Nanobodies are smallest intact antibody fragment with subnanomolar affinity against antigen.

Nanobodies are powerful tools as targeting agents for targeted delivery in cancer therapy.

Mutation is hallmark of cancerous cells, so antigen drift is probable in these cells.

Four different clones of nanobody, target different epitopes on HER2 receptor, were expressed and purified.

Using oligo-clonal nanobodies in targeting enhance affinity and avidity of targeting moiety in comparison to monoclonal one.