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The ELISA or Enzyme-Linked Immunosorbent Assay is the most established method of protein detection and quantification. The technique is commonly used in a wide variety of applications spanning from the basic research bench to clinical laboratories. The ELISA is a labeled assay, which means that it requires the use of a label to detect an antibody-antigen binding event. The label is commonly a fluorescent probe, chemiluminescent system, or enzymatic colorimetric reaction.

The earliest chemists were on the hunt for new elements to add to the periodic table. Most of the chemistry that they were interested in doing was purification with the end goal of reaching a pure elemental substance. These chemists relied on a litany of methods—filtration, evaporation, distillation, and crystallization were some of the most used purification techniques for these discoveries. As the chemists were defining the elements, the biologists were trying to understand the human body, the cell, cellular organelles, and microbes. The point here is that in order to develop anything new we must first understand what everything is made of at the most basic and pure level. In modern science this means that we are trying to define matter beyond subatomic particles and we are attempting to map out every molecular pathway of disease. Our efforts to define complex systems by their purest constituents are rewarded by deep understanding and an ability to mimic, to engineer, develop, and create.

If you look closely at the product information for many commercial antibodies, you will see that they are protein A purified. Protein A is a surface protein that was originally found in the cell wall of staphyloccoccus aureus bacteria. On the surface of bacteria it serves as a defense against the host immune system and allows the bacteria to survive longer and be more virulent. Protein A binds the Fc portion of IgG antibodies.

The International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human use (ICH) was founded in 1990 as a way to standardize the introduction of new drug substances to the worldwide market. The council wrote and maintains guidelines for how new pharmaceutical products must be tested for stability and quality before they can be approved for worldwide distribution. The guidelines protect consumers and allow new therapeutic drugs to reach patients across international borders more quickly. The ICH has written guidelines for the stability testing of new drug substances and products. There is a general document known as Q1A(R2) that outlines the details of every stability test that a new drug substance must undergo before being registered. These tests examine how the drug degrades in high temperature or high humidity over time. It outlines methods for  defining the mechanism of degradation for the new drug, and how to test proposed protective packaging for efficacy. A supplementary document (Q1B) contains additional details specifically about photostability testing.