pSIVA: Polarity Sensitive Indicator of Viability & Apoptosis

A new tool for flow cytometry and microscopy.
IMGENEX introduces pSIVA, the first reversible probe for detecting phosphatidylserine (PS) exposure on plasma membranes.

pSIVA is an Annexin XII-based, polarity sensitive probe for the spatiotemporal analysis of apoptosis and other forms of cell death. pSIVA binding is reversible enabling researchers, for the first time, to detect transient PS exposure which is associated with normal physiological processes as well as with reversible or rescuable apoptotic/cell death events.

pSIVA is conjugated to IANBD, a polarity sensitive dye that fluoresces only when pSIVA is bound to the cell membrane. pSIVA’s membrane-bound dependent fluorescence and reversible binding properties are a technological leap for detecting PS exposure and offer additional information on apoptotic process and cell survival compared to Annexin V conjugates.

CytoGLO™ pSIVA-IANBD Apoptosis/Viability Flow Kit
IMG-6700K-100 (100 Test Size): 248 €
IMG-6700K-25 (25 Test Size) 121 €

CytoGLO™ pSIVA-IANBD Apoptosis/Viability Microscopy Set
IMG-6701K (Sufficient for 10 ml Staining Solution): 248 €

Comparison of pSIVA-IANBD and Annexin V-FITC in Flow Cytometry. The staining patterns were similar for the two dyes: 1. Untreated: Primarily negative indicating healthy cells. The small positive population represents the basal level of cell death in the culture; 2. Staurosporine (1h): Large positive population indicating active apoptosis. Staining in the “negative” population gate has spread out, indicating movement towards cell death; 3. Staurosporine (3h): Nearly the entire population is positive indicating massive apoptosis.

pSIVA Product Citations

Engineering a polarity–sensitive biosensor for time-lapse imaging of apoptotic processes and degeneration. Kim YE, J Chen, JR Chan, R Langen. Nat Methods 7:67-73 (2010). Real-time live-cell imaging and time-lapse microscopy of apoptosis: Fig 2 (Cos-7 cells), Fig 3 (neuronal degeneration), Fig 4 (axonal degeneration), Fig 5 (rescue of neuronal degeneration as visualized by pSIVA)
Monitoring apoptosis and neuronal degeneration by real-time detection of phosphatidylserine externalization using a polarity-sensitive indicator of viability and apoptosis. Kim YE, J Chen, R Langen, JR Chan. Nature Protocols 5:1396-1405 (2010). Fig 2: Time-lapse microscopy of neurons in normal survival conditions and after NGF deprivation. pSIVA demonstrated transient exposure of PS associated with homeostasis.

	Annexin V-FITC	pSIVA-IANBD
Non-toxic	+	+
FACS	+	+
Detect early apoptosis	+	+
Live-cell imaging		+
in vivo imaging		+
High-throughput screen		+
No washing required		+
Viability assessment		+

pSIVA: Use in Microscopy

pSIVA is a novel phosphatidylserine (PS) exposure reporter for monitoring cell death, apoptosis and survival by live-cell imaging. Live-cell imaging is a vital application for studying dynamic biological processes such as apoptosis in real time. However, prior to the advent of pSIVA, there had been a lack of available reporters for studying cell death/survival processes.

Ephemeral or fleeting pSIVA-IANBD fluorescence signals accompany transient PS exposures associated with normal physiological or homeostatic events. When PS flips back to the inner membrane following transient PS exposure, pSIVA-IANBD will be released back into the medium and fluorescence lost. Potential areas of study are shown in the cartoon. Note: The phenomenon of transient pSIVA-IANBD fluorescence exposure has been observed in unperturbed cultures as rapid on/off fluorescence, and is thought to represent normal membrane event. However, this is a wide open area of study and details remain to be elucidated.

First developed by Dr. Ralf Langen and his colleagues at USC in 2010, pSIVA already has several impressive publications (1-3). pSIVA’s most notable live-imaging applications including monitoring the subcellular onset of PS externalization, tracking PS exposure throughout the death process (Movies 1 and 2), and demonstrating reversible PS exposure events associated with rescuable cell death (Movies 3). The demonstration of reversible PS exposure by pSIVA is considered to be among the most significant assay advances in the Cell Death and Apoptosis field today. In addition to live cell imaging, pSIVA can also be used for standard fluorescence microscopy, in vivo analysis of cell death and flow cytometry.


Time-lapse imaging of primary rat dorsal ganglion (DRG) sensory neurons induced to undergo apoptosis by NGF deprivation. Images were taken from 9 hr after NGF withdrawal, and the movies were compiled at 6 frames per second with 20 min intervals between image frames. Movies 1 and 2 are of different neurons. pSIVA-IANBD (detects PS exposure): green. PI (detects loss of membrane integrity): red. Note that pSIVA-IANBD labels the axon prior to the cell body, and that pSIVA-IANBD fluorescence appears prior to PI staining.

		Time-lapse imaging of rat DRG recovery from the brink of death showing reversibility of apoptosis for the first time. Neurons were deprived of NGF for 10 h to induce apoptosis. After 10 h, NGF was added back to the culture to induce rescue. Images were taken from 7.5 h after NGF withdrawal and the movie was compiled at 4 frames per second with a 30 min interval between image frames. pSIVA-IANBD: green. PI: red. Boxes highlight specific areas where the intensity of pSIVA-IANBD fluorescence reverses.

CytoGLO™ pSIVA-IANBD Apoptosis/Viability Flow Kit
IMG-6700K-100 (100 Test Size): 248 €
IMG-6700K-25 (25 Test Size) 121 €

CytoGLO™ pSIVA-IANBD Apoptosis/Viability Microscopy Set
IMG-6701K (Sufficient for 10 ml Staining Solution): 248 €

pSIVA (Apoptosis Pathway Kinetics) Product Citations

Engineering a polarity–sensitive biosensor for time-lapse imaging of apoptotic processes and degeneration. Kim YE, J Chen, JR Chan, R Langen. Nat Methods 7:67-73 (2010).
Monitoring apoptosis and neuronal degeneration by real-time detection of phosphatidylserine externalization using a polarity-sensitive indicator of viability of apoptosis. Kim YE, J Chen, R Langen, JR Chan. Nature Protocols 5:1396-1405 (2010).
Zhang CQ, Yeh T-l, A Leyva, LG Frank, J Miller, YE Kim, R Langen, S Finkbeiner, ML Amzel, CA Ross, MA Poirier. A compact B model of huntingtin toxicity. JBC 286:8188-8196 (2011).