Effect of the ammonium salt anion on the structure of doxorubicin complex and PEGylated liposomal doxorubicin nanodrugs

• Published in: Biochimica et biophysica acta. General subjects Vol. 1865; no. 5; p. 129849
• Main Authors: Schilt, Yaelle, Berman, Tal, Wei, Xiaohui, Nativ-Roth, Einat, Barenholz, Yechezkel, Raviv, Uri
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.05.2021
• Subjects: Confinement; Palmar-plantar Erythrodysesthesia; PEGylated liposomal doxorubicin; SAXS; WAXS; Confinement; PPE; EPR; MS; PEGylated liposomal doxorubicin; PLD; WAXS; ES; SAXS; Palmar-plantar Erythrodysesthesia; 4-HBS; PEG; S; 3-HPS
• ISSN: 0304-4165; 1872-8006
• DOI: 10.1016/j.bbagen.2021.129849

In Doxil®, PEGylated nanoliposomes are created by hydration of the lipids in ammonium sulfate, and are remotely loaded with doxorubicin by a transmembrane ammonium gradient. The ammonium sulfate is then removed from the external aqueous phase, surrounding the liposomes, and replaced by an isoosmotic sucrose solution in 10 mM histidine buffer at pH 6.5. We prepared PEGylated liposomal doxorubicin (PLD) with a series of ammonium monovalent salts that after remote loading became the intraliposome doxorubicin counteranions. We analyzed the liposomes by solution X-ray scattering, differential scanning calorimetry, and electron micropscopy. PLDs prepared with sulfonic acid derivatives as counteranion exhibited chemical and physical stabilities. We determined the effect of these ammonium salt counteranions on the structure, morphology, and thermotropic behavior of the PEGylated nanoliposomes, formed before and after doxorubicin loading, and the bulk properties of the doxorubicin-counteranion complexes. By comparing the structure of the doxorubicin complexes in the bulk and inside the nanoliposomes, we revealed the effect of confinement on the structure and doxorubicin release rate for each of the derivatives of the ammonium sulfonic acid counteranions. We found that the extent and direction of the doxorubicin confinement effect and its release rate were strongly dependent on the type of counteranion. The counteranions, however, neither affected the structure and thermotropic behavior of the liposome membrane, nor the thickness and density of the liposome PEG layers. In an additional study, it was demonstrated that PLD made with ammonium-methane sulfonate exhibit a much lower Hand and Foot syndrome. The structure, physical state, and pharmacokinetics of doxorubicin in PEGylated nanoliposomes, prepared by transmembrane remote loading using gradients of ammonium salts, strongly depend on the counteranions. •PEGylated liposomal doxorubicin (PLD) was prepared by transmembrane remote loading driven by ammonium monovalent sulfonate gradients.•The structure of the doxorubicin aggregates varies with the ammonium salt counteranion, whereas the liposome membrane stays unchanged.•The physical state of the doxorubicin inside the nanoliposome affects its release under in vitro conditions, mimicking tumor microenvironment.