What is Human Tissue for Biomarker Research?

Fresh frozen vs FFPE tissue — when to use which

Parameter	Fresh Frozen	FFPE
Protein integrity	✅ Excellent — native conformation preserved	⚠️ Crosslinked — antigen retrieval required for IHC
RNA quality	✅ High RIN — suitable for RNA-seq, qPCR	⚠️ Degraded — short amplicons required, FFPE-specific kits
Morphology	⚠️ Freezing artefacts — not suitable for standard histology	✅ Excellent — standard H&E, IHC, ISH
Storage	−80°C — expensive long-term	Room temperature — indefinitely stable
IHC/ISH	⚠️ Possible but suboptimal — cryosections	✅ Standard format — 4 µm sections on APES-coated slides
Proteomics	✅ Full protein extraction	⚠️ Crosslinking reduces recovery — specialised extraction needed
Companion diagnostic development	⚠️ Not standard clinical format	✅ Standard — CDx assays validated on FFPE
Biomarker discovery	✅ Preferred for discovery phase	✅ Validation phase — retrospective archives

CSF — cerebrospinal fluid as a speciality biomarker matrix

Cerebrospinal fluid (CSF) is produced by the choroid plexus and circulates around the brain and spinal cord. It reflects the biochemical state of the central nervous system more directly than blood — making it the primary matrix for CNS biomarker assays. CSF is collected by lumbar puncture (spinal tap) under sterile conditions — a more invasive procedure than blood draw, which limits the volume available and requires specialist collection.

Key CSF biomarkers in current IVD use: total tau and phospho-tau 181 (neuronal damage and tangle formation in Alzheimer's disease), amyloid-β42 and amyloid-β42/40 ratio (amyloid plaque burden), neurofilament light chain NFL (axonal damage — elevated in ALS, MS, Parkinson's, traumatic brain injury), and GFAP (astrocyte damage). These analytes are present at pg/mL to ng/mL concentrations in CSF, requiring highly sensitive immunoassay platforms.

IgG-depleted and steroid-depleted serum — when needed

IgG-depleted serum is human serum from which immunoglobulins have been removed by Protein A/G affinity depletion. Standard human serum contains 8–12 mg/mL IgG — at these concentrations, IgG dominates the protein background and can interfere with sandwich immunoassays for low-abundance biomarkers where IgG occupies non-specific binding sites. IgG-depleted serum provides the albumin, transferrin, and other matrix proteins of human serum without the IgG background — useful as a calibrator diluent for assays where endogenous IgG would otherwise confound the calibration curve.

Steroid-depleted serum is human serum from which steroid hormones (estradiol, testosterone, progesterone, cortisol, DHEA) have been removed by charcoal-dextran adsorption. It is used as the zero-calibrator matrix for steroid hormone immunoassays — ensuring that the blank calibrator contains no endogenous hormone that would create a non-zero baseline.

HAMA interference — why it matters for tissue-based research

Human Anti-Mouse Antibodies (HAMA) are antibodies in human serum that recognise murine IgG. HAMA are produced by patients who have been exposed to mouse antibodies — through diagnostic imaging (radiolabelled murine antibodies), cancer therapy (murine mAb), or laboratory accidents. HAMA interfere with sandwich immunoassays that use murine capture and detection antibodies — the HAMA bridges the two antibodies creating a false positive signal. HAMA-positive serum is a required interference material for performance evaluation of any IVD that uses murine antibodies in a sandwich format. SeamlessBio supplies HAMA positive and HAMA high positive serum for interference testing.

Key Facts

• Fresh frozen tissue: snap-frozen in liquid nitrogen or at −80°C immediately after collection — preserves protein activity, RNA integrity (RIN >7 preferred), and enzymatic function for proteomics, transcriptomics and functional assays
• FFPE tissue: fixed in 10% neutral buffered formalin for 12–24 hours then embedded in paraffin wax — preserves morphology for IHC/ISH but causes protein crosslinking and RNA degradation (shorter amplicons required for PCR)
• Cerebrospinal fluid (CSF) is a liquid biopsy of the central nervous system — the primary matrix for neurological biomarker assays (tau, phospho-tau, amyloid-β42, NFL, GFAP) for Alzheimer's and Parkinson's diagnostics
• Human tissue is essential for companion diagnostic (CDx) development — IHC/ISH assays that determine patient eligibility for targeted therapy require validated tissue panels with confirmed biomarker expression status
• Tissue biobanks must operate under IRB/ethics board approval with full donor informed consent — tissue collected without ethical clearance cannot be used in IVD regulatory submissions
• Cold ischaemia time (time from blood supply interruption to tissue preservation) is the critical quality parameter for fresh frozen tissue — <30 minutes preferred for protein integrity, <60 minutes for RNA
• SeamlessBio supplies human frozen thyroid tissue (1–100 g), FFPE tumour tissue, fresh frozen liver and pancreatic tissue, and CSF (25 mL or 250 mL) — full ethical clearance and chain-of-custody included

Further Reading

• Human Tissues & Speciality Biomaterials
• Disease State Serum Panels
• What is Disease State Serum?
• Human IVD Quality Controls
• Human Biomaterials & IVD — Overview

SeamlessBio GmbH · Passau, Germany · info@seamlessbio.de · +49 851 37932226