Degradable coronas comprising polyelectrolyte complexes of PDMAEMA and gelatin for pH-triggered antibiotic release

Carboxyl-modified polystyrene (PS) nanospheres were used as sacrificial cores upon which cross-linked gelatin (CGA) was assembled through successive immobilization with poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA), forming polyelectrolyte complexes (PECs) stabilized through electrostatic interactions and hydrogen bonding. The PEC coronas, possessing hollow structure, of the PEC CGA@PDMAEMA after removing the PS cores were obtained. At pH 2.2, the protonated PDMAEMA swelled the PEC coronas completely, leading to the disappearance of the inner cavities, which reappeared after increasing the pH to 5.5. Further increasing the pH to 8.1 caused the deprotonated PDMAEMA to collapse completely to cover the CGA surface, generating a solid shell. This pH-responsive structural change of the PEC coronas suggested that they could be used as drug capsules. Accordingly, amoxicillin (AMX) was loaded into the coronas as a medium to inhibit the bacterial viability of Escherichia coli and Staphylococcus aureus. Both of bacterial growth rates of E. coli and S. aureus in solution at pH 8.1 in the presence of the AMX-loaded PEC coronas did not change significantly within 8 h comparing with that in a blank experiment, indicating that the PEC coronas confined the AMX units within the hollow structure. With decrease of the pH to 5.5, the bacterial growth rates were inhibited obviously within 2 h relative to that in a blank experiment, confirming that the AMX units could be released from the PEC coronas by tuning pH value.