Cell-surface sensors for real-time probing of cellular environments

Center for Regenerative Therapeutics & Department of Medicine, Brigham & Women's Hospital, 65 Landsdowne Street, Cambridge, Massachusetts 02139, USA.
Nature Nanotechnology (Impact Factor: 34.05). 07/2011; 6(8):524-31. DOI: 10.1038/nnano.2011.101
Source: PubMed


The ability to explore cell signalling and cell-to-cell communication is essential for understanding cell biology and developing effective therapeutics. However, it is not yet possible to monitor the interaction of cells with their environments in real time. Here, we show that a fluorescent sensor attached to a cell membrane can detect signalling molecules in the cellular environment. The sensor is an aptamer (a short length of single-stranded DNA) that binds to platelet-derived growth factor (PDGF) and contains a pair of fluorescent dyes. When bound to PDGF, the aptamer changes conformation and the dyes come closer to each other, producing a signal. The sensor, which is covalently attached to the membranes of mesenchymal stem cells, can quantitatively detect with high spatial and temporal resolution PDGF that is added in cell culture medium or secreted by neighbouring cells. The engineered stem cells retain their ability to find their way to the bone marrow and can be monitored in vivo at the single-cell level using intravital microscopy.

Download full-text


Available from: Jeffrey M Karp
  • Source
    • "It would be significant to report the viability, differentiation, and even cell functions.3, 113 One idea is to design a smart NP with sensors, which detects stimuli associated with cell viability and functions.114 The stimuli includes chemicals secreted during cell differentiation, physical contact with neighboring cells during stem cell engraftment, intercellular pH changes during cell death, and certain moleculesin the cell microenvironment that trigger stem cell differentiation.115 "
    [Show abstract] [Hide abstract]
    ABSTRACT: Stem cell therapy provides promising solutions for diseases and injuries that conventional medicines and therapies cannot effectively treat. To achieve its full therapeutic potentials, the homing process, survival, differentiation, and engraftment of stem cells post transplantation must be clearly understood. To address this need, non-invasive imaging technologies based on nanoparticles (NPs) have been developed to track transplanted stem cells. Here we summarize existing commercial NPs which can act as contrast agents of three commonly used imaging modalities, including fluorescence imaging, magnetic resonance imaging and photoacoustic imaging, for stem cell labeling and tracking. Specifically, we go through their technologies, industry distributors, applications and existing concerns in stem cell research. Finally, we provide an industry perspective on the potential challenges and future for the development of new NP products.
    Full-text · Article · Jul 2013 · Theranostics
  • Source
    • "Because aptamers are small and change conformation upon binding of their target, they can be engineered so that specific binding releases a quencher or generates a FRET pair, thus reducing non-specific staining [143]. So far, aptamers have been used to label mesenchymal stem and progenitor cells ex vivo and to visualize them in mouse bone marrow following transplantation [143]. The small size of Fab fragments and aptamers is also potentially their main limitation: owing to limited availability of lysine residues for chromophore binding, they are often less bright than traditional antibodies. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Intravital microscopy has become increasingly popular over the past few decades because it provides high-resolution and real-time information about complex biological processes. Technological advances that allow deeper penetration in live tissues, such as the development of confocal and two-photon microscopy, together with the generation of ever-new fluorophores that facilitate bright labelling of cells and tissue components have made imaging of vertebrate model organisms efficient and highly informative. Genetic manipulation leading to expression of fluorescent proteins is undoubtedly the labelling method of choice and has been used to visualize several cell types in vivo. This approach, however, can be technically challenging and time consuming. Over the years, several dyes have been developed to allow rapid, effective and bright ex vivo labelling of cells for subsequent transplantation and imaging. Here, we review and discuss the advantages and limitations of a number of strategies commonly used to label and track cells at high resolution in vivo in mouse and zebrafish, using fluorescence microscopy. While the quest for the perfect label is far from achieved, current reagents are valuable tools enabling the progress of biological discovery, so long as they are selected and used appropriately.
    Full-text · Article · Jun 2013 · Interface focus: a theme supplement of Journal of the Royal Society interface
  • Source
    • "In situ fluorescent bio-imaging is also of great significance for visualizing the expression and activity of particular molecules, cells, and biological processes that influence the behavior of tumors and/or their responsiveness to therapeutic drugs3. Therefore, a wide range of fluorescent components have been explored in the in vivo bio-imaging study, including the bio-marking of tumor tissues4, angiogenic vasculature5, and sentinel lymph nodes6. In this respect, several kinds of nanomaterials such as quantum dots2, noble metal nanoparticles7, upconverted nanoparticles8, and new hybrid nanocomposites of reduced graphene oxide and gold nanoparticles9 have demonstrated great potential for highly sensitive optical imaging of cancer on both cellular and animal levels. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Fluorescence imaging in vivo allows non-invasive tumor diagnostic thus permitting a direct monitoring of cancer therapies progresses. It is established herein that fluorescent gold nanoclusters are spontaneously biosynthesized by cancerous cell (i.e., HepG2, human hepatocarcinoma cell line; K562, leukemia cell line) incubated with micromolar chloroauric acid solutions, a biocompatible molecular Au(III) species. Gold nanoparticles form by Au(III) reduction inside cells cytoplasms and ultimately concentrate around their nucleoli, thus affording precise cell imaging. Importantly, this does not occur in non-cancerous cells, as evidenced with human embryo liver cells (L02) used as controls. This dichotomy is exploited for a new strategy for in vivo self-bio-imaging of tumors. Subcutaneous injections of millimolar chloroauric acid solution near xenograft tumors of the nude mouse model of hepatocellular carcinoma or chronic myeloid leukemia led to efficient biosynthesis of fluorescent gold nanoclusters without significant dissemination to the surrounding normal tissues, hence allowing specific fluorescent self-bio-marking of the tumors.
    Full-text · Article · Jan 2013 · Scientific Reports
Show more