Immunoliposome-PCR: a generic ultrasensitive quantitative antigen detection system

Table 1 Parameters of the liposome detection reagent ^a)

Parameter	Value
Hydrodynamic diameter ^b)	117 ± 20 nm
Exposed biotin/lipid molar ratio ^c)	5.1 ± 0.2 mmol/mol
Reporter DNA/lipid molar ratio ^d)	2.1 ± 0.4 mmol/mol
CV of liposome reagent reproducibility ^e)	6 %
Liposome reagent stability ^f)	1.5 years at 4 °C

^a) The parameters were determined using measurements from 4 replicate preparations of the liposome detection reagent.
^b) The hydrodynamic diameter of the liposomes was determined by dynamic light scattering using a number-weighted Gaussian size distribution.
^c) The average number of biotin molecules exposed on the surface of the liposomes was estimated using a 4'-hydroxyazobenzene-2-carboxylic acid-avidin displacement quantification assay and the total lipid concentration. The total lipid concentration was determined from the absorbance of DHPE-rhodamine.
^d) The ratio of reporter DNA to total lipid, where the reporter concentration was measured by its absorbance at 260 nm.
^e) The CV for the reproducibility of the liposome detection reagent preparation was determined from the four replicate preparations by measuring the Ct value associated with equal concentrations of total lipid.
^f) The liposome detection reagent stability was defined as the length of time the liposomes could be stored at 4°C without observing a reduction in either the LOD or dynamic range when performing the CEA assay. See Table 2 for the LOD and dynamic range of the ILPCR assay for CEA in human serum.

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