Hybrid Mesoporous Nanoparticles for pH-Actuated Controlled Release

• Published in: Nanomaterials (Basel, Switzerland) Vol. 9; no. 3; p. 483
• Main Authors: Gonçalves, José L M, Crucho, Carina I C, Alves, Sérgio P C, Baleizão, Carlos, Farinha, José Paulo S
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 26-03-2019; MDPI
• Subjects: Addition polymerization; Biomedical materials; Cationic polymerization; Caustic soda; Chains (polymeric); Coils; Collapse; Conformation; Controlled release; Corrosion; Drug delivery systems; Dyes; Electrostatic properties; mesoporous silica nanoparticles; Molecular conformation; Nanomaterials; Nanoparticles; Nanotechnology; pH effects; pH-responsive; polymer shell; Polymerization; Polymers; RAFT polymerization; Silica; Silicon dioxide; smart hybrid nanoparticles; Sodium; Surface stability; United States > US; mesoporous silica nanoparticles; controlled release; polymer shell; RAFT polymerization; smart hybrid nanoparticles; pH-responsive
• ISSN: 2079-4991; 2079-4991
• DOI: 10.3390/nano9030483

Among a variety of inorganic-based nanomaterials, mesoporous silica nanoparticles (MSNs) have several attractive features for application as a delivery system, due to their high surface areas, large pore volumes, uniform and tunable pore sizes, high mechanical stability, and a great diversity of surface functionalization options. We developed novel hybrid MSNs composed of a mesoporous silica nanostructure core and a pH-responsive polymer shell. The polymer shell was prepared by RAFT polymerization of 2-(diisopropylamino)ethyl methacrylate (pKa ~6.5), using a hybrid grafting approach. The hybrid nanoparticles have diameters of ca. 100 nm at pH < 6.5 and ca. 60 nm at pH > 6.5. An excellent control of cargo release is achieved by the combined effect of electrostatic interaction of the cargo with the charged silica and the extended cationic polymer chains at low pH, and the reduction of electrostatic attraction with a simultaneous collapse of the polymer chains to a globular conformation at higher pH. The system presents a very low (almost null) release rate at acidic pH values and a large release rate at basic pH, resulting from the squeezing-out effect of the coil-to-globule transition in the polymer shell.