Table 1.

Overview of analytical strategies to monitor NP- protein interactions

Functional purpose	Analysis strategy	Advantage	Limitation	Reference
Binding affinity and ratio	UV-vis	Faster, more flexible, less complicated	Absorption spectrum show different characters for varied NPs	11–23
	Fluorescence spectroscopy	Quantitative, sensitive	NPs or proteins should have intrinsic or labeled fluorescence	16, 20, 24–37
	Dynamic light scattering	Size distribution of NPs	Not suitable to non-spherical nanoparticles	13, 22, 35, 38–41
	Atomic force microscopy	3-D surface profile	Limited scanning area	23, 42–44
Conformational changes of NP-bound proteins	Circular dichroism	Secondary structures of proteins in the absence or presence of NPs	No the residue-specific information	17, 18, 31, 34, 35, 45–54
	Fourier transform infrared spectroscopy	NP-bound protein amide bands	Objects have to be dried down	15, 35, 55–57
	Raman spectroscopy	NP-bound protein amide bands in aqueous solution	Fluorescence and raleigh scattering noise	48
	X-ray crystallography	3-D structure of nanoparticle-protein complex	Objects have to be crystallized	58
	Nuclear magnetic resonance	NP-bound protein binding site mapping	Line broadening in spectrum when proteins bind to NPs	17, 59
Isolation and separation of NP-bound proteins	Chromatography	Quantitative	Limited application range	11, 17, 24, 27, 38, 60, 61
	Capillary electrophoresis	Quantitative, no need of desorption procedure	Limited detection sensitivity	62, 63
	1-D electrophoresis	Simper, faster	Less effectively separation	11, 29, 38, 53, 57, 60, 64–68
	2-D electrophoresis	Higher ability of separating proteins	More complex, less repeat ability	47, 62, 63, 69–71
Identification of NP-bound proteins	Mass spectroscopy	Efficient, low quantity of protein samples	Less quantitative	24, 46, 60, 63–65, 72, 73
	N-terminal microsequencing	Obtaining directly amino acids sequences of proteins	Less quantitative, restrictiveness of N-terminal amino acid	74–79
Kinetics	Quartz crystal microbalance	Real-time, label-free, sensitive, quantitative;	Immobilization of one party on the chip	80, 81
	Surface plasmon resonance	Real-time, label-free, sensitive and quantitative	Immobilization of one party on the chip	10, 21, 82