Bioavailability
Bioavailability — The fraction of a compound that reaches systemic circulation in an active form after administration, a key consideration in peptide research design.
What Is Bioavailability?
Bioavailability is the fraction of an administered compound that reaches the systemic circulation in its active form. For peptides, oral bioavailability is typically below 2% due to enzymatic degradation in the GI tract and poor membrane permeability. This is why most research peptides are administered by injection in experimental protocols.
Barriers to Peptide Bioavailability
- Enzymatic degradation: Gastric pepsin, pancreatic trypsin/chymotrypsin, and brush border peptidases rapidly cleave peptide bonds
- Size: Most peptides exceed the 500 Da threshold for passive membrane permeation (Lipinski's Rule of Five)
- Charge: Multiple ionizable groups create high polar surface area, preventing transcellular absorption
- First-pass metabolism: Hepatic peptidases further reduce the fraction reaching circulation
Enhancement Strategies
Researchers overcome bioavailability challenges through PEGylation (extended half-life), cyclization (protease resistance), D-amino acid substitution (enzyme resistance), lipidation (albumin binding), and advanced delivery systems including nanoparticles and dissolving microneedles.
Frequently Asked Questions
What is Bioavailability?
The fraction of a compound that reaches systemic circulation in an active form after administration, a key consideration in peptide research design.
Why is Bioavailability important in peptide research?
Bioavailability is a fundamental concept in pharmacology as it relates to peptide science. It directly influences experimental design, compound characterization, and the reliability of research outcomes across biochemistry and molecular biology disciplines.
Authority Sources
- Bioavailability on Wikipedia
- Search Bioavailability on PubChem (NIH)
- Research articles on ScienceDirect