A study of calcein as an index for evaluation of the pH-sensitivity fusion induce materials and liposomes

Objective:To establish a simple and quick method to evaluate pH sensitivity of fusogenic materials, such as polymers and peptides,and pH-sensitive liposome.Methods:Calcein will self-quenching when it is trapped inner of liposome,and the self-quenching will disappear when calcein releases from liposome.Through measuring the calcein fluorescence releasing intensity of trapped calcein,the pH-sensitivity fusion induces cell membrane permeability of pH-sensitivity polymer and liposome can be reflected.Results:Liposmes with different phospholipids constituent all can trap the high concentration of calcein successfully and the trapped calcein can keep stable and shield its emitted light.Under acidic conditions the pH-sensitivity polymer induces membrane dis- ruption and fusion and the trapped ealeein releases from the liposome.The pH-sensitivity fusion of material,acidity of the solution and phospholipids constituent all can affect trapped calein releasing from liposome.The calcein inten- sity is influenced the of the solution but this influence will very little at pH 6.5-10.0.Conclusion:The simple and quick method to evaluate the pH-sensitivity fusion induces cell membrane permeability of pH-sensitivity of poly- mer and liposome is established base on the shelf shield property of the high concentration of calcein trapped in li- posome.All results indicate that this method is simple and reliable.