A facile,one‐step method for the determination of accessible surface primary amino groups on solid carriers

Amino‐functionalized microspheres are emerging as promising candidates for biomedical applications. Quantification of surface amino groups is of great significance to achieve a rational surface design and to facilitate subsequent bioconjugation. In this paper, we describe a facile method named as subtractive 2‐iminothiolane (ITL)/bicinchnoninic acid (BCA) method] to determine the accessible surface primary amino groups using BCA and ITL on the basis of the rapid color reaction between ITL and BCA at ambient temperature. ITL was used to quantitatively label the surface amino groups, and the ITL consumed by the amino groups was determined by BCA in a solution reaction. The amino density of amino‐functionalized silica microspheres, polystyrene microspheres and magnetic microspheres were determined. The present method we proposed exhibits great simplicity (one‐step labeling and immediate detection without washing procedure) with high precision (standard error <5% for each concentration point of standards) and specificity. Copyright © 2012 John Wiley & Sons, Ltd.