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properties. Transmission electron microscopy (TEM), scanning electron micros-
copy (SEM), and zeta potential measurement are commonly used to evaluate the
size, shape, and charge on the nanoparticle (Verhaegh and Van 1994 ; Nyffenegger
et al. 1993 ). Dynamic light scattering (DLS) technique is used to measure NP size in
aqueous media while providing NP size, concentration, and relative dispersion
(Van and Vrij 1993 ).
The comparative analysis study of prepared bioconjugates with different
nanoparticles and DNA can be done by mixing them in a certain mass ratio and
checked by performing:
(a) Mobility assay on agarose gel electrophoresis
(b) Spectrophotometer, TEM, and LM 20 analysis
10.2.5 Electron Microscopy
The SEM and TEM images of both nanoparticles and nanoparticle/DNA complexes
can be analyzed to evaluate the surface characteristics, i.e., size and shape.
10.2.6 Zeta Potential and Size Measurement
The zeta potential measurement of a particle designates the overall charge that the
particle acquires in a particular medium. The zeta potential value can be used to
determine the colloidal stability of the NP and their conjugate. If the nanoparticles
in suspension possess a large positive, i.e., greater than +30, or less negative charge,
i.e.,
30, zeta potential, they will repel each other and will avoid the NP agglom-
eration, whereas the zeta potential value between +30 and
30 will result in
flocculation or coagulate loosely depending upon the charge. Therefore, surface
modification can change the net charge on the particle surface in a particular
medium and is important to improve the long-term stability of NPs. Cui
et al. ( 2012 ) have reported that after conjugation with nucleic acid, the zeta
potential of pure nanoparticles decreases due to the net negative charge present
on the DNA molecule, which can neutralize the positive charge on the surface of
metal nanoparticles (Cui et al. 2012 ).
10.2.7 Combination and Protection Analysis
Effectiveness of bioconjugated nanoparticles for gene transfer can be checked
depending upon their capacity to protect the DNA from nuclease and sonication
to demonstrate how DNA is protected by nanoparticle complex by physical and
chemical agents by performing the following assays (Zou et al. 2009 ):
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