Aggregation of amyloid beta-proteins (A beta) mediated by metal ions such as Zn2+ has been suggested to be implicated in the progression of Alzheimer's disease (AD). Hence, development of bifunctional agents capable of inhibiting A beta aggregation and modulating metal-A beta species is an effective strategy for the treatment of AD. In this work, we modified iminodiacetic acid (IDA) onto human lysozyme (hLys) surface to create an inhibitor of Zn2+-mediated A beta aggregation and cytotoxicity. The IDA-modified hLys (IDA-hLys) retained the stability and biocompatibility of native hLys. Extensive biophysical and biological analyses indicated that IDA-hLys significantly attenuated Zn2+-mediated A beta aggregation and cytotoxicity due to its strong binding affinity for Zn2+, whereas native hLys showed little effect. Stopped-flow fluorescence spectroscopy showed that IDA-hLys could protect A beta from Zn2+-induced aggregation and rapidly depolymerize Zn2+-A beta aggregates. The research indicates that IDA-hLys is a bifunctional agent capable of inhibiting A beta fibrillization and modulating Zn2+-mediated A beta aggregation and cytotoxicity as a strong Zn2+ chelator.