Article Category: Reagents

Optical Surgical Navigation Clinical Trials with IRDye Infrared Dyes

Recent blog posts have highlighted some of the most exciting clinical developments of IRDye® near-infrared fluorescent dyes as surgical aides. Beyond these examples, IRDye infrared dye products are being used in more than 20 clinical trials around the globe, many of which involve the deadliest and most common cancers.

Brain and Pancreatic Cancer

Glioblastoma and glioma brain and pancreatic adenocarcinoma tumors are particularly aggressive forms of cancer that are difficult to treat. IRDye dye-conjugated optical probes are currently being investigated as an alternative to traditional surgical treatments for these cancers.

Very recently in April 2018, Deling Li and colleagues announced the results their first-in-human study a novel 68Ga-IRDye 800CW-BBN positron emission tomography (PET) and near-infrared fluorescent (NIRF) dual modality optical probe in patients with glioblastoma multiforme (GBM) [1, 2]. The authors used preoperative PET and intraoperative fluorescence-guided surgery methods, demonstrating that the “novel dual model imaging technique is feasible for integrated pre- and intra-operative targeted imaging via the same molecular receptor improved intraoperative GBM visualization and maximum safe resection” [1]. GBM is the deadliest and most aggressive glioma type, and novel GBM therapies have the potential to impact many lives.

Learn More About Dual Imaging Modalities with IRDye Optical Probes.


Figure 1. Intraoperative images of glioblastoma multiforme resection with IRDye 800CW-BBN fluorescent dyes [1].

The Dartmouth-Hitchcock Medical Center is sponsoring an investigatory study utilizing IRDye 800CW for ABY-029 in patients with recurrent glioma to determine if proper tumor/background ratio is present for surgical resection [3]. This study is expected to conclude in September 2019. A similar study is being conducted by Eben Rosenthal (Stanford University) to evaluate the effectiveness of IRDye 800CW-panitumumab in glioma surgery for distinguishing tumor cells from other central nervous system tissue [5]. Rosenthal’s study is set to conclude in 2022. Rosenthal has also studied Cetuximab-IRDye 800CW intraoperatively in patients with malignant glioma [4].

Pancreatic cancer has one of the highest mortality rates of all cancers. G.M. van Dam at the University Medical Center Groningen is currently evaluating dosing of IRDye 800CW-bevacuzimab conjugates for pancreatic adenocarcinoma [7]. Similar studies set to conclude soon by Eben Rosenthal are also evaluating the intraoperative potential of IRDye conjugates in pancreatic cancer [6].

Breast and Colorectal Cancer

Breast and colon cancers are some of the most common cancers around the globe with millions of cases diagnosed each year. Two very recent clinical trials by G.M. van Dam at University Medical Center Groningen in collaboration with Martini Hospital Groningen and UMC Utrecht have evaluated the anti-vascular endothelial growth factor antibody-IRDye 800CW-bevacizumab conjugate in breast cancer study [8, 9]. van Dam’s studies are currently assessing dosing, uptake, quantification, and localization of the optical probe, as well as determining if the conjugate is appropriate for intraoperative breast cancer surgery [8, 9].

Learn More About Optical Probe Validation and Parameters.

Colorectal cancer is also a very common diagnosis around the world. Two recent clinical trials by W.B. Nagengast of the University Medical Center Groningen evaluated IRDye 800CW-bevacizumab for colorectal cancer diagnosis [10, 11]. Nagengast noted “there is a need for better visualization of polyps during surveillance endoscopy in patients with hereditary colon cancer syndromes like Familial Adenomatous Polyposis (FAP) and Lynch Syndrome (LS), to improve adenoma detection rate,” also stating that “optical molecular imaging of adenoma associated biomarkers is a promising technique to accommodate this need” [10]. In addition to detection, IRDye 800CW-bevacizumab is also being investigated as an aid for narrowing down specific colon cancer management surgeries and therapies [11].

Other Clinical Applications

While the focus of this blog post series has been on pre-clinical and clinical applications of IRDye conjugates for cancer, these are not the only applications. Currently, IRDye fluorophores are being evaluated in several trials for clinical use in non-cancer surgeries, like abdominal and urological. Ureters, the path for urine between the kidneys and bladder, and the urethra, often present difficulties in abdominal and urological surgery. By illuminating these pathways with fluorescent dyes, the anatomy is bright and clear, which may allow surgeons to more precisely navigate around them during surgery.

A study published in 2017 by T.G. Barnes et.al. in Techniques in Coloproctology demonstrated urethra illumination in cadavers with IRDye 800BK as a method for enhancing low rectal surgical navigation [15]. The authors concluding that “IRDye 800BK is a promising alternative to ICG [indocyanine green] in visualizing the urethra,” and that “Its greater depth of penetration may allow earlier detection of the urethra during surgery and prevent wrong plane surgery sooner” [15].


Figure 2: Intraoperative images of low rectal surgery demonstrating urethral fluorescence at various depths of incision. The first row of images shows how IRDye 800BK illuminates the urethra through layers of tissue to better guide further incisions [15].

LI-COR Biosciences is currently sponsoring a clinical trial being conducted at the University of Alabama-Birmingham evaluating the dose response and safety/toxicity of IRDye 800BK for ureter delineation, which is expected to conclude soon [12]. A similar study is being conducted at the University of Oxford, sponsored by the Oxford University Hospitals NHS Trust, and is evaluating the signal/background ratio of IRDye 800BK in the ureter [13]. This trial will likely conclude later this year.


Figure 3: Intraoperative laproscopic images showing ureter delineation with IRDye 800BK. In minimally invasive surgery (such as laproscopy) ureters may be difficult to see in white light without fluorescent illumination [16].

One final application of IRDye fluorescent dyes is in endometriosis surgery. G.M. van Dam at the University Medical Groningen is investigating the feasibility of IRDye 800CW-bevacizumab for endometriosis surgery [14]. van Dam noted that “incomplete resection of endometriosis lesions often results in recurrence of symptoms and the need for repeated surgery, with considerable associated morbidity” [14]. This is the first feasibility study for IRDye 800CW and endometriosis, and is expected to conclude in early 2019.

Conclusion

This blog series on optical surgery navigation has illuminated the potential of IRDye fluorescent dyes as surgical aids. From the deadliest cancers to routine, minimally-invasive gynecological surgeries, IRDye fluorophores present a valuable opportunity for visualizing, understanding, and ultimately treating various diseases.

Could your probe be our next clinical study? For questions regarding probe development services, contact LI-COR Custom Services.

More information about the studies mentioned can be found at ClinicalTrials.gov at the locations mentioned below or on our Optical Probe Development and Molecular Activity Measurement web pages.

IRDye fluorophores are only used for investigative purposes in clinical trials.

References

  1. Li, D., Zhang, J., Chi, C., Xiao, X., Wang, J., Lang, L., & Ali, I. (2018, April 3). First-In-Human Study of PET and Optical Dual-Modality Image-Guided Surgery in Glioblastoma Using 68Ga-IRDye800CW-BBN. Theranostics, 8(9), 2508-2520. doi:10.7150/thno.25599
  2. ClinicalTrials.gov [Internet]. Bethesda (MD): National Library of Medicine (US). Identifier NCT02901925, A Microdose Evaluation Study in Recurrent Glioma (ABY-029); 2016 December. Available from: https://clinicaltrials.gov/ct2/show/NCT02901925.
  3. ClinicalTrials.gov [Internet]. Bethesda (MD): National Library of Medicine (US). Identifier NCT02910804, IRDye800CW-BBN PET-NIRF Imaging Guiding Surgery in Patients With Glioblastoma; 2015 November. Available from: https://clinicaltrials.gov/ct2/show/NCT02910804.
  4. ClinicalTrials.gov [Internet]. Bethesda (MD): National Library of Medicine (US). Identifier NCT02855086, Cetuximab-IRDye 800CW in Detecting Tumors in Patients With Malignant Glioma Undergoing Surgery; 2016 October. Available from: https://clinicaltrials.gov/ct2/show/NCT02855086.
  5. ClinicalTrials.gov [Internet]. Bethesda (MD): National Library of Medicine (US). Identifier NCT03510208, Panitumumab-IRDye800 in Diagnosing Participants With Malignant Glioma Undergoing Surgery; 2018 May 14. Available from: https://clinicaltrials.gov/ct2/show/NCT03510208.
  6. ClinicalTrials.gov [Internet]. Bethesda (MD): National Library of Medicine (US). Identifier NCT02736578, Cetuximab-IRDye800CW and Intraoperative Imaging in Finding Pancreatic Cancer in Patients Undergoing Surgery; 2016 July. Available from: https://clinicaltrials.gov/ct2/show/NCT02736578.
  7. ClinicalTrials.gov [Internet]. Bethesda (MD): National Library of Medicine (US). Identifier NCT02743975, Near-Infrared Image Guided Surgery in Pancreatic Adenocarcinoma (PENGUIN); 2016 September. Available from: https://clinicaltrials.gov/ct2/show/NCT02743975.
  8. ClinicalTrials.gov [Internet]. Bethesda (MD): National Library of Medicine (US). Identifier NCT02583568, Fluorescence Guided Surgery in Breast Cancer (MARGIN); 2015 October. Available from: https:/clinicaltrials.gov/ct2/show/NCT02583568.
  9. ClinicalTrials.gov [Internet]. Bethesda (MD): National Library of Medicine (US). Identifier NCT01508572, VEGF-Targeted Fluorescent Tracer Imaging in Breast Cancer; 2011 October. Available from: https://clinicaltrials.gov/ct2/show/NCT01508572.
  10. ClinicalTrials.gov [Internet]. Bethesda (MD): National Library of Medicine (US). Identifier NCT02113202, Molecular Fluorescence Endoscopy in Patients With Familial Adenomatous Polyposis, Using Bevacizumab-IRDye800CW (FLUOFAP); 2014 March. Available from: https://clinicaltrials.gov/ct2/show/NCT02113202.
  11. ClinicalTrials.gov [Internet]. Bethesda (MD): National Library of Medicine (US). Identifier NCT01972373, Visualization of Rectal Cancer During Endoscopy, Using a Fluorescent Tracer (RAPIDO-TRACT);2013 October. Available from: https://clinicaltrials.gov/ct2/show/NCT01972373.
  12. ClinicalTrials.gov [Internet]. Bethesda (MD): National Library of Medicine (US). Identifier NCT03106038, Dose-Escalation Study of a Constrant Agent for Delineation of Urological Anatomy in Minimally Invasive Surgery; 2017 May 4. Available from: https://clinicaltrials.gov/ct2/show/NCT03106038.
  13. ClinicalTrials.gov [Internet]. Bethesda (MD): National Library of Medicine (US). Identifier NCT03387410, Ureter Identification with IRDye 800BK; 2018 April 6. Available from: https://clinicaltrials.gov/ct2/show/NCT03387410.
  14. ClinicalTrials.gov [Internet]. Bethesda (MD): National Library of Medicine (US). Identifier NCT02975219, Feasibility Study of Using Molecular Fluorescence Guided Surgery in Endometriosis (Endo-Light); 2017 May 1. Available from: https://clinicaltrials.gov/ct2/show/NCT02975219.
  15. Barnes, T. G., Volpi, D., Cunningham, C., Vonjovic, B., & Hompes, R. (2018, February 19). Improved Urethral Fluorescence During Low Rectal Surgery: A New Dye and a New Method. Techniques in Coloproctology, 22, 115-119. doi:10.1007/s1051-018-1757-6
  16. Al-Taher, M., van den Bos, J., Schols, R. M., Kubat, B., Bouvy, N. D., & Stassen, L. S. (2018, February 2). Evaluation of a Novel Dye for Near-Infrared Fluorescence Delineation of the Ureters During Laparoscopy. British Journal of Surgery BJS Open. doi:10.1002/bjs5.59

Use of IRDye Infrared Dye-Labeled Optical Probes for Intraoperative Tumor Visualization

A major challenge in cancer surgery is being certain that all the tumor has been removed, including the residual cancer cells not immediately identified with the naked eye after resection. Surgeons need intraoperative methods of imaging tumors to assist them in identifying healthy and diseased tissue. These methods need to be safe and effective. Near-infrared (NIR) fluorescent optical probes may provide a viable solution.

Near-infrared fluorescent optical probes have been used intraoperatively in clinical trials. These NIR dye-conjugated compounds offer several advantages for use in the operating room. NIR probes can be used safely, unlike other imaging modalities that require radiation (such as CT, PET, and SPECT).

IRDye® dye-conjugated optical probes have been shown to be sensitive and biomarker-specific and their fluorescent signal correlates with tumor location observed by other imaging methods and traditional pathology. Because fluorescence from NIR optical probes is invisible to the human eye, visualization of the surgical field of view with white light is unimpeded.

Fluorescence from tissue excised during surgery can be visualized while in the operating room and used to assess whether resection of the tumor is complete. Traditional pathologic examination can then be done for confirmation. Specialized NIR imaging equipment, such as the Pearl® Imaging System, has been used successfully to image tumor sections during an operation.
The following two studies involved the intraoperative use of near-infrared fluorescence optical probes.

IRDye 800CW Dye-Conjugated Probes Provide Verification of Tumor

In this study by van Driel, et al., investigators evaluated the Artemis imaging system, developed in collaboration with the Center for Translational Molecular Medicine. The goal of the study “was to evaluate the Artemis camera in two oncological procedures in which real-time NIR fluorescence could be of added value: (a) radical tumor resection; and (b) detection of sentinel lymph nodes. . .” [1]
For the evaluation of the Artemis imaging system, the investigators used ICG and two IRDye® 800CW infrared dye-conjugated nanobodies. “IRDye 800CW (LI-COR, Lincoln, NE, USA, λex=774 nm, λem=789 nm) was chosen because it is one of two novel fluorophores in the process of clinical translation.” [1] The study assessed the sensitivity and utility of the Artemis system for intraoperative detection of head-and-neck tumors and sentinel lymph nodes in xenograft mouse models. [1]

Fluorescent images were concurrently acquired with the Pearl® Impulse Small Animal Imager (LI-COR). [1] “The Pearl system is expected to be an order of magnitude more sensitive than the Artemis, and therefore, these images serve as a ground truth comparison.” [1]

IRDye 800CW Dye-Labeled Probes Target VEGF and HER2

Research performed by Terwisscha van Scheltinga, et al. used IRDye 800CW dye-labeled antibodies to investigate their use in targeting certain tumors for optical surgical navigation [2]. The group concluded that “NIR fluorescence-labeled antibodies targeting VEGF or HER2 can be used for highly specific and sensitive detection of tumor lesions in vivo. These preclinical findings encourage future clinical studies with NIR fluorescence–labeled tumor-specific antibodies for intraoperative-guided surgery in cancer patients.” [2]

In this preclinical mouse study, fluorescent optical imaging with IRDye 800CW NHS ester coupled to bevacizumab was compared to PET imaging with 89Zr (5 MBq)-labeled bevacizumab or trastuzimab along with a non-specific antibody control, 111In-IgG (1 MBq). [2]

The researchers of this study stated, “IRDye 800CW is a NIR fluorophore with optimal characteristics for clinical use, allowing binding to antibodies when used in its N-hydroxy-succinimide (NHS) ester form. A preclinical toxicity study with IRDye 800CW carboxylate showed no toxicity in doses of up to 20 mg/kg intravenously or intradermally.” [2] They concluded that “In a preclinical setting, NIR fluorescence–labeled antibodies targeting VEGF or HER2 allowed highly specific and sensitive detection of tumor lesions in vivo.” [2]

IRDye 800CW dye-conjugated optical probes are currently involved in over a dozen clinical trials for a wide range of different cancers. These studies demonstrate the use of IRDye probes for optical surgical navigation. Several studies have employed the use of dual-labeled probes showing the strength of combining near-infrared fluorescence with other imaging modalities.

Examples of optical probe applications are detailed on Optical Probe Development and Molecular Activity Measurement web pages.

Do you have questions about how IRDye infrared dye-labeled probes could be used in your research or need help conjugating your optical probe? If so, please contact LI-COR Custom Services.

References:

  1. van Driel, P.B.A.A., et al. Characterization and Evaluation of the Artemis Camera for Fluorescence-Guided Cancer Surgery Mol Imaging Biol (2015) 17:413Y423. doi: 10.1007/s11307-014-0799-z
  2. Terwisscha van Scheltinga, A.G.T., et al. Intraoperative Near-Infrared Fluorescence Tumor Imaging with Vascular Endothelial Growth Factor and Human Epidermal Growth Factor Receptor 2 Targeting Antibodies J Nucl Med 2011; 52:1778–1785. doi: 10.2967/jnumed.111.092833.

The Gold Standard for Western Blot Normalization: Total Protein Staining



In the instructions to authors for the Journal of Biological Chemistry, they state:

While you have choices for your Western blot normalization strategy – you can still use housekeeping proteins as long you have validated that their expression is not changing – total protein staining detection is becoming the “gold standard” for normalization of protein loading.

After transfer, but prior to immunodetection, the membrane is treated with a total protein stain to assess actual sample loading across the blot. Because this internal loading control uses the combined signal from many different sample proteins in each lane, error and variability are minimized. This antibody-independent method corrects for variation in both sample protein loading and transfer efficiency, and monitors protein transfer across the blot at all molecular weights. The figure at the left shows that REVERT Total Protein Stain provides highly efficient protein staining on nitrocellulose or Immobilon®-FL PVDF membranes in under 10 minutes. Complete figure legend.

REVERT™ Total Protein Stain is a near-infrared fluorescent membrane stain used for total protein detection and normalization. REVERT staining is imaged at 700 nm, and fluorescent signals are proportional to sample loading.

The REVERT Total Protein Stain Normalization protocol describes how to use REVERT Total Protein Stain for Western blot normalization and quantitative analysis. It includes step-by-step instructions on how to use REVERT stain. There is also detailed information on normalization calculations, analysis of replicates, and data interpretation.

Replication is an important part of quantitative Western blot analysis and is used to confirm the validity of observed changes in protein levels. Biological and technical replications should both be done, since they are both important but meet different needs.

LI-COR has several other protocols to help you meet publication guidelines and requirements. In all of them, key factors for success, data analysis and interpretation are covered as well as links to additional educational resources.

With these protocols and our scientific experts, we can help you collect accurate, reliable data that will meet even the toughest publication standards. Protocols are also available in an online format at protocols.io

Download your copy of REVERT Total Protein Stain Normalization protocol and use the gold standard to determine your protein loading concentrations. Let us help you be confident in the Western blotting data you submit for publication.

Need Visible Fluorescent Secondary Antibodies for Flow Cytometry or Microscopy?

If you are doing flow cytometry or microscopy and need dye-labeled secondary antibodies in the visible fluorescence range, we can help. LI-COR now offers IRDye® and VRDye™ dye-labeled secondary antibodies for 650nm, 549nm, and 490nm detection.

VRDye secondary antibodies are are highly cross-adsorbed – just like our IRDye secondary antibodies, making them suitable for multi-color detection.

Here is an example of immunofluorescence staining using VRDye 490 Goat anti-Rabbit Secondary Antibody.

Immunofluorescence Staining of Tubulin in HeLa Cells.Immunofluorescence staining of tubulin protein in HeLa cells. Cells were cultured on cover slips. After fixation and permeabilization, cells were incubated with rabbit anti-tubulin mAb (CST), followed by VRDye 490 Goat anti-Rabbit IgG (P/N 926-49020). Nuclei were stained with DAPI. Image acquired with Olympus IX81 microscope.

Are you ready to try IRDye Infrared Dyes and secondary conjugates or VRDye visible fluorescent secondaries on your epifluorescent microscope? Check out the recommended configurations for Olympus and Zeiss microscopes – and go image!

Need to Strip Both PVDF and Nitrocellulose Membranes? Try NewBlot™ IR Stripping Buffer!

NewBlot IR Stripping BufferDoes your lab have both researchers that use PVDF membranes and researchers that use nitrocellulose for infrared Western blots? Are you still spending your valuable time making homemade stripping buffer?

NewBlot™ IR Stripping Buffer
to the rescue! NewBlot IR is the latest member of the LI-COR NewBlot Stripping Buffer family.

All NewBlot buffers can be used for stripping and reprobing infrared fluorescent Western blots, and there is a formulation that works for whichever membrane type (or types) you use.

What makes NewBlot IR unique?

  • It strips both membrane types so you won’t need to buy separate stripping buffers for nitrocellulose and PVDF.
  • It is the most affordable, saving you money to spend on other items for your lab.

This robust reagent removes primary and secondary antibodies while maintaining target antigen integrity for efficient reprobing and does not require hazardous shipping, unlike many other stripping buffers.

Note: NewBlot IR Stripping Buffer is not recommended for loading amounts over 30 µg.

Below are data showing that you can indeed strip and reprobe three times and still detect your proteins of interest.
NewBlot IR Strip and Reprobe Image

Figure 1. Strip and reprobe nitrocellulose or PVDF membranes effectively with NewBlot IR Stripping Buffer. EGFR and phospho-ERK levels were compared in EGF-stimulated (+) and non-stimulated (-) A431 lysate (1 µg total protein). The membrane was probed with mouse anti-EGFR, mouse anti-pERK1/2, and β-tubulin rabbit polyclonal (LI-COR P/N 926-42211), then detected with IRDye 800CW Goat anti-Mouse (LI-COR P/N 926-32210) and IRDye 680RD Goat anti-Rabbit (LI-COR P/N 926-68071). The blot was scanned with an Odyssey® CLx Imaging System (Original blot). The blot was then stripped with NewBlot IR Stripping Buffer (LI-COR P/N 928-40028), and scanned again (Strip #1). The blot was detected with the same primary and secondary antibodies and scanned again (Reprobe #1). The process was repeated 2 more times (Strip and Reprobe #2-3). Image display settings for all stripped and reprobed images are identical to the original image.

To make sure you are successful when stripping and reprobing, here are some factors that can affect stripping efficiency:

  • Amount of time the blot is in the stripping buffer
  • Sample type and preparation
  • Blot handling conditions
  • Buffer concentration and temperature used for stripping

Save your valuable time and money! Order NewBlot IR Stripping Buffer today for your infrared fluorescent Western blot stripping and reprobing needs.

Need Pre-stained Protein Ladders for Visible and Near-Infrared Detection?

chameleon largerIf you are doing Western blots, then you are most likely using a protein ladder. And, if you need pre-stained protein molecular weight ladders that you can see AND detect with near-infrared fluorescence, then you need Chameleon™ Pre-stained Protein Ladders. These new ladders are multi-colored for easy molecular weight identification. So, you can easily identify gel migration and protein size and orient your gel and membrane quickly.

And, you have choices!

  1. Try the Chameleon Duo Pre-stained Protein Ladder if you are doing two-color infrared fluorescent detection. This Chameleon Ladder is a pre-mixed protein MW marker format– ready to use!
  2. Or, if you would like to mix your own to customize fluorescence intensities and are doing multiplex detection, try the Chameleon Kit Pre-stained Protein Ladder (includes 250 μL each of the Chameleon 700 and the Chameleon 800 Pre-stained Protein Ladders).
  3. Of course, if you are doing just one-channel analysis of your Western blot, you can try the
    1. Chameleon 700 Pre-stained Protein Ladder – for 700nm channel analysis.
    2. Or, try the

    3. Chameleon 800 Pre-stained Protein Ladder for analysis in the 800nm channel.

chameleon all
So, you choose! Then, experience the sharp, vibrant colors of LI-COR Chameleon Pre-stained Protein Ladders in your near-infrared fluorescent Western blot applications.

Avoid Milk Blocking Buffer – Use NEW! Odyssey® Blocking Buffer (TBS)

Odyssey Blocking Buffer (TBS)

In previous posts, we’ve talked about Western blot blocking buffers and how important it is to optimize your blocking conditions to get the best results. As many of Western blot users do, you may just routinely use homemade TBS-milk blocking buffer. It’s inexpensive, and it does the job. . . well, most of the time. . .

What you may not know is using milk blocking buffer can cause issues with certain targets. This may give you the wrong information about the presence or the amount of your target. One good way to determine which blocking buffer system to use is to check to see what the primary antibody vendor recommends. Most recommend TBS-based buffer systems. If the primary antibody requires a TBS-based buffer system, we recommend new Odyssey® Blocking Buffer (TBS).

When should you avoid milk blocking buffer?

  • When using anti-goat secondary antibodies.
    • Reason: Milk contains bovine IgG. Anti-goat secondary antibodies may recognize bovine IgG, resulting in high background.
  • When detecting phosphorylated proteins.
    • Reason: Milk contains phosphorylated proteins, which may result in low to no signal and high background.
  • When using streptavidin-biotin detection systems.
    • Reason: Milk contains endogenous levels of biotin. Streptavidin will detect this, resulting in high background.

OBB TBS and milkHere are the results of an experiment evaluating the use of milk and Odyssey Blocking Buffer (TBS). As you can see, milk masked the detection of this protein and is not a good blocking buffer choice.

Figure 1. Effect of various blocking agents on detection of pAkt and total Akt in Jurkat lysate after stimulation by calyculin A. Total and phosphorylated Akt were detected in calyculin A-stimulated (+) and non-stimulated (-) Jurkat lysate at 10 µg; 5 µg; and 2.5 µg/well. Blots were probed with pAkt Rabbit mAb (Santa Cruz P/N sc‑135650) and Akt mAb (CST P/N 2967) and detected with IRDye® 800CW Goat anti-Rabbit IgG (LI‑COR P/N 926-32211) and IRDye 680RD Goat anti-Mouse IgG (LI‑COR P/N 926‑68070); scanned on Odyssey® CLx (auto scan 700 & 800). pAkt (green) is only detected with Odyssey Blocking Buffer (TBS).

So be sure to optimize your Western blot blocking conditions! The time you spend finding the best blocker will be worth it – and save you from making the wrong conclusions about your experimental data in the future.

Annotate Visible Protein Ladders on Chemiluminescent Westerns with the WesternSure® Pen

Demonstrating the WesternSure PenIf you doing chemiluminescent Western blots, and are imaging either with film or with a digital imager, the WesternSure™ Pen can be a very useful addition to your experimental process. This newest member of the LI-COR WesternSure chemiluminescent reagent line can be used to annotate visible protein ladders prior to chemiluminescent Western blot detection.

The pen is optimized for detection using the C-DiGit® Blot Scanner or the Odyssey® Fc Imaging System, and is suitable for use with film or other imaging systems. The WesternSure Pen is a unique marker that delivers an ink which emits light when incubated with commonly-used chemiluminescent substrates, including WesternSure PREMIUM Chemiluminescent Substrate. The ink is faintly visible for easy identification of marked membranes.

Here are a few tips to get the best performance from your WesternSure Pen:

  • Lightly touching the pen to the membrane should be enough to transfer ink to the membrane.
  • Do not push down on the nib so hard that it creates an uneven surface on the membrane.
  • Membranes may be annotated when damp after transfer, or when dry.
  • Annotated membranes may be stored dry at ambient temperature or 4 ºC for up to 1 week before starting the Western blot detection process.
  • If ink is not flowing smoothly onto a damp membrane, trace over the band until it is annotated to the desired effect.

Data using the WesternSure PenFigure 1. Chemiluminescent detection of visible protein standards. The WesternSure Pen (LI‑COR P/N 926‑91000) was used to mark the blue protein standards (panel A) for chemiluminescent Western blot detection. The blot was exposed to WesternSure PREMIUM chemiluminescent substrate and imaged on Odyssey Fc Imaging System (panel B).

If you would like some tips on how to troubleshoot chemiluminescent Western blots, read Good Westerns Gone Bad – Maximizing Sensitivity on Chemiluminescent Western Blots.

Troubleshooting Chemiluminescent Western Blots: Possible Cause 4 for Weak Signals – Blot Processing

Sometimes life in the lab gets crazy, right? You are finishing a Western blot and you realize that you are supposed to be at an important lecture across campus in 10 min!! Or, your spouse calls to say that one of the kids needs to be picked up as soon as possible. Yikes! The challenge is that blots should be processed and detected on the same day. And, the secondary antibody should be incubated the day of imaging and fresh substrate added just before imaging. Is it that important to your results? Yes, it is and just to prove it, we did a few experiments.

In Table 1, we studied performance differences when the same blot is imaged immediately after processing vs. stored overnight dry and then imaged. In Table 2, we looked at performance differences when the same blot is imaged immediately after processing vs. stored overnight wet and then imaged. Blots in both tables were all imaged on the C-DiGit® Blot Scanner. (And, all images are normalized to the Lookup Tables (LUT) of the respective optimal blot.)

For both experiments, you can see that saving the blot to image the next day is not a very good choice. This is because the secondary antibody and/or the chemiluminescent Western blot substrate is not stable enough for acceptable photon emission when digitally images after the day it is applied.

Table 1 Optimal Blot Unsatisfactory Blot Unsatisfactory Blot
Images Optimal Chemiluminescent Western Blot Unsatisfactory Chemiluminescent Western Blot Unsatisfactory Chemiluminescent Western Blot
Conditions:
Substrate SuperSignal® West Dura1 SuperSignal West Dura1 SuperSignal West Dura1
Processing Time Same Day Next Day Next Day
Detection Process HRP secondary incubated, washed, and substrate added immediately before imaging. HRP secondary incubated, washed, and substrate added day before imaging. HRP secondary incubated, washed, and substrate added day before imaging, then re-incubated with HRP secondary and substrate added immediately before imaging.
Storage Conditions Blot stored overnight dry, at room temperature Blot stored overnight dry, at room temperature
Performance LOD – 640 ng LOD – None detected LOD – 1.25 μg
Table 2 Optimal Blot Unsatisfactory Blot Unsatisfactory Blot
Images Optimal Chemiluminescent Western Blot Unsatisfactory Optimal Chemiluminescent Western Blot Unsatisfactory Optimal Chemiluminescent Western Blot
Conditions:
Substrate SuperSignal® West Dura1 SuperSignal West Dura1 SuperSignal West Dura1
Process Time Same day Next day Next day
Detection Process HRP secondary incubated, washed, and substrate added immediately before imaging. HRP secondary incubated, washed, and substrate added day before imaging. HRP secondary incubated, washed, and substrate added day before imaging, then re-incubated with HRP secondary and substrate added immediately before imaging.
Storage Conditions Blot stored overnight wet in PBS, at room temperature Blot stored overnight wet in PBS, at room temperature
Performance LOD – 640 ng LOD – None detected LOD – 1.25 μg

1SuperSignal West Dura results are comparable to those obtained with WesternSure® PREMIUM Chemiluminescent Substrate.

For more hints and tips, stay tuned to future blog posts. And if you would like to try some FREE Western Blot Analysis Software, download Image Studio™ Lite today!

Related posts:

Use Near-Infrared Fluorescent Probes for Pharmacokinetics and Biodistribution Studies

In Vivo Imaging with NIR Fluorescent ProbesNon-invasive preclinical imaging methods are critical for development of imaging agents and targeted therapeutics. Pharmacokinetics is the study of what the body does to a drug with respect to biodistribution and clearance. Traditionally-used radiolabeled probes have limitations such as cost, access, and safety. Near-infrared (NIR) fluorescence imaging offers a powerful alternative to radiolabeled probes for pharmacokinetics and biodistribution studies. NIR fluorescent optical imaging agents can be used to image the whole animal over time. And, more than one agent can be tracked in the same animal if each agent is labeled with a spectrally-distinct fluorophore.

In this webinar, Dr Amy Geschwender examines several case studies from the literature, and discusses:

  • Why NIR fluorescent probes are widely used for in vivo imaging
  • How fluorescence imaging of excised tissues and tissue sections is used to examine biodistribution in more detail
  • How to measure serum half-life and % injected dose per gram with NIR fluorescent probes


This webinar features data from the Pearl® Small Animal Imaging System, which was recently honored by Frost & Sullivan, in addition to advancements in NIR technology. Click here to learn more about this award.

Visit our website to learn more about BrightSite™ Optical Imaging Agents and IRDye® infrared dyes that can be used for your pharmacokinetic and biodistribution studies.