Polymer Structure-Guided Self-Assisted Preparation of Poly(ester-thioether)-Based Hollow Porous Microspheres and Hierarchically Interconnected Microcages for Drug Release.

Porous polymer microspheres (PPMs) have been widely applied in various biomedical fields. Herein, the self-assisted preparation of poly(ester-thioether)-based porous microspheres and hierarchical microcages, whose pore sizes can be controlled by varying the polymer structures, is reported. Poly(ester-thioether)s with alkyl side chains (carbon atom numbers were 2, 4, and 8) can generate hollow porous microspheres; the longer alkyl chain length, the larger pore size of microspheres. The allyl-modified poly(ester-thioether) (PHBDT-g-C3 ) can form highly open, hierarchically interconnected microcages. A formation mechanism of these PPMs is proposed; the hydrophobic side chains-mediated stabilization of oil droplets dictate the droplet aggregation and following solvent evaporation, which is the key to the formation of PPMs. The hierarchically interconnected microcages of PHBDT-g-C3 are due to the partially crosslinking of polymers. Pore sizes of PPMs can be further tuned by a simple mixing strategy of poly(ester-thioether)s with different pore-forming abilities. The potential application of these PPMs as H2 O2 -responsive vehicles for delivery of hydrophobic (Nile Red) and hydrophilic (doxorubicin hydrochloride) cargos is also investigated. The microspheres with larger pore sizes show faster in vitro drug release. The poly(ester-thioether)-based polymer microspheres can open a new avenue for the design of PPMs and provide a H2 O2 -responsive drug delivery platform.