Carrier-Free Antibodies: the What, Why and How

Sometimes you need the antibody and nothing else. When you buy an antibody, typically it has a couple of small additions to the mix: bovine serum albumin (BSA) and sodium azide. These additions, referred to as “carriers”, aren’t there just for the sake of it; BSA acts as a protein-stabilizer while the sodium azide works as a preservative to prevent bacterial growth. In almost all cases, carriers don’t significantly impact but your assay, but sometimes, you might want them stripped out for a super clean, carrier-free, antibody mix.

Why Remove Carriers?

For really sensitive work, like a complex conjugation preparation or an assay like cytometry by time of flight (CyTOF), removing anything extra from your antibodies can be really beneficial. Sodium azide can be cytotoxic, so you might want to strip it out before adding an antibody solution to your precious cell cultures. Removing BSA can enhance assay sensitivity, as it prevents the potential interference in antibody-target binding, crucial for the accurate detection and quantification of analytes in multiplex assays.

The compatibility of carrier-free antibodies with conjugation processes is another significant advantage. The absence of carrier proteins simplifies the attachment of various labels – fluorophores, metals, and enzymes – to the antibodies, making them highly versatile for diverse assay designs.

Then there’s the improved compatibility offered by carrier-free antibodies. Without having to worry about additional unwanted interactions, you’re free to pick optimal antibody clones, concentrations, and buffer compositions, giving you complete control over your experimental setups.

In short, carrier-free antibodies support advanced research by offering improved sensitivity, reduced cross-reactivity, enhanced signal clarity, and greater flexibility in assay design and customization

A Carrier-Free Case Study

In a landmark paper, published in Neuron, a team created gold nanoparticles (AuNPs) conjugated to an antibody to target neurons for optical stimulation in a fascinating potential alternative to optogenetics. 

To achieve this antibody-AuNP conjugate, the team for biotinylated our Anti-P2X3 Receptor (extracellular) antibody (APR-026) – this is where antibodies are chemically modified to include biotin, a small molecule that strongly binds to streptavidin. But first, they had to meticulously remove sodium azide by dialysis and then remove the BSA via a dedicated kit from their antibody. This generation of a carrier-free antibody helped to ensure the biotinylation occurs efficiently and specifically, without interference from carriers.

As essential as the carrier-removal was, it was likely a labor-intensive and costly process. Yet, this step could have been bypassed entirely with a carrier-free option directly from Alomone Labs. It could have been as simple as selecting how much carrier -free antibody was needed and then us getting this made and sent straight from our lab, to theirs. 

But, back to the science! After biotinylation, the antibody-biotin conjugates were introduced to AuNP-Streptavidin to form stable antibody-AuNP complexes. The 20 nm AuNPs used for this study were chosen because they can convert light into heat, enabling photothermal stimulation of neurons. 

The conjugation process culminated in the formation of a complex where the antibody maintains its ability to specifically bind to its target antigen but is now equipped with the photothermal capabilities of the AuNP. This antibody-AuNP conjugate represents a powerful tool for neuroscience research, letting researchers target and manipulate specific neuronal populations with the need for extensive genetic manipulation.

A Carrier-Free Future Awaits – If You Need it

Standard antibodies with inclusion of BSA and sodium azide are what most people need for most applications. But when need to go carry-free, it’s always nice to know that those antibodies are there. The option to conveniently choose carrier-free antibodies as and when you need them brings a level of on-demand specificity, flexibility, and efficiency to demanding immunoassays and advanced forms of microscopy. We’ve worked hard to make sure that you now have easy access to a treasure trove of high-quality, carrier-free antibodies that allow you to answer whatever questions your research raises. So, as you plan your next scientific endeavor, consider going carrier-free. And you need help picking out a custom setup, just get in touch. 

Get your reagents exactly how you need them.

Reference

J. L. Carvalho-de-Souza, J. S. Treger, B. Dang, S. B. H. Kent, D. R. Pepperberg, F. Bezanilla, Photosensitivity of neurons enabled by cell-targeted gold nanoparticles. Neuron 86, 207–217 (2015). DOI: https://doi.org/10.1016/j.neuron.2015.02.033.