Why does Izon use ProClin™ 200 in the qEV column storage buffer?

qEV columns are stored in a buffer containing ProClin™ 200 as a preservative. Izon selected ProClin™ 200 based on in-house studies conducted in 2023. Compared with sodium azide, another commonly used preservative, ProClin™ 200 offers broader antimicrobial action and a better health and environmental hazard profile.

What is ProClin™ 200?

ProClin™ 200 is a biocide widely used in in vitro diagnostics. It is an aqueous mixture of the active ingredients chloromethylisothiazolinone (CMIT) and methylisothiazolinone (MIT), allowing for broad spectrum antimicrobial properties, which act against gram-positive and gram-negative bacteria and fungi. Sodium azide is less effective against gram-positive bacteria, so ProClin™ 200 offers broader protection.

Flushing and storing your column

Flush the storage buffer from the column before use, following the instructions in your qEV user manual.

Note: Once flushed, the column is no longer protected by ProClin™ 200. To store a column for future use, follow the cleaning and flushing instructions in your qEV user manual. Then store it in PBS containing 0.05% ProClin™ 200, or in 20% ethanol.

In-house studies

Microbial challenge study

Four different wildtype bacterial strains were plated and incubated in PBS only, PBS with 0.1% sodium azide, and PBS with 0.1% ProClin™ 200. PBS only and sodium azide showed no antimicrobial effect on the four strains. ProClin™ 200 strongly inhibited bacterial growth at both room temperature and 30 °C (Table 1).

Table 1. ProClin™ 200 versus sodium azide microbial challenge

Test solution	Inoculation (CFU/mL)	14-day count
PBS only	3.2 × 10⁸	TMTC
PBS with 0.1% sodium azide	3.2 × 10⁸	TMTC
PBS with 0.1% ProClin™ 200 (15 ppm active ingredient)	3.2 × 10⁸	< 10

Results were the same at 30 °C and room temperature. TMTC: too many to count. CFU: colony-forming units.

Concentration study

In an additional in-house study, the microbial challenge was repeated across a range of ProClin™ 200 concentrations. The lowest concentration tested, 1 ppm active ingredient (≈0.007% ProClin™ 200), was just as effective as 15 ppm active ingredient (0.1% ProClin™ 200) in preventing microbial growth (Table 2).

Table 2. ProClin™ 200 concentration microbial challenge

Test solution	Inoculation (CFU/mL)	7-day count
PBS only	2.6 × 10¹⁰	TMTC
PBS with 15 ppm active ingredient ProClin™ 200	2.6 × 10¹⁰	0
PBS with 7 ppm active ingredient ProClin™ 200	2.6 × 10¹⁰	0
PBS with 3.5 ppm active ingredient ProClin™ 200	2.6 × 10¹⁰	0
PBS with 1 ppm active ingredient ProClin™ 200	2.6 × 10¹⁰	0

Plates incubated at 30 °C. ProClin™ 200 contains 1.5% active ingredient (CMIT/MIT). TMTC: too many to count. CFU: colony-forming units.

Column performance

In-house testing shows that ProClin 200 does not affect qEV column performance. EV isolates from plasma samples were passed through qEV columns (qEVoriginal / 70 nm Gen 2) stored in either ProClin 200 (0.1%) or sodium azide (0.05%). The two storage buffers showed:

no difference in mean or median particle diameter
no difference in elution profiles
no significant difference in EV concentration or in the percentage of protein eluting in later volumes

The columns were also sent to an independent laboratory to test eluted samples for aerobic bacteria. No bacteria were detected in columns stored in either ProClin 200 (0.1%) or sodium azide (0.05%) buffers.

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Why does Izon use ProClin™ 200 in the qEV column storage buffer?

ProClin™ 200 provides broad-spectrum antimicrobial protection with a better health and environmental hazard profile, without affecting qEV column performance.