Picrosirius Red Staining 2026: Protocol & Quantification

Introduction

Picrosirius Red Staining (hereinafter PSR Staining) is a histological method for specifically detecting collagen fibers in tissue sections. It is widely regarded as the gold standard for assessing fibrosis in preclinical research across liver (MASH/NASH), lung (IPF), kidney (CKD/UUO), skin (scleroderma), and cardiac fibrosis models.

Compared to Masson's Trichrome (MT) staining, PSR offers superior specificity for collagen and excellent suitability for automated digital image analysis — making it the preferred choice when objective, quantitative endpoints (such as % Fibrosis Area) are required for drug efficacy studies.

This comprehensive guide covers everything from the fundamental chemistry to practical troubleshooting, ensuring you get clean, reproducible, publication-quality results.

Quick Answer: Picrosirius Red (PSR) staining is a collagen-specific method using Sirius Red F3B dissolved in saturated picric acid, incubated for 60 min and washed with 0.5% acetic acid (NEVER water). Bright-field imaging enables objective % Area quantification (ImageJ + Color Deconvolution), while polarized light reveals fiber maturity (red-orange = Type I / thick, green = Type III / thin).

1. Picrosirius Red vs Sirius Red: What Is the Difference?

This is one of the most frequently searched questions about this stain — and getting it wrong can compromise your entire experiment.

It is a common point of confusion among researchers, but "Sirius Red" and "Picrosirius Red" are distinct entities:

• Sirius Red (Direct Red 80, C.I. 35782): This refers merely to the red dye molecule itself. On its own, this dye does not exhibit sufficient specificity for collagen. It will stain collagen, but also cytoplasm and other tissue components, producing a poor signal-to-noise ratio.

• Picrosirius Red (PSR) Solution: This is the staining solution created by dissolving Sirius Red in a saturated aqueous solution of picric acid. The picric acid transforms the dye's behavior completely.

Why is Picric Acid Necessary?

Picric acid serves a dual purpose:

1. Background suppression: It stains cytoplasm, muscle, and non-collagenous proteins yellow, providing a clean contrasting background.
2. Mordant action: More crucially, picric acid acts as a powerful mordant that drastically enhances the specific binding affinity of Sirius Red to the basic amino acid residues of collagen molecules. Without picric acid, the Sirius Red dye binds non-specifically and produces high background.

Bottom line: For rigorous fibrosis assessment, the dye must always be used as "Picrosirius Red" — never Sirius Red alone.

2. How to Prepare Picrosirius Red Staining Solution

If you prefer a commercial kit over in-house preparation, see our head-to-head comparison of Sirius Red Staining Kits (5+ suppliers compared by price, contents, and slide capacity).

Many researchers purchase ready-made PSR staining kits (e.g., from Polysciences #24901, Abcam #ab150681, or ScyTek Laboratories), but preparing the solution in-house is straightforward and far more economical for high-volume labs.

Recipe (0.1% Picrosirius Red Solution)

Reagent	Amount	Supplier Examples
Sirius Red F3B (Direct Red 80)	0.5 g	Sigma-Aldrich #365548, Polysciences
Saturated Aqueous Picric Acid	500 mL	Sigma-Aldrich #P6744 (pre-made) or dissolve ~1.3 g/100 mL in distilled water

Preparation steps:

1. Weigh 0.5 g of Sirius Red F3B powder on an analytical balance.
2. Add the powder to 500 mL of saturated aqueous picric acid in a glass bottle.
3. Stir with a magnetic stirrer until fully dissolved (~30 minutes). Filter through Whatman #1 paper if any particulates remain.
4. Store at room temperature in the dark (amber glass bottle or wrapped in foil). The solution is stable for 3+ years¹.

Also Prepare: Acidified Wash Water

• 5 mL glacial acetic acid in 1 L distilled water = 0.5% acetic acid wash solution.
• This is used instead of water for the critical washing step.

[CAUTION] Picric acid is potentially explosive when dry. Always keep it in aqueous solution. Dispose of waste according to institutional hazardous materials guidelines. Never let picric acid bottles dry out.

3. Principle of Staining: Why the Protocol Steps Matter

Sirius Red F3B (C.I. 35782) is a strong acidic, anionic dye carrying four sulfonate groups (negative charges). In the strongly acidic environment of saturated picric acid (pH ~2), the basic amino acid residues of collagen—lysine, hydroxylysine, and arginine—become protonated (positively charged). This creates strong electrostatic interactions between the anionic dye and the cationic collagen². Furthermore, the elongated structure of the Sirius Red molecule aligns along the grooves of the collagen triple helix, which produces the intense birefringence observed under polarized light³.

Understanding the chemical rationale behind each protocol step helps troubleshoot problems and optimize results:

Why Wash with Acetic Acid, Not Water?

The binding between Sirius Red and collagen is reversible (non-covalent, primarily electrostatic), meaning pH directly controls binding stability. If sections are washed with pure water (pH ~7), the positive charges on collagen's basic residues diminish, and the dye rapidly dissociates (leaches out) from the tissue. By maintaining a mildly acidic environment (0.5% acetic acid, pH ~3) during washing:

• Collagen residues remain protonated, preserving the electrostatic bonds with the anionic dye
• The yellow picric acid background is cleanly washed away
• The resulting red-on-yellow contrast is maximized

Why Does Staining Time Matter?

The 60-minute staining time ensures that the dye fully penetrates thick collagen bundles. Shorter times (e.g., 30 min) may produce weak staining of deep fibrotic zones, while longer times (>90 min) do not typically cause over-staining because the dye binds stoichiometrically.

4. Experimental Protocol

Reagents

• Picro-Sirius Red Solution: 0.1% Sirius Red F3B in saturated aqueous picric acid (see Section 2).
• Acidified Wash Water: 0.5% acetic acid in distilled water.
• Others: Xylene, Ethanol series (100%, 95%, 90%, 80%), Mounting medium (e.g., Permount, Entellan).
• [Optional]: Weigert's iron hematoxylin for nuclear counterstaining.

Step-by-Step Procedure

1. Deparaffinization & Rehydration: Xylene (3 changes, 5 min each) → Ethanol series (100% → 95% → 90% → 80%, 2 min each) → Distilled water (2 min).

2. [Optional] Nuclear Counterstain: Stain nuclei with Weigert's iron hematoxylin for 5–10 minutes, then wash in running tap water for 10 minutes.

   [TIP] Use Weigert's (iron-based) hematoxylin, not Mayer's or Harris (aluminum-based). Aluminum hematoxylin is easily decolorized by the acidic PSR solution.

3. Staining: Incubate sections in Picro-Sirius Red Solution for 60 minutes at room temperature. Ensure sections are fully submerged.

4. Washing (CRITICAL STEP): Wash in two changes of acidified water (0.5% acetic acid), gently agitating for 30 seconds each.

   [WARNING] Do NOT wash with water at this stage. Water will rapidly leach the red dye from collagen, ruining your staining.

5. Dehydration & Mounting: Physically blot excess liquid from slides. Dehydrate quickly in three changes of 100% ethanol (10–15 seconds each). Clear in xylene (2 changes, 2 min each). Mount with a resinous medium.

   [TIP] Speed is important during ethanol dehydration. Prolonged immersion in alcohol can also cause dye leaching, though much less than water.

Recommended Section Thickness

• Bright-field quantification: Standard 4–5 μm sections work well.
• Polarized light observation: Use 6–7 μm sections. Thicker sections may appear excessively yellow-orange and make color interpretation unreliable³.

5. Polarized Light Microscopy: Assessing Collagen Fiber Maturity

Under a polarized light microscope, the Sirius Red molecules align parallel to the collagen fiber axis, enhancing the natural birefringence of collagen. This reveals fiber characteristics that are invisible under standard bright-field illumination.

Setup for Polarized Observation

1. Place the PSR-stained slide on the microscope stage.
2. Insert both the polarizer (below the condenser) and the analyzer (above the objective).
3. Rotate the analyzer until the background appears completely black (crossed polarizers / crossed Nicols).
4. Collagen fibers will now appear as brilliantly colored structures against a dark background.

Interpreting the Colors

Observed Color	Fiber Characteristic	Typical Collagen Type
Red / Orange / Yellow	Thick, densely packed, mature fibers	Primarily Type I collagen
Green	Thin, loosely arranged, immature fibers	Primarily Type III collagen (reticular fibers)

Important Caveats

The color difference primarily reflects fiber thickness and packing density, not collagen type per se. A thin Type I fiber may appear green, and tightly packed Type III bundles could appear red-orange. For strict collagen typing, immunohistochemistry (IHC) with type-specific antibodies (anti-Collagen I, anti-Collagen III) must be used in conjunction with PSR polarization.

Polarized observation is particularly valuable in:

• Tracking fibrosis maturation over time in longitudinal studies
• Evaluating anti-fibrotic efficacy — successful treatment often shifts the balance from thick red fibers (mature) toward thin green fibers (remodeling)
• Assessing whether newly deposited collagen (wound healing) is mature or immature

6. Picrosirius Red vs Second Harmonic Generation (SHG) Imaging

Over the last decade, Second Harmonic Generation (SHG) microscopy has emerged as a label-free alternative for collagen imaging. Since many preclinical programs now weigh SHG against PSR when designing quantitative fibrosis endpoints, the comparison below summarizes the practical trade-offs.

How SHG Differs in Principle

SHG is a non-linear optical process: when intense pulsed laser light (typically femtosecond 800–920 nm) interacts with non-centrosymmetric biological structures such as fibrillar collagen (Types I, II, III, V), two photons are combined into a single photon at exactly half the wavelength. No staining, no dye, no photobleaching — the signal originates from the intrinsic molecular order of the collagen triple helix itself⁵.

PSR, by contrast, relies on electrostatic dye binding (Section 3). The signal depends on sample preparation, dye lot, washing chemistry, and mounting medium, all of which introduce batch variability that SHG does not have.

Head-to-Head Comparison

Aspect	Picrosirius Red (PSR)	SHG Microscopy
Staining required	Yes (60-min protocol)	No (label-free)
Equipment	Standard bright-field + polarizer (<$10k)	Multiphoton/2-photon microscope ($300k–$600k)
Sample type	FFPE paraffin sections (4–7 µm)	FFPE, fresh, or even intravital (thick ≥100 µm)
Collagen types detected	Types I & III (thick/thin fibers)	Fibrillar collagen (I, II, III, V)
Quantitative readouts	% Area, CPA, polarization hue	Integrated SHG intensity, fiber coherency, alignment, waviness
Reproducibility (CV%)	15–25% (operator-dependent thresholding)	5–15% (physics-based, instrument-stable)
Regulatory familiarity	Decades of FDA/EMA submission precedent	Emerging; supporting endpoint rather than primary
Throughput	High (whole-slide scan + ImageJ)	Moderate (tiled acquisition, slower)
Cost per slide	$5–$15 (reagents + pathology)	$50–$150 (instrument time, specialized operator)

When to Choose Which

• Primary quantification for drug-efficacy studies → PSR %Area remains the default. Regulators, pathologists, and CROs all recognize it, and the equipment cost barrier is negligible.
• Fiber architecture / remodeling mechanism → SHG is superior. Coherency and alignment metrics reveal whether anti-fibrotic treatment is resolving mature crosslinked collagen or merely preventing new deposition.
• Thick tissue / in vivo / ex vivo tracking → SHG wins. PSR cannot be applied to live tissue or >10 µm sections without artifacts.
• Publishing high-impact mechanistic work → a combined PSR (static % Area) + SHG (fiber order) readout is increasingly expected in top-tier journals (e.g., Sci Transl Med, Nat Commun).

For most preclinical CRO studies, PSR stays the mandatory deliverable and SHG is added as a mechanistic layer when budget allows. See our Fibrosis Quantification Hub for a full decision matrix.

7. Comparison with Masson's Trichrome Staining

For evaluating fibrosis, PSR and Masson's Trichrome (MT) are frequently compared. Selecting the appropriate stain depends on the study's specific endpoints. See also Masson's Trichrome vs Sirius Red: Choosing the Right Stain for a full side-by-side decision guide.

Component	PSR Staining	MT Staining
Collagen Fibers (Thick bundles, Type I)	Red (strongly positive)	Blue (dense staining)
Reticular Fibers (Thin mesh, Type III)	Red (detected)	Light Blue / Often missed
Elastic Fibers (Elastin)	Not stained (Yellow background)	Not stained (Reddish)
Muscle / Cytoplasm	Not stained (Yellow background)	Red
Polarized Light	✅ Yes (fiber maturity assessment)	❌ Not applicable

Summary:

• PSR is superior for quantification because it specifically stains collagen red while leaving other components yellow, making automated thresholding and % Area calculation much more accurate.
• MT is excellent for morphological overview, as it clearly distinguishes muscle (red) from collagen (blue), and is commonly paired with semi-quantitative scoring systems (e.g., Ashcroft Score for lung, Ishak Score for liver).

For a deeper analysis of when to choose which stain, see Masson's Trichrome vs Sirius Red: Choosing the Right Stain for Fibrosis Assessment.

In practice: When a study protocol calls for strict, digital, operator-independent quantification of collagen (Collagen Proportional Area / CPA), PSR is the standard choice. When the primary endpoint is pathologist-scored grading of overall tissue architecture, MT may be preferred.

Collagen Staining Method Selection Flowchart

Which stain fits your study? Decide top-down by primary endpoint:

Primary Need	Recommended Method	Rationale
Rapid fibrosis screening	PSR + polarization	Single-stain, bright-field + fiber maturity in one prep
Absolute collagen mass	Hydroxyproline assay + PSR	Biochemical total + spatial distribution (dual readout)
Multi-component histology (fibrin, muscle, collagen)	MT staining	Differentiates muscle (red) from collagen (blue)
Thick / fresh / in vivo tissue	SHG microscopy	Label-free, works up to 500 µm depth
Fiber architecture & remodeling mechanism	SHG (± PSR polarization)	Coherency / alignment metrics
FDA/EMA regulatory submission	PSR %Area + Hydroxyproline (dual)	Accepted combined standard
Clinical liver biopsy scoring	MT + Ishak / NAS score	Legacy pathologist protocols
Drug efficacy in CRO preclinical package	PSR %Area (primary) + biomarker panel	Highest cost-effectiveness, recognized by regulators

8. Picrosirius Red vs Hydroxyproline Assay — Dual Readout Strategy

In drug-efficacy programs, PSR and the hydroxyproline assay are complementary rather than competing. Understanding when to combine them — or to pick only one — directly impacts statistical power and FDA submission readiness.

What Each Method Measures

Aspect	PSR (% Area)	Hydroxyproline
Signal type	Histological (spatial, 2D slice)	Biochemical (total tissue pool)
What it measures	Collagen-stained pixel fraction per tissue section	Total collagen content via hydroxyproline residues (μg/mg tissue)
Spatial resolution	High — reveals regional distribution	None — one aggregate number per sample
Sample amount needed	~5-µm section (minimal)	50–100 mg fresh/frozen tissue
Typical CV%	15–25% (thresholding + sampling variability)	5–10% (colorimetric, well-controlled)
Dynamic range	Limited at very low fibrosis (noise floor)	Excellent across 4 orders of magnitude
Regulatory precedent	Decades of use in FDA/EMA submissions	Same — the biochemical gold standard

Why the Two Numbers Rarely Match Perfectly

Reported correlation coefficients between PSR % Area and hydroxyproline content typically fall in r = 0.70–0.85 across liver, lung, and kidney models⁶. Discordance is expected, not a mistake, because:

• Fibrosis is spatially heterogeneous: PSR samples a 5-µm slice while hydroxyproline digests the whole lobe.
• Thresholding choices shift PSR values by 20–30% without affecting hydroxyproline.
• Dense mature collagen plateaus PSR saturation but keeps increasing hydroxyproline linearly.
• Cross-linked collagen resists extraction in some hydroxyproline protocols (alkaline vs acid hydrolysis).

Dual-Readout Best Practices

1. Report both numbers for any pivotal preclinical efficacy study. A drug effect that reaches significance in both PSR and hydroxyproline is far more defensible to FDA reviewers than either alone.
2. Anticipate minor discordance: a compound may reduce PSR %Area by 30% but hydroxyproline by only 15%, because it blocks new deposition (visible histologically) without clearing established crosslinked collagen (retained biochemically).
3. Sample allocation: split each animal's target organ — typically half for fixation + histology (PSR + MT), half for snap-freezing + biochemistry (Hyp + qPCR) — rather than running serial sections of a single lobe.
4. Pair with a CRO that runs both in-house: transferring frozen samples between vendors adds variability. Select a CRO that delivers PSR histology and hydroxyproline biochemistry as a single integrated package (see our Fibrosis CRO Landscape 2026 for a vendor comparison).

For a broader comparison of all fibrosis quantification methods (biochemistry, histology, AI pathology, imaging), see the Fibrosis Quantification Methods Hub.

9. Practical Guide to ImageJ Quantification

The high contrast between red (collagen) and yellow (background) makes PSR ideal for objective, reproducible quantification using image analysis software such as ImageJ/Fiji, HALO, or QuPath.

Step-by-Step ImageJ Analysis

1. Load Image: Open your bright-field PSR-stained image in ImageJ/Fiji. Use images captured under consistent, calibrated lighting conditions.

2. Color Deconvolution (Recommended): Setting a simple RGB threshold often confuses red fibers with the yellow background. Instead:

   • Go to Image > Color > Color Deconvolution
   • Select the H&E or User values vector to separate the stains
   • This produces three grayscale images; use the channel corresponding to the red PSR stain

   Pro Tip (LAB Stack Method): A more robust alternative is to convert the image via Image > Type > LAB Stack. The "a channel"* (red-green axis) cleanly isolates the red collagen from the yellow background with minimal manual tuning and is particularly resistant to variations in illumination and white balance.

3. Thresholding: On the isolated grayscale image representing the red channel, go to Image > Adjust > Threshold. Adjust the sliders to highlight the collagen meshwork while ignoring background noise. Use the same threshold values across all images in a study for consistency.

4. ROI Selection: If you need to exclude non-tissue areas (e.g., vessel lumens, airways), manually draw a Region of Interest (ROI) around the tissue area before measuring.

5. Measure: Go to Analyze > Measure to calculate the % Area — the percentage of the thresholded positive area (collagen) relative to the total tissue area (ROI).

Best Practices for Reproducible Quantification

• Capture ≥5 non-overlapping fields per section at 100× or 200× magnification
• Use consistent white balance and exposure across all images
• Report mean ± SEM of % Area per animal (not per field)
• Consider using AI-powered digital pathology for whole-slide analysis, which eliminates field selection bias

10. Common Artifacts & Extended Troubleshooting

[Deep Dive] For a more exhaustive troubleshooting resource covering color fading, background contamination, polarization issues, and quantification variability, see our dedicated PSR Staining Troubleshooting Guide.

A comprehensive troubleshooting guide — covering the most common issues encountered during PSR staining and quantification:

Problem	Possible Cause	Solution
Weak/faint red staining	Old or degraded staining solution	Check solution age. Filter to remove precipitate. Prepare fresh if >3 years old or if solution appears turbid.
Weak staining (fresh solution)	Insufficient staining time	Ensure a full 60-minute incubation. For thick sections (>7 µm) or dense fibrotic tissue, extend to 90 min.
High yellow background	Insufficient acetic acid washing	Use two full changes of 0.5% acetic acid, with gentle agitation. If background persists, add a third wash.
Loss of red color during processing	Washing with water instead of acetic acid	Never wash with pure water. Use 0.5% acetic acid only.
Loss of red color during dehydration	Prolonged time in ethanol	Keep ethanol dehydration steps brief (10–15 seconds per change in 100% ethanol).
Cytoplasm stains red	Dye hydrolysis (degraded solution)	Picric acid in the solution can break down over time if contaminated with water. Prepare fresh solution. Also check for incomplete deparaffinization.
Cytoplasm stains red	Incomplete deparaffinization	Extend xylene treatment. Ensure paraffin is fully removed — residual wax traps dye non-specifically.
Sections detach from slides	Poor adhesion	Use positively charged slides (SuperFrost Plus or Poly-L-Lysine coated). Dry sections thoroughly at 60°C for 1 hour before staining.
Polarization colors appear all yellow	Section too thick	Reduce section thickness to 6–7 µm. Thicker sections cause additive birefringence that shifts all colors toward yellow.
Inconsistent quantification across slides	Variable staining intensity	Stain all study slides in the same batch with the same solution and timing. Use a coverslipping machine for consistent mounting.

FAQ

Can I use PSR staining without a polarized microscope?

Yes. Bright-field observation (standard microscopy) is perfectly sufficient for quantifying total collagen (fibrosis area %). Polarized observation is an optional, additional tool for assessing fiber orientation, maturity, and remodeling status.

How long can PSR-stained slides be stored?

PSR-stained slides are very stable. If stored in the dark at room temperature, they remain usable for years without significant fading — one of the major advantages over fluorescent stains.

Does Picrosirius Red stain elastin?

No. Elastin (elastic fibers) does not bind Sirius Red; it appears yellow/colorless (background). This is a key specificity advantage over some other connective tissue stains.

Can I use PSR on frozen sections?

Yes, with modifications. Fix frozen sections in 10% neutral buffered formalin for 10 minutes before staining. Adhesion-coated slides are strongly recommended.

How does PSR compare to Second Harmonic Generation (SHG) microscopy?

SHG is a label-free, non-destructive technique that images fibrillar collagen via non-linear optics. PSR remains the regulatory default due to equipment cost ($10k vs $300k+) and FDA submission precedent, but SHG is superior for fiber architecture and in vivo work. See Section 6 above for the detailed head-to-head comparison.

How does PSR compare with AI-based digital pathology?

AI-powered digital pathology (CNN/ViT models) removes inter-observer variability in thresholding and enables whole-slide analysis, typically improving CV% from 20% to 5–10%. However, AI quantification is built on top of PSR (or MT) staining — it still needs the underlying stain. For the current state of the art and vendor landscape, see AI-Powered Digital Pathology for Fibrosis.

What CV% should I expect for PSR % Area measurements?

In experienced hands with consistent lighting, standardized thresholding, and ≥5 non-overlapping fields per animal, inter-animal CV typically lands at 15–25%. Whole-slide AI analysis can reduce this to 5–10%. If you observe CV >30%, the most common culprits are (1) inconsistent exposure or white balance across captures, (2) operator-dependent thresholding, and (3) too few fields sampled per section.

11. Applications in Fibrosis Models

PSR staining (specifically the % Fibrosis Area metric) is the primary endpoint for assessing fibrosis and therapeutic efficacy in the following validated preclinical models:

• Liver: CCl4-Induced Liver Fibrosis Model
• Liver: MASH (Diet-Induced) AMLN and GAN Models
• Lung: Bleomycin-Induced Pulmonary Fibrosis Model
• Kidney: UUO (Unilateral Ureteral Obstruction) Model
• Kidney: Adenine-Induced CKD Model
• Skin: Scleroderma (Bleomycin-Induced SSc) Models

For a comprehensive overview of all available fibrosis quantification methods (histology, biochemistry, AI pathology, and in vivo imaging), see our Fibrosis Quantification Hub.

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Planning a fibrosis efficacy study? See our comparative guides to AI-powered digital PSR quantification, hydroxyproline dual-readout workflows, and the 2026 Fibrosis CRO Landscape covering liver, lung, kidney, skin, and cardiac models. For editorial inquiries, contact us.

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12. References

1. Emory University Histology Services. "Picrosirius Red Staining Procedure for Collagen."

2. Junqueira LC, Bignolas G, Brentani RR. Picrosirius staining plus polarization microscopy, a specific method for collagen detection in tissue sections. Histochem J. 1979;11(4):447-455. PubMed

3. MedChemExpress. "Picro-Sirius Red Staining Kit Protocol."

4. Lattouf R, et al. Picrosirius red staining: a useful tool to appraise collagen networks in normal and pathological tissues. J Histochem Cytochem. 2014;62(10):751-758. PubMed

5. Campagnola PJ, Loew LM. Second-harmonic imaging microscopy for visualizing biomolecular arrays in cells, tissues and organisms. Nat Biotechnol. 2003;21(11):1356-1360. PubMed

6. James J, Bosch KS, Aronson DC, Houtkooper JM. Sirius red histophotometry and spectrophotometry of sections in the assessment of the collagen content of liver tissue and its application in growing rat liver. Liver. 1990;10(1):1-5. Demonstrated highly significant correlation between Sirius Red densitometry and hydroxyproline content in liver tissue. PubMed

How to Cite This Article

This protocol article is released for citation and reuse in research and educational contexts.

APA format:

Fibrosis-Inflammation Lab. (2026). Picrosirius Red Staining Protocol: Complete Guide to Sirius Red Collagen Quantification & Troubleshooting. Retrieved from https://www.fibrosis-inflammation.com/en/insights/tech_sirius_red_staining

BibTeX:

@misc{fibrosisinflammation_siriusred_2026,
  author = {{Fibrosis-Inflammation Lab}},
  title  = {Picrosirius Red Staining Protocol: Complete Guide to Collagen Quantification and Troubleshooting},
  year   = {2026},
  url    = {https://www.fibrosis-inflammation.com/en/insights/tech_sirius_red_staining},
  note   = {Accessed: YYYY-MM-DD}
}

License: This article is licensed under the Creative Commons Attribution 4.0 International License (CC BY 4.0). You are free to copy, modify, and use this content commercially, provided you give appropriate attribution.

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