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A. Antony and J.-H. Boo
6 Several Characterization Methods of MONMs
in Biomedical Application Context
Metal oxide NMs does not produce any surface plasmon resonance (SPR) thus application of UV-visible spectroscopy is not much useful to identify size. The size exclusion chromatography is performed during the synthesis process at a periodic interval
to study size and growth. After synthesis, other well-known methods such as scanning
electron microscopy, transmission electron microscopy, X-ray diffraction and chemical analysis such as X-ray photoelectron spectroscopy etc. can be performed. Some
specific methods routinely used with respect to MONMs for biomedical applications
are detailed below.
6.1 Size Exclusion Chromatography (SEC)
This technique is used to analyze growth, size and shapes of MONMs during synthesis
stage and to separate it. The SEC is a process working based on an entropy control.
There is no interaction that occurs between the stationary phase and the analytes thus
separation is done exclusively from the pores of the stationary phase. The size-specific
separation is achieved based on the hydrodynamic volume of the nanoparticles. At
the same time, the shape-specific nanoparticles are separated based on the combined
effect of size-exclusion and adsorption. In both cases, large molecules elute initially
as compared to the small nanoparticles through the column packing material [38]. For
practical application, the elution time should be reproducible since it is an indication
of the nanomaterial size with minimal standard deviation (Fig. 3).
6.2 Hydrophilicity or Hydrophobicity of Nanomaterials
Surface
Hydrophilicity or hydrophobicity is a measurement to determine the interaction of
NMs with bio-systems. For example, NMs’ interaction with biological membranes,
cellular uptake, immune response, protein adsorption and hemolytic effects are
strongly dependent on the hydrophobic nature. In the case of NMs powder such
measurement was considered impossible through direct water contact angle measurement (which is conventionally used for thin films and polymers) but some indirect
methods are available recently. By measuring the surface energy through possibly
four implicit methods it is performed. Those are (a) AFM based adhesion force
measurement between the functionalized (hydrophilic/hydrophobic) tips and immobilized NPs on silicon surface [40], (b) the NMs surface adsorption assays based on
rose bengal (RB) dye. In this method, amount of RB dye adsorbed on to the NMs is
taken as a measure of hydrophobicity. The binding constant and the maximum amount
A. Antony and J.-H. Boo
6 Several Characterization Methods of MONMs
in Biomedical Application Context
Metal oxide NMs does not produce any surface plasmon resonance (SPR) thus application of UV-visible spectroscopy is not much useful to identify size. The size exclusion chromatography is performed during the synthesis process at a periodic interval
to study size and growth. After synthesis, other well-known methods such as scanning
electron microscopy, transmission electron microscopy, X-ray diffraction and chemical analysis such as X-ray photoelectron spectroscopy etc. can be performed. Some
specific methods routinely used with respect to MONMs for biomedical applications
are detailed below.
6.1 Size Exclusion Chromatography (SEC)
This technique is used to analyze growth, size and shapes of MONMs during synthesis
stage and to separate it. The SEC is a process working based on an entropy control.
There is no interaction that occurs between the stationary phase and the analytes thus
separation is done exclusively from the pores of the stationary phase. The size-specific
separation is achieved based on the hydrodynamic volume of the nanoparticles. At
the same time, the shape-specific nanoparticles are separated based on the combined
effect of size-exclusion and adsorption. In both cases, large molecules elute initially
as compared to the small nanoparticles through the column packing material [38]. For
practical application, the elution time should be reproducible since it is an indication
of the nanomaterial size with minimal standard deviation (Fig. 3).
6.2 Hydrophilicity or Hydrophobicity of Nanomaterials
Surface
Hydrophilicity or hydrophobicity is a measurement to determine the interaction of
NMs with bio-systems. For example, NMs’ interaction with biological membranes,
cellular uptake, immune response, protein adsorption and hemolytic effects are
strongly dependent on the hydrophobic nature. In the case of NMs powder such
measurement was considered impossible through direct water contact angle measurement (which is conventionally used for thin films and polymers) but some indirect
methods are available recently. By measuring the surface energy through possibly
four implicit methods it is performed. Those are (a) AFM based adhesion force
measurement between the functionalized (hydrophilic/hydrophobic) tips and immobilized NPs on silicon surface [40], (b) the NMs surface adsorption assays based on
rose bengal (RB) dye. In this method, amount of RB dye adsorbed on to the NMs is
taken as a measure of hydrophobicity. The binding constant and the maximum amount