Miller A, Adams S, Zhang JZ and Lihua Wang
Understanding the interaction between metal nanostructures and common metal ions is essential for biomedical applications of metal nanostructures including imaging and therapy. A systemic study of the interaction of citratecapped hollow gold nanospheres (HGNs), a unique metal nanostructure that has demonstrated high efficiency for photothermal ablation (PTA) therapy of cancer cells, with common metal ions: Na+, Ca2+, Mg2+, Cu2+, Zn2+, and Al3+ was carried out with the goal to determine how these metal ions may affect the properties and thereby performance of HGNs in biomedical applications. Specifically, the study focuses on the issue of metal ion induced aggregation of HGNs since aggregation can strongly influence the optical and photothermal properties of the HGNs. The level of HGNs aggregation caused by interaction with metal ions was found to depend on the nature and concentration of the metal ions present in the solution as well as the properties of the HGNs. The larger the stability constant of the metal ion citrate complex (logK1) is, the stronger the interaction between the metal ions and the HGNs was found to be. Lower HGN concentrations and higher levels of dispersion were correlated to enhanced sensitivity of the HGNs towards metal ion induced aggregation. The results demonstrate that metal ions can strongly affect how nanostructures like HGNs can be used in biomedical applications including imaging and therapy.