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Silver and Gold Nanocomposites Promising as Cell Biomarkers
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Silver and gold are precious metals that may be the key ingredients of nanocomposites designed to measure the actual amounts of drugs being absorbed by cancer cells, according the results of a study led by Lajos P. Balogh, PhD, co-director of the NanoBiotechnology Center at Roswell Park Cancer Institute, in Buffalo, NY.
Quantitative imaging of cells would be an important tool for diagnosis of cancer, as well as for understanding how much drug was actually delivered to individual cancer cells and how the cells reacted.
Traditionally, various fluorescent organic dyes have been used to provide spectacular intracellular images and reveal cellular details. However, measuring the actual amount of drug taken up by cells is often problematic because, when illuminated, these dyes generate reactive oxygen species, breaking down the dye molecules themselves.
Quantum dots (crystalline semiconductor nanoparticles) have been used recently, but they may be sensitive to chemical decomposition; thus many of them are toxic.
The research team from Roswell Park and the University of Michigan, was able to synthesize nanosized composite particles from spherical nanosized polymers (dendrimers) by encapsulating silver and gold atoms.
“These nanocomposites are non-toxic, fluorescent, water soluble, and stable at biologic pH levels,”according to Dr. Balogh. “Further, their surface properties can be adjusted, which is important, because it is the surface that primarily determines how nanoparticles interact with cells.”
The nanocomposites were made in different discrete sizes (5, 11, and 22 nm) with positively and negatively charged and neutral surfaces.
Experiments with these nanocomposites for in vitro labeling in normal and cancer cells demonstrated that cells interacted with the materials as a function of their surface charge; the positively charged nanodevices were internalized the most.
The researchers also were able to calculate uptake by individual cells in vitro, and found no clinical toxicity in vivo.
“These results clearly point to the potential of nanocomposites of silver and gold as quantifiable cell biomarkers,” concluded Dr. Balogh.
