stability 1. Ability to maintain constant characteristics in the presence of forces that threaten to disturb them; resistance to change.
Resistance to structural, chemical, and biological changes in composition caused by such factors as light, temperature, and
storage (shelf) time. 2. A defined characteristic of a given product; stability profile means the types of chemical degradations,
rates, and expected shelf life that characterize a product.
stabilizer A chemical additive that helps maintain solution stability or drug product stability.
staining A procedure of labeling tissues, organisms, or molecules (such as DNA or proteins) with colored or fluorescent dyes to allow
visualization by microscopic or macroscopic techniques.
starting material European term meaning raw materials used in cGMP manufacturing, but excluding components. (See component, active starting
material, raw material)
statistical process control Monitoring and controlling a process using statistical analysis with the aim of managing variability at critical process control
stereoisomer Any of a group of isomers in which atoms are linked in the same order but differ in their spatial arrangement.
sterile Absolutely free of any microbiological contamination; an absolute state that cannot be proven unless all of a material is
consumed in the test. In practical terms, sterility assurance is demonstrated by showing that less than 1 in 106 units may
be contaminated. (See USP Sterility Test)
stoichiometry The study of proportional (quantitative) relationships between two or more substances during a chemical reaction.
strain A population of cells all descended from a single cell.
structural isomers Any isobaric species that has the same elemental composition (and assumed basic structure) but differs in the arrangement
of the elements, often assumed to be functional groups for biomolecules.
subcutaneous Referring to the layer of tissue (subcutis) directly underlying the cutis, which is mainly composed of adipose tissue. Subcutaneous
(abbr: subq or sc) injections are given by injecting a fluid into the subcutis. It is relatively painless and an effective
way to administer particular types of medication. Certain depot injections are a solid or oil-based medication, which is administered
subcutaneously where it releases its agent slowly over a period of weeks.
sublimation Passing directly from a solid to a vapor state without first melting into a liquid.
substrate Reactive material, the substance on which an enzyme acts.
substratum The solid surface on which a cell moves or on which cells grow.
sulfation The formation of sulfuric acid esters from alcohols or olefins (synthetic fibers, such as polypropylene).
sulfhydryl group Any compound of sulfur and another element, usually made by direct reaction of the elements.
supernatant Material floating on the surface of a liquid mixture (often the liquid component that has the lowest density); the overlying
fluid layer that remains after precipitation of a solid component through centrifugation.
supercritical fluids Common gases, such as carbon dioxide, when under pressure contain a liquid form of the gas. This liquid is useful in a variety
of biotechnology applications.
surface plasmon resonance A phenomenon used in analytical chemistry whereby plasmons (electromagnetic waves formed by electrons) propagating along the
surface of a thin metal layer resonate with light coming through a prism at a specific angle, stopping that light from reflecting.
The electrical field thus created is very sensitive to chemical changes (such as molecular interactions) in a solution interfacing
with the surface, which causes specific measurable differences in the angle of light necessary for the phenomenon to perpetuate.
SPR biosensors detect and measure those changes.
surfactant Any substance that changes the nature of a surface, such as lowering the surface tension of water.
suspension Particles floating in (not necessarily on) a liquid medium, or the mix of particles and liquid itself.
sustained delivery Drug delivery in which the duration of release, action, and bioavailability are controlled and reproducible; usually a depot
(reservoir) of drug is created in the body (at the injection site, for example), and the delivery matrix releases the therapeutic
molecules over a period of time. Biodegradable polymers are under study as microspheres and other methods of sustained delivery
symbiotic Living together for mutual benefit.
synthesis Creating products through chemical and enzymatic reactions. Bioprocessing lets living cells or organisms do this work.