Sircol™ - Insoluble Collagen assay kit

As collagens mature, they become increasingly crosslinked and insoluble - characteristics necessary for key biophysical role that collagen plays in living organisms. Biocolor’s Sircol™ INSOLUBLE Collagen Kit is a dye-binding assay designed for accurate quantification and measurement such collagens. It is ideal for analyzing crosslinked / insoluble collagens from sources such as tissues, bone, and calcified tissue.
Colorimetric Detection (556nm) (Endpoint)
The previous S1000 Sircol Soluble Collagen assay can be found here.
NB: For quantification of soluble/immature collagens we recommend our Sircol 2.0 soluble collagen kit. here.
No items found.

What is Collagen?

Collagen is a fundamental component of the extracellular matrix, and the predominant protein in animals, constituting around 30% of total protein mass. A glycoprotein, it is well known for its triple helical structure. This is formed from three polypeptide α-chains with Gly-X-Y repeating residues (Gly for Glycine, X for proline, and Y for hydroxyproline).

Types of Collagen

Over 28 types of collagens have been identified, with Type I collagen being the most abundant. It's prevalent in ligaments, tendons, skin, and bone tissue. Its mature, insoluble form grants it remarkable strength, making it vital for the mobility of organisms. Collagen also has biochemical functions, influencing cell growth, proliferation, and differentiation.

This version of the kit is designed to detect and measure INSOLUBLE forms of collagen. Chose our Sircol 2.0 collagen kit if you need to analyse SOLUBLE collagen.

Applications of Collagen

Collagen, with its diverse properties, finds utility in various industries. It plays a role in medicine for wound healing and has an expanding role in tissue engineering and cell culture for biomedical purposes. It's gaining popularity in the cosmetic industry for skin rejuvenation and is used in chemical formulations and the food industry as a functional food supplement and additive.

How does the Sircol assay detect collagen?

Sircol dye reagent contains Sirius Red - a linear anionic dye with sulphonic acid side chain groups. Under assay conditions the Sircol dye binds the basic groups of soluble collagen molecules. Maximal binding occurs in collagens possessing intact triple helix organisation as the highly ordered Gly-X-Yn helical structure of tropocollagen further contributes to dye binding. This results in a high degree of dye-collagen specificity. Affinity is progressively reduced during heat denaturation 4ºC due to the unwinding of the triple helix and formation of random chains.

Overview of the Sircol assay process:

Step 1. Samples being assayed for insoluble collagen must first undergo a 2-3 hour pre-treatment with Sircol Fragmentation reagent. This converts insoluble collagen into water-soluble gelatin can then be assayed.

Step 2. Addition of Sircol Dye Reagent to these pre-treated insoluble collagen samples results in the formation of a denatured collagen-dye complex. This complex then precipitates during the dye incubation period and is subsequently isolated by centrifugation, followed by washing to remove unbound dye. The Denatured collagen-bound dye is then  eluted and measured spectrophotometrically.

Step 3. The insoluble collagen content of unknown samples is quantified by comparison against a calibration curve prepared using a the denatured collagen standard supplied with the kit.

A list of suggested sample types can be found under the 'Assay Specification' tab.

Assay range

100 - 1000 µg/ml

Limit of Detection


Detection Method

Colorimetric Detection (556nm) (Endpoint)

Measurements per kit

110 in total (allows a maximum of 46 samples to be run in duplicate alongside a standard curve).

Suitable Samples

The assay can be used to assess the rate of production of newly laid down collagen fibres during periods of rapid growth, development, tissue repair, remodeling and wound healing. Sources of material includes tissues, bone and calcified tissue.

*Insoluble collagens must be converted into soluble form prior to assay. Instructions and regents are provided with the kit., depending on sample this will require prior salt/acid/acid-pepsin extraction.

**non-mammalian collagens may result in a reduced limit of detection. We recommend use of an assay standard matched to the species under assay.

Many customers have found that the straightforward sample processing and analysis of Sircol make it a good alternative to conventional hydroxyproline analysis.


This kit is designed for research use only. Not for use in diagnostic procedures.
Kit requires access to a centrifuge, water bath / heated block, as well as a spectrophotometer/colorimeter capable of absorbance detection at 556nm.
Specific sample preparation protocols may require customer to provide further reagents, consult assay manual for further information.

Sircol Insoluble Collagen kit contents:

1. Sircol Dye Reagent (1x110ml)

2. Denatured Collagen Reference Standard (1x5ml, 1.0mg/ml)

3. Acid-Salt Wash Reagent (1x20ml)

4. Fragmentation Reagent (1x110ml)

5. Alkali Reagent (1x110ml)

6. 2ml screw-cap tubes for preparation of samples.

7. Assay kit manual

NB: Additional reagents may be required for sample preparation prior to assay. Consult manual or contact us for further details.

You might also be interested in.....

Sircol-2.0 Soluble Collagen assay kit

Experience user-friendly detection & measurement of Soluble Collagen with Sircol™ 2.0! Our latest kit simplifies collagen quantification within in-vivo / in-vitro samples. Sircol 2.0 offers enhanced sensitivity and accuracy compared to our previous Sircol kit.

Learn more

Purple-Jelley Hyaluronic Acid assay kit

Biocolor’s Purple-Jelley assay kit is the perfect tool for accurate measurement of hyaluronic acid / Hyaluronan levels in your samples. This colorimetric assay is optimised for quantitative analysis in-vivo, tissue-derived hyaluronic acid / Hyaluronan and includes full step-by-step instructions.

Learn more

Fastin™ - Elastin assay kit

Introducing the Fastin Assay Kit: Your Straightforward Solution for Elastin Quantification! Our user-friendly kit utilizes a dye-based method to measure elastin from in-vivo and in-vitro sources. It can be used to quantify various elastin forms, spanning from immature tropoelastin to mature, 'insoluble' elastin fibers.

Learn more