Design of Polypeptide-Functionalized Polystyrene Microspheres

In this contribution, the principle of spontaneous surface segregation has been applied for the preparation of polypeptide-functionalized polystyrene microspheres. For that purpose, an amphiphilic diblock copolymer was introduced in the mixture styrene/divinylbenzene and polymerized using AIBN as initiator. During the polymerization, cross-linked particles were obtained in which the diblock copolymer was encapsulated. The amphiphilic diblock copolymers used throughout this study contain a hydrophilic polypeptide segment, either poly(l-lysine) or poly(l-glutamic acid) and a hydrophobic polystyrene block. After 4 h of polymerization, rather monodisperse particles with sizes of ∼3−4 µm were obtained. Upon annealing in hot water, the hydrophilic polypeptides migrate to the interface, hence, either positively charged or neutral particles were obtained when poly(l-lysine) is revealed at the surface and exposed to acidic or basic pH, respectively. On the opposite, negatively charged particles were achieved in basic pH water by using poly(l-glutamic acid) as additive. The surface chemical composition was modified by changing the environment of the particles. Thus, exposure in toluene provoked a surface rearrangement, and due to its affinity, the polystyrene block reorients toward the interface.