiotic incorporation were made by prilling and followed lyophilisation, with additional chitosan coating. Such microcapsules presented a novel probiotic delivery system that enabled their survival during processing and storage, their revival and activity. Thus, such a system could serve as an efficient probiotic delivery system into the periodontal pockets. This doctoral dissertation is defining new knowledge on the topics of polyelectrolyte complexation, electrospinning of polysaccharides and encapsulation of bacterial cells that will enable wider use of polyelectrolytes for development of advanced delivery systems for drugs and probiotics.

• Language: English
• Keywords: zdravilne učinkovine, probiotiki, parodontalne bolezni, zdravljenje, alginat, kompleksiranje, nanodelci, nanovlakna, elektrostatsko sukanje
• Work type: Dissertation
• Typology: 2.08 - Doctoral Dissertation
• Organization: FFA - Faculty of Pharmacy
• Place of publishing: Ljubljana
• Publisher: [J. Mirtič]
• Year: 2020
• Number of pages: XIV, 217 str.
• PID: 20.500.12556/RUL-137111
• UDC: 615:620.3(043.3)
• COBISS.SI-ID: 19071491
• Publication date in RUL: 01.06.2022

Secondary language

• Language: Slovenian
• Title: Neizkoriščen potencial polielektrolitov za razvoj naprednih dostavnih sistemov za zdravilne učinkovine in probiotike

Abstract

Polielektroliti so polimeri, katerih monomerne enote nosijo skupine, ki jih je mogoče ionizirati, zaradi česar imajo naboj. Glavni cilj te doktorske disertacije je bil raziskati nove možnosti uporabe polielektrolitov pri razvoju naprednih dostavnih sistemov za zdravilne učinkovine in probiotične bakterije. Poudarek je bil na polielektrolitih, ki izvirajo iz narave (tj. polisaharidi: alginat, hitosan) in so biokompatibilni ter biorazgradljivi, s primarnim ciljem zdravljenja parodontalne bolezni. Parodontalna bolezen je vnetna bolezen, katere primarni vzrok je mikrobno neravnovesje. Trenutni terapevtski pristopi ne vodijo do popolne ozdravitve, zato obstaja potreba po razvoju novih načinov zdravljenja, ki bi zmanjšali bakterijske zobne obloge, ponovno vzpostavili ustno mikrobno ravnovesje, modulirali imunski odziv in obnovili parodontalna tkiva. V prvem delu smo raziskali in opisali polielektrolitno kompleksiranje alginata z različnimi premreževali kot metodo za tvorbo nanodelcev. Dokazali smo, da nanodelci nastanejo spontano v entropijsko vodenem procesu, ne glede na uporabljeno vrsto premreževal. Slednja vplivajo predvsem na molsko razmerje komponent, v katerem nastanejo nanodelci in na njihove lastnosti. Za inovativne nanodelce izdelane s kompleksiranjem površinsko aktivne snovi in polielektrolita, smo dokazali kooperativnost interakcij med površinsko aktivno snovjo in polielektrolitom. Razvite cetilpiridin-alginatne nanodelce smo uporabili za povečanje topnosti ibuprofena v vodi, kjer smo kot prvi pokazali izredno zanimivo strukturiranost nanodelcev, ki nastanejo ob kompleksiranju. V drugem delu samo uspešno izdelali nanovlakna z visokim deležem alginata z metodo elektrostatskega sukanja. Z dodajanjem poli(etilen oksida) visoke molekulske mase smo pripravili mešanice polimernih raztopin z ustreznimi reološkimi in prevodnimi lastnostmi, ki so omogočile elektrostatsko sukanje. Uporaba multivariatne analize in spreminjanje parametrov raztopine omogoči prilagaje premera nanovlaken, kar omogoča razvoj ogrodij uporabnih v regenerativni medicini. Zadnji del je bil usmerjen na vgrajevanje bakterijskih celic. Z metodo nanooblaganja smo obložili posamezne celice. Večje količine probiotičnih bakterij pa smo vgradili v alginatne mikrokapsule. V prvem primeru smo preizkusili različne polielektrolite in kot prvi uporabili mikroskopijo z vzbujenim praznjenjem emisije za vizualizacijo učinkov polielektrolitnega oblaganja. Ti so bili v nasprotju s pričakovanji odvisni predvsem od uporabljenega seva bakterijskih celic in ne od lastnosti polielektrolita. Alginatne mikrokapsule z vgrajenim probiotikom smo izdelali z metodo ekstruzije curka tekočine z vibrirajočo membrano in sledečo liofilizacijo ter z dodatno hitosansko oblogo. Razvite mikrokapsule predstavljajo nov dostavni sistem za probiotike, ki omogoča njihovo preživetje med izdelavo in shranjevanjem, njihovo oživitev in aktivnost, zaradi česar bi lahko bile uporabne za dostavo probiotikov v parodontalne žepe. Doktorska disertacija opredeljuje nova znanja s področja polielektrolitnega kompleksiranja, elektrostatskega sukanja polisaharidov in vgrajevanja bakterij, ki bodo omogočila širšo uporabo polielektrolitov za razvoj naprednih dostavnih sistemov za zdravilne učinkovine in probiotike.