Using the radioligand-receptor binding assay for paralytic shellfish toxins: A case study on shellfish from Morocco

Area of Science:

• Marine Biology
• Food Safety
• Analytical Chemistry

Background:

• Paralytic Shellfish Poisoning (PSP) events are a recurring threat along Morocco's coast, impacting fisheries and aquaculture.
• Current regulatory monitoring relies on the mouse bioassay (MBA) for saxitoxin (STX) detection, facing ethical and practical challenges.
• Increasing intensity and frequency of toxic algal blooms necessitate improved detection methods.

Purpose of the Study:

• To evaluate the performance of a nuclear-based radioligand-receptor binding assay (RBA) as an alternative to the MBA for PSP toxin detection.
• To compare the RBA and MBA methods using commercially important shellfish species from Moroccan waters.

Main Methods:

• The RBA method was validated using reference materials and critical assay parameters.
• Over 50 shellfish samples, including cockles, razor shells, oysters, and mussels, were analyzed.
• Samples included routine monitoring collections and those previously identified as toxic by MBA.

Main Results:

• The RBA demonstrated robustness and provided STX-equivalent activity measurements from 33 to 8500 μg/kg.
• RBA results showed a strong significant correlation (r=0.96, P<0.0001) with MBA data.
• The RBA exhibited a 10-fold lower limit of quantification (35.24 μg/kg) compared to the MBA (325 μg/kg), detecting toxins at lower levels.

Conclusions:

• The RBA is a reliable, rapid, and user-friendly alternative to the MBA for PSP toxin detection.
• The RBA's higher sensitivity and ethical advantages make it suitable for routine monitoring, especially with increasing harmful algal bloom risks.
• This method supports enhanced food safety and sustainable aquaculture practices in Morocco and globally.