Unique insights into the intestinal absorption, transit, and subsequent biodistribution of polymer-derived microspheres.

Polymeric microspheres (MSs) have received attention for their potential to improve the delivery of drugs with poor oral bioavailability. Although MSs can be absorbed into the absorptive epithelium of the small intestine, little is known about the physiologic mechanisms that are responsible for their cellular trafficking. In these experiments, nonbiodegradable polystyrene MSs (diameter range: 500 nm to 5 µm) were delivered locally to the jejunum or ileum or by oral administration to young male rats. Following administration, MSs were taken up rapidly (≤ 5 min) by the small intestine and were detected by transmission electron microscopy and confocal laser scanning microscopy. Gel permeation chromatography confirmed that polymer was present in all tissue samples, including the brain. These results confirm that MSs (diameter range: 500 nm to 5 µm) were absorbed by the small intestine and distributed throughout the rat. After delivering MSs to the jejunum or ileum, high concentrations of polystyrene were detected in the liver, kidneys, and lungs. The pharmacologic inhibitors chlorpromazine, phorbol 12-myristate 13-acetate, and cytochalasin D caused a reduction in the total number of MSs absorbed in the jejunum and ileum, demonstrating that nonphagocytic processes (including endocytosis) direct the uptake of MSs in the small intestine. These results challenge the convention that phagocytic cells such as the microfold cells solely facilitate MS absorption in the small intestine.

Microencapsulated choroid plexus epithelial cell transplants for repair of the brain.

The choroid plexuses (CPs) play pivotal roles in basic aspects of neural function including maintaining the extracellular milieu of the brain by actively modulating chemical exchange between the CSF and brain parenchyma, surveying the chemical and immunological status of the brain, detoxifying the brain, secreting a nutritive "cocktail" of polypeptides and participating in repair processes following trauma. Even modest changes in the CP can have far reaching effects and changes in the anatomy and physiology of the CP have been linked to several CNS diseases. It is also possible that replacing diseased or transplanting healthy CP might be useful for treating acute and chronic brain diseases. Here we describe the wide-ranging functions of the CP, alterations of these functions in aging and neurodegeneration and recent demonstrations of the therapeutic potential of transplanted microencapsulated CP for neural trauma.

On the use of hydrogels in cell encapsulation and tissue engineering system.

Regenerative medicine requires the coordinated rebuilding of tissue and preservation of normal physiologic function. Cellular therapy incorporating tissue engineering principals has been among the most effective therapies, due to specific interactions between materials, cells, factors, and ligands that have been delineated over the last 5 decades. The current generation of these modalities incorporates the ability to control integration in vivo in a time- and space-dependent fashion. Hydrogels have been used as biofunctional vehicles for the introduction of these cell-based systems, and new techniques allow for the control of cell adhesion, proliferation, differentiation, and other biologic functions in vivo. With these more robust methods in place, and the ability to scale up and manufacture clinical materials, additional innovations have evolved that allow for ectopic or orthotopic administration of cellular therapies to treat disorders that have previously seen limited therapeutic promise due to inability to provide time-matched therapy. As such, critical discoveries have gained a unique niche portfolio of novel patents, accounting for a large portion of those newly filed in the field of biotechnology. These include the novel hydrogel compositions engineered by David Mooney and his colleagues, various tissue bulking and reconstructive applications invented by Hubbell and others, and other important patents in this field. The inventions described here provide insight into important aspects of this overall movement, and demonstrate significant immediate clinical utility in a variety of indications.

NT-501: an ophthalmic implant of polymer-encapsulated ciliary neurotrophic factor-producing cells.

Neurotech Pharmaceuticals Inc is developing NT-501, an implantable polymeric device containing a genetically modified cell line that secretes ciliary neurotrophic factor, for the potential treatment of retinitis pigmentosa (RP) and age-related macular degeneration (AMD). Phase III clinical trials for RP and a phase II clinical trial for dry AMD are ongoing. A phase I clinical trial showed that NT-501 treatment was well tolerated with variable, but positive improvements in visual acuity.

Multifunctional peptide-based nanosystems for improving delivery and molecular imaging.

Nanotechnology is a multidisciplinary scientific field impacting on various facets of preclinical and clinical research. One of the areas most affected is the development of medical treatments, that is, nanomedicine. In particular, drug delivery is expected to benefit from the unique ability of nanoparticles to selectively target different tissues and cellular compartments. In this review, advances using nanoparticles to improve the delivery of peptides by rendering them more stable, less susceptible to degradation, and able to cross physical barriers that typically restrict circulatory system access are discussed. In addition, the use of peptide-nanoparticle conjugates to target normal and diseased tissues to deliver therapeutic agents or to image them for diagnostic and screening purposes, or both, are highlighted. In the next few years these technologies are expected to allow control of drug delivery, targeting, and imaging that is currently unattainable.

Transplants of encapsulated rat choroid plexus cells exert neuroprotection in a rodent model of Huntington's disease.

Choroid plexus (CP) epithelial cells secrete several neurotrophic factors and have been used in transplantation studies designed to impart neuroprotection against central nervous system (CNS) trauma. In the present study, CP was isolated from adult rats, encapsulated within alginate microcapsules, and transplanted unilaterally into the rat striatum. Three days later, unilateral injections of quinolinic acid (QA; 225 nmol) were made into the ipsilateral striatum to mimic the pathology observed in Huntington's disease (HD). After surgery, animals were tested for motor function using the placement test. Rats receiving CP transplants were significantly less impaired on this test. Nissl-stained sections demonstrated that CP transplants significantly reduced the volume of the striatal lesion produced by QA. Quantitative analysis of striatal neurons further demonstrated that choline acetyltransferase-immunoreactive, but not diaphorase-positive, neurons were protected by CP transplants. These data demonstrate that transplanted CP cells can be used to protect striatal neurons from excitotoxic damage and that the pattern of neuroprotection varies across specific neuronal populations.

Intraventricular implant of encapsulated CNTF-secreting fibroblasts ameliorates motor deficits in aged rats.

The impact of intraventricular ciliary neurotrophic factor (CNTF) on motor function in aged rats was evaluated. Spontaneous locomotion and motor coordination were quantified in young (5-6 months) and aged (24-25 months) rats. Relative to young animals, aged rats were significantly less active, fell more rapidly from a rotating rod, and were unable to maintain their balance on a wooden beam. Aged animals received bilateral intraventricular implants of polymer-encapsulated fibroblasts that were genetically modified to secrete CNTF. Controls received either no implant or capsules loaded with mock transfected cells. One month after implantation the aged animals that received CNTF implants were significantly more active and were improved on the rotorod and beam balance tests. The improvement in performance on the rotorod and beam balance tests was dependant on the task difficulty and dissipated at higher rotations (rotorod) and smaller beam widths (beam balance). No recovery was seen in aged animals receiving control implants. Postmortem removal of the encapsulated cells confirmed that they continued to secrete CNTF. These data are the first to suggest that intracerebral delivery of CNTF might be useful for slowing or reversing age-related changes in motor function.

Aging reduces the neuroprotective capacity, VEGF secretion, and metabolic activity of rat choroid plexus epithelial cells.

Delivery of neurotrophic molecules to the brain has potential for preventing neuronal loss in neurodegenerative disorders. Choroid plexus (CP) epithelial cells secrete numerous neurotrophic factors, and encapsulated CP transplants are neuroprotective in models of stroke and Huntington's disease (HD). To date, all studies examining the neuroprotective potential of CP transplants have used cells isolated from young donor animals. Because the aging process significantly impacts the cytoarchitecture and function of the CP the following studies determined whether age-related impairments occur in its neuroprotective capacity. CP was isolated from either young (3-4 months) or aged (24 months) rats. In vitro, young CP epithelial cells secreted more VEGF and were metabolically more active than aged CP epithelial cells. Additionally, conditioned medium from cultured aged CP was less potent than young CP at enhancing the survival of serum-deprived neurons. Finally, encapsulated CP was tested in an animal model of HD. Cell-loaded or empty alginate capsules (control group) were transplanted unilaterally into the rat striatum. Seven days later, the animals received an injection of quinolinic acid (QA; 225 nmol) adjacent to the implant site. Animals were tested for motor function 28 days later. In the control group, QA lesions severely impaired function of the contralateral forelimb. Implants of young CP were potently neuroprotective as rats receiving CP transplants were not significantly impaired when tested for motor function. In contrast, implants of CP from aged rats were only modestly effective and were much less potent than young CP transplants. These data are the first to directly link aging with diminished neuroprotective capacity of CP epithelial cells.

In vitro exposure of cultured porcine choroid plexus epithelial cells to immunosuppressant, anti-inflammatory, and psychoactive drugs.

Delivery of neurotrophic molecules to the CNS is a potential treatment for preventing the neuronal loss in neurological disorders such as Huntington's disease (HD). Choroid plexus (CP) epithelial cell transplants secrete several neurotrophic factors and are neuroprotective in rat and monkey animal models of HD. HD patients receiving CP transplants would likely receive a course of immunosuppressant/anti-inflammatory treatment postsurgery and would remain on psychoactive medications to treat their motor, psychiatric, and emotional symptoms. Therefore, we examined whether CP epithelial cells are impacted by incubation with cyclosporine A (CsA), dexmethasone, haloperidol, fluoxetine, and carbamezapine. In each case, DNA was quantified to determine cell number, a formazen dye-based assay was used to quantify cell metabolism, and vascular endothelial growth factor (VEGF) levels were measured as a marker of protein secretion. Except for the highest dose of fluoxetine, none of the drugs tested exerted any detrimental effect on cell number. Incubation with CsA or dexamethasone did not have any consistent significant effect on VEGF secretion or cell metabolism. Carbamazepine was without effect while only the highest dose of haloperidol tested modestly lowered cell metabolism. VEGF secretion and cell metabolism was not measurable from CP cells exposed to 100 microM fluoxetine. These data continue to support the potential use of CP transplants in HD.

Targeted nanoparticle-based drug delivery and diagnosis.

Nanotechnology, or systems/device manufacture at sizes generally ranging between 1 and 100 nm, is a multidisciplinary scientific field undergoing explosive development. The genesis of nanotechnology can be traced to advances in medicine, communications, genomics and robotics. One of the greatest values of nanotechnology will be in the development of new and effective medical treatments (i.e. nanomedicine). This review focuses on the potential of nanomedicine as it relates to the development of nanoparticles for enabling and improving the targeted delivery of therapeutic and diagnostic agents. We highlight the use of nanoparticles for specific intra-compartmental analysis using the examples of delivery to malignant cancers, to the central nervous system, and across the gastrointestinal barriers.

Transplants of Encapsulated Rat Choroid Plexus Cells Exert Neuroprotection in a Rodent Model of Huntington's Disease.

Choroid plexus (CP) epithelial cells secrete several neurotrophic factors and have been used in transplantation studies designed to impart neuroprotection against central nervous system (CNS) trauma. In the present study, CP was isolated from adult rats, encapsulated within alginate microcapsules, and transplanted unilaterally into the rat striatum. Three days later, unilateral injections of quinolinic acid (QA; 225 nmol) were made into the ipsilateral striatum to mimic the pathology observed in Huntington's disease (HD). After surgery, animals were tested for motor function using the placement test. Rats receiving CP transplants were significantly less impaired on this test. Nissl-stained sections demonstrated that CP transplants significantly reduced the volume of the striatal lesion produced by QA. Quantitative analysis of striatal neurons further demonstrated that choline acetyltransferase-immunoreactive, but not diaphorase-positive, neurons were protected by CP transplants. These data demonstrate that transplanted CP cells can be used to protect striatal neurons from excitotoxic damage and that the pattern of neuroprotection varies across specific neuronal populations.

In vitro culture duration does not impact the ability of encapsulated choroid plexus transplants to prevent neurological deficits in an excitotoxin-lesioned rat model of Huntington's disease.

Delivery of neurotrophic molecules to the CNS is a potential treatment strategy for preventing the neuronal loss accompanying many neurological disorders. Choroid plexus (CP) epithelial cells secrete a cocktail of neurotrophic factors, and encapsulated CP transplants are neuroprotective in animal models of stroke and Huntington's disease (HD). Prior to clinical use, it is essential to identify and optimize parameters such as the length of time that transplant products such as encapsulated CP can be maintained. In the present study, neonatal porcine CP was encapsulated within alginate microcapsules and maintained in vitro for 1, 2, or 7 months. The encapsulated cells remained viable (>80%) at all time points and were transplanted unilaterally into the rat striatum. Seven days later, the same animals received unilateral injections of quinolinic acid (QA; 225 nmol) adjacent to the implant site. Separate groups of animals served as controls and received QA alone. After surgery, animals were periodically evaluated for weight loss and were tested for motor function 14 days post-QA. In controls, QA lesions produced a significant loss of body weight and impaired function of the contralateral forelimb. In contrast, implants of CP were potently neuroprotective as rats receiving CP transplants did not lose body weight and were not significantly impaired when tested for motor function. These benefits were independent of the length of time that the cells were held in vitro and demonstrate that the potential potency of alginate encapsulated CP cells can be retained for extremely long periods of time in vitro.

The pinpoint promise of nanoparticle-based drug delivery and molecular diagnosis.

Nanotechnology, or systems/device manufacture at the molecular level, is a multidisciplinary scientific field undergoing explosive development. The genesis of nanotechnology can be traced to the promise of revolutionary advances across medicine, communications, genomics and robotics. Without doubt one of the greatest values of nanotechnology will be in the development of new and effective medical treatments (i.e., nanomedicine). This review focuses on the potential of nanomedicine as it specifically relates to (1) the development of nanoparticles for enabling and improving the targeted delivery of therapeutic agents; (2) developing novel and more effective diagnostic and screening techniques to extend the limits of molecular diagnostics providing point-of-care diagnosis and more personalized medicine.

Extensive neuroprotection by choroid plexus transplants in excitotoxin lesioned monkeys.

Huntington's disease (HD) results from degeneration of striatal neurons. Choroid plexus (CP) cells secrete neurotrophic factors, and CP transplants are neuroprotective in rat models of HD. To determine if similar neuroprotective effects could be obtained in primates, porcine CP was encapsulated in alginate capsules. PCR confirmed that the CP cells expressed transthyretin and immunocytochemistry demonstrated typical ZO-1 and tubulin staining. In vitro, CP conditioned media enhanced the survival and preserved neurite number and length on serum deprived neurons. Cynomolgus primates were transplanted with CP-loaded capsules into the caudate and putamen followed by quinolinic acid (QA) lesions 1 week later. Control monkeys received empty capsules plus QA. Choroid plexus transplants significantly protected striatal neurons as revealed by stereological counts of NeuN-positive neurons (8% loss vs. 43% in controls) and striatum volume (10% decrease vs. 40% in controls). These data indicate that CP transplants might be useful for preventing the degeneration of neurons in HD.

Choroid plexus transplants in the treatment of brain diseases.

The choroid plexus (CP) produces and secretes numerous biologically active neurotrophic factors into the cerebrospinal fluid (CSF). These circulate throughout the brain and spinal cord, maintaining neuronal networks and associated cells. In neurodegenerative disease and in acute brain injury there is local up-regulation of neurotrophin production close to the site of the lesion. Treatment by direct injection of neurotrophins and growth factors close to these lesion sites has repeatedly been demonstrated to improve recovery. It has therefore been proposed that transplanting viable choroid plexus cells close to the lesion might provide a novel means for continuous delivery of these molecules directly to the site of injury. Recent publications describe how transplanted CP, either free or in an immunoprotected encapsulated form, deliver therapeutic molecules to the desired site. This review briefly describes the accumulated evidence that CP cells support neuronal cells in vitro and have therapeutic properties when transplanted to treat acute and chronic brain disease and injury in animal models.

Intraperitoneal stability of alginate-polyornithine microcapsules in rats: an FTIR and SEM analysis.

Alginate-polycation microcapsule systems have been used over decades as delivery vehicles for cell and protein therapy. These systems have been unpredictable across a range of indications with questions resulting around the inherent stability of the alginate polysaccharide and failure mode of the delivery system. The current study focuses on such a system using 5 different alginates, 2 of which are commercially purified, which are crosslinked by polyornithine. Capsules formed by frequency-generated droplet formation were studied in the peritoneal cavity of Long-Evans rats over the course of 3 months by morphometry, Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy of the surface. Individual capsule components were also investigated on FTIR and a relative stability index was generated by titration for comparison to explanted samples over time. Using these techniques, a distinct degradation pattern was noted and is compared between the 5 alginate sources.

Intracompartmental delivery of CNTF as therapy for Huntington's disease and retinitis pigmentosa.

Ciliary neurotrophic factor (CNTF) is a cytokine with neurotrophic activity across a broad spectrum of peripheral and central nervous system (CNS) cells. While its therapeutic potential for CNS diseases has been clear for sometime, the blood brain barrier (BBB) hinders the systemic delivery of CNTF and direct bolus injections are not suitable due to the short half-life of CNTF. One means of overcoming the BBB while providing continuous delivery of CNTF is with immunoisolated cellular implants that produce and deliver CNTF directly to the region of interest. Cells can be protected from host rejection by encapsulating, or surrounding, them within an immunoisolatory, semipermeable membrane that admits oxygen and required nutrients and releases bioactive cell secretions, but restricts passage of larger cytotoxic agents from the host immune defense system. The selective membrane eliminates the need for chronic immunosuppression of the host and allows the implanted cells to be obtained from nonhuman sources. In this review we discuss cell immunoisolation for Huntington's disease and retinitis pigmentosa. These two indications are highlighted because of extensive pre-clinical data supporting the general concept and recent clinical data that both strengthens the theoretical role of CNTF for treating neurodegeneration and justifies additional clinical evaluation in these and other diseases.

A role of the choroid plexus in transplantation therapy.

The choroid plexuses (CPs) play pivotal roles in the most basic aspects of neural function. Some of the roles of the CP include maintaining the extracellular milieu of the brain by actively modulating chemical exchange between the CSF and brain parenchyma, surveying the chemical and immunological status of the brain, detoxifying the brain, secreting a nutritive "cocktail" of polypeptides, and participating in repair processes following trauma. This diversity of functions suggests that even modest changes in the CP can have far reaching effects. Indeed, changes in the anatomy and physiology of the CP have been linked to several CNS diseases. It is also possible that replacing diseased CP or transplanting healthy CP might be useful for treating acute and chronic brain diseases. Here we describe the wide-ranging functions of the CP, alterations of these functions in aging and neurodegeneration, and recent demonstrations of the therapeutic potential of transplanted CP for neural trauma.

Sustained secretion of ciliary neurotrophic factor to the vitreous, using the encapsulated cell therapy-based NT-501 intraocular device.

The objective of this study was to evaluate the in vivo secretion profile of ciliary neurotrophic factor (CNTF) from either of two genetically engineered cell lines contained in the encapsulated cell therapy (ECT)-based NT-501 device. ECT devices were loaded with either a low or high CNTF-secreting cell line and implanted into rabbit eyes for 1, 3, 7, 14, 30, 60, 90, 135, 180, or 365 days. After explantation, the vitreous was sampled and devices were allowed to incubate in endothelial serum-free medium for 24 h at 37 degrees C. Both the vitreous and the conditioned medium were assayed for CNTF using an ELISA. Device and vitreous CNTF, were plotted against time, and regression analysis was used to calculate half-life. Devices loaded with either cell line showed stable in vivo output for the duration of the study, with populations of healthy cells remaining in the device at study termination. For the low-dose CNTF-secreting cell line, with the final time point at 6 months, the halflife was estimated as 71 days, whereas the high-dose devices, with a final time point of 1 year, had an associated half-life of approximately 198 days. The NT-501 device is capable of delivering CNTF to the vitreous for at least 1 year. This ECT-based device, which has been shown to be safe and effective by our group, is a well-engineered ECT-based controlled delivery system capable of protein output on the order of years.

Nanotechnology and medicine.

Nanotechnology, or systems/device manufacture at the molecular level, is a multidisciplinary scientific field undergoing explosive development. The genesis of nanotechnology can be traced to the promise of revolutionary advances across medicine, communications, genomics and robotics. On the surface, miniaturisation provides cost effective and more rapidly functioning mechanical, chemical and biological components. Less obvious though is the fact that nanometre sized objects also possess remarkable self-ordering and assembly behaviours under the control of forces quite different from macro objects. These unique behaviours are what make nanotechnology possible, and by increasing our understanding of these processes, new approaches to enhancing the quality of human life will surely be developed. A complete list of the potential applications of nanotechnology is too vast and diverse to discuss in detail, but without doubt one of the greatest values of nanotechnology will be in the development of new and effective medical treatments (i.e., nanomedicine). This review focuses on the potential of nanotechnology in medicine, including the development of nanoparticles for diagnostic and screening purposes, artificial receptors, DNA sequencing using nanopores, manufacture of unique drug delivery systems, gene therapy applications and the enablement of tissue engineering.