sdAbs Library Construction

 Single-domain antibodies(sdAbs) have many advantages: High affinity with small size antibody, good physicochemical properties and downstream engineering easily. The characteristics of single-domain and ease of gene manipulation of the single-domain antibody (sdAb) make it suitable for affinity maturation in vitro.

 As a professional supplier in the field of phage display and antibody engineering, Alpha Lifetech Inc. can offer rapid production of single-domain antibody libraries. Our proprietary phage display technologies allow scientists to specify their requirements for expression and characterization.


Phage Display Library –Single Domain Antibody Library Construction Service


Single-domain antibodies (sdAbs), or nanoantibodies, are part of a class of recombinant antibody fragments, representing the smallest antibody that was proven of great usefulness. With a molecular weight of 12-15 kDa, single-domain antibodies, which consist only of a single heavy-chain variable domain and engineer from single monomeric variable domains of either camelids' heavy-chain antibody (VHH) or cartilaginous fishes' IgNAR (VNAR) without loss of antigen-binding ability. On the other hand, scientists can also develop sdAbs from camelized antibodies, such as camelized human and other species antibodies.

sdAb is similar to conventional VH domains (Ig VH) in that VHHs contain four framework regions (FRs) that form the core structure of the immunoglobulin domain and three complementarity-determining regions (CDR1, CDR2 and CDR3) that are involved in antigen binding. This contrasts with shark single-domain antibodies (IgNAR V) that have a vestigial CDR2 that does not contribute to antigen binding. Compared with traditional antibodies, single-domain antibodies have been shown to remain functional at 90°C and recognize antigenic sites that are normally not recognized by conventional antibodies such as enzyme active sites.


Single-domain antibody

Conventional antibody

Small, only one heavy chain domain (VHH)~13 kDa

Large, both heavy and light chains~120-150 kDa

Monomeric VHH subunit required for antigen binding

Both chains required for antigen binding and stability

Highly amenable to downstream engineering

Relatively low engineering flexibility due to complex structure

Maintains stability and potency at extreme pH and temperatures

Cannot tolerate extreme pH or temperatures

Multiple routes of administration

Administered through injection, cannot be administered orally

Easy to manufacture in yeast or microbial systems

Challenging and costly to manufacture


Alpha Lifetech Inc. can offer two kinds of single-domain antibody (sdAb) libraries as below:


Construction of Immunized Single Domain Antibody Library


The scientists at Alpha Lifetech Inc. have extensive experience in constructing and expressing recombinant antibodies based on our proprietary phage display platform. An immunized single-domain antibody library is suitable for the generation of high-affinity and antigen-special VHH or NAR V antibodies, thus avoiding time-consuming in vitro antibody affinity maturation effort. Here, we produce an antigen-special single-domain antibody library for our clients from immunized alpaca, camel, llama or shark, and even humans (PBL cells activated by antigens in vitro). By reverse transcription and polymerase chain reaction, a library of single-domain antibodies containing 10-100 million clones is regularly produced.


Construction of Synthetic Single Domain Antibody Library


Synthetic single-domain antibody libraries often developed from the CDR1 and CDR3 of either naïve VHH or VNAR. This synthetic antibody library is by definition a naïve library and has a high complexity of 3x1010 VHHs ensuring a very satisfying diversity. It is naïve so it does not require llama or shark immunization. This helps us save a lot of time to get a specific antibody and makes possible antibody selection for non-immunogenic or conserved proteins. Such synthetic libraries represent a good source of single-domain antibodies against self, non-immunogenic, and toxic antigens since the libraries are usually sufficiently vast and diverse. In case the selection of high-soluble single-domain antibodies is a concern, we have designed a shuttle phagemid vector system, including several phagemids, which can express the single-domain antibodies in E. coli (yeast) or display them on the surface of phage particles.

Alpha Lifetech Inc. is proud to offer comprehensive sdAbs library construction services to meet the diverse needs of global researchers. We aim to understand and meet the demands of different customers and to assist with any upcoming and emerging problems in research work.

   Please feel free to contact us at any time, our sales representative or technical support manager will prepare a detailed quote accordingly.