Preparation and pH controlled release of polyelectrolyte complex of poly(l-malic acid-co-d,l-lactic acid) and chitosan

•Poly(l-malic acid-co-d,l-lactic acid) was prepared through a direct condensation showing merits of using simple procedure, cheap materials and no organics.•The copolymers were used to prepare polyelectrolyte complex (PEC) with chitosan, forming nano particles.•Doxorubicin was loaded on the nano particles by adsorption and self-aggregation to form secondary particles.•The drug displayed slow and sustained release in acidic media, and the nano particles have promising application as an oral administration system.

The copolymer of poly(l-malic acid-co-d,l-lactic acid) (PML) was synthesized through a direct polycondensation of l-malic acid (MA) and d,l-lactic acid (LA). Then, a new polyelectrolyte complex (PEC) based on the complexation between the copolymer (PML) and chitosan (CS) was prepared. The PEC formed stable nano particles in aqueous solutions with pH 3–5, and the nano particles had the diameters in a range of 316–590 nm (varied with the components of PML and CS). Doxorubicin (DOX) as a model drug was loaded on the nano particles through the physical adsorption and complexation, and part of DOX formed the secondary particles by self-aggregation. The high drug loading efficiency (16.5%) and the sustained release patterns in acidic media were observed, and the release accelerated in alkaline solutions. The nano particles could be potentially applied as pH sensitive drug vehicles for controlled release.

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