Although single domain antibodies isolated from antibody libraries derived from gene synthesis and immunized or naïve animals generally exhibit reasonable affinity, it is often desirable to further increase their affinity. Quantitative library sorting by phage display or yeast surface display is used for improving the affinity of single domain antibodies. In particular, we have developed a proprietary DNA mutagenesis technique that is able to create a huge number (e.g. 1010) variants of the parental antibody with defined positions mutated. In combination with our first class phage display antibody library construction and screening technologies, 10-100 fold increase in affinity for parental single domain antibodies of low nM affinity is frequently achieved. This is often possible for other companies for antibodies of 100nM affinity or worse.

http://www.creative-biolabs.com/Nanobody-Affinity-Maturation.html