Abstract
Self-assembled nanogels made of hydrophobized pullulan were obtained using a versatile, simple, reproducible and low-cost method. In a first reaction pullulan was modified with hydroxyethyl methacrylate or vinyl methacrylate, further modified in the second step with hydrophobic 1-hexadecanethiol, resulting as an amphiphilic material, which self-assembles in water via the hydrophobic interaction among alkyl chains. Structural features, size, shape, surface charge and stability of the nanogels were studied using hydrogen nuclear magnetic resonance, fluorescence spectroscopy, cryo-field emission scanning electron microscopy and dynamic light scattering. Above the critical aggregation concentration spherical polydisperse macromolecular micelles revealed long-term colloidal stability in aqueous medium, with a nearly neutral negative surface charge and mean hydrodynamic diameter in the range 100–400 nm, depending on the polymer degree of substitution. Good size stability was observed when nanogels were exposed to potential destabilizing pH conditions. While the size stability of the nanogel made of pullulan with vinyl methacrylate and more hydrophobic chains grafted was affected by the ionic strength and urea, nanogel made of pullulan with hydroxyethyl methacrylate and fewer hydrophobic chains grafted remained stable.
Highlights
Pullulan is a water soluble, linear, neutral extracellular biodegradable homopolysaccharide of glucose produced by the fungus Aureobasidium pullulans (Pullularia pullulans) [1,2,3,4]
Pullulan arose as a promising polymer for various biomedical applications [10], such as surface modification of polymeric materials to improve blood compatibility [11,12], for gene [13,14] and drug delivery [5,15,16,17,18,19], as a carrier for quantum dots for intracellular labeling to be used as a fluorescent probe for diagnostic bioimaging [20] and tissue engineering [21]
In the present work, hydrophobized pullulan was obtained with a two-step synthesis
Summary
Pullulan is a water soluble, linear, neutral extracellular biodegradable homopolysaccharide of glucose produced by the fungus Aureobasidium pullulans (Pullularia pullulans) [1,2,3,4]. Cholesteryl group-bearing pullulan complexed with the truncated HER-2 protein, delivered a HER-2 oncoprotein containing an epitope peptide to the major histocompatibility complex class I pathway, and was able to induce CD8+ cytotoxic T lymphocytes against HER-2+ tumors and caused complete rejection of tumors. The results suggested this hydrophobized polysaccharide may help soluble proteins to induce cellular immunity with potential benefit in cancer prevention and cancer therapy [30]. Nanogel formulations, described as potential drug and vaccine delivery systems, have the potential to modify the drug, gene, protein, peptide, oligosaccharide or immunogen profile and the ability to cross biological barriers, the biodistribution and pharmacokinetics, improving their efficacy and safety, as well as the patient compliance [36]
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