Search tips
Search criteria

Results 1-9 (9)

Clipboard (0)

Select a Filter Below

Year of Publication
Document Types
1.  Intravenous Hemostatic Nanoparticles Increase Survival Following Blunt Trauma Injury 
Biomacromolecules  2012;13(11):3850-3857.
Trauma is the leading cause of death for people ages 1-44, with blood loss comprising 60-70% of mortality in the absence of lethal CNS or cardiac injury. Immediate intervention is critical to improving chances of survival. While there are several products to control bleeding for external and compressible wounds including pressure dressings, tourniquets or topical materials (e.g. QuikClot, HemCon), there are no products that can be administered in the field for internal bleeding. There is a tremendous unmet need for a hemostatic agent to address internal bleeding in the field.
We have developed hemostatic nanoparticles (GRGDS-NPs) that reduce bleeding times by ~50% in a rat femoral artery injury model. Here, we investigated their impact on survival following administration in a lethal liver resection injury in rats. Administration of these hemostatic nanoparticles reduced blood loss following the liver injury and dramatically and significantly increased 1-hour survival from 40 and 47% in controls (inactive nanoparticles and saline, respectively) to 80%. Furthermore, we saw no complications following administration of these nanoparticles. We further characterized the nanoparticles’ effect on clotting time (CT) and maximum clot firmness (MCF) using rotational thromboelastometry (ROTEM), a clinical measurement of whole-blood coagulation. Clotting time is significantly reduced, with no change in MCF. Administration of these hemostatic nanoparticles after massive trauma may help staunch bleeding and improve survival in the critical window following injury, and this could fundamentally change trauma care.
PMCID: PMC3496064  PMID: 22998772
hemostasis; survival; clotting; platelets; bleeding
2.  Tissue Engineering the Retinal Ganglion Cell Nerve Fiber Layer 
Biomaterials  2013;34(17):4242-4250.
Retinal degenerative diseases, such as glaucoma and macular degeneration, affect millions of people worldwide and ultimately lead to retinal cell death and blindness. Cell transplantation therapies for photoreceptors demonstrate integration and restoration of function, but transplantation into the ganglion cell layer is more complex, requiring guidance of axons from transplanted cells to the optic nerve head in order to reach targets in the brain. Here we create a biodegradable electrospun (ES) scaffold designed to direct the growth of retinal ganglion cell (RGC) axons radially, mimicking axon orientation in the retina. Using this scaffold we observed an increase in RGC survival and no significant change in their electrophysiological properties. When analyzed for alignment, 81% of RGCs were observed to project axons radially along the scaffold fibers, with no difference in alignment compared to the nerve fiber layer of retinal explants. When transplanted onto retinal explants, RGCs on ES scaffolds followed the radial pattern of the host retinal nerve fibers, whereas RGCs transplanted directly grew axons in a random pattern. Thus, the use of this scaffold as a cell delivery device represents a significant step towards the use of cell transplant therapies for the treatment of glaucoma and other retinal degenerative diseases.
PMCID: PMC3608715  PMID: 23489919
3.  Engineering Therapies in the CNS: What works and what can be translated 
Neuroscience Letters  2012;519(2):147-154.
Engineering is the art of taking what we know and using it to solve problems. As engineers, we build tool chests of approaches; we attempt to learn as much as possible about the problem at hand, and then we design, build, and test our approaches to see how they impact the system. The challenge of applying this approach to the central nervous system (CNS) is that we often do not know the details of what is needed from the biological side. New therapeutic options for treating the CNS range from new biomaterials to make scaffolds, to novel drug-delivery techniques, to functional electrical stimulation. However, the reality is that translating these new therapies and making them widely available to patients requires collaborations between scientists, engineers, clinicians, and patients to have the greatest chance of success. Here we discuss a variety of new treatment strategies and explore the pragmatic challenges involved with engineering therapies in the CNS.
PMCID: PMC3377833  PMID: 22330751
CNS; translation; biomaterials; drug-delivery; scaffold; engineering
4.  Exogenous modulation of intrinsic optic nerve neuroprotective activity 
To characterize the molecular and functional status of the rat retina and optic nerve after acute elevation of intraocular pressure (IOP).
Retinal ischemia was induced in rats by increasing the IOP (110 mmHg/60 minutes). Microarray analysis, quantitative RT-PCR (qRT-PCR) and immunohistochemistry were used to characterize retinal tissue. PLGA microspheres containing neurotrophic factors (BDNF, GDNF, or CNTF) or empty microspheres were injected into the vitreous of operated animals 1 day after elevation of IOP. Pupil light reflex (PLR) parameters and electroretinograms (ERG) were monitored at multiple time points during the 60-day postoperative recovery period.
Molecular analysis showed a significant intrinsic up-regulation of CNTF at 10 and 25 days after induction of the acute ocular hypertension (p=0.0067). Molecular tissue analysis of GDNF and its receptors (GDNFR1, GDNFR2), and BDNF and its receptor (trkB) showed no change in expression. Animals that received CNTF microspheres had no significant functional recovery compared to animals which received blank microspheres (p>0.05). Animals that received GDNF or BDNF microspheres showed significant PLR recovery (p<0.05 and p<0.001 respectively) compared to non-treated animals.
Continuous release of neurotrophic growth factors (NGFs) significantly protects optic nerve function in the experimental model of retinal ischemia observed by PLR analysis.
PMCID: PMC3678383  PMID: 20229104
Neuroprotection; Retina; BDNF; GDNF; CNTF
5.  Nanospheres Delivering the EGFR TKI AG1478 Promote Optic Nerve Regeneration: The Role of Size For Intraocular Drug Delivery 
ACS nano  2011;5(6):4392-4400.
Promoting nerve regeneration involves not only modulating the post-injury microenvironment but also ensuring survival of injured neurons. Sustained delivery of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) has been shown to promote the survival and regeneration of neurons, but systemic administration is associated with significant side effects. We fabricated poly(lactic-co-glycolic acid) (PLGA) microspheres and nanospheres containing the EGFR TKI 4-(3-chloroanilino)-6,7-dimethoxyquinazoline (AG1478) for intravitreal administration in a rat optic nerve crush injury model. Upon administration, less backflow from the injection site was observed when injecting nanospheres compared to microspheres. Two weeks after intravitreal delivery, we were able to detect microspheres and nanospheres in the vitreous using coumarin-6 fluorescence, but fewer microspheres were observed compared to the nanospheres. At four weeks only nanospheres could be detected. AG1478 microspheres and nanospheres promoted optic nerve regeneration at two weeks, and at four weeks evidence of regeneration was found only in the nanosphere-injected animals. This observation could be attributed to the ease of administration of the nanospheres versus the microspheres, which in turn led to an increased amount of spheres delivered to the vitreous in the nanosphere group compared to the microsphere group. These data provide evidence for use of PLGA nanospheres to deliver AG1478 intravitreally in a single administration to promote nerve regeneration.
PMCID: PMC3136352  PMID: 21619059
optic nerve regeneration; nanospheres; microspheres; PLGA; epidermal growth factor receptor; AG1478
6.  Synthetic Platelets: Nanotechnology to Halt Bleeding 
Science translational medicine  2009;1(11):11ra22.
Blood loss is the major cause of death in both civilian and battlefield traumas. Methods to staunch bleeding include pressure dressings and absorbent materials. For example, Quik-clot effectively halts bleeding by absorbing large quantities of fluid and concentrating platelets to augment clotting, but these treatments are limited to compressible and exposed wounds. An ideal treatment would halt bleeding only at the injury site, be stable at room temperature, be administered easily, and work effectively for internal injuries. We have developed synthetic platelets, based on Arg-Gly-Asp functionalized nanoparticles, that halve bleeding time after intravenous administration in a rat model of major trauma. The effects of these synthetic platelets surpass other treatments including recombinant factor VIIa, which is used clinically for uncontrolled bleeding. Synthetic platelets were cleared within 24 hours at a dose of 20 mg/ml, and no complications were seen out to 7 days after infusion, the longest time point studied. These synthetic platelets may be useful for early intervention in trauma and demonstrate the role that nanotechnology can have in addressing unmet medical needs.
PMCID: PMC2992987  PMID: 20371456
PLGA; nanoparticles; PEG; hemostasis; coagulation cascade; trauma
7.  Functionalized Poly(lactic-co-glycolic acid) Enhances Drug Delivery and Provides Chemical Moieties for Surface Engineering while Preserving Biocompatibility 
Acta biomaterialia  2009;5(8):2860-2871.
Poly(lactic-co-glycolic acid) (PLGA) is one of the more widely used polymers for biomedical applications. Nonetheless, PLGA lacks chemical moieties that facilitate cellular interactions and surface chemistries. Furthermore, incorporation of hydrophilic molecules is often problematic. The integration of polymer functionalities would afford the opportunity to alter device characteristics, thereby enabling control over drug interactions, conjugations, and cellular phenomena. In an effort to introduce amine functionalities and improve polymer versatility, we synthesized two block copolymers (PLGA-PLL 502H and PLGA-PLL 503H) comprised of PLGA and Poly(ε-carbobenzoxy-L-lysine) utilizing dicyclohexyl carbodiimide (DCC) coupling. PLGA-PLL micropsheres encapsulated approximately six-fold (502H) and three-fold (503H) more vascular endothelial growth factor (VEGF), and 41% (503H) more ciliary neurotrophic factor (CNTF) than their PLGA counterparts. While the amine functionalities were amenable to the delivery of large molecules and surface conjugations, they did not comprise polymer biocompatibility. With the versatile combination of properties, biocompatibility, and ease of synthesis, these block copolymers have the potential for diverse utility in the fields of drug delivery and tissue engineering.
PMCID: PMC2749076  PMID: 19433141
Block Copolymers; PLGA; Poly(amino acid); CNTF; VEGF
8.  Engineering the CNS stem cell microenvironment 
Regenerative medicine  2009;4(6):865-877.
The loss of neural tissue underlies the symptomatology of several neurological insults of disparate etiology, including trauma, cerebrovascular insult and neurodegenerative disease. Restoration of damaged neural tissue through the use of exogenous or endogenous neural stem or progenitor cells is an enticing therapeutic option provided one can control their proliferation, migration and differentiation. Initial attempts at CNS tissue engineering relied on the intrinsic cellular properties of progenitor cells; however, it is now appreciated that the microenvironment surrounding the cells plays an indispensible role in regulating stem cell behavior. This article focuses on attempts to engineer the neural stem cell microenvironment by utilizing the major cellular components of the niche (endothelial cells, astrocytes and ependymal cells) and the extracellular matrix in which they are embedded.
PMCID: PMC2884372  PMID: 19903005
microenvironment; neural progenitor cell; neural stem cell; neural stem cell niche
9.  Engineering angiogenesis following spinal cord injury: A coculture of neural progenitor and endothelial cells in a degradable polymer implant leads to an increase in vessel density and formation of the blood-spinal cord barrier 
Angiogenesis precedes recovery following spinal cord injury (SCI), and its extent correlates with neural regeneration suggesting that angiogenesis may play a role in repair. An important precondition for studying the role of angiogenesis is the ability to induce it in a controlled manner. Previously, we showed that a coculture of endothelial cells (ECs) and neural progenitor cells (NPCs) promoted the formation of stable tubes in vitro and stable, functional vascular networks in vivo in a subcutaneous model. We sought to test whether a similar coculture would lead to formation of stable functional vessels in the spinal cord following injury. We created microvascular networks in a biodegradable two component implant system and tested the ability of the coculture or controls (lesion control, implant alone, implant plus ECs, or implant plus NPCs) to promote angiogenesis in a rat hemisection model of spinal cord injury. The coculture implant led to a four fold increase in functional vessels compared to the lesion control, implant alone, or implant plus NPCs groups and a 2 fold increase in functional vessels over the implant plus ECs group. Furthermore, half of the vessels in the coculture implant exhibited positive staining for the endothelial barrier antigen, a marker for formation of the blood spinal cord barrier (BSB). No other groups showed positive staining for the BSB in the injury epicenter. This work provides a novel method to induce angiogenesis following SCI and a foundation for studying its role in repair.
PMCID: PMC2764251  PMID: 19120441
rat; microvasculature; neural progenitor cells; endothelial cells; hydrogel; scaffold; PLGA; blood-spinal cord barrier

Results 1-9 (9)