Nanoparticle and Protein Corona - Protein-Nanoparticle Interactions - page 30

2.4.1 Surface Charge of Nanoparticle

Nanoparticle surface charge is another important factor in protein interaction. It has
been reported that by increasing the surface charge of nanoparticles, the protein
adsorption increases. Positively charged nanoparticles prefer to adsorb proteins
with isoelectric points (pI)

5.5 such as albumin, while the negative surface charge
enhances the adsorption of proteins with pI

<

5.5 such as IgG [ 5 ]. Using negatively
charged polymeric nanoparticles, Gessner et al. [ 21 ] observed an increase in plasma
protein adsorption with increasing surface charge density. Other studies from the
same group with polystyrene nanoparticles reveal that positively charged particles
predominantly adsorb proteins with pI

>

< 5.5, such as albumin, whereas negatively

>

charged particles adsorb proteins with pI 5.5, such as IgG.

Bradley et al. [ 22 ] reported binding of complement (C1q) to anionic liposomes.
Significant plasma protein binding to vesicles containing cationic lipids has been
reported [ 23 ]. This may arise from electrostatic interactions between the cationic
lipids and most of the negatively charged plasma proteins.
Surface charge can also denature the adsorbed proteins. In a recent study on the
gold nanoparticles with positive, negative, and neutral ligands, it was found that
proteins denature in the presence of charged ligands, either positive or negative, but
the neutral ligands keep the natural structure of proteins [ 7 ].

2.4.2 Nanoparticle Material

The study of the plasma proteins bound to single-walled carbon nanotubes
(SWCNT) and nano-sized silica indicated different patterns of adsorption. Serum
albumin was found to be the most abundant protein coated on SWCNT but not on
silica NP. TiO 2 , SiO 2 , and ZnO NP of similar surface charge bind to different
plasma proteins (Table 2.1 )[ 24 ].

2.4.3 Surface Functionalization and Coatings

Pre-coating and surface functionalization can be employed to decrease the adsorp-
tion of proteins or engineer the protein corona composition. Studies on polystyrene
nanospheres coated with Poloxamine 908 showed a reduction of fibronectin adsorp-
tion. In other studies on functionalization of CNT and SiO 2 nanoparticles with
Pluronics F127, a reduction of serum proteins' adsorption was noticed. A summary
of the role of various coatings such as PEG, poloxamer, poloxamine, dextran,
Pluronic F127, polysorbate, and poly(oxyethylene) on the quantity of adsorbed
plasma protein, phagocytic uptake, and biodistribution is tabulated by Aggarwal
et al. [ 5 ]. It should be mentioned that the available data on the role of functional