pH-responsive mesoporous silica nanocarriers based on layer-by-layer self-assembly.

Significant progress has been achieved in the field of pH-sensitive drug delivery system in recent years. For layer-by-layer self-assembly nanocarriers, various pH values can induce the change of permeability and structural stability of the outer polyelectrolyte multi-layers, resulting in the release of the loaded drug. In the present study, carboxyl-modified mesoporous silica nanoparticles (MSNs-COOH) were prepared as reservoirs to hold model cargo, i.e. Rhodamine B (RhB). Polycations, including 1, 4-butanediamine (BDA)-modified linear poly (glycerol methacrylate) (L-B) or BDA-modified star-shaped poly (glycerol methacrylate) (S5-B) and 1,2-ethanediamine (EDA)-modified star-shaped poly (glycerol methacrylate) (S5-E), and polyanion, i.e. poly (acrylic acid) (PAA), are self-assembled by electrostatic interactions as coating. The loading process of RhB was characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, thermo-gravimetric analysis, and dynamic light scattering, and the release of RhB was controlled by changing the pH of phosphate buffer saline. The results showed that the loading capacity and entrapment efficiency of RhB were the highest for S5-B/PAA, which were 10.1% and 44.4%, respectively. In addition, the release of RhB was about 90% at pH 2.0 and 35% at pH 7.4, which was indicative of obvious pH-responsivity. The MSNs-COOH coated by S5-B/PAA proposed in the present study show potential applications in targeted drug delivery.