Agriculture Reference
In-Depth Information
10.2.3
Isolation of the Plasmid and Coupling
with the Nanoparticles
Isolation of plasmid DNA from
E. coli
and
A. tumefaciens
can be done by using an
alkaline lysis method (Sambrook and Russell
2001
).
The fractionalizing of nanoparticles approach, i.e., imparting functional groups
to the surface of nanoparticles. The functional groups like carboxylic acids are often
used for stabilizing the nanoparticles by electrostatic repulsion and making them
more water soluble; these functionalized nanoparticles can be exploited for the
conjugation of other molecules to the nanoparticles. Even other functional groups
can be introduced on the surface of nanoparticles by their ligand molecules or a
mixture of different ligands. The dodecanethiol monolayer of Au nanoparticles can
be amended with bifunctional ligands by place-exchange reactions to introduce
functional groups like bromide, ferrocene, hydroxyl, and carboxyl (Ingram
et al.
1997
; Templeton et al.
2000
). Fractionalizing of nanoparticles approach can
also be useful for phase transfer reaction by ligand exchange, during this incoming
ligand already contains the desired functional group, as revealed for hydrophobic
CdSe/ZnS quantum dots and ligands comprising, e.g., -COOH, -OH, -NH2
(Wuister et al.
2003
; Hoshino et al.
2004
; Susumu et al.
2007
; Bansod et al.
2013
),
or CdTe and, for instance, a mixture of MPA and aminoethylthiol. Iron oxide
nanoparticles modified with (di)mercaptosuccinic acid have been shown to exhibit
both carboxylic and thiol functional groups (Wilhelm et al.
2003
). Bifunctional
groups can change the functional groups present on the surface of the nanoparticles.
Reactions may harm the stability of the nanoparticles; to overcome this situation,
generally mild reactions are preferred like the ones applied to the chemical modifi-
cation of biomolecules (bioconjugation chemistry), and a large number of dysfunc-
tional molecules are available commercially (Wilhelm et al.
2003
; Hermanson
2008
). The most common type of reaction found can be of carboxylic groups reacted
with primary amines by means of a condensation reaction to yield amide bonds.
Protein fragment or peptides with known sequence of amino acid allow the
rational design of ligand molecules that can be optimized to stabilize nanoparticles
(Levy et al.
2004
) or present various functional groups on the surface (Wang
et al.
2005
; Medintz et al.
2006
; Garanger et al.
2008
). Slocik et al. (
2005
) have
reported the synthesis of gold nanoparticles by using peptides. Making use of the
versatility of biological functionality of peptides, the nanoparticles uptake by cells
can be specifically optimized by conjugating nanoparticles with the corresponding
peptide; similar approach has been reported for Au nanoparticles (Nativo
et al.
2008
) or quantum dots (Pinaud et al.
2004
). In this approach the ligand
exchange with cysteine-containing peptides was performed to modulate reaction
of immune system toward nanoparticles by peptide coating (Bastus et al.
2009
).
Peptide can also be modified by covalent conjugation chemistry, as reported for
quantum dots with amino groups (Cai et al.
2006
) or for iron oxide nanoparticles
with amine groups (Josephson et al.
1999
; Schellenberger et al.
2004
). The quantum
dots are also modified with streptavidin (available commercially) which can be
