Utilization of natural stabilizer to prepare liposomal conjugate for the newly developed aptamer

Background: Aptamers are peptide or oligonucleotides that have the capacity to bind to a specific target molecule in human body. One of the newly developed aptamers named BAS aptamer. For targeting improvement of the aptamer, liposomal conjugate was adapted utilizing phosphatidylcholine as a natural lipid stabilizer in a comparison to synthetic one. Method: Two types of blank DSPE-PEG 2000-maleimide liposomes were prepared using two types of stabilizers; synthetic (Dipalmitoylphosphatidylcholine; DPPC) and natural lipids (phosphatidylcholine) then conjugated with BAS-aptamer through introducing thiol moiety. The liposomal conjugates then evaluated by H1-NMR and urea polyacrylamide gel electrophoresis and its efficacy on binding affinity, anticancer activity against MCF-7 breast cancer as well as its stability in plasma and buffers were estimated. Results: The binding affinity study revealed a significantly higher affinity of the naturally stabilized BAS aptamer conjugated liposomes towards drug receptor (SIRT1) than the synthetically stabilized one (KD= 38.5 ± 0.985 and 68± 0.967; respectively). The cytotoxic effect of the liposomal conjugates was higher than those of pure BAS aptamer and its thiol derivative in all concentrations used. The stability study in plasma showed that naturally stabilized liposomes remained stable for up to 6 days while the synthetically prepared liposomes showed partial degradation after 5 days and both gave higher stability than the pure BAS aptamer while the stability study in phosphate buffer at pH 7.4 and 5.5 revealed non-significant decline in the absorbance of the drug started after 6 days in its naturally stabilized conjugate and after 3 days (at pH5.5) its synthetically stabilized liposomal. Conclusion: Using natural stabilizer for liposomal conjugates gave better physical properties as well as significant binding affinity for the aptamer conjugated liposomes to the receptor (SIRT1) and higher cytotoxic effect as well as better stability in plasma and buffers.