Product DescriptionLipid droplets (LDs) are composed of neutral lipids such as triacylglycerol & cholesteryl ester that are surrounded by phospholipid monolayers and are seen ubiquitously, not only in adipocytes¹⁾. LDs were originally thought to serve as a lipid storage unit, until a recent study showing that LDs play an important role in regulating lipid metabolism, autophagy²⁾ and cellular senescence³⁾. Therefore, LDs have gained great attention as an important tool to elucidate the mechanisms of their formation, growth, fusion, and retraction.

1) T. Fujimoto et al., “Lipid droplets: a classic organelle with new outfits.” Histochem Cell Biol., 2008, 130(2), 263.2) R. Singh et al., “Autophagy regulates lipid metabolism.” Nature, 2009, 458(7242), 1131.3) M. Yokoyama et al., “Inhibition of endothelial p53 improves metabolic abnormalities related to dietary obesity.” Cell Reports, 2014, 7(5), 1691.

For more information on Lipi-series and examples, please refer to the publication below:

4) Tatenaka, Y. et al., “Monitoring Lipid Droplet Dynamics in Living Cells by Using Fluorescent Probes” Biochemistry.“, 2019, 58(6), 499-503.Notes: Lipi-Series is Patent Pending.

Oleic acid treated HeLa cells with Lipi Product Series

<Staining Condition>A medium that contained oleic acid (200 μmol/l) was added and incubated overnight. Then, the supernatant was removed and the cells were washed with PBS. Each Lipi product series (1 μmol/l) was added and the cells were incubated for 15 minutes.

<Detection Condition>Lipi-Blue: Ex. 405 nm / Em. 450 – 500 nmLipi-Green: Ex. 488 nm / Em. 500 – 550 nmLipi-Red: Ex. 561 nm / Em. 565 – 650 nmLipi-Deep Red: Ex.640 nm / Em.650-700 nm

Reagent Comparison

*Leaks in GFP filter

High Intracellular RetentivityLive HepG2 cells were stained with each of the Lipi products, Nile Red, and Reagent B.

Lipi-Blue and Lipi-Green had higher retention in cells after 24 hours post staining than Lipi-Red, Nile Red, and Reagent B.

High Correlation with Antibody Detection Method: Lipi-Blue (LD01)After fixing HepG2 with 4% PFA, cells are stained with 100 nmol/l Lipi-Blue. Then, Adipophilin (ADFP) expressed on lipid-droplet membrane was labeled with anti-ADFP antibody

Scale Bar: 20 μm<Detection Condition>Lipi-Blue: Ex. 405 nm / Em. 450 – 500 nmAnti-ADFP antibody (Alexa Fluor® 647): Ex. 640 nm / Em. 650 – 700 nm

High Selectivity toward Lipid DropletLive HeLa cells were treated with Oleic acid and were stained with 100 nmol/l Lipi-Blue and 100 nmol/l Nile Red. Nile red had high background due to the limit in selectivity toward lipid droplets.<Detection Condition>Lipi-Blue: Ex. 405 nm / Em. 450 -500 nmLipi-Green: Ex. 488 nm / Em. 500 – 550 nmLipi-Red: Ex. 561 nm / Em. 565 – 650 nmLipi-Deep Red: Ex. 640 / Em. 650 – 700 nmNile Red: Ex. 561 nm / Em. 565 – 650 nm

Filter Leakage Rate (Lipi-Red vs Nile Red)

HepG2 cells were stained with Lipi-Red and Nile Red. Lipi-Red was imaged with Green excitation (G), but not Blue excitation (B). However, Nile Red was imaged in both filter. Lipi-Red is preferable for multi-staining.

Multiple Staining: Lipi-Deep Red (Purple) co-staining with GFP fluorescence (green) in HeLa cells

After adding Lipi-Deep Red (0.1 μmol/l) to the Arf4-GFP expressed Hela cells and the cells were incubated for 30 minutes, the cells were treated with 4% PFA (PBS) to fix, and washed with PBS three times. Fluorescent imaging was conducted by confocal microscopy.

<Detection Condition>GFP: Ex/Em=488/400-552 nmLDs:  Ex/Em=640/630-700 nm

Multiple Staining:  Lipi-Deep Red (RED) co-staining with GFP fluorescence (green) in HeLa cells

*Data was kindly provided by Dr. G. Belov, at University of Maryland, College Park

Lipi-Blue co-staining with GFP and RFP fluorescence in hMGEC (Multiple Staining)

In the following article, hMGEC treated with rosiglitazone (Rosi) was co-stained with tandem RFP-GFP-tagged LC3B and Lipi-Blue to observe autophagosome /autophagolysosome and lipid droplets. It was observed lipid droplets in hMGEC treated with Rosi for 4 days and 14 days was accumulated. For details about the experiment, please visit the reference below.

Kim, S. et al., “Eicosapentaenoic acid (EPA) activates PPARγ signaling leading to cell cycle exit, lipid accumulation, and autophagy in human meibomian gland epithelial cells (hMGEC)“, The Ocular Surface, 2020, 18(3), 427-437.

Adipocyte with Lipi Series

Lipid droplets in adipocyte were clearly detected by staining adipocytes, derived from 3T3-L1 preadipocytes, with Lipi-Series.

<Protocol>1. HeLa cells were seeded on a μ-slide 8-well plate and cultured at 37 ℃ overnight in a 5% CO₂ incubator.2. A conventional method was used to induce adipocyte differentiation.3. The supernatant was removed and the cells were washed twice with DMEM (25 mmol/l glucose, 10% FBS, phenol red free).5. The Lipi-series working solution (in DMEM (25 mmol/l glucose, 10% FBS, phenol red free)) was added and the cells were incubated at 37 ℃ for 24 hours in a 5% CO₂ incubator.6. The cells were observed using a fluorescence microscope.

*Dye Concentration: 2.5 µmol/L each.

Mouse liver adipose tissue (Frozen section) with Lipi Series

After adding Lipi series to the 4% PFA (PBS) fixed mouse liver adipose tissue and the tissue were incubated for overnight, and washed with PBS. Fluorescent imaging was observed by fluorescence microscopy.

Quantitative analysisChanges in lipid droplets were examined after the addition of oleic acid or Triacsin C (acyl-CoA synthetase inhibitor) to the HepG2 cell culture medium. For analysis, the number and total area of lipid droplets per cell were computed from the images acquired with CQ1, a confocal quantitative image cytometer (Yokogawa Electric Corporation).

<Imaging of lipid droplets and cell nuclei>

CQ1 captured images of lipid droplets with a 447/60 nm bandpass filter and cell nuclei with a 525/50 nm bandpass filter. Lipid droplets and cell nuclei were individually identified and computed the number and total area by using the CellPathfinder analysis software.Imaging conditions:Plate: 96 well plate, objective lens: x 20excitation: 405 nm (Lipi-Blue), blue/488 nm (SYBR Green), Green

<Analysis by the number and total area of lipid droplets>

Based on the detected data of cell nuclei and lipid droplets, the number and total area of lipid droplets per cell computed were shown in the graphs below. Compared to the control value, the number and total area of lipid droplets per cell were increased 7-10 times by the addition of oleic acid, but the addition of Triacsin C inhibited lipid droplet formation and showed a 50-60% decrease.Experimental conditionsHepG2 cells (1 x 10³ cells) were disseminated on a 96-well plate and incubated overnight. After the culture supernatant was removed, the cells treated with DMEM plus FBS only (control), DMEM plus FBS and 200 μmol/L oleic acid (Oleic acid), and DMEM plus FBS and 5 μmol/L Triacsin C (Triacsin C) were incubated overnight. Cells were then washed twice with PBS buffer, fixed with 4% PFA for 5 minutes at room temperature, and washed twice with PBS buffer again. Finally, cells were stained in the dark for 2 hours at room temperature with 0.5 μmol/L Lipi-Blue working solution, and quantitative analysis was performed through CQ1.

Related Product Information

Recommended Filter: Wavelength for Excitation and Emission

Inducing lipid droplets(1) Incubate cells for 24 hours at 37˚C in a 5% CO₂ atmosphere.(2) Add 200 µmol/L working solution (prepared from oleic acid stock solution) to culture medium and incubate for further 24 hours.