Hollow Core−Porous Shell Structure Poly(acrylic acid) Nanogels with a Superhigh Capacity of Drug Loading

Poly(acrylic acid) (PAA) nanogels with a hollow core-porous shell structure were prepared by the direct polymerization of an acrylic acid monomer in the presence of hydroxypropylcellulose (HPC) and a cross-linking agent, N,N-methylenebisacrylamide, followed by removal of HPC from the generated HPC-PAA nanoparticles in a basic environment. The properties of PAA nanogel were characterized by dynamic light scattering, FT-IR, transmission electron microscopy, and atomic force microscopy. It is found that the nanogels have a hollow core-porous shell structure. Protein, bovine serum albumin (BSA), and an antitumor agent, doxorubicin hydrochloride, were used as model drugs to investigate their loading abilities as versatile drug-delivery vehicles. The nanogel exhibits surprisingly high loading ability to both protein and small molecular drugs. For example, the maximum BSA loading capacity of PAA nanogel can reach as high as 800% (i.e., 1 mg of nanogel can load about 8.0 mg of BSA). This high loading capacity may be related with the hollow core-porous shell structure of PAA nanogels. PAA nanogels have also shown sustained drug release properties and can cross biological barriers to deliver loaded cargo inside cells. Considering the high stability of the materials, simple and mild preparation procedure, high loading capacity, sustained-release property, and ability to protect biological agents from denaturation, PAA nanogels should be promising drug-delivery carriers for drug-delivery systems.