Controlled and highly efficient preparation of carbohydrate-based vaccines: squaric acid chemistry is the way to go

Evolution of the method and practical aspects of the conjugation of single amino group-containing carbohydrates to protein carriers is described. Proven protocols for conjugation of low-and high-molecular-weight carbohydrates are also provided. It is concluded from the experimental evidence in authors' laboratory and elsewhere that the squaric acid-based method is the most efficient means for converting proteins to glycoconjugates with predictable carbohydrate-carrier ratios.