TY - BOOK
T1 - Photophysical Investigation of Polyamidoamine Dendrimers as Versatile Platforms in the Nanomedicine Landscape
AU - Paolucci, Valentina
PY - 2017
Y1 - 2017
N2 - Dendrimers represent a unique class of polymers that have fueled the interest of the scientic community over the last decades with promising applicability in the nanomedical field. Despite the fruitful work done in the academic area, the transition to the market has shown to be hampered as witnessed by the limited number of clinically approved dendrimer-based formulations. The scope of this project was to gain a major comprehension of the physical and optical properties that can have an impact on the ultimate pharmaceutical performance of dendrimers. In this perspective, a special focus was directed to define the spectroscopic properties which are primarily responsible for the correct interpretation of bioimaging studies. Thus, a photophysical investigation of polyamidoamine (PAMAM) dendrimers and their functionalization as potent versatile nanoplatforms was carried out. Attention was initially focused on native PAMAM dendrimers prior to any further modications. Size exclusion chromatography equipped with multi-angle light scattering and refractive index detectors (SEC-MALS-RI) equipment was installed as part of this PhD project and was employed to characterize molar mass distributions. High purity and monodispersity could be confirmed for the synthesized dendrimers. Because of the low fluorescence efficiency detected for the unique blue emission of native PAMAM dendrimers, an innovative and robust fluorescent-tagged PAMAM dendrimer was developed using an organic chromophore (sulforhodamine B) as emissive core for bioimaging applications. Fluorescence quantum yields together with fluorescence lifetimes showed good accordance with the dendrimer size indicating that, as the dendritic branches grew longer, a more rigid environment surrounded the central organic chromophore which resulted in minimizing the non-radiative processes. A specific attention was devoted to the photophysical properties which are primarily responsible for the correct interpretation of the final fluorescent signal in the biological investigation. Formation of aggregates could be excluded and the fluorescence efficiency of these fluorescent labeled dendrimers showed great stability upon changes of pH and temperature. Bioevaluation of the novel dendrimers showed that they were primarily internalized in endothelial cells by energy-dependent mechanism and largely localized in the lysosomes after 24 hours. The nanomedical potentiality of dendrimers was further explored and their ability to serve as attractive nanovehicles for photosensitizers such as hydrophobic phthalocyanine in photodynamic therapy was investigated. PAMAM dendrimers with pyrrolidone as surface groups showed to efficiently load phthalocyanine peripherally substituted with carboxylic group and to form stable water-soluble complexes. Such dendrimer-phthalocyanine formulations displayed interesting cytotoxicity when illuminated with light in the NIR region along with no detectable dark-toxicity in absence of radiation. These represented promising characteristics for future applications in photodynamic therapy. The attention was additionally directed to an alternative class of nanoplatforms, the liposomes. Speciffically, it was determined that, compared to commercially available liposomes comprised of diacyl lipids, archaea-inspired liposomes could improve the retention of small nucleoside-based drugs, representing a potential nanovehicle for this class of anti-viral and anti-cancer.
AB - Dendrimers represent a unique class of polymers that have fueled the interest of the scientic community over the last decades with promising applicability in the nanomedical field. Despite the fruitful work done in the academic area, the transition to the market has shown to be hampered as witnessed by the limited number of clinically approved dendrimer-based formulations. The scope of this project was to gain a major comprehension of the physical and optical properties that can have an impact on the ultimate pharmaceutical performance of dendrimers. In this perspective, a special focus was directed to define the spectroscopic properties which are primarily responsible for the correct interpretation of bioimaging studies. Thus, a photophysical investigation of polyamidoamine (PAMAM) dendrimers and their functionalization as potent versatile nanoplatforms was carried out. Attention was initially focused on native PAMAM dendrimers prior to any further modications. Size exclusion chromatography equipped with multi-angle light scattering and refractive index detectors (SEC-MALS-RI) equipment was installed as part of this PhD project and was employed to characterize molar mass distributions. High purity and monodispersity could be confirmed for the synthesized dendrimers. Because of the low fluorescence efficiency detected for the unique blue emission of native PAMAM dendrimers, an innovative and robust fluorescent-tagged PAMAM dendrimer was developed using an organic chromophore (sulforhodamine B) as emissive core for bioimaging applications. Fluorescence quantum yields together with fluorescence lifetimes showed good accordance with the dendrimer size indicating that, as the dendritic branches grew longer, a more rigid environment surrounded the central organic chromophore which resulted in minimizing the non-radiative processes. A specific attention was devoted to the photophysical properties which are primarily responsible for the correct interpretation of the final fluorescent signal in the biological investigation. Formation of aggregates could be excluded and the fluorescence efficiency of these fluorescent labeled dendrimers showed great stability upon changes of pH and temperature. Bioevaluation of the novel dendrimers showed that they were primarily internalized in endothelial cells by energy-dependent mechanism and largely localized in the lysosomes after 24 hours. The nanomedical potentiality of dendrimers was further explored and their ability to serve as attractive nanovehicles for photosensitizers such as hydrophobic phthalocyanine in photodynamic therapy was investigated. PAMAM dendrimers with pyrrolidone as surface groups showed to efficiently load phthalocyanine peripherally substituted with carboxylic group and to form stable water-soluble complexes. Such dendrimer-phthalocyanine formulations displayed interesting cytotoxicity when illuminated with light in the NIR region along with no detectable dark-toxicity in absence of radiation. These represented promising characteristics for future applications in photodynamic therapy. The attention was additionally directed to an alternative class of nanoplatforms, the liposomes. Speciffically, it was determined that, compared to commercially available liposomes comprised of diacyl lipids, archaea-inspired liposomes could improve the retention of small nucleoside-based drugs, representing a potential nanovehicle for this class of anti-viral and anti-cancer.
UR - https://rex.kb.dk/permalink/f/h35n6k/KGL01012062739
M3 - Ph.D. thesis
BT - Photophysical Investigation of Polyamidoamine Dendrimers as Versatile Platforms in the Nanomedicine Landscape
PB - Department of Chemistry, Faculty of Science, University of Copenhagen
ER -
