Biomedical Engineering Reference
In-Depth Information
alone. Introducing the guanidino group at the primary side of a-, b-, and g-CDs
resulted in per(6-guanidino-6-deoxy)-cyclodextrins, which could condense DNA
into nanoparticles (Mourtzis et al. 2007 ). However, these derivative and their analogs
heptakis- and octakis(6-guanidinoalkylamino-6-deoxy)-b- and -g-cyclodextrins
could not effectively mediate the transfection of DNA in vitro (Mourtzis et al.
2008 ). On the contrary, relatively high efficient transfection and GFP expression
was observed for the per-(6-aminoalkylamino-6-deoxy)-cyclodextrins in HEK
293T and HEK 283 cells. To obtain an efficient vector from b-CD, Diaz-Moscoso
et al. synthesized an amphiphilic b-CD derivative conjugated with seven positively
charged amino moieties and fourteen alkyl groups at primary and secondary
hydroxyl positions, respectively (Diaz-Moscoso et al. 2008 ). This polycation with
reduced cytotoxicity exhibited high efficient transfection of pDNA in BNL-CL2
cells, which was even comparable to that of PEI25. By conjugating oligoethyle-
neamines to the primary hydroxyl sites of b-CD via click coupling chemistry, a
novel series of multivalent polycationic b-CD “click clusters” have been created
(Srinivasachari et al. 2008 ). The cellular gene delivery experiments revealed that all
these cationic b-CD derivatives could efficiently deliver Cy5-labeled pDNA and
pDNA encoding the luciferase reporter gene into HeLa and H9c2 cells in Opti-
MEM. The level of reporter gene expression was found to be increased with an
increase in oligoethyleneamine number within the cluster arms, and derivatives
armed with tetraethylenepentamine pentaethylenehexamine are the most effective
and promising vectors that deserve further development. Cytotoxicity evaluation
based on protein, MTT and lactate dehydrogenase assays demonstrated that all the
click clusters remained nontoxic within the expected dosage range, while the posi-
tive controls, Jet PEI and Superfect, were highly cytotoxic.
3.3.2
CD-Containing Cationic Polymers
On the other hand, CDs-containing cationic polymers have been systematically
examined for gene delivery in recent years. Davis and coworkers designed and
synthesized a class of linear, cationic, b-CD-containing polymers (bCDPs) by
copolymerizing difunctionalized b-CD monomers with other difunctionalized
comonomers (Gonzalez et al. 1999 ). Table 7 shows a representative structure of this
type of polycation. These polymers have low in vitro and in vivo toxicity. Polyplexes
with size of <200 nm can be assembled by the condensation of pDNA using
bCDPs. Importantly, in vitro transfection efficiency with bCDPs was comparable
to those based on PEI (branched 25 kDa) and Lipofectamine. The transfection
activity and cell toxicity are critically related to the structure of this type of carbo-
hydrate polycations (Hwang et al. 2001 ), which is mainly determined by the
comonomer structure, charge center type as well as the cyclodextrin type and func-
tionalization (Reineke and Davis 2003a, b ; Popielarski et al. 2003 ). The colloidal
stability in biological fluids can be furthered increased by a surface decoration of
the assembled polyplexes using PEG-Ada, which is achieved through the host-
guest interactions between b-CD and Ada group(Mishra et al. 2004 ). Furthermore,
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