Improved Accuracy of Saxitoxin Measurement Using an Optimized Enzyme-Linked Immunosorbent Assay

Abstract

Paralytic shellfish poisoning (PSP) is precipitated by a family of toxins produced by harmful algae, which are consumed by filter-feeding and commercially popular shellfish. The toxins, including saxitoxin, neosaxitoxin, and gonyautoxins, accumulate in shellfish and cause intoxication when consumed by humans and animals. Symptoms can range from minor neurological dysfunction to respiratory distress and death. There are over 40 different chemical congeners of saxitoxin and its analogs, many of which are toxic and many of which have low toxicity or are non-toxic. This makes accurate toxicity assessment difficult and complicates decisions regarding whether or not shellfish are safe to consume. In this study, we describe a new antibody-based bioassay that is able to detect toxic congeners (saxitoxin, neosaxitoxin, and gonyautoxins) with little cross-reactivity with the low or non-toxic congeners (decarbamoylated or di-sulfated forms). The anti-saxitoxin antibody used in this assay detects saxitoxin and neosaxitoxin, the two most toxic congers equally well, but not the relatively highly toxic gonyautoxins. By incorporating an incubation step with L-cysteine, it is possible to convert a majority of the gonyautoxins present to saxitoxin and neosaxitoxin, which are readily detected. The assay is, therefore, capable of detecting the most toxic PSP congeners found in commercially relevant shellfish. The assay was validated against samples whose toxicity was determined using standard HPLC methods and yielded a strong linear agreement between the methods, with R2 values of 0.94–0.96. As ELISAs are rapid, inexpensive, and easy-to-use, this new commercially available PSP ELISA represents an advance in technology allowing better safety management of the seafood supply and the ability to screen large numbers of samples that can occur when monitoring is increased substantially in response to toxic bloom events

Current Trends and Challenges for Rapid SMART Diagnostics at Point-of-Site Testing for Marine Toxins

“…By combining two antibodies, Huang et al [ 89 ] were able to increase the sensitivity and specificity of their test to detect total PSP levels similar to the MBA. McCall et al [ 90 ] have developed a similar ELISA capable of detecting STX-analogues using a single monoclonal antibody (mAb) that recognizes STX and NEO, but does not cross-react very well with GTX1/4 nor GTX2/3. In this assay, GTX must be converted to STX by incubating the sample with L-cysteine.…”

Paralytic and Amnesic Shellfish Toxins Impacts on Seabirds, Analyses and Management

“…These tests can be used for screening in a variety of shellfish, since they are fast, simple, cost effective and, for certain toxins, more sensitive than other methods. However, they may have drawbacks, such as false positive or negative results and/or the fact that the antibodies employed are selective for binding of only certain PSTs [ 107 ], and therefore do not allow the detection of all the analogs. Some of these tests have been tried in seabird samples since they are an efficient tool for screening large numbers of samples.…”

“…Early studies to analyze PSTs in seabirds were conducted with MBA, which is not sensitive enough to detect the very low PSTs levels that could cause seabird death [ 106 ]. Some of the more recent studies used ELISA kits that, although useful for screening purposes, do not cover most PSTs for which standards are available [ 107 ]. Furthermore, most seabird MMEs incidence reports are likely to severely underestimate the number of affected individuals [ 29 ] and this could be related to the sampling procedure employed (i.e., collecting only carcasses found in beaches).…”

An Electrochemical Ti3C2Tx Aptasensor for Sensitive and Label-Free Detection of Marine Biological Toxins

“…Thus, it is important to detect STX in seafood or drinking water. Traditional approaches for STX analysis include mouse bioassay [ 8 ], enzyme-linked immunosorbent assay (ELISA) [ 9 ], cell assay [ 10 ], high-performance liquid chromatography (HPLC) [ 11 ], and liquid chromatography-tandem mass spectrometry (LC-MS) [ 12 ]. Although respective advantages in sensitivity and specificity have been achieved by these methods, there are some challenges: for example, HPLC and LCMS need sophisticated equipment and complex pre-treatments [ 13 , 14 ], and ELISA requires tedious lab work [ 15 ].…”