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Forward thinking for current and future in vitro diagnostic assay reagents

The many challenges to overcome when developing and manufacturing an in vitro diagnostic (IVD) are well known, but one recent consideration is threatening new and venerable assays alike: sustainability.

In recent years, there has been significant interest beyond the reliability and efficacy of diagnostic assays and their components, with discussions around environmental health and safety considerations of use and disposal. Environmental agencies around the globe have been researching and tracking key chemicals used in a variety of industries, including medical diagnostic assay development and manufacturing. While the environmental monitoring of chemicals for health and safety, with occasional regulatory warnings or phase-outs, is nothing new, more recent targeting of some ubiquitous assay reagents with decades of usage is getting the attention of assay designers and manufacturers alike.

When biocide preservatives are too good at killing 

The challenge with choosing preservatives for diagnostic assays is in getting the right spectrum of coverage without interfering with other assay components or being overly toxic to users or environment. This has been a challenge for years. The traditional preservatives used to prevent microbe growth in in vitro diagnostic products are not ideal. Thimerosal is expensive and, because it contains mercury, is classified as toxic for disposal. It is banned from use in some countries, including Japan. Sodium azide is primarily biostatic, not biocidal, at levels normally used, thus it might not effectively control microorganisms in a product. As a powder, sodium azide is both hazardous and inconvenient to work with. In acidic solutions, it can release harmful vapors. Antibiotics offer protection against specific groups of microorganisms, rather than broad-spectrum protection. Combinations of antibiotics expand the range of protection, but combinations become complicated and expensive, and protection remains incomplete.

Tightening environmental regulations restrict options

The recent addition of sodium azide, a well-used biostatic preservative, to the European REACH list of to-be-phased out IVD reagents is a good case in point. With thimerosal and sodium azide being phased out, diagnostics designers and manufacturers now need to intensify efforts to find reliable, more sustainable options for assay components.

Ecofriendlier alternatives? But at what cost to performance?

New preservative materials can eliminate the drawbacks associated with traditional preservatives. Two isothiazolones, the active ingredient in ProClin™ 150, ProClin™ 200, ProClin™ 300 and ProClin™ 950 preservatives, have a unique mechanism of action that both inhibits bacterial, fungal, and yeast growth and causes cell death. Within minutes after contacting a microorganism, these molecules penetrate the cell wall and inhibit specific enzymes in the Krebs cycle, the central metabolic cycle of the cell, inhibiting growth, macromolecule synthesis, and respiration, and causing intracellular energy levels to fall rapidly. With energy production disrupted, the cell cannot synthesize chemicals for routine operation or repair, and ultimately dies. Because the target enzymes are central to the cell’s ability to function, microbes are afforded little chance to develop resistance. Unlike traditional preservatives, there are no disposal restrictions on the isothiazolones when they are used at recommended levels; the ProClin™ 150, ProClin™ 200, ProClin™ 300 and ProClin™ 950 preservatives as supplied can be neutralized and disposed of as nonhazardous waste.

Can eco-friendly equal high performance?

There is a pervasive concern in many industries that compliance with changing environmental regulatory directives will create an undesirable trade-off between health and safety and efficacy.  As with other chemical substitutions, biocide preservatives for diagnostic assays do not reduce performance.

The active ingredients in ProClin™ preservatives are effective at very low concentrations, 6-20 ppm, and the effectiveness of these materials relative to traditional preservatives has recently been established (link to our comparison article). The research concluded that 15 ppm ProClin™ 150 preservative, 15 ppm ProClin™ 300 preservative, and 0.005% thimerosal effectively preserved a phosphate buffered saline/TWEEN® 20 solution from a range of microorganisms under the conditions specified. 0.1% sodium azide did not preserve phosphate buffered saline/TWEEN® 20. The study indicates that ProClin™ 150 and ProClin™ 300 preservatives can be effective replacements for thimerosal, and offer better protection than sodium azide, without the handling and disposal concerns associated with either traditional preservative. Additional information the United States Pharmacopeia (USP)-like efficacy study is also available at sigmaaldrich.com/proclin.

Rethinking diagnostic assay development

While developing and commercializing in vitro diagnostic assays will never be easy, careful consideration of shifting regulatory trends, awareness of reagent environmental risk and a robust risk mitigation plan including supply chain security can get your assay to market faster – and keep it there.

Proclin™ preservative samples and technical expertise are available for your in vitro diagnostic assay manufacturing.

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