Antibodies are the most commonly used capture and detection agents used in Biosensors. Immunoglobulins however are multidomain large molecules with specificity and sensitivity that need to be tuned at great expense. Llamas on the other hand have single domain antibodies (SdAb) or nanobodies that are 1/10th the size of conventional antibodies that are very soluble, can refold after denaturation and can access buried epitopes not accessible to regular antibodies. This last property is very important for binding Botulinum toxins that are normally shielded by neurotoxin accessory proteins (NAPs). Recent paper in PLoS is now reporting generating SdAbs against all seven botulinum neurotoxin serotypes by a single immunization with a cocktail of seven toxoids. These antibodies were generated using phage display library and selected using live toxins.
Using Luminex multiplexing platform it is shown that all seven toxoids can be sensitively and selectively detected in several food items including milk, carrot juice, orange juice and cola. Moreover, these antibodies were able to bind to toxoids shielded by NAPs something not easily done using conventional antibodies. Because of their exquisite sensitivity and specificity SdAbs promises very sensitive biosensors.