Going hand in glove

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  • Published: Jan 5, 2009
  • Author: Steve Down
  • Channels: Base Peak
thumbnail image: Going hand in glove

Latex products are in regular and common use in today's society and one of the most common applications is the fabrication of gloves for the healthcare market to be worn by patients and carers. However, natural latex has been associated with allergic reactions for some years now and the increased sales of latex gloves have compounded the problem. Up to 10% of healthcare workers have reported type I allergic reactions and a massive 64% of patients with urogenital diseases, such as spina bifida, have been affected. In the worst case, this allergy can lead to anaphylactic shock.

Type I allergies are caused by proteins that fall into three general types. Water-soluble proteins can be removed easily by washing during production and starch-bound proteins can be avoided by not using corn starch powder to dust the latex products after manufacture. The third group, latex-bound proteins, are the ones that tend to be problematical. They are strongly trapped in the 3D latex matrix and are likely to remain in the latex after glove production.

The two main latex protein allergens are hevein, which is the N-terminal domain of prohevein, and rubber elongation factor (REF). They do not appear to be evenly distributed throughout the glove, probably due to the production process in which the moulded glove is pulled from the mould and turned inside out. This is supported by the fact that healthcare workers are mostly in contact with the inner surfaces and show allergies to hevein whereas spina bifida patients are in contact with the outer surfaces and show immunoreactions to REF and hevein.

There have been several attempts to measure these two proteins in latex products, based on immunological methods, and some have been adopted by ASTM and the EU. However, scientists at the Vienna University of Technology claim that quantitative extraction of the proteins is still difficult to achieve. Their solution is to measure the proteins in situ, using imaging mass spectrometry. Martina Marchetti-Deschmann and Gunter Allmaier from the Institute of Chemical Technologies and Analytics introduced a special surface treatment step that released sufficient protein for analysis.

The gloves were cut into 1 x 1 cm pieces and the inner and outer surfaces were rinsed with water to remove unwanted particles. The pieces were fixed to a stainless steel MALDI target, carefully noting whether the inner or outer surface was exposed. Direct analysis by MALDI mass spectrometry revealed no significant protein signals, confirming their bound status.

A simple pretreatment step changed all that. When the fixed latex pieces were washed with trifluoroacetic acid, strong protein signals were obtained. The release mechanism might involve leaching, swelling and surface roughening, but the researchers were unclear at this stage. The important point was the appearance of good signals over the whole cross section with a binary matrix of alpha-cyano-4-hydroxycinnamic acid in acetonitrile-formic acid and 2,5-dihydroxybenzoic acid in acetonitrile-trifluoroacetic acid.

Nine different brands of latex gloves were examined and the inner surfaces of most, but not all, revealed the presence of three major allergens: hevein, REF and a truncated form of REF (tREF). Other forms of hevein were also found, illustrating ragged C-termini.

In contrast, the outer surfaces of the gloves revealed different protein compositions to the inner surfaces. No allergens were detected in any brand but other polymer signals attributed to lubricants and antifriction agents were observed.

The inner surfaces of the glove segments were then subjected to imaging mass spectrometry by rastering over 800 x 400 µm sections within each latex piece. This allowed 2D distribution maps of the allergens to be built up across the inner surfaces.

The maps showed that hevein was localised at specific areas on the inner surfaces rather than being distributed smoothly across the surface. This also occurred to some extent for REF and tREF but these two were always found at the same locations as each other in the same glove. The relative proportions of the proteins varied from brand to brand. In total, hevein was found in 36% of the studied area and REF and tREF were found on 25%.

This first reported use of imaging mass spectrometry for studying natural polymer surfaces has illustrated the ease with which protein allergens on latex gloves can be identified and mapped without extraction. The different distributions on the inner and outer surfaces account for their different allergenic properties.

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.




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