Targeted delivery approaches for cancer therapeutics have shown a steep rise over the past few de... more Targeted delivery approaches for cancer therapeutics have shown a steep rise over the past few decades. However, compared to the plethora of successful pre-clinical studies, only 15 passively targeted nanocarriers (NCs) have been approved for clinical use and none of the actively targeted NCs have advanced past clinical trials. Herein, we review the principles behind targeted delivery approaches to determine potential reasons for their limited clinical translation and success. We propose criteria and considerations that must be taken into account for the development of novel actively targeted NCs. We also highlight the possible directions for the development of successful tumor targeting strategies.
Prostate cancer is the second leading cause of cancer-related deaths in American men. Despite con... more Prostate cancer is the second leading cause of cancer-related deaths in American men. Despite considerable advances in prostate cancer research, there is a major need for a systemic delivery platform that efficiently targets anti-cancer drugs to sites of disseminated prostate cancer while minimizing host toxicity. Human mesenchymal stem cells (MSCs) are excellent candidates for cell-based drug delivery since they display tropism towards cancer sites and clinical studies have demonstrated that hundreds of millions of allogeneic human MSCs can be safely administered intravenously without adverse effects in a variety of pathological settings. Furthermore, we have previously documented that MSCs can be detected in radical prostatectomy tissue from men with prostate cancer. In this proof-of-concept study, human MSCs were loaded with poly(lactic-co-glycolic acid) (PLGA) microparticles (MPs) encapsulating the macromolecule G114, a thapsigargin-based prostate specific antigen (PSA)-activate...
There is a clinical need for new, more effective treatments for chronic and debilitating inflamma... more There is a clinical need for new, more effective treatments for chronic and debilitating inflammatory bowel disease (IBD), including Crohn's disease and ulcerative colitis. Targeting drugs selectively to the inflamed intestine may improve therapeutic outcomes and minimize systemic toxicity. We report the development of an inflammation-targeting hydrogel (IT-hydrogel) that acts as a drug delivery system to the inflamed colon. Hydrogel microfibers were generated from ascorbyl palmitate, an amphiphile that is generally recognized as safe (GRAS) by the U.S. Food and Drug Administration. IT-hydrogel microfibers loaded with the anti-inflammatory corticosteroid dexamethasone (Dex) were stable, released drug only upon enzymatic digestion, and demonstrated preferential adhesion to inflamed epithelial surfaces in vitro and in two mouse colitis models in vivo. Dex-loaded IT-hydrogel enemas, but not free Dex enemas, administered every other day to mice with colitis resulted in a significant...
Due to their size and tailorable physicochemical properties, nanomaterials are an emerging class ... more Due to their size and tailorable physicochemical properties, nanomaterials are an emerging class of structures utilized in biomedical applications. There are now many prominent examples of nanomaterials being used to improve human health, in areas ranging from imaging and diagnostics to therapeutics and regenerative medicine. An overview of these examples reveals several common areas of synergy and future challenges. This Nano Focus discusses the current status and future potential of promising nanomaterials and their translation from the laboratory to the clinic, by highlighting a handful of successful examples.
Cell surfaces are fertile ground for chemists and material scientists to manipulate or augment ce... more Cell surfaces are fertile ground for chemists and material scientists to manipulate or augment cell functions and phenotypes. This not only helps to answer basic biology questions but also has diagnostic and therapeutic applications. In this review, we summarize the most recent advances in the engineering of the cell surface. In particular, we focus on the potential applications of surface engineered cells for 1) targeting cells to desirable sites in cell therapy, 2) programming assembly of cells for tissue engineering, 3) bioimaging and sensing, and ultimately 4) manipulating cell biology. 1. targeting cells to desirable sites in cell therapy, 2. programming assembly of cells with substrates or cells in tissue engineering,
ASME 2008 6th International Conference on Nanochannels, Microchannels, and Minichannels, 2008
Cell separation based on markers present on the cell surface has extensive biological application... more Cell separation based on markers present on the cell surface has extensive biological applications. However, current separation methods involve labeling and label removal steps which are often slow and intrusive. We envisioned that the ability to control the direction of transport of cells based on specific receptors on the cell surface without labeling and label removal steps would enable simple continuous-flow microfluidic cell separation systems with minimal processing steps and active components. We therefore explored whether receptor patterning could be used to direct the transport of cells in a label-free manner through the formation of transient receptor-ligand bonds that result in cell rolling.
Wiley interdisciplinary reviews. Nanomedicine and nanobiotechnology
Cell-surface sensors are powerful tools to elucidate cell functions including cell signaling, met... more Cell-surface sensors are powerful tools to elucidate cell functions including cell signaling, metabolism, and cell-to-cell communication. These sensors not only facilitate our understanding in basic biology but also advance the development of effective therapeutics and diagnostics. While genetically encoded fluorescent protein/peptide sensors have been most popular, emerging cell surface sensor systems including polymer-, nanoparticle-, and nucleic acid aptamer-based sensors have largely expanded our toolkits to interrogate complex cellular signaling and micro- or nano-environments. In particular, cell-surface sensors that interrogate in vivo cellular microenvironments represent an emerging trend in the development of next generation tools which biologists may routinely apply to elucidate cell biology in vivo and to develop new therapeutics and diagnostics. This review focuses on the most recent development in areas of cell-surface sensors. We will first discuss some recently report...
Proceedings of the National Academy of Sciences, 2012
Capture and isolation of flowing cells and particulates from body fluids has enormous implication... more Capture and isolation of flowing cells and particulates from body fluids has enormous implications in diagnosis, monitoring, and drug testing, yet monovalent adhesion molecules used for this purpose result in inefficient cell capture and difficulty in retrieving the captured cells. Inspired by marine creatures that present long tentacles containing multiple adhesive domains to effectively capture flowing food particulates, we developed a platform approach to capture and isolate cells using a 3D DNA network comprising repeating adhesive aptamer domains that extend over tens of micrometers into the solution. The DNA network was synthesized from a microfluidic surface by rolling circle amplification where critical parameters, including DNA graft density, length, and sequence, could readily be tailored. Using an aptamer that binds to protein tyrosine kinase-7 (PTK7) that is overexpressed on many human cancer cells, we demonstrate that the 3D DNA network significantly enhances the captur...
Cell therapies enable unprecedented treatment options to replace tissues, destroy tumors and faci... more Cell therapies enable unprecedented treatment options to replace tissues, destroy tumors and facilitate regeneration. The greatest challenge facing cell therapy is the inability to control the fate and function of cells after transplantation. We have developed an approach to control cell phenotype in vitro and after transplantation by engineering cells with intracellular depots that continuously release phenotype-altering agents for days to weeks. The platform enables control of cells' secretome, viability, proliferation and differentiation, and the platform can be used to deliver drugs or other factors (e.g., dexamethasone, rhodamine and iron oxide) to the cell's microenvironment. The preparation, efficient internalization and intracellular stabilization of ~1μm drug-loaded microparticles are critical for establishing sustained control of cell phenotype. Herein we provide a protocol to generate and characterize micrometer-sized agent-doped poly(lactic-co-glycolic) acid (PLGA) particles by using a single-emulsion evaporation technique (7 h), to uniformly engineer cultured cells (15 h), to confirm particle internalization and to troubleshoot commonly experienced obstacles.
The ability to explore cell signalling and cell-to-cell communication is essential for understand... more 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
Nanotechnology has the potential to revolutionize cancer diagnosis and therapy. Advances in prote... more Nanotechnology has the potential to revolutionize cancer diagnosis and therapy. Advances in protein engineering and materials science have contributed to novel nanoscale targeting approaches that may bring new hope to cancer patients. Several therapeutic nanocarriers have been approved for clinical use. However, to date, there are only a few clinically approved nanocarriers that incorporate molecules to selectively bind and target cancer cells. This review examines some of the approved formulations and discusses the challenges in translating basic research to the clinic. We detail the arsenal of nanocarriers and molecules available for selective tumour targeting, and emphasize the challenges in cancer treatment.
Exogenous cell therapy aims to replace/repair diseased or dysfunctional cells and promises to rev... more Exogenous cell therapy aims to replace/repair diseased or dysfunctional cells and promises to revolutionize medicine by restoring tissue and organ function. To develop effective cell therapy, the location, distribution and long-term persistence of transplanted cells must be evaluated. Nanoparticle (NP) based imaging technologies have the potential to track transplanted cells non-invasively. Here we summarize the most recent advances in NP-based cell tracking with emphasis on (1) the design criteria for cell tracking NPs, (2) protocols for cell labeling, (3) a comparison of available imaging modalities and their corresponding contrast agents, (4) a summary of preclinical studies on NP-based cell tracking and finally (5) perspectives and future directions. (Some figures in this article are in colour only in the electronic version) Nanobiotechnology, the intersection of nanotechnology and biology, permits the development of new research tools and effective therapies [1]. A great example of nanobiotechnology is the development of drug delivery nanoparticles (NPs) [2-4]. Many biopharmaceuticals including protein, siRNA and DNA suffer from short half-life and poor bioavailability in vivo limiting their therapeutic effect [5]. Consequently, nanosized carriers (e.g. drug nanocrystals, liposomes, polymeric NPs) have emerged as an effective means to control the delivery of multiple classes of drugs and biomolecules [6, 7]. This paper focuses on the use of nanobiotechnology for tracking the fate and function of cells post-transplantation. Exogenous cell therapy utilizes transplanted cells, in particular stem and progenitor cells, to replace or regenerate damaged or diseased tissue [8]. Transplanted cells may home to diseased tissue, regenerate tissues through (trans) differentiation and/or provide regenerative cues that facilitate regeneration through trophic factors and cell-cell interactions [9, 10]. Over the past 50 years, several effective cell therapies have been
We envisioned that label-free control of the transport of cells in two dimensions through recepto... more We envisioned that label-free control of the transport of cells in two dimensions through receptorligand interactions would enable simple separation systems that are easy to implement, yet retain the specificity of receptor-ligand interactions. Here we demonstrate nanomechanical control of cell transport in two dimensions via transient receptor-ligand adhesive bonds by patterning of receptors that direct cell rolling through an edge effect. HL-60 cells rolling on P-selectin receptor patterns were deflected at angles of 5-10° with respect to their direction of travel. Absence of this effect in the case of rigid microsphere models of cell rolling suggests that this twodimensional motion depends on nanomechanical properties of the rolling cell. This work suggests the feasibility of simple continuous-flow microfluidic cell separation systems that minimize processing steps and yet retain the specificity of receptor-ligand interactions.
Targeted delivery approaches for cancer therapeutics have shown a steep rise over the past few de... more Targeted delivery approaches for cancer therapeutics have shown a steep rise over the past few decades. However, compared to the plethora of successful pre-clinical studies, only 15 passively targeted nanocarriers (NCs) have been approved for clinical use and none of the actively targeted NCs have advanced past clinical trials. Herein, we review the principles behind targeted delivery approaches to determine potential reasons for their limited clinical translation and success. We propose criteria and considerations that must be taken into account for the development of novel actively targeted NCs. We also highlight the possible directions for the development of successful tumor targeting strategies.
Prostate cancer is the second leading cause of cancer-related deaths in American men. Despite con... more Prostate cancer is the second leading cause of cancer-related deaths in American men. Despite considerable advances in prostate cancer research, there is a major need for a systemic delivery platform that efficiently targets anti-cancer drugs to sites of disseminated prostate cancer while minimizing host toxicity. Human mesenchymal stem cells (MSCs) are excellent candidates for cell-based drug delivery since they display tropism towards cancer sites and clinical studies have demonstrated that hundreds of millions of allogeneic human MSCs can be safely administered intravenously without adverse effects in a variety of pathological settings. Furthermore, we have previously documented that MSCs can be detected in radical prostatectomy tissue from men with prostate cancer. In this proof-of-concept study, human MSCs were loaded with poly(lactic-co-glycolic acid) (PLGA) microparticles (MPs) encapsulating the macromolecule G114, a thapsigargin-based prostate specific antigen (PSA)-activate...
There is a clinical need for new, more effective treatments for chronic and debilitating inflamma... more There is a clinical need for new, more effective treatments for chronic and debilitating inflammatory bowel disease (IBD), including Crohn's disease and ulcerative colitis. Targeting drugs selectively to the inflamed intestine may improve therapeutic outcomes and minimize systemic toxicity. We report the development of an inflammation-targeting hydrogel (IT-hydrogel) that acts as a drug delivery system to the inflamed colon. Hydrogel microfibers were generated from ascorbyl palmitate, an amphiphile that is generally recognized as safe (GRAS) by the U.S. Food and Drug Administration. IT-hydrogel microfibers loaded with the anti-inflammatory corticosteroid dexamethasone (Dex) were stable, released drug only upon enzymatic digestion, and demonstrated preferential adhesion to inflamed epithelial surfaces in vitro and in two mouse colitis models in vivo. Dex-loaded IT-hydrogel enemas, but not free Dex enemas, administered every other day to mice with colitis resulted in a significant...
Due to their size and tailorable physicochemical properties, nanomaterials are an emerging class ... more Due to their size and tailorable physicochemical properties, nanomaterials are an emerging class of structures utilized in biomedical applications. There are now many prominent examples of nanomaterials being used to improve human health, in areas ranging from imaging and diagnostics to therapeutics and regenerative medicine. An overview of these examples reveals several common areas of synergy and future challenges. This Nano Focus discusses the current status and future potential of promising nanomaterials and their translation from the laboratory to the clinic, by highlighting a handful of successful examples.
Cell surfaces are fertile ground for chemists and material scientists to manipulate or augment ce... more Cell surfaces are fertile ground for chemists and material scientists to manipulate or augment cell functions and phenotypes. This not only helps to answer basic biology questions but also has diagnostic and therapeutic applications. In this review, we summarize the most recent advances in the engineering of the cell surface. In particular, we focus on the potential applications of surface engineered cells for 1) targeting cells to desirable sites in cell therapy, 2) programming assembly of cells for tissue engineering, 3) bioimaging and sensing, and ultimately 4) manipulating cell biology. 1. targeting cells to desirable sites in cell therapy, 2. programming assembly of cells with substrates or cells in tissue engineering,
ASME 2008 6th International Conference on Nanochannels, Microchannels, and Minichannels, 2008
Cell separation based on markers present on the cell surface has extensive biological application... more Cell separation based on markers present on the cell surface has extensive biological applications. However, current separation methods involve labeling and label removal steps which are often slow and intrusive. We envisioned that the ability to control the direction of transport of cells based on specific receptors on the cell surface without labeling and label removal steps would enable simple continuous-flow microfluidic cell separation systems with minimal processing steps and active components. We therefore explored whether receptor patterning could be used to direct the transport of cells in a label-free manner through the formation of transient receptor-ligand bonds that result in cell rolling.
Wiley interdisciplinary reviews. Nanomedicine and nanobiotechnology
Cell-surface sensors are powerful tools to elucidate cell functions including cell signaling, met... more Cell-surface sensors are powerful tools to elucidate cell functions including cell signaling, metabolism, and cell-to-cell communication. These sensors not only facilitate our understanding in basic biology but also advance the development of effective therapeutics and diagnostics. While genetically encoded fluorescent protein/peptide sensors have been most popular, emerging cell surface sensor systems including polymer-, nanoparticle-, and nucleic acid aptamer-based sensors have largely expanded our toolkits to interrogate complex cellular signaling and micro- or nano-environments. In particular, cell-surface sensors that interrogate in vivo cellular microenvironments represent an emerging trend in the development of next generation tools which biologists may routinely apply to elucidate cell biology in vivo and to develop new therapeutics and diagnostics. This review focuses on the most recent development in areas of cell-surface sensors. We will first discuss some recently report...
Proceedings of the National Academy of Sciences, 2012
Capture and isolation of flowing cells and particulates from body fluids has enormous implication... more Capture and isolation of flowing cells and particulates from body fluids has enormous implications in diagnosis, monitoring, and drug testing, yet monovalent adhesion molecules used for this purpose result in inefficient cell capture and difficulty in retrieving the captured cells. Inspired by marine creatures that present long tentacles containing multiple adhesive domains to effectively capture flowing food particulates, we developed a platform approach to capture and isolate cells using a 3D DNA network comprising repeating adhesive aptamer domains that extend over tens of micrometers into the solution. The DNA network was synthesized from a microfluidic surface by rolling circle amplification where critical parameters, including DNA graft density, length, and sequence, could readily be tailored. Using an aptamer that binds to protein tyrosine kinase-7 (PTK7) that is overexpressed on many human cancer cells, we demonstrate that the 3D DNA network significantly enhances the captur...
Cell therapies enable unprecedented treatment options to replace tissues, destroy tumors and faci... more Cell therapies enable unprecedented treatment options to replace tissues, destroy tumors and facilitate regeneration. The greatest challenge facing cell therapy is the inability to control the fate and function of cells after transplantation. We have developed an approach to control cell phenotype in vitro and after transplantation by engineering cells with intracellular depots that continuously release phenotype-altering agents for days to weeks. The platform enables control of cells' secretome, viability, proliferation and differentiation, and the platform can be used to deliver drugs or other factors (e.g., dexamethasone, rhodamine and iron oxide) to the cell's microenvironment. The preparation, efficient internalization and intracellular stabilization of ~1μm drug-loaded microparticles are critical for establishing sustained control of cell phenotype. Herein we provide a protocol to generate and characterize micrometer-sized agent-doped poly(lactic-co-glycolic) acid (PLGA) particles by using a single-emulsion evaporation technique (7 h), to uniformly engineer cultured cells (15 h), to confirm particle internalization and to troubleshoot commonly experienced obstacles.
The ability to explore cell signalling and cell-to-cell communication is essential for understand... more 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
Nanotechnology has the potential to revolutionize cancer diagnosis and therapy. Advances in prote... more Nanotechnology has the potential to revolutionize cancer diagnosis and therapy. Advances in protein engineering and materials science have contributed to novel nanoscale targeting approaches that may bring new hope to cancer patients. Several therapeutic nanocarriers have been approved for clinical use. However, to date, there are only a few clinically approved nanocarriers that incorporate molecules to selectively bind and target cancer cells. This review examines some of the approved formulations and discusses the challenges in translating basic research to the clinic. We detail the arsenal of nanocarriers and molecules available for selective tumour targeting, and emphasize the challenges in cancer treatment.
Exogenous cell therapy aims to replace/repair diseased or dysfunctional cells and promises to rev... more Exogenous cell therapy aims to replace/repair diseased or dysfunctional cells and promises to revolutionize medicine by restoring tissue and organ function. To develop effective cell therapy, the location, distribution and long-term persistence of transplanted cells must be evaluated. Nanoparticle (NP) based imaging technologies have the potential to track transplanted cells non-invasively. Here we summarize the most recent advances in NP-based cell tracking with emphasis on (1) the design criteria for cell tracking NPs, (2) protocols for cell labeling, (3) a comparison of available imaging modalities and their corresponding contrast agents, (4) a summary of preclinical studies on NP-based cell tracking and finally (5) perspectives and future directions. (Some figures in this article are in colour only in the electronic version) Nanobiotechnology, the intersection of nanotechnology and biology, permits the development of new research tools and effective therapies [1]. A great example of nanobiotechnology is the development of drug delivery nanoparticles (NPs) [2-4]. Many biopharmaceuticals including protein, siRNA and DNA suffer from short half-life and poor bioavailability in vivo limiting their therapeutic effect [5]. Consequently, nanosized carriers (e.g. drug nanocrystals, liposomes, polymeric NPs) have emerged as an effective means to control the delivery of multiple classes of drugs and biomolecules [6, 7]. This paper focuses on the use of nanobiotechnology for tracking the fate and function of cells post-transplantation. Exogenous cell therapy utilizes transplanted cells, in particular stem and progenitor cells, to replace or regenerate damaged or diseased tissue [8]. Transplanted cells may home to diseased tissue, regenerate tissues through (trans) differentiation and/or provide regenerative cues that facilitate regeneration through trophic factors and cell-cell interactions [9, 10]. Over the past 50 years, several effective cell therapies have been
We envisioned that label-free control of the transport of cells in two dimensions through recepto... more We envisioned that label-free control of the transport of cells in two dimensions through receptorligand interactions would enable simple separation systems that are easy to implement, yet retain the specificity of receptor-ligand interactions. Here we demonstrate nanomechanical control of cell transport in two dimensions via transient receptor-ligand adhesive bonds by patterning of receptors that direct cell rolling through an edge effect. HL-60 cells rolling on P-selectin receptor patterns were deflected at angles of 5-10° with respect to their direction of travel. Absence of this effect in the case of rigid microsphere models of cell rolling suggests that this twodimensional motion depends on nanomechanical properties of the rolling cell. This work suggests the feasibility of simple continuous-flow microfluidic cell separation systems that minimize processing steps and yet retain the specificity of receptor-ligand interactions.
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Papers by Jeffrey Karp