New Core Shell Silica Nanoparticle Copolymers Produced by Biomineralization of Tetramethyl Orthosilicate (TMOS) by British and Japanese Chemists

There is growing academic and industrial interest in the synthesis and applications of nanoparticles, most particularly nanoparticles having a core-shell structure in view of their potential use as delivery vehicles for active materials such as drugs. Consequently, much research effort is devoted to the preparation of nano-sized particles of this type.  

In U.S. Patent Application 20100009001, University of Sheffield Professor of Chemistry Steven Armes (Sheffield, GB) and bioengineer Jian-Jun Yuan (Osakidai, JP) reveal novel nano core-shell silica-copolymer nanoparticles, methods for their preparation, and their potential uses.  Silica-based core-shell nanoparticles have been suggested for various bioanalytical applications, such as drug delivery, bioimaging and biolabeling.

The two inventors developed a method to produce core-shell silica nanoparticles obtained by biomineralization of tetramethyl orthosilicate (TMOS) using either shell crosslinked (SCL) or non-crosslinked cationic block copolymer micelles as templates. Both routes lead to well-defined, core-shell copolymer-silica nanoparticles. The use of non-crosslinked micelles, as shown in the upper route, additionally leads to in situ silica crosslinking.  

Armes and Yuan have established that the nanostructure of these copolymer-silica core-shell particles can be simply controlled by tuning the amount of tetramethyl orthosilicate (TMOS)  used for silica deposition. Thus, for example, silica particles with thin shells and large copolymer cores were obtained when using lower levels of TMOS.

These nanoparticles have a number-average diameter of around 35 nm, which is in reasonably good agreement with the dimensions of the precursor micelles. However, in addition to the formation of templated silica nanoparticles, some ill-defined, non-templated silica structures are also produced.

Perhaps the most significant advantage of their nanofabrication process, however, lies in the fact that the core-forming PDPA block in the claimed compositions is pH-responsive, and this offers the possibility of pH-triggered release of hydrophobic actives from the cores of the hybrid copolymer-silica nanoparticles.

FIG. 6 shows a transmission electron micrograph of silica nanoparticles, the silica crosslinked micelles retain their spherical core/shell structures after direct dispersion and drying. It illustrates the potential use of these new core-shell copolymer-silica nanoparticles in encapsulation/ controlled release applications. .

 The use of ABC triblock copolymers has found particular success in the preparation of predominantly anisotropic rod-like copolymer-silica particles, and the said nanorods should allow zero-order diffusional release to be achieved.

U.S. Patent Application 20100009001 was published on January 14 and was among at least 290 nanotechnology related patents published on that day.