Competition Between Heparin and Polyethylene Glycol as Biofunctionalization for Improving Stability of Liposomal Doxorubicin

Abstract

In order to improve liposomal doxorubicin stability, differentiation between Heparin and Polyethylene Glycol (PEG) as biofunctionalization for liposomal doxorubicin has been investigated by measuring the entrapment efficiency, size distribution, zeta potential, evaluating the in vitro potential cytotoxicity against MCF-7 (Breast cancer cell) and stability in serum by measuring the drug release rate. We synthesized Four liposomal formulations: (A) Conventional liposomes; DPPC:DOX, (B) Positively charged PEGylated liposomes; DPPC:CHOL:SA:PEG:DOX (C) Negatively charged PEGylated liposomes: DPPC:CHOl:DCP:PEG:DOX (D) positively charged liposomes to conjugate heparin; DPPC:CHOL:SA:DOX. Entrapment efficiency of doxorubicin dramatically increased after PEGylation and conjugation with heparin. In addition, zeta potential was changed upon the encapsulation of doxorubicin into conventional and PEGylated liposomes which indicates that DOX encapsulated completely into liposomes. For heparin conjugated liposomes, zeta potential was slightly changed. Sulphorhodamine-B (SRB) assay showed a greater cytotoxic effect of the liposomal doxorubicin formulations at different concentrations with respect to free drug against MCF-7 cell lines. The anticancer activity order was observed between the various liposome formulations, especially those observed with conjugated heparin liposomes. Slower drug release rate showed an order of D > C > B > A that means stability showed an order of D > C > B > A. From above results, the most stable liposomal doxorubicin formulation was the liposomal formulation D. The results optimized using heparin than PEG as biofunctionalization. Further studies are suggested for better understanding why heparin improves the stability of liposomal doxorubicin.