Biomedical Engineering Reference
In-Depth Information
4.9 NMR
Hellstrand et al. [
30
] showed by size-exclusion chromatography and Nuclear
magnetic resonance (NMR) that copolymer NPs bind lipophilic molecules like
cholesterol, triglycerides, or phospholipids from human plasma. The lipid and
protein binding patterns correspond closely with the composition of high-density
lipoprotein (HDL). Apolipoproteins have been identified as binding to many other
NPs, suggesting that lipid and lipoprotein binding is a general feature of NPs under
physiological conditions.
Stayton et al. [
31
] have studied by solid-state NMR technique in situ secondary-
structure determination of statherin peptides on hydroxyapatite (HAP) surfaces.
The molecular insight provided by these studies has also led to the design of
biomimetic fusion peptides that utilize nature's crystal-recognition mechanism to
display accessible and dynamic bioactive sequences from the HAP surface.
4.10 X-Ray
X-ray crystallography is also used routinely to determine how a drug interacts with
its protein target and what changes might improve this interaction. Prakasham et al.
[
32
] have investigated diastase enzyme immobilized on nickel-impregnated silica
paramagnetic nanoparticles and characterized using Fourier transform infrared
spectroscopy and X-ray crystallography. Analysis of enzyme-binding nature with
these nanoparticles at different physiological conditions revealed that binding
pattern and activity profile varied with the pH of the reaction mixture. The
immobilized enzyme was further characterized for its biocatalytic activity. Para-
magnetic nanoparticle-immobilized enzyme showed more affinity for substrate
compared to free one.
4.11 Differential Centrifugation Sedimentation
Walczyk et al. [
33
] have studied the structure and stability of protein-NP
complexes in human plasma. They determined that the protein corona is about
10 nm thick for many nanomaterials. Differential centrifugation sedimentation
(DCS) allows measuring the size distribution of NP-protein complexes in a semi-
quantitative way in the presence of the complex protein mixture.
Sometimes, NP dispersion in biological environment results in some aggregation
or a shift in the particle size distribution. Unlike classical light-scattering techniques,
the nanoparticle tracking and analysis (NTA) technique allows nanoparticles to be
sized in suspension on a particle-by-particle basis allowing higher resolution and
therefore better understanding of aggregation. Montes-Burgos et al. [
34
]showed
