Indeed, providing a biocompatible organic coating is often used to reduce toxicity of metal oxide nanoparticles. Polyethylene glycol (PEG) is a well-known biocompatible compound used for nanoparticle coating. As metal oxides react well with silanes, one way to coat your ZnO nanoparticles might be to let them react with PEG-silane. Some publications using this protocol are: DOI: http://dx.doi.org/10.101/j.jmmm.2012.01.032

or http://dx.doi.org/10.1007/s11051-012-1100-5

PEGylated ZnO..

Just cover with gold, and then modify accordingly if additional functionality is needed. For more details luck for publication.

Article Magnetic Gold Nanoparticles in SERS-Based Sandwich Immunoass...

Another method cover by polypyrrole, which is bio-compatible.

Article Biocompatibility of polypyrrole particles: An in-vivo study in mice

Another method cover by polypyrrole, which is bio-compatible. Basic preparation of polypyrrole in attachment.

Article Polymerization Model for Hydrogen Peroxide Initiated Synthes...

Indeed, providing a biocompatible organic coating is often used to reduce toxicity of metal oxide nanoparticles. Polyethylene glycol (PEG) is a well-known biocompatible compound used for nanoparticle coating. As metal oxides react well with silanes, one way to coat your ZnO nanoparticles might be to let them react with PEG-silane. Some publications using this protocol are: DOI: http://dx.doi.org/10.101/j.jmmm.2012.01.032

or http://dx.doi.org/10.1007/s11051-012-1100-5

As the first link appears to fail, here the correct link:

http://dx.doi.org/10.1016/j.jmmm.2012.01.032

All the links worked well except the first one that the DOI was missing, thanks indeed Ward Brullot. Thanks also for all the answers above.

Surly, the toxicity is depended on dimension, crystallite size and so on. How about their shape of the same size/surface area, rod, plate, sphere, etc. what shape is the most favoured and least toxic. Or there is nothing concerned to this point of view.

Toxicity of the metal nps can be reduced by encapsulating them using a polymer matrix.

Look when you are talking about cytotoxicity of metallic nanoparticles then you should be very clear on concentration level as even for metallic nanoparticles may not show cytotoxicity below a critical concentration level. The otherway you can functionalize or encapsulate the metallic nanoparticles with some bio-degradable/bio-compatible polymer or even lipids .

How do you deal with the issue as all kind of coatings change the behavior and (surface) characteristics of your material.

Of course, depends on the purpose of application - it might not matter.

But using nanoparticles i.e. As transport vehicles via protein-surface bonds might be not possible anymore upon coating...

Hi Natakan,

I also work with metal oxide nanoparticles for biomedical applications. I have to agree with others above that coating with PEG is probably the best way to go as this stops proteins adsorbing on the surface of the nanoparticles in vivo and thus stops the body from recognising that there is an invading species. I've just had a quick search and found that catechols are good ligands towards ZnO, follow this link to a recent paper of my group, there you can find the protocol for conjugating catechols to PEG, this way you can then adsorb PEG directly on the surface of your nanoparticles:

http://pubs.acs.org/doi/abs/10.1021/la3012958

If you would prefer I can send you a step by step protocol if that would help?

All the best,

Chris

Thanks Christopher Cadman, good link, nice work indeed. Please kindly send me your step by step protocal.

Regarding your question on the role of morphology and crystallite size on cytotoxicity, our group has looked at these two parameters in ZnO and TiO2 nanostructures (eg, wires, particles, 3D urchin structures etc.) the findings show that both parameters are significant in these systems and can lead to cellular death in several different modes. One must also consider the solubility of Zn2+ in the cellular media. You can read more in the following two publications:

1. Effect of morphology of ZnO nanostructures on their toxicity to marine algae

Aquatic Toxicology, 102(3-4), 186-196 (2011)

http://www.sciencedirect.com/science/article/pii/S0166445X1100021X

2. Evaluating Cytotoxicity and Cellular Uptake from the Presence of Variously Processed TiO2 Nanostructured Morphologies

Chem. Res. Toxicol., 23(5), 871-879 (2010)

http://pubs.acs.org/doi/abs/10.1021/tx900418b?journalCode=crtoec&quickLinkVolume=23&quickLinkPage=871&selectedTab=citation&volume=23

Excellence, Christopher Koenigsmann. Both items help, gives us a guidance to do it in different hosts including cells.