Two-Photon Excitation Microscopy (TPE)

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Labels and bioconjugates

Molecular Probes® fluorophores have been tried and tested in TPE applications as conjugates of antibodies, proteins, dextrans, and other biomolecules. Use the list below to select the fluorophore with the best wavelength. The TPE excitation is shown in the table—citations are listed for each. Typically, Alexa Fluor® dyes have been used as bioconjugates for TPE in experiments to investigate cytoskeleton organization or neuronal tracing. Qdot® probes conjugated to antibodies have been used in immunohistochemical analysis. By following the links for each fluorophore you can also find all of the respective bioconjugates currently available to target your molecule of interest; the list ranges from antibodies and phalloidins to growth factors and lectins. If you don't find the conjugate you need on the list, the links will also show you reactive dye forms or optimized labeling kits to enable you to create your own bioconjugate probes.

Ion indicators

A range of Molecular Probes® ion indicators have been used in TPE applications, primarily in neurons. Oregon Green® 488 BAPTA-1 has been used to image calcium signaling in the rat brain; fura-2 and X-rhod-1 have been used in Purkinje cells; and Fluo-5F has been referenced in publications on dendrites and dendritic spines. Other ions studied using TPE include sodium gradients in rat cardiomyocytes using SBFI and chlorine concentrations in olfactory neurons using MQAE.

The table below shows indicators used in TPE. You can also see a wider range of ion indicators organized by performance criteria in conventional imaging applications.

Oxidative stress detection

TPE can be used to detect the localized release of reactive oxygen species and the redox state of the cell using a variety of indicators. Specifically, glutathione, H₂O₂, or generalized oxidative stress can be measured with a number of probes that have been shown to work well for TPE and offer a range of wavelength options. Citations are included for each probe as well as the TPE excitation wavelength used.

The table below shows indicators used in TPE. You can also see a wider range of reactive oxygen indicators organized by performance criteria in conventional imaging applications.

Cell structure probes

Cell structure probes exhibiting good results for TPE include nuclear stains, membrane stains, and cell-tracing dyes. Nuclear stains are available for use in both live (Hoechst 33342) and fixed (DAPI) cells, both with blue emission and a similar TPE excitation. Cell membrane probes offer a choice of red (FM® 1-43 dye) or far-red (DiD) emissions, and the cell-tracking dyes range from green through orange.

The table below shows the probes used in TPE, together with citations and TPE excitation. You can also see a wider range of cell structure probes organized by performance criteria in conventional imaging applications.