Table 3.

Structural and biomechanical features of liposomes vs RBCs. Calculations of the liposome surface area and volume assumes 5 nm thick bilayer and range of particle diameters from 50-250 nm [18].

Features	Parameters	Liposomes	RBC
Particle	Character and source	Artificial, synthesis	Natural, blood
	General structure	Vesicle	Vesicle
	Size	50-250 nm	5,000 nm
	Shape	Spheres and elongated	Bi-concave disks
	Surface charge	Variable	Negative
	Homogeneity	Variable	Exceptionally high
	Inner volume	3.3x10−5-7.2x10−3 μm3	94 μm3 [16]
	Surface area	7.85x10−3- 0.20 μm2	136 μm2
Membrane	General structure	Phospholipid bilayer	Similar to liposomes
	Leaflet asymmetry	Can be engineered	Yes (PS inside)
	Common lipid additions	Cholesterol	Diverse [17]
	Exotic lipid additions	Sphingomyelin, steroids	Diverse
	Main non-lipid components	None	Glycoproteins
	Outer surface additions	PEG, targeting moieties	Glycocalyx, sialic acids
	Inner surface additions	May contain some above	Membrane cytoskeleton
	General features	Relatively simple	Complex
Biomechanics	Deformability	Variable	High
	Mechanical sturdiness	Limited	Exceptionally high
	Role in the longevity	Unknown	Very important
	Distribution in flow	Marginal zone	Main stream
	“Collective behavior”	Not known	Form stacks

Abbreviations: PS - phosphatidylserine