small particles in a liquid suspension. The method is practiced in conjunction with
an ultramicroscope, which permits small particles in liquid suspension to be
envisaged moving under Brownian motion.
A few studies have validated the fact that nanoparticles of submicron size have
advantages over microparticles as a drug delivery system. Due to their higher
intracellular acceptance in comparison to microparticles and their widespread
array of biological targets owing to their small size and relative mobility,
nanoparticles are considered before any other particle range.
5.2 Particle Morphology
The physical and chemical properties of nanoparticles have a deep impact because
they govern the relationship of nanoparticles with the environment and biological
systems. The techniques used to examine the morphology of nanoparticle are SEM,
transmission electron microscopy (TEM) and AFM, along with particle size and
distribution analyses. Other parameters like morphology or surface roughness of the
nanoparticles are also determined.
For TEM, the sample has to be ultrathin for the electron transmittance, and the
dispersion is deposited onto support grids or films. Negative staining material is
used to withstand the instrument vacuum and facilitate handling. However, SEM is
different in that the solution is primarily changed into a dry powder, which is then
stranded on a sample holder and tracked by coating with a conductive metal, such as
gold, using a sputter coater. The sample is then scanned with a focused fine beam of
electrons.
5.3 Particle Stability
Nanoparticle suspensions are moderately stable due to their colloidal nature. In
general, colloidal suspensions are unwavering and have very little tendency to
separate as a consequence of deliberate deposition, which is a result of the mixing
tendencies of diffusion and convection. However, some agglomeration can occur.
Colloidal stability can be analyzed through the zeta potential of nanoparticles. The
zeta potential reflects the electrical potential of particles and is influenced by the
composition of the particle and the medium in which it is dispersed. This potential is
an indirect measure of the surface charge. Due to the small particle size and
amplified surface area, nanoparticles tend towards a more thermodynamically stable
state driven by an increased free energy. Thus, without adequate equilibrium, the
accumulation of nanoparticles in the medium will occur shortly soon after particle
formation, and at least during long-term storage. Nanoparticles have high particle
mobility due to Brownian motion and, thus, the particles collide with each other. The
probability of particle–particle interactions proliferates with reduced size. Most
colloidal particles have negative zeta potential values ranging from about À100 to
À5 mV. Surface charges inhibit the aggregation of nanoparticle polymer dispersions
because of strong electrostatic repulsion, thereby augmenting the stability of the
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A.K. Anal and A. Tuladhar
an ultramicroscope, which permits small particles in liquid suspension to be
envisaged moving under Brownian motion.
A few studies have validated the fact that nanoparticles of submicron size have
advantages over microparticles as a drug delivery system. Due to their higher
intracellular acceptance in comparison to microparticles and their widespread
array of biological targets owing to their small size and relative mobility,
nanoparticles are considered before any other particle range.
5.2 Particle Morphology
The physical and chemical properties of nanoparticles have a deep impact because
they govern the relationship of nanoparticles with the environment and biological
systems. The techniques used to examine the morphology of nanoparticle are SEM,
transmission electron microscopy (TEM) and AFM, along with particle size and
distribution analyses. Other parameters like morphology or surface roughness of the
nanoparticles are also determined.
For TEM, the sample has to be ultrathin for the electron transmittance, and the
dispersion is deposited onto support grids or films. Negative staining material is
used to withstand the instrument vacuum and facilitate handling. However, SEM is
different in that the solution is primarily changed into a dry powder, which is then
stranded on a sample holder and tracked by coating with a conductive metal, such as
gold, using a sputter coater. The sample is then scanned with a focused fine beam of
electrons.
5.3 Particle Stability
Nanoparticle suspensions are moderately stable due to their colloidal nature. In
general, colloidal suspensions are unwavering and have very little tendency to
separate as a consequence of deliberate deposition, which is a result of the mixing
tendencies of diffusion and convection. However, some agglomeration can occur.
Colloidal stability can be analyzed through the zeta potential of nanoparticles. The
zeta potential reflects the electrical potential of particles and is influenced by the
composition of the particle and the medium in which it is dispersed. This potential is
an indirect measure of the surface charge. Due to the small particle size and
amplified surface area, nanoparticles tend towards a more thermodynamically stable
state driven by an increased free energy. Thus, without adequate equilibrium, the
accumulation of nanoparticles in the medium will occur shortly soon after particle
formation, and at least during long-term storage. Nanoparticles have high particle
mobility due to Brownian motion and, thus, the particles collide with each other. The
probability of particle–particle interactions proliferates with reduced size. Most
colloidal particles have negative zeta potential values ranging from about À100 to
À5 mV. Surface charges inhibit the aggregation of nanoparticle polymer dispersions
because of strong electrostatic repulsion, thereby augmenting the stability of the
284
A.K. Anal and A. Tuladhar