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Polyethylene Glycol (PEG) Surface

Polyethylene glycol (PEG) is a polyether compound that consists of repeating units of ethylene oxide. It is a safe compound that is used in a wide variety of application including food additives, as an excipient in pharmaceutical products, and as a stealth coating in biomedical applications to reduce non-specific binding and to evade the body’s immune system. The PEG surface is the most stable of our surfaces in buffers containing high salt concentrations found in culture media or other high ionic buffers. The PEG surface functionality disperses very well in water and protic solvents, increasing compatibility in biological systems. The methoxy PEG surface has a slightly negative to neutral surface charge which is advantageous for in-vivo or in-vitro applications.

nanoComposix provides two different PEG functionalizations, either a lipoic acid derivative of PEG with a terminal acid group (see Carboxyl functionalization) and a 5 kDa methoxy polyethylene glycol sulfhydryl (m-PEG-SH). The methoxy terminated PEG is available on both gold and silver nanoparticles increasing particle stability in a wide range of solvents. Our m-PEG-SH functionalized metal particles have the highest salt stability of any of our surfaces.


  • High salt stability
  • Sterically induced stability
  • Biologically compatible

Representative Source: methoxy PEG Thiol MW 6000 (Sigma Aldrich, 729159)

Comparison to Alternatives

  • Displaceable: Not displaceable – strongly bound to the particle surface via the thiol
  • Neutrally charged (zeta potential between –15 mV and 15 mV at pH 7.4)
  • Excellent salt stability: stable in many salt solutions
  • Toxicity: low toxicity and high biocompatibility
  • Solvent compatibility: Water, ethanol, chloroform, many other polar solvents


  • Biodiagnostic and nanomedicine applications
  • Photothermal applications
  • In-vitro and in-vivo toxicology experiments