Browsing by Subject "nanoformulations"

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  • Kinnunen, Moonika (Helsingin yliopisto, 2022)
    In this project, poly(2-methyl-2-oxazoline)-block-poly(2-n-butyl-2-oxazine)-block-poly(2-methyl-2- oxazoline) (PMeOx-b-PnBuOzi-b-PMeOx) and poly(2-methyl-2-oxazoline)-block-poly(2-n-propyl-2- oxazine) (PMeOx-b-PnPrOzi) with block lengths of 35-20-35 and 100-100, respectively, were synthesized. When dispersed in water these thermoresponsive polymers aggregate into micellar aggregates or form hydrogels. Polymers were characterized with 1H-NMR, GPC, and DLS. Age-related macular edema and diabetic macular edema are the most common reasons for blindness in industrialized countries. The triamcinolone acetonide, a corticosteroid used to treat both of these macular edemas, was loaded into the polymeric micelles or hydrogel of synthesized polymers using the thin film method. The loading efficiency for a triblock copolymer ((PMeOx35-b-PnBuOzi20- b-PMeOx35) polymeric micelles was 4 % at the polymer/drug ratio of 10/4 and for a hydrogel (PMeOx100-b-PnPrOzi100) it was 48 % with the same polymer/drug ratio. The properties of the PMeOx100-b-PnPrOzi100 hydrogel formulations with the drug were studied with rheological measurements, DSC, DLS, and GPC of formulations. The formulation showed storage modulus of 3 kPa and the gelation temperature at 16 °C. From the DSC two glass transition temperatures were obtained, Tg1 at around 12 °C and Tg2 at around 74 °C. The particle size distribution of the formulation obtained with DLS showed that there were assumingly micelles or vesicles with a hydrodynamic radius between 20 and 80 nm. The drug release from the hydrogel formulation was studied with the dialysis membrane method and all the drug was released within 24 hours. Both copolymers formed quite unstable formulations with the drug. The results from this study gives information how polyoxazoline- and polyoxazine-based materials can be used to encapsulate and release corticosteroids, such as triamcinolone acetonide. To increase the drug loading capacity and to stabilize formulations, some surfactants for the drug could be tested in the future.
  • Haider, Malik Salman; Luebtow, Michael M.; Endres, Sebastian; Forster, Stefan; Flegler, Vanessa J.; Boettcher, Bettina; Aseyev, Vladimir; Pöppler, Ann-Christin; Luxenhofer, Robert (2020)
    Polymeric micelles are typically characterized as core-shell structures. The hydrophobic core is considered as a depot for hydrophobic molecules, and the corona-forming block acts as a stabilizing and solubilizing interface between the core and aqueous milieu. Tremendous efforts have been made to tune the hydrophobic block to increase the drug loading and stability of micelles, whereas the role of hydrophilic blocks is rarely investigated in this context, with poly(ethylene glycol) (PEG) being the gold standard of hydrophilic polymers. To better understand the role of the hydrophilic corona, a small library of structurally similar A-B-A-type amphiphiles based on poly(2-oxazoline)s and poly(2-oxazine)s is investigated by varying the hydrophilic block A utilizing poly(2-methyl-2-oxazoline) (pMeOx; A) or poly(2-ethyl-2-oxazoline) (pEtOx; A*). In terms of hydrophilicity, both polymers closely resemble PEG. The more hydrophobic block B bears either a poly(2-oxazoline) and poly(2-oxazine) backbone with C3 (propyl) and C4 (butyl) side chains. Surprisingly, major differences in loading capacities from A-B-A > A*-B-A > A*-B-A* is observed for the formulation with two poorly water-soluble compounds, curcumin and paclitaxel, highlighting the importance of the hydrophilic corona of polymer micelles used for drug formulation. The formulations are also characterized by various nuclear magnetic resonance spectroscopy methods, dynamic light scattering, cryogenic transmission electron microscopy, and (micro) differential scanning calorimetry. Our findings suggest that the interaction between the hydrophilic block and the guest molecule should be considered an important, but previously largely ignored, factor for the rational design of polymeric micelles.