MetSTICK^TM
Heavy Metal Toxicity Testing

MetSTICK-S^TM

In the MetSTICK-S™ heavy metal toxicity test, immobilized bacteria are used to detemine the heavy metal toxicity of solids such as sediments, soils, and biosolids. As for MedPAD and MetPLATE, the test is specifically sensitive to heavy metals.

Figure 1 above shows the test bacteria solidly immobilized on a plastic slide.

The MetSTICK-S™ kit tests 4 samples in triplicate and includes the following:

• 12 Slides with immobilized bacteria in individual plastic bags
• 1 amber serum bottle of MetSTICK-S™ enzyme substrate
• 1 serum bottle of moderately hard water

Enzyme Assay in the Laboratory
Briefly, the enzyme is assayed directly on the plastic slide. 0.3 ml of enzyme substrate is added on top of the immobilized test bacteria. The slide is incubated at 35C for 30 min and the fluorescence is measured using a fluorometer. To calculate the percent inhibition we compare the fluorescence AFTER exposure to the toxic sample to the fluorescence measured BEFORE exposure of the bacteria to the toxic sample (i.e., each slide serves as it own negative control).

MetSTICK-S™ can also be used as a qualitative test by using a long-range UV lamp and visually compare the fluorescence of the bacteria AFTER and BEFORE exposure to the toxic sample.

Negative Control	Toxic Sample
Figure 2 above shows a fluorescent spot for the negative control and a lower fluorescent spot for the toxic sample.

Use of MetSTICK™ Under Field Conditions
The MetSTICK™ slides are assayed at time 0 for enzyme activity. To test sediment toxicity, a slide is attached to a wooden stick with a plastic tape to expose the immobilized bacteria in situ to the sediment. The wooden stick is inserted into the sediment to the desired depth and allowed to remain in the sediment for 4 hrs. Several slides can be attached to the wooden stick to determine metal toxicity in both the sediment and the water column, Following the 4-hr exposure period, the slides are assayed for enzyme activity in the laboratory. The percent inhibition is calculated according to the MetSTICK™ Instructions.

Soils must be saturated with deionized water and allowed to reach equilibrium for 4 hrs. Then. the toxicity test is carried out as for sediments.
 

Storage and Shipping of MetSTICK™ Slides
The MetSTICK™ slides can be stored in a refrigerator for a few months without any significant loss of enzyme activity. They can also be conveniently shipped in a padded envelope across continents without any significant loss of activity.

Equipment Needed to Run a MetSTICK™ Test:

• Pipettor and tips
• Incubator
• Fluorometer with filters: 360 nm for exitation and 485 nm for emission

For more information see:
MetSTICK™ Instructions (PDF)

MetSTICK-W^TM

MetSTICK-W™ is useful  for assessing metal toxicity in water, especially waters with high color or high turbildity and is based on immobilized test bacteria. Each plastic slide has three wells with immobilized bacteria in each well.

The MetSTICK-W™ kit includes:

• 5 slides
• An amber bottle containing freeze-dried enzyme substrate
• A bottle of moderately hard water for the negative control

The kit tests 5 samples in triplicate.

Read about our other heavy metal toxicity testing kits:
MetPAD^TM heavy metal toxicity testing kit
MetPLATE^TMheavy metal toxicity testing kit