Zeta potential mediated reaction monitoring on nano and microparticles.

Nano and microparticles are widely used across the life science interface, with applications ranging from chemical probes of biological function to fluorescent particles for flow cytometry and cellular tracking. Increasingly, particles are modified with a variety of chemistries to boost their functionality and broaden their biological applicability. However, although particle modification has become standard laboratory practice, the ability to determine the extent and efficiency of chemical modification is often very limited and empirical in nature. Herein, we report the use of zeta potential analysis as a simple and rapid "direct-on-particle" approach allowing levels of bead modification and derivatization to be evaluated. As a proof-of-concept, aminomethyl-functionalized nano and microparticles were derivatized to display a variety of surface functionalities and their zeta potentials measured, allowing verification of the applicability of the approach for particle analysis. We demonstrate that zeta potential measurement is a convenient approach which allows multistep reaction sequences to be followed, and show that this method can be used to verify and validate successful particle modification.