and the absorbance. Aliquot (approximately 10 ml) of purified IgG
(0.1 mg/ml) was added drop-wise to l00 ml of colloidalgold solution (pH8.0) followed by the addition of 10ml of
filtered 10% ovalbumin, pH8.0 with gentle stirring for 20–25min. The solution was incubated for 1 h at 4
oC and centrifuged at 15,000g for 30 min at 4o
C. The supernatant was discarded and the loose precipitate of gold conjugate was
re-suspended in 5ml conjugate dilution buffer (0.01M Tris,3% ovalbumin, 2% sucrose, 0.2% NaCl and 0.03% sodium
azide) and stored at 4oC, as described previously (Lai et
al., 2010).