in vivo imaging

Expert Insights: A Look Forward at Multiplexing for in vivo Bioluminescence Imaging

Posted on by Simon Moe

Bioluminescent in vivo imaging tools

NanoLuc, NLuc

With advancements made over the past few decades, the future of in vivo bioluminescence imaging (BLI) continues to gain momentum. In vivo BLI provides a non-invasive way to image endogenous biological processes in whole animals. This provides an easier method to assess relevant systems and functions. Unlike fluorescent imaging, BLI relies on a combination of enzymes and substrates to produce light, greatly reducing background signal (Refaat et al., 2022). Traditional fluorescent tags are also quite large and may interfere with normal biological function. In vivo BLI research has been around for quite some time, primarily utilizing Firefly luciferase (Luc2/luciferin). A recent advancement was the creation of the small and bright NanoLuc® luciferase (NLuc). Promega offers an wide portfolio of NLuc products that provide ways to study genes, protein dynamics, and protein:protein interactions. To fully grasp the power of these tools, I interviewed several key investigators to determine their perspectives on the future of in vivo BLI. I was specifically interested in their thoughts on NLuc multiplexing potential with Firefly (FLuc), and future research areas. These two investigators are Dr. Thomas Kirkland, Sr. Scientific Investigator at Promega, and Dr. Laura Mezzanotte, Associate Professor at Erasmus MC.

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Illuminating the Brain with a New Bioluminescence Imaging Substrate

Posted on by Kari Kenefick

Bioluminescence imaging is a powerful tool for non-invasive studies of the effect of treatments on cells and tissues. The luminescent signal is strong, and can be used in vivo, enabling repeated observations over time, allowing longitudinal study of cellular changes for hours or days. Bioluminescence imaging can be used in live animals over varying periods of time, without interfering with normal cellular processes.

Fluorescence imaging is also used in cellular studies. Although it can provide a stronger signal than luminescence, fluorescence requires light for excitation, and thus its in vivo use is limited at a tissue or cell depth greater than 1mm.

NanoLuc® Luciferase. Small, bright and now useful in brain bioluminescence imaging.

In addition, autofluorescence can be an issue with fluorescence imaging, as cellular components and surrounding proteins and cells can fluoresce when exposed to light. Autofluorescence can result in high background signals, making it difficult to distinguish true fluorescence from background.

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Seeing is Believing: How NanoLuc® Luciferase Illuminates Virus Infections

Posted on by Jordan Nutting
Artists interpretation of in vivo imaging of viral infections in mice using NanoLuc luciferase.

Wearing blue surgical gowns and white respirator hoods, research scientist Pradeep Uchil and post-doctoral fellow Irfan Ullah carry an anesthetized mouse to the lab’s imaging unit. Two days ago, the mouse was infected with a SARS-CoV-2 virus engineered to produce a bioluminescent protein. After an injection of a bioluminescence substrate, a blue glow starts to emanate from within the mouse’s nasal cavity and chest, visible to the imaging unit’s camera and Uchil’s eyes.

“We were never able to see this kind of signal with retrovirus infections.” Uchil is a research scientist at the Yale School of Medicine whose work focuses on the in vivo imaging of retroviral infections. Normally, the mouse would have to be sacrificed and “opened up” for viral bioluminescent signals from internal tissues to be imaged directly.

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NanoLuc® Luciferase: Brighter Days Ahead for In Vivo Imaging

Posted on by Ken Doyle
nanoluc in vivo imaging

The development of NanoLuc® luciferase technology has provided researchers with new and better tools to study endogenous biology: how proteins behave in their native environments within cells and tissues. This small (~19kDa) luciferase enzyme, derived from the deep-sea shrimp Oplophorus gracilirostris, offers several advantages over firefly or Renilla luciferase. For an overview of NanoLuc® luciferase applications, see: NanoLuc® Luciferase Powers More than Reporter Assays.

The small size of NanoLuc® luciferase, as well the lack of a requirement for ATP to generate a bioluminescent signal, make it particularly attractive as a reporter for in vivo bioluminescent imaging, both in cells and live animals. Expression of a small reporter molecule as a fusion protein is less likely to interfere with the biological function of the target protein. NanoLuc® Binary Technology (NanoBiT®) takes this approach a step further by creating a complementation reporter system where one subunit is just 11 amino acids in length. This video explains how the high-affinity version of NanoBiT® complementation (HiBiT) works:

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HaloTag® Research Application: Detection of Cancer Biomarkers

Posted on by Gary Kobs

10242TAAntibodies labelled with radioisotopes or the sequential administrationof an antibody and a radioactive secondary agent facilitate the in vivo detection and/or characterisation of cancers by positron emission tomography (PET) or by single-photon emission computed tomography (SPECT) imaging.

There are drawbacks to both methods, including prolonged exposure to radiation and  ensuring that both the antibody and the radiolabelled secondary agent are suitably designed so that they bind rapidly upon contact at the tumor.

A recent publication (1) investigated a alternative method utilizing the HaloTag® dehalogenase enzyme HaloTag® is a dehalogenase enzyme (33 kDa) that contains an engineered cavity designed to accommodate the reactive chloroalkane group of a HaloTag® ligand (HTL). Upon entering the enzyme cavity, the terminal chlorine atom rapidly undergoes nucleophilic displacement, and a covalent adduct is formed, effectively anchoring the HaloTag® ligand in a precise location.

Three new HaloTag® ligands were synthesized and each labelled with the SPECT radionuclide indium-111  111In-HTL-1  and the dual-modality HaloTag® ligands,111In-HTL-2 and111;In-HTL-3 containing TMR which allows complementary imaging data).

For the validation of the pretargeting strategy based on these HaloTag® ligands, the target human epidermal growth factor receptor 2 (HER2)was selected. Trastuzumab (Herceptin®) was selected as the primary targeting agent and was modified with HaloTag® protein via the trans-cyclooctene/tetrazine ligation.

All three 111In-labelled HaloTa®g ligands exhibited significantly higher binding to the HER2 expressing when compared to negative controls.

Literature Cited

Knight, J. C et al.(2015) Development of an enzymatic pretargeting strategy for dual-modality imaging. Chem. Commun. 51, 4055–8.

Tracking the Progression of Plague Using Bioluminescence

Posted on by Sara Klink

Sequencing Yersinia pestis, the bacterium that caused the Black Plague in Europe during 1348–50, is an amazing accomplishment. Y. pestis infection still occurs sporatically and causes fatalities despite the Age of Antibiotics. Even with animal models, there are questions remaining about the progression of infection. Nham et al. used in vivo imaging to examine the course of infection in a mouse animal model using a bioluminescent clone of Y. pestis. Continue reading “Tracking the Progression of Plague Using Bioluminescence”