The Vroman effect

Appeared earlier in the IACIS Newsletter 56 of April 2014.

Leo Vroman (1915-2014)

On the 22nd of February, Leo Vroman, a prolific poet mainly in Dutch and an illustrator, passed away at the age of 98 in Fort Worth (USA). In 1946, he published his first poems in the Netherlands, and since then has won almost every Dutch literary poetry prize possible. On we find about him: Leo Vroman is the “grand old man” of Dutch poetry. He began writing poems well before World War Two and is still regarded as one of the most lively poets writing in Dutch. This liveliness has much to do with the form and tone of his work, at once loosely conversational and full of ingenious rhymes and playful neologisms.

So, a poet died … and a dutch one at that! Why should we care?

It is indeed not because of his poetry that Leo Vroman is remembered here. He was a scientist, a hematologist to be more precise, that discovered the now called Vroman effect which is exhibited by blood serum protein adsorption. The effect is, that proteins with the highest mobility, and not necessarily with the highest surface affinity, arrive first to the surface and adsorb. The slower proteins arrive later and replace the first-comers when they have a higher surface affinity. This does require some mobility of the already adsorbed proteins. The classical example is when fibrinogen displaces earlier adsorbed proteins on a biopolymer surface to be subsequently replaced by high molecular mass kininogen.
The topic has been studied for over 50 years by now and in 1992 a Festschrift appeared in honour of Vroman’s 75th birthday that was fully devoted to this. As of today scientists are investigating the effect. On the one hand, one tries to find a rationale for the behaviour and on the other hand there is the desire to obtain better control for biomaterial design and maintenance. What is maybe the most striking phenomenon is that protein adsorption is at least partially reversible; for synthetic polymers this is at times hard to achieve. But then, protein replacement is also far from trivial involving “tricks” like head on adsorption of the second to the first, turning around of the complex, and subsequent detachment of the first from the second that is now adsorbed at its bottom. It will be some time from now before such a trick will be performed by a synthetic molecule.
Leo Vroman himself called himself unbelievably lucky to observe the phenomenon and to do further research on it. His driving force was the development of blood-compatible materials, a topic that he followed until late in life. Even in 2009 he contributed a review where he enthusiastically reports on the development of live blood vessels. Indeed, he significantly contributed to his field but the effect is surely of interest to Colloid and Interface Scientists as well.

Ger Koper, NL editor.

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