Polymeric nanoparticles (NPs) are colloids in the nanometric size that find application in several field, such as optics, coating and medicine. In this latter case, they are used as drug delivery systems for different therapeutics ranging from lipophilic drugs to oligonucleotides in order to improve their pharmacological profile, efficacy and to avoid possible side effects in the treatment of several illness, such as cancer. These nano-colloids are generally made up of polyesters as long as they are able to degrade into safe and easy removable compounds, such as lactic acid and hydroxycaproic acid. However, NP production is often a complex process that requires mixing devices. In addition, expensive purification steps are necessary to eliminate the unloaded drug and the high amount of organic solvent used in the NP production step. In the end, a lyophilization step is general adopted to assure a good shelf-life of the final product. All the above-mentioned steps hamper the cost-effective use of a re-formulation of the same therapeutic agent and, in turn, reduce the availability of these treatments among the patient population. For this reason, in this PhD thesis, a novel NP production protocol that consists only in the use of a syringe and a needle without the need of subsequent purification and freeze-drying steps has been developed. This has been possible by the optimization of the hydrophilic/lipophilic balance of block-copolymers that are able to directly self-assemble in water. The additional degree of freedom necessary for this optimization was introduced via the synthesis of these materials thorough the combination of the reversible addition-fragmentation chain transfer (RAFT) polymerization, a technique that allows to control over the structure and the molecular weight of the aliphatic polymers, and the ring opening polymerization (ROP), the most diffused process adopted for the production of polyesters. Firstly, the kinetic of the RAFT polymerization of water soluble monomers has been studied (Chapter 3). Subsequently, a novel geometrical theory on the conformation of the NP composed of block-copolymers produced via RAFT polymerization has been developed and a method to decouple the NP size and the block-copolymer MW has been found via the adoption of macromolecular surfmers (Chapter 4). The same technology has been also used to obtain fluorinated NPs with different surface charges that are useful for optical applications and that are, otherwise, very difficult to obtain and/or that require very dangerous chemicals (Chapter 5). Then the use of RAFT macro-surfmers has been combined with ROP to produce a library of biodegradable amphiphilic block-copolymers able to self-assemble in water via the use of only a syringe in order to avoid all the post-process steps necessary to store them (Chapter 6). As a proof of concept, Trabectedin and Paclitaxel (Chapter 7), two anticancer therapeutics, have been loaded into these novel NPs showing the same antitumor activity of the commercially available formulations, but with a better toxicological profile and a potentially lower cost. In fact, they can be produced directly at the bed of the patient starting from the native dry block-copolymer. In addition, the possibility to synthesize safer gene delivery carriers by combining ROP and the Michael addition step-growth polymerization is shown (Chapter 8).
Le nanoparticelle polimeriche (NPs) sono colloidi della dimensione nanometrica che trovano applicazione in diversi campi, come l'ottica, i rivestimenti e la medicina. In quest'ultimo caso, sono utilizzati come sistemi di somministrazione dei farmaci per diverse terapie che vanno dai farmaci lipofili agli oligonucleotidi per migliorarne il profilo farmacologico, l'efficacia ed evitare possibili effetti collaterali nel trattamento di diverse malattie, come il cancro. Questi nanocolloidi sono generalmente costituiti da poliesteri poiché siano in grado di degradare in composti sicuri e facilmente eliminabili, come l'acido lattico e l'acido idrossicaproico. Tuttavia, la produzione di NPs è spesso un processo complesso che richiede dispositivi di miscelazione. Inoltre, sono necessarie costose fasi di purificazione per eliminare il farmaco non caricato e l'elevata quantità di solvente organico utilizzato nella fase di produzione della NP. Infine, una fase di liofilizzazione è generalmente adottata per garantire una buona durata di conservazione del prodotto finale. Tutte le fasi sopra descritte ostacolano l'uso economicamente conveniente di una riformulazione dello stesso agente terapeutico e, a loro volta, riducono la disponibilità di questi trattamenti tra i pazienti. Per questo motivo, in questa tesi di dottorato, è stato sviluppato un nuovo protocollo di produzione delle NPs che consiste nell' utilizzo di una siringa e di un ago senza la necessità di successive fasi di purificazione e liofilizzazione. Ciò è stato possibile grazie all' ottimizzazione dell'equilibrio idrofilico/lipofilo di copolimeri a blocchi che sono in grado di auto-assemblarsi direttamente in acqua. L' ulteriore grado di libertà necessario per questa ottimizzazione è stato introdotto con la sintesi di questi materiali attraverso la combinazione della polimerizzazione RAFT, una tecnica che permette di controllare la struttura e il peso molecolare dei polimeri alifatici, e la polimerizzazione ad apertura ad anello (ROP), il processo più diffuso per la produzione di poliesteri. In primo luogo, è stata studiata la cinetica della polimerizzazione RAFT dei monomeri solubili in acqua (capitolo 3). Successivamente, è stata sviluppata una nuova teoria geometrica sulla conformazione delle NPs composte da copolimeri a blocchi prodotti attraverso la polimerizzazione RAFT ed è stato trovato un metodo per disaccoppiare la dimensione della NP e i pesi molecolari del copolimero a blocchi attraverso l'adozione di tensioattivi macromolecolari (capitolo 4). La stessa tecnologia è stata utilizzata anche per ottenere NPs fluorurate con diverse cariche superficiali che sono utili per applicazioni ottiche e che generalmente sono molto difficili da ottenere e/o che richiedono sostanze chimiche molto pericolose (capitolo 5). Poi l'uso di questi surfattanti macromolecolari è stato abbinato alla ROP per produrre una libreria di copolimeri a blocchi anfifilici biodegradabili in grado di autoassemblarsi in acqua attraverso l'utilizzo di una siringa per evitare tutte le fasi di post-trattamento necessarie allo stoccaggio (capitolo 6). A riprova del concetto, Trabectedina e Paclitaxel (capitolo 7), due farmaci antitumorali, sono stati caricati in queste nuove NPs mostrando la stessa attività antitumorale delle formulazioni disponibili in commercio, ma con un migliore profilo tossicologico e un costo potenzialmente inferiore. Infatti, esse possono esser prodotte direttamente al letto del paziente partendo dal copolimero a blocchi secco. Inoltre, viene mostrata la possibilità di sintetizzare sistemi di somministrazione di geni più sicuri combinando ROP e la polimerizzazione per addizione di Michael (Capitolo 8).
The combination of ROP and RAFT polymerization for the synthesis of polymeric nanoparticles
CAPASSO PALMIERO, UMBERTO
Abstract
Polymeric nanoparticles (NPs) are colloids in the nanometric size that find application in several field, such as optics, coating and medicine. In this latter case, they are used as drug delivery systems for different therapeutics ranging from lipophilic drugs to oligonucleotides in order to improve their pharmacological profile, efficacy and to avoid possible side effects in the treatment of several illness, such as cancer. These nano-colloids are generally made up of polyesters as long as they are able to degrade into safe and easy removable compounds, such as lactic acid and hydroxycaproic acid. However, NP production is often a complex process that requires mixing devices. In addition, expensive purification steps are necessary to eliminate the unloaded drug and the high amount of organic solvent used in the NP production step. In the end, a lyophilization step is general adopted to assure a good shelf-life of the final product. All the above-mentioned steps hamper the cost-effective use of a re-formulation of the same therapeutic agent and, in turn, reduce the availability of these treatments among the patient population. For this reason, in this PhD thesis, a novel NP production protocol that consists only in the use of a syringe and a needle without the need of subsequent purification and freeze-drying steps has been developed. This has been possible by the optimization of the hydrophilic/lipophilic balance of block-copolymers that are able to directly self-assemble in water. The additional degree of freedom necessary for this optimization was introduced via the synthesis of these materials thorough the combination of the reversible addition-fragmentation chain transfer (RAFT) polymerization, a technique that allows to control over the structure and the molecular weight of the aliphatic polymers, and the ring opening polymerization (ROP), the most diffused process adopted for the production of polyesters. Firstly, the kinetic of the RAFT polymerization of water soluble monomers has been studied (Chapter 3). Subsequently, a novel geometrical theory on the conformation of the NP composed of block-copolymers produced via RAFT polymerization has been developed and a method to decouple the NP size and the block-copolymer MW has been found via the adoption of macromolecular surfmers (Chapter 4). The same technology has been also used to obtain fluorinated NPs with different surface charges that are useful for optical applications and that are, otherwise, very difficult to obtain and/or that require very dangerous chemicals (Chapter 5). Then the use of RAFT macro-surfmers has been combined with ROP to produce a library of biodegradable amphiphilic block-copolymers able to self-assemble in water via the use of only a syringe in order to avoid all the post-process steps necessary to store them (Chapter 6). As a proof of concept, Trabectedin and Paclitaxel (Chapter 7), two anticancer therapeutics, have been loaded into these novel NPs showing the same antitumor activity of the commercially available formulations, but with a better toxicological profile and a potentially lower cost. In fact, they can be produced directly at the bed of the patient starting from the native dry block-copolymer. In addition, the possibility to synthesize safer gene delivery carriers by combining ROP and the Michael addition step-growth polymerization is shown (Chapter 8).File | Dimensione | Formato | |
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https://hdl.handle.net/10589/136971