Design and synthesis of N4,N9-disubstituted spermines for non-viral siRNA delivery--structure-activity relationship studies of siFection efficiency versus toxicity.
OBJECTIVE
To study the effect of sequentially changing the chain length, oxidation level, and charge distribution in N4,N9-diacyl and N4,N9-dialkyl spermines on siRNA formulation, and then to compare their lipoplex transfection efficiency in cell lines.


METHODS
Eight N4,N9-diacyl polyamines: N4,N9-[didecanoyl, dilauroyl, dimyristoyl, dimyristoleoyl, dipalmitoyl, distearoyl, dioleoyl and diretinoyl]-1,12-diamino-4,9-diazadodecane were synthesized. Their abilities to bind to siRNA and form nanoparticles were studied using a RiboGreen intercalation assay and particle sizing. Two diamides were also reduced to afford tetraamines N4,N9-distearyl- and N4,N9-dioleyl-1,12-diamino-4,9-diazadodecane. Delivery of fluorescein-labelled Label IT RNAi Delivery Control was studied in FEK4 primary skin cells and in an immortalized cancer cell line (HtTA), and compared with TransIT-TKO.


RESULTS
The design, synthesis, and structure-activity relationship studies of a series of N4,N9-disubstituted spermines as efficient vectors for non-viral siRNA delivery to primary skin and cancer cell lines is reported. These non-liposomal cationic lipids are promising siRNA carriers based on the naturally occurring polyamine spermine showing that C-18 is a better chain length as shorter chains are more toxic.


CONCLUSIONS
N4,N9-Distearoyl spermine and N4,N9-dioleoyl spermine are efficient siRNA formulation and delivery vectors, even in the presence of serum, comparable to TransIT-TKO. However, four positive charges distributed as in spermine was significantly more toxic.
Soltan
Moustafa K
MK
Department of Pharmacy and Pharmacology, University of Bath, Bath, BA2 7AY, UK.
Ghonaim
Hassan M
HM
El Sadek
Mohamed
M
Kull
M Abou
MA
El-aziz
Lubna Abd
LA
Blagbrough
Ian S
IS
D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D005260:Female; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D005456:Fluorescent Dyes; D006367:HeLa Cells; D006801:Humans; D008055:Lipids / Q000138:chemical synthesis / Q000633:toxicity; D008856:Microscopy, Fluorescence; D015394:Molecular Structure; D010316:Particle Size; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000737:chemistry / Q000378:metabolism*; D012867:Skin / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D013096:Spermine / Q000031:analogs & derivatives / Q000138:chemical synthesis / Q000378:metabolism* / Q000633:toxicity; D013329:Structure-Activity Relationship; D014162:Transfection; D002583:Uterine Cervical Neoplasms / Q000235:genetics / Q000378:metabolism
D005456:Fluorescent Dyes; D008055:Lipids; D034741:RNA, Small Interfering; D013096:Spermine