One year on: Live Cell Imaging with SiR-actin, SiR-tubulin & SiR-DNA


Fig 1: 3D-SIM microscopy image of labeled Actin stress fibers in human primary dermal fibroblasts.

Launched just over a year ago,  SiR-Actin (Fig 1) and SiR-Tubulin (Fig 2) have been available on the market providing the most convenient tools to stain F-actin and Microtubules in living cells. In the meantime, Spirochrome  have launched a third stain based on the SiR-technology – SiR-DNA (Fig 3) to stain DNA in living cells.
These stains meet the central requirements for live cell imaging tools:

SiR Tubulin tebu-bio's fluorescent dye

Fig 2: 3D-SIM microscopy image of labeled microtubules in primary rat cortex neuron body.

  • high selectivity
  • minimal toxicity
  • fluorogenic for wash-free imaging
  • applicable in different cell types and tissues
  • excited by far-red light
  • suitable for super-resolution microscopy

SiR DNA picture 3 - speroid

Fig 3: Live MCF10A cells spheroid stained with SiR-DNA and imaged by confocal microscopy. Courtesy of C. Conrad and K. Jechow (Heidelberg).

In particular,  SiR-Actin and SiR-Tubulin are the only stains available on the market which enable live cell imaging of the major cytoskeletal cellular structures – without the need to transfect cells with vectors carrying the information for fluorescently labeled tubulin or actin or related binding proteins.

The proprietary bright and photostable silicon rhodamine-like (SiR) technology is compatible with most microscopes. It can be used with standard Cy5 settings. The combination of all these properties set SiR-based probes apart from other fluorescent probes. The SiR dyes are coupled to binding components which specifically bind to F-actin (Jasplakinolide natural compound), Microtubules (Docetaxel), or the DNA minor groove binder bisbenzimide (Hoechst).

SiR stains for Live Cell Imaging Results per Cell Type

Table 1: Cell and tissue types tested with SiR-Actin and/or SiR-Tubulin; N.D. = not determined; + / – = no uniform staining of the cell population.

What do users do with these stains?

Cell biologists work with a number of cell and tissue types and of course every cell types shows some specific characteristics concerning the uptake of tools like our SiR-stains. It is known that the commonly used drug Verapamil which belongs to a group of calcium channel blockers enhances the uptake of SiR-stains in some cell types (for further info, read more here); that is why Verapamil is added to all SiR-stain kits routinely. To give users a good overview which cell types have been already successfully stained with SiR-Actin and SiR-Tubulin, we are building up a data base in cooperation with Spirochrome. Table 1 gives you a quick overview about the data we collected so far from our own and users’ experience. One of the few cells/organisms which could not be successfully stained are fungal cells like yeast or dictyostelium cells. If you are interested in details about the experimental setups used or if you have experience (positive or negative) with other cell or tissue types, we invite you to get in touch by leaving a comment below.

Results recently obtained by SiR-stain users

Erik T. Valent - SiR-tubulin - HUVECs

Fig 1: HUVECs stained with SiR-tubulin (60 min at 100 – 200 nM without Verapamil). Courtesy by Erik T. Valent, VU Medisch Centrum, Amsterdam, The

M. van den Berg - SiR-Actin - HUVECs

Fig 2: HUVECs on a layer of Human Brain pericytes, fixed in 4% PFA, have been stained for 1 hr at RT with 100nM/ml SIR-Actin. Courtesy by Bernard M. van den Berg, LUMC, Leiden, The Netherlands

Fig 1 and 2 show results provided by Erik T. Valent from the VU Medisch Centrum, Amsterdam, The Netherlands (Fig 1) and Bernard M.van den Berg from the LUMC, Leiden, The Netherlands (Fig 2). Both labs stained Human umbilical vein endothelial cells (HUVECs) either with SiR-Actin or with SiR-Tubulin.

Interested in more SiR stain user results in Live Cell Imaging?

More and more results have been published over the past months using the SiR-stains and showing their applicability on miscellaneous cell and tissue samples and in diverse microscopic set-ups.

We’ve compiled a selection of the latest publications using SiR-stains. In this overview you’ll also find first publications with the recently launched SiR-DNA as well as publications in which SiR-derivatives such as SiR-NHS or SiR-tetrazine have been referenced.

See more results with SiR-stains in live cell imaging experiments – Download your copy here.

Written by Ali El Baya, PhD
Ali el Bayâ is the Sales Manager at tebu-bio for the North of Europe.