Therapeutic‐Gas‐Responsive Hydrogel

Nitric oxide (NO) is a crucial signaling molecule with various functions in physiological systems. Due to its potent biological effect, the preparation of responsive biomaterials upon NO having temporally transient properties is a challenging task. This study represents the first therapeutic‐gas (i.e., NO)‐responsive hydrogel by incorporating a NO‐cleavable crosslinker. The hydrogel is rapidly swollen in response to NO, and not to other gases. Furthermore, the NO‐responsive gel is converted to enzyme‐responsive gels by cascade reactions from an enzyme to NO production for which the NO precursor is a substrate of the enzyme. The application of the hydrogel as a NO‐responsive drug‐delivery system is proved here by revealing effective protein drug release by NO infusion, and the hydrogel is also shown to be swollen by the NO secreted from the cultured cells. The NO‐responsive hydrogel may prove useful in many applications, for example drug‐delivery vehicles, inflammation modulators, and as a tissue scaffold.     

Nanoparticles of Mesoporous SO3H‐Functionalized Si‐MCM‐41 with Superior Proton Conductivity

Nanometer‐sized mesoporous silica particles of around 100‐nm diameter functionalized with a large amount of sulfonic acid groups are prepared using a simple and fast in situ co‐condensation procedure. A highly ordered hexagonal pore structure is established by applying a pre‐hydrolysis step in a high‐dilution synthesis approach, followed by adding the functionalization agent to the reaction mixture. The high‐dilution approach is advantageous for the in situ functionalization since no secondary reagents for an effective particle and framework formation are needed. Structural data are determined via electron microscopy, nitrogen adsorption, and X‐ray diffraction, proton conductivity values of the functionalized samples are measured via impedance spectroscopy. The obtained mesoporous SO₃H‐MCM‐41 nanoparticles demonstrate superior proton conductivity than their equally loaded micrometer‐sized counterparts, up to 5 × 10^?2 S cm^?1. The mesoporosity of the particles turns out to be very important for effective proton transport since non‐porous silica nanoparticles exhibit worse efficient proton transport, and the obtained particle size dependence might open up a new route in rational design of highly proton conductive materials.