Nano Biosols goldblog

nanoparticles for biological solutions

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

Welcome to the Nano Biosols gold-blog: a potted history of the technology


Welcome to the Nano Biosols gold-blog.  Nano Biosols is a new start up supplying gold nanoparticles to industry and  the bio-medical research community with a view to developing the technology in the future.  In the 1970’s  we were introduced to the concept of immunogold. The only application was in immonoelectron microscopy where particles were visualised as  black dots where they bound on biological samples. Through innovative steps the particles were also used in light microscopy and protein blotting techniques  in combination with silver enhancement techniques. The second generation of gold based reagents were developed to be used  in lateral flow in-vitro diagnostic assays due to their macroscopic ruby red colour. It was around the new millennium in 2000 that the term nanoparticle appeared in relation to gold and the concept of the third major application surfaced in the form of therapeutics. The concept of nanomedicine , i.e. use of nanomaterials as therapeutic agents in medicine had developed. It is expected that these theranostics will have multi-modal properties of targeting, imaging and delivering a therapeutic effect. The future looks bright for the continuous development of applications of gold nanoparticles  even in other non biological sectors such as catalysis and solar energy. Who knows where the next  innovative application of these versatile materials will take us ? I hope this blog can be a sounding board for new ideas, applications and problem solving in the nano gold community.


11/11/2015 Posted by | News | | 1 Comment