Nano Biosols goldblog

nanoparticles for biological solutions

Real time quantification of gold nanoparticles in experimental use. As simple as plug and play.

The main problem with using gold nanoparticles in life science research is the lack of a simple real time quantification method. Use of mass spectrometry is very accurate but also very expensive and definitely not in real time. It is now possible to quantify gold nanoparticles in real time in experimental procedures by using the chemisorption of Iodine -125 to the gold particles. This simple labelling step involves just mixing the two components. Take your functionalised gold particles and add the isotope. As simple as plug and play. Applications include quantifying in-vitro cell uptake of particles and the potential for imaging in-vivo small animal particle distribution using SPECT (I-125) or PET (I-124) procedures. If nanomedicine is to become a reality, then simple real time methods of imaging and quantification need to be developed. Silver nanoparticles can also be quantified by this method also. Details of our work in understanding the chemistry can be found in a recent publication of the Journal of Nanoparticle Research.

03/07/2017 Posted by | Quantification | Leave a Comment

Nanoparticle quantification. When is a mole not a mole ?

The answer is when referring to the “molar” concentration of nanoparticles. There is some ambiguity in discussion groups, blogs and publications regarding the quantification of gold nanoparticles in cell uptake experiments. Some publications refer to gold nanoparticles in terms of molarity. Molarity actually refers to the amount material in a homogeneous solution of molecules  ( or atoms) as a fraction of  its molecular weight in a litre. A property of  1 Mole of material is that it contains 6.023 E23 molecules i.e. Avagadros’ number. Molarity cannot apply to nanoparticles because they are not molecules or homogenous in size. The stated size is a mean based on a spread of slightly different sizes.  If you consider 50 ug/ml of 10nm gold particles there would be about 5 E12 particles and a molarity of 0.25 mM with respect to elemental gold. A 50 ug/ml of 20 nm gold particles would be of the same molarity (0.25mM) but would contain about 0.6 E12 particles. So quoting molarity of gold has to refer to the amount of gold atoms present but without the mean particle size as well the molarity would be meaningless.  To confuse the issue even more  there are some publications where they refer to the Molar extinction coefficients of nanoparticles which appear to be based on Avagadros number rather than molecular weight as nanoparticles don’t have a molecular weight .  This is quite a useful was to express the number of particles used but the nomenclature leads to ambiguity.  A specific term such as the “particulate molarity” would distinguish  quantification based on numbers of particles rather than gold atoms. To summarise whatever method is used to state the quantity of gold particles used it should be clear that molarity  refers to elemental gold  and that quantity based on Avagadros’ number should be expressed in a more specific term than just molarity. Personally I just prefer to use g/l or particles/ml but also including the mean particle size.


18/11/2015 Posted by | Quantification | | Leave a Comment