Influence of Surfactant Structure on Photoluminescent ?-Conjugated Polymer Nanoparticles: Interfacial Properties and Protein Binding

π-Conjugated polymer nanoparticles (CPNs) are under investigation as photoluminescent agents for diagnostics and bioimaging. To determine whether the choice of surfactant can improve CPN properties and prevent protein adsorption, five nonionic polyethylene glycol alkyl ether surfactants were used to produce CPNs from three representative π-conjugated polymers. The surfactant structure did not influence size or yield, which was dependent on the nature of the conjugated polymer. Hydrophobic interaction chromatography, contact angle, quartz crystal microbalance, and neutron reflectivity studies were used to assess the affinity of the surfactant to the conjugated polymer surface and indicated that all surfactants were displaced by the addition of a model serum protein. In summary, CPN preparation methods which rely on surface coating of a conjugated polymer core with amphiphilic surfactants may produce systems with good yields and colloidal stability in vitro, but may be susceptible to significant surface alterations in physiological fluids

Formation of supramolecular gels from host-guest interactions between PEGylated chitosan and α-cyclodextrin

Chitosan-based hydrogels were prepared via the formation of polypseudorotaxanes (PPR), by selectively threading α-cyclodextrin (α-CD) macrocycles onto polymeric chains, which, through the formation of microcrystalline domains, acted as junction points for the network. Specifically, host-guest inclusion complexes were formed between α-CD and PEGylated chitosan (PEG-Ch), resulting in the formation of supramolecular gels. PEG-grafted chitosan was obtained with a reaction yield of 79.8%, a high degree of grafting (50.9% GW) and water solubility (~16 mg/mL), as assessed by turbidimetry. A range of compositions for mixtures of PEG-Ch solutions (0.2-0.8 %w/w) and α-CD solutions (2−12 %w/w, or 0.04-0.2 %mol) were studied. Regardless of PEG content, gels were not formed at low α-CD concentrations (< 4%). Dynamic rheology measurements revealed stiff gels (G’ above 15k) and a narrow linear viscoelastic region, reflecting their brittleness. The highest elastic modulus was obtained for a hydrogel composition of 0.4% PEG-Ch and 6% α-CD. Steady-state measurements with cycling between low and high shear rate values confirmed the thixotropic nature of the gels, demonstrating their capacity to fully recover their mechanical properties after being exposed to high stress, making them good candidates to use as in-situ gel-forming materials for drug delivery to topical or parenteral sites

Formation of supramolecular gels from host-guest interactions between PEGylated chitosan and alpha-Cyclodextrin

Chitosan-based hydrogels are prepared via the formation of polypseudorotaxanes (PPR), by selectively threading alpha-cyclodextrin (alpha-CD) macrocycles onto polymeric chains, which, through the formation of microcrystalline domains, act as junction points for the network. Specifically, host-guest inclusion complexes are formed between alpha-CD and PEGylated chitosan (PEG-Ch), resulting in the formation of supramolecular gels. PEG-grafted chitosan is obtained with a reaction yield of 79.8%, a high degree of grafting (50.9% GW) and water solubility (approximate to 16 mg mL(-1)), as assessed by turbidimetry. A range of compositions for mixtures of PEG-Ch solutions (0.2-0.8% w/w) and alpha-CD solutions (2-12% w/w, or 0.04-0.2% mol) are studied. Regardless of PEG content, gels are not formed at low alpha-CD concentrations (<4%). Dynamic rheology measurements reveal stiff gels (G' above 15k) and a narrow linear viscoelastic region, reflecting their brittleness. The highest elastic modulus is obtained for a hydrogel composition of 0.4% PEG-Ch and 6% alpha-CD. Steady-state measurements, cycling between low and high shear rates, confirm the thixotropic nature of the gels, demonstrating their capacity to fully recover their mechanical properties after being exposed to high stress, making them good candidates to use as in-situ gel-forming materials for drug delivery to topical or parenteral sites