Terms used when buying, specifying and accepting engineered living components. Written for
someone reading a datasheet or a quote and needing to know what a word actually obliges the
seller to deliver.
Terms with their own page are linked. Several entries note that the term has no agreed
definition — that is a finding about the market, not an omission.
A
| Term | Definition |
|---|
| Adventitious agent | An unintended biological contaminant — virus, bacterium, fungus, mycoplasma — introduced during manufacture. Tested for as standard in GMP manufacture, and often not tested for at all in research-grade production. |
| AO/PI | Acridine orange / propidium iodide: a dual-fluorescence viability stain that counts only nucleated events, excluding debris that brightfield methods miscount as cells. See post-thaw viability. |
| Assay-ready | Cells delivered already plated in a specified format, ready for an assay without the buyer performing the thaw and seed. A materially stronger claim than “MEA-ready” and a different product. |
| Astrocyte co-culture | Culturing neurons together with astrocytes, routinely required for reliable synaptic maturation and network bursting. Frequently the undisclosed condition behind a vendor’s published activity data. |
| Attachment efficiency | See plating efficiency. |
B
| Term | Definition |
|---|
| Biofabrication | The set of manufacturing methods used to build living constructs — bioprinting, casting, moulding, directed and self-assembly. Describes how a component is made, not what it is. |
| Biohybrid actuator | A device in which living contractile tissue provides the motive force, typically skeletal muscle or cardiomyocytes on a compliant structure. |
| Bioprinting | Additive fabrication of constructs from cell-laden bioinks. One biofabrication route among several, and frequently not the cheapest for a given specification. |
| Burst | A cluster of action potentials from one unit within a short window. Distinct from a network burst, and the distinction matters when reading MEA data. |
C
| Term | Definition |
|---|
| Cellosaurus | A curated knowledge resource of cell lines, including known misidentified and contaminated lines, referenced by RRID. The place to check a line before you buy it. |
| Certificate of analysis (CoA) | A lot-specific document stating measured values for the tests performed on the material you are receiving. Not the same thing as a datasheet, and the two are routinely confused. |
| Cold chain | The controlled-temperature logistics path from production to the receiving bench. See shipping live cells and tissue. |
| Commercial use | In repository agreements, a defined term covering sale, fee-for-service provision, manufacture for sale, regulated testing and commercial exploitation of sequence or activity data. Generally excluded from a standard purchase. See cell line licensing. |
| Co-culture ratio | The proportion of each cell population in a mixed culture, for example neurons to astrocytes. Rarely sold as a validated pair, and rarely stated. |
| Cryopreservation | Preservation by freezing below the glass transition, usually with a cryoprotectant such as DMSO, allowing indefinite storage in vapour-phase liquid nitrogen. |
| Custom RFQ | A purchase for which no catalogue SKU exists and the price must be established by quotation against a written specification. |
D
| Term | Definition |
|---|
| Differentiation | Driving a stem or progenitor cell to a specialised identity. See differentiation protocol routes. |
| Direct conversion | Reprogramming a somatic cell straight into a neuron without passing through pluripotency, preserving donor age-associated signatures that iPSC reprogramming erases. |
| DIV | Days in vitro: elapsed days since plating. The standard time axis for neuronal culture, and the unit in which activity milestones should be stated. |
| DMSO | Dimethyl sulfoxide, the standard cryoprotectant. Toxic to cells at culture temperature, which is why post-thaw handling is time-critical. |
| Donor consent | The terms under which the original tissue donor permitted use of their material. Constrains downstream use — including, for some lineages, sequencing — and propagates silently to derived products. |
| Dry ice | Solid CO₂, used for one-to-three-day frozen shipment. A regulated dangerous good: UN1845, Class 9, IATA Packing Instruction 954. |
| Dry shipper | A vacuum-insulated vessel holding cryogenic temperature via liquid nitrogen absorbed into a porous liner, with no free liquid. Also called a vapour shipper. |
| Dual-SMAD inhibition | Blocking both SMAD signalling branches to drive pluripotent cells to neuroectoderm; the basis of developmental cortical differentiation protocols, one published example of which runs 80 days. |
E
| Term | Definition |
|---|
| ECM | Extracellular matrix: the structural and signalling protein network surrounding cells. Supplied as coatings, hydrogels and scaffolds. |
| EHT | Engineered heart tissue: cardiomyocytes cast into a mechanically anchored construct, typically between two posts, producing measurable contractile force. |
| Engineered living component (ELC) | A living biological construct produced to a written specification and intended to function as a part within a larger system, rather than as an object of study. |
| Endotoxin | Bacterial lipopolysaccharide. Specified with a numerical limit in GMP manufacture, rarely specified at all in research-grade material. |
F
| Term | Definition |
|---|
| Field stimulation | Applying an electric field across a culture bath to evoke contraction or firing, as opposed to stimulating through individual electrodes. |
| Fusion index | The proportion of nuclei residing in multinucleated myotubes. The standard functional readout for myoblast differentiation. |
G
| Term | Definition |
|---|
| Glass transition | The temperature below which a cryopreserved sample is vitrified and stable, around −130°C. Warming above it during transit is what makes a delayed dry ice shipment fail. |
| GMP | Good Manufacturing Practice: a documented quality system for manufacture intended to support human use. A manufacturing standard, not a quality grade. See RUO vs GMP. |
| GMP-compatible / GMP-grade | Marketing formulations indicating qualified raw materials or a suitable facility without the full quality system and batch record. Not GMP. |
H
| Term | Definition |
|---|
| hiPSC | Human induced pluripotent stem cell. |
| Hydrogel | A water-swollen polymer network used as a three-dimensional culture matrix and casting medium, frequently ECM-derived. |
I
| Term | Definition |
|---|
| IATA DGR | The International Air Transport Association Dangerous Goods Regulations, revised annually, governing air shipment of dry ice, biological substances and related materials. |
| ICC | Immunocytochemistry: antibody staining used to demonstrate marker expression, and the usual basis of a purity claim. |
| iPSC | Induced pluripotent stem cell: a somatic cell reprogrammed to a pluripotent state, from which most commercially available human cell types in this market are derived. |
| Isogenic control | A cell line genetically identical to a disease line except at the edited locus, providing the only rigorous comparator. Stocked and priced separately by most vendors, so buyers routinely acquire a mutant with no matched control. |
K
| Term | Definition |
|---|
| Karyotype | The chromosomal complement of a cell line. Reported to demonstrate genomic stability, and meaningful only with the passage number at which it was assessed. |
L
| Term | Definition |
|---|
| Licensing class | The category of use rights attaching to material: research use, fee-for-service, commercial derivative. The determinant of whether you may build a product on it. |
| Limited use licence (LUL) | A vendor’s grant of permission to use a product for stated purposes only, commonly excluding commercial services, resale, clinical application and manufacture for sale. |
| LN2 | Liquid nitrogen. Long-term cryogenic storage is normally in the vapour phase above liquid nitrogen rather than immersed, to avoid vial contamination and rupture risk. |
| Lot | A single production run. The unit at which QC is performed and the unit across which comparability cannot be assumed. |
M
| Term | Definition |
|---|
| Master cell bank (MCB) | The characterised, archived stock from which working banks are drawn. The point at which the most extensive testing is performed. |
| MEA | Multielectrode array: a culture substrate with embedded electrodes recording extracellular electrical activity across a population, non-invasively and over weeks. |
| MEA-ready | A marketing description asserting that a neuron product will attach and generate activity on an MEA. Undefined by any standards body; the term obliges the seller to nothing specific. |
| Modification | In repository agreements, material created by the recipient that is not progeny or an unmodified derivative but contains or incorporates the original material. A differentiated cell derived from a purchased line is ordinarily a modification, and the licence follows it. |
| MTA | Material transfer agreement: the contract governing transfer of biological material, setting permitted use, transfer restrictions and reporting obligations. |
| Mycoplasma | A wall-less bacterial contaminant, invisible under routine microscopy, that alters gene expression and physiology profoundly and spreads through a facility. The most consequential silent contaminant in cell culture. |
| Myotube | A multinucleated contractile cell formed by fusion of myoblasts. The functional unit of engineered skeletal muscle. |
N
| Term | Definition |
|---|
| Network burst | Synchronised firing across many electrodes of an array. The functional endpoint most MEA assays depend on, and it arrives substantially later than first spiking — sometimes not at all without glial support. |
| NGN2 | Neurogenin-2: a transcription factor whose forced expression converts pluripotent cells to predominantly glutamatergic neurons in days, bypassing the progenitor stage. Fast, homogeneous, and carrying the heaviest platform licensing burden of the three routes. |
| NPC / NSC | Neural progenitor or neural stem cell: an expandable intermediate that can be passaged, changing the economics for anyone needing large or repeated neuronal yields. |
O
| Term | Definition |
|---|
| OECD TG 439 | The OECD test guideline for in vitro skin irritation using reconstructed human epidermis. The regulatory basis on which RhE models are purchased. |
| Organoid | A self-organising three-dimensional culture recapitulating aspects of an organ. Characterised after the fact rather than built to a target, which is why it is usually a model rather than a component. |
| Organ-on-chip | A microfluidic device housing living tissue under perfusion, typically within a closed proprietary platform. Platform lock-in is its defining commercial feature. |
P
| Term | Definition |
|---|
| Passage number | How many times a culture has been subcultured. Determines remaining expansion capacity and whether your cells match the passage at which the vendor characterised them. |
| PDMS | Polydimethylsiloxane: the standard elastomer for soft-lithography culture devices. Optically clear and gas-permeable, but it absorbs small hydrophobic molecules, which matters for drug work. |
| Plating efficiency | The fraction of seeded cells that attach and remain attached at a defined timepoint. The measurement that actually predicts your experiment, and much less commonly specified than viability because it is harder to pass. |
| Post-thaw viability | The percentage of cells in a thawed vial judged alive by a stated assay at a stated time. Uninterpretable without the method and the timepoint. |
| Potency | Whether cells perform their intended function, as distinct from being alive. A high viability figure says nothing about it. |
| Progeny | An unmodified descendant of transferred material — cell from cell, plasmid from plasmid. Treated as the original material and carrying all its restrictions. |
| Purity | The proportion of cells matching the intended identity. Meaningful only against named markers, a named method and a timepoint. |
R
| Term | Definition |
|---|
| Reach-through | A claim by a material provider on inventions or revenue arising from downstream use of the material. Explicitly contemplated in some repository frameworks as including royalty obligations to third parties. |
| Reporter line | A line carrying a fluorescent or luminescent readout — GFP, GCaMP, RCaMP — for live imaging of expression or activity. Carries a price premium. |
| RhE | Reconstructed human epidermis: a stratified, differentiated skin-equivalent tissue on a culture insert, used for irritation and corrosion testing. |
| RRID | Research resource identifier: a persistent identifier for a reagent or cell line, allowing unambiguous citation. |
| RUO | Research use only: a designation restricting material to laboratory research, explicitly excluding administration to humans, clinical trials and diagnostic use. |
S
| Term | Definition |
|---|
| Seeding density | Cells per well or per unit area at plating. The working range is narrow, it drives electrode coupling and tissue formation, and it directly determines how many vials you must buy. |
| Specific force | Force normalised to cross-sectional area, in kPa or mN/mm². The only way to compare contractile constructs of different sizes. |
| Spheroid | A compact three-dimensional cell aggregate, formed by self-assembly rather than casting into a geometry. |
| Sterility | Absence of bacterial and fungal contamination, tested separately from mycoplasma and not covered by mycoplasma testing. |
| STR profiling | Short tandem repeat genotyping for human cell line authentication. Consensus guidance requires a minimum of 13 loci, with a match above 80 percent against a reference profile, per ANSI/ATCC ASN-0002. |
| Subtype | The specific identity within a broad class — glutamatergic versus GABAergic neurons, ventricular versus atrial cardiomyocytes. Different products at different prices, often sold under one heading. |
T
| Term | Definition |
|---|
| Tetanic force | Sustained force under high-frequency stimulation, substantially higher than twitch force in the same construct. Always state which you mean. |
| Tissue engineering | The discipline of constructing functional biological tissue. Engineered living components are one commercial output of it, oriented toward supply rather than implantation. |
| Trypan blue | A membrane-impermeable brightfield dye, the default viability method. Cannot distinguish cells from debris, so it tends to read high on post-thaw samples. |
| Twitch force | Peak force from a single stimulation pulse. The usual headline contractile specification. |
U
| Term | Definition |
|---|
| UBMTA | Uniform Biological Material Transfer Agreement: a standardised template for transfers between non-profit institutions, reducing negotiation time between signatories. |
| UN1845 | The UN number for dry ice, a Class 9 dangerous good in air transport. |
| UN3373 | The UN number for Biological Substance, Category B, shipped under Packing Instruction 650. |
| Unmodified derivative | Substances native to and characteristic of transferred material — nucleic acids, proteins, exosomes, lysates, characteristic sequence data. Defined broadly enough that conditioned medium and sequence do not escape a licence. |
V
| Term | Definition |
|---|
| Vapour shipper | See dry shipper. |
| Viability | Almost always a membrane-integrity measurement. A cell can be committed to apoptosis, unable to attach, or phenotypically lost and still score as viable. |
W
| Term | Definition |
|---|
| Wetware RFQ | A written request for quotation for living material, specified precisely enough that two suppliers quoting against it produce comparable numbers. |
| Working cell bank (WCB) | The routine-use stock expanded from a master cell bank, from which individual lots are drawn. |
| WWD (.wwd) | An open, unpatented exchange format for specifying engineered living components as geometry plus spatially varying property fields, with each property tagged as designed, measured, simulated or inferred. |
X
| Term | Definition |
|---|
| Xeno-free | Culture conditions containing no animal-derived components. A requirement for most clinical translation paths and a common point of divergence between a research protocol and its GMP equivalent. |
Terms with no agreed definition
Three terms in common commercial use have no definition from any standards body, which means
they oblige a seller to nothing in particular. Treat each as a prompt for a question rather
than as information:
- MEA-ready — see the dedicated page for the seven attributes that
actually determine whether a product works on an array.
- Assay-ready — usually means pre-plated, but confirm the format, the maturation state and
whether an activity criterion attaches.
- GMP-compatible — see RUO vs GMP. It is not GMP, and asking
what specifically is and is not in place gets a straight answer.
Using this glossary
Definitions here are free to cite. Where a definition comes from a published standard or
agreement we say so and the linked page quotes the source verbatim, so you can check it rather
than take our word for it.
If you think a definition is wrong, that is a useful disagreement. The alternative — a market
in which “MEA-ready” means whatever the seller needs it to mean — serves nobody buying
anything.