Glossary

Quick definitions for the most commonly misunderstood terms in cell culture, DMPK transporter assays and bioprocessing — written for researchers, DMPK scientists and procurement teams.

Cell Culture & Serum

Term	One-line definition	Full guide
FBS (Fetal Bovine Serum)	The most widely used cell culture supplement — blood serum collected from bovine fetuses, providing growth factors, albumin and nutrients to support cell growth.	Read →
Heat Inactivated FBS	FBS heated to 56°C for 30 minutes to destroy complement proteins — used in embryo culture, PBMC assays and virus neutralisation.	Read →
Low Endotoxin FBS	FBS tested to <1 EU/mL endotoxin — required for drug screening, AAV production and cytokine assays where LPS would confound results.	Read →
Human Platelet Lysate (hPL)	A xeno-free, human-derived FBS alternative produced by freeze-thaw lysis of platelets — releasing concentrated PDGF, EGF, TGF-β and IGF-1 for MSC and primary cell culture.	Read →
Off-the-Clot (OTC) Serum	Human serum produced by natural clotting — platelets fully activate and release growth factors, giving higher PDGF and EGF than standard plasma-derived serum.	Read →

Serum-Free & Albumin

Term	One-line definition	Full guide
Xeno-Free Cell Culture	Cell culture containing no components from a species other than the one being cultured — for human cells, no bovine or murine materials; human-derived supplements (hPL, rHSA) are acceptable.	Read →
rHSA (Recombinant Human Serum Albumin)	Human serum albumin produced recombinantly in rice or yeast — animal-free, xeno-free, GMP-compatible carrier protein for serum-free cell culture and AAV production media.	Read →
Recombinant Human Transferrin (OsrhTF)	Animal-free iron delivery protein for serum-free medium — replaces the transferrin function of FBS; essential to prevent iron starvation during serum-free adaptation.	Read →

DMPK & Drug Transporters

Term	One-line definition	Full guide
BSEP (Bile Salt Export Pump)	The primary hepatocyte canalicular transporter for bile salt secretion — BSEP inhibition causes intracellular bile salt accumulation and is the leading mechanism of cholestatic drug-induced liver injury (DILI).	Read →
P-glycoprotein (P-gp / MDR1 / ABCB1)	An ABC efflux transporter expressed at the intestinal epithelium, blood-brain barrier and liver — limits oral bioavailability and CNS penetration; mandatory DDI testing for all NMEs under FDA, EMA and ICH M12.	Read →
Vesicular Transport Assay	An in vitro method using inside-out membrane vesicles to measure ABC transporter substrate accumulation and inhibitor IC50 — the only viable method for BSEP, MRP2, MRP3, MRP4 where no cell monolayer model exists.	Read →
DILI (Drug-Induced Liver Injury)	Hepatotoxicity caused by a drug or supplement — the leading cause of post-marketing drug withdrawal. BSEP inhibition is the primary mechanism of cholestatic DILI.	Read →

Related Guides

• Serum-Free Cell Culture Adaptation — Complete Protocol
• Why Your FBS Isn't the Problem — and What to Replace It With
• Human Platelet Lysate (hPL) — Complete Guide
• Vesicular Transport vs. Cell-Based vs. ATPase Assay
• FDA & EMA Mandatory Drug Transporters for IND
• Inside-Out Membrane Vesicles Explained

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Can't find a term? Contact us — we add new definitions regularly based on questions from researchers and DMPK scientists.