RESUMO
We report on a novel type of shaped hydrogel microparticles which undergo large, rapid, and reversible volume changes in response to solution pH. The cubic hydrogels are produced as interconnected poly(methacrylic acid) (PMAA) network replicas of mesoporous manganese oxide templates by sequential infiltration of (PMAA) and poly(N-vinylpyrrolidone) (PVPON), followed by cross-linking of PMAA and template dissolution. The integrated advantages of the porous cubic sacrificial templates and responsive PMAA matrix enable synthesis of monodisperse and pH-sensitive hydrogel cubes in a rapid, facile, and reproducible manner. These hydrogel cubes display a reversible 2-fold change in size while maintaining their shape in response to pH variations. The swelling behavior of cubic and spherical hydrogel particles is controlled by the network structure which is regulated by the PMAA molecular weight. These networks maintain their three-dimensional shapes in the dry state. No cytotoxicity is found for cubic and spherical hydrogels upon their interactions with human cancer cells for various time intervals. Finally, pH-triggered loading and release of doxorubicin to and from the cubic hydrogels is shown and their anticancer effect is demonstrated. The viability of A549 and HeLa cancer cells was significantly decreased upon interaction with doxorubicin-loaded cubic hydrogels. The approach presented here provides a new platform of multi-functional particles with highly-controlled geometry, size, composition, and responsive properties to be potentially used in targeted drug delivery for cancer therapy.
RESUMO
This study analyzes the adhesion behavior of the gram positive bacteria, Staphylococcus aureus (S. aureus), and the gram negative bacteria, Escherichia coli (E. coli), on polypyrrole (PPY) surfaces in the presence of poly(ethylene glycol) methacrylate (PEGMA) chains and plasma proteins (bovine serum albumin and bovine plasma fibrinogen) either preadsorbed on the film surface or in the bacterial suspension. Bacterial adhesion experiments performed in a suspension of bacterial cells and protein may give important insights on the behavior of bacterial adhesion in an in vivo environment. Protein adsorption and bacterial adhesion on PEGMA-grafted PPY films were reduced by about a factor of 2-4 compared with those on the pristine PPY films. In addition, the number of bacterial cells adhering on the substrate is dependent not only on the type of protein present, but also the sequence of exposure to the protein relative to the bacteria. Furthermore, bacteria-surface adhesion force was measured using the atomic force microscopy with increasing lateral force to detach the individual cell. The adhesion force of S. aureus is influenced by PEGMA and plasma protein modification and is significantly higher than that of E. coli for all substrates tested. The number of adherent cells on the substrate is shown to be directly correlated to the bacterial adhesion force.
