Encapsulation and release of lisozyme by temperature/pH-responsive tubule-based hydrogels

Abstract

Stimuli-responsive colloidal assemblies based on amino acid-based surfactants are rather promising systems for drug delivery [1], because of their versatility and enhanced human biocompatibility. In addition to forming micelles and liposomes, some amino acid-based amphiphiles can self-organize into other complex supramolecular structures, such as fibers, twisted ribbons, helical tapes and nanotubes [2-4]. In this work, we have focused on the structural characterization of hydrogels formed by double-chained lysinebased amphiphiles, nLysm, that self-assemble into tubular structures, and on their ability to encapsulate and release a model biomolecule, lysozyme (LZM). To obtain structural insight on the tubular assemblies, microscopic techniques such as video-enhanced light microscopy (VELM), scanning electron microscopy (SEM), cryogenic scanning electron microscopy (cryo-SEM), cryogenic transmission electron microscopy (cryo-TEM) and atomic force microscopy (AFM) were used (figure 1). Interactions of the tubules with the protein lysozyme, under varying experimental conditions, was investigated by DSC microcalorimetry and UV/VIS spectroscopy, with the main goal of assessing the efficiency of the tubules as pH- and temperature-sensitive nanocarriers. Results on the toxicity of the tubules per se and the tubule/LZM aggregates in human cells will also be presented.