X-Message-Number: 32564
Date: Sun, 18 Apr 2010 13:36:40 -0700 (PDT)
From: 
Subject: First Evidence That Chitosan Could Repair Spinal Damage


[Membrane damage is a component of vitrification solution toxicity. Could 
chitosan nanoparticles completely block this?]

First Evidence That Chitosan Could Repair Spinal Damage

ScienceDaily (Apr. 16, 2010) - Richard Borgens and his colleagues from the 
Center for Paralysis Research at the Purdue School of Veterinary Medicine have a
strong record of inventing therapies for treating nerve damage. From Ampyra, 
which improves walking in multiple sclerosis patients to a spinal cord simulator
for spinal injury victims, Borgens has had a hand in developing therapies that 
directly impact patients and their quality of life.


Another therapy that is currently undergoing testing is the use of polyethylene 
glycol (PEG) to seal and repair damaged spinal cord nerve cells. By repairing 
the damaged membranes of nerve cells, Borgens and his team can restore the 
spinal cord's ability to transmit signals to the brain.

However, there is one possible clinical drawback: PEG's breakdown products are 
potentially toxic. Is there a biodegradable non-toxic compound that is equally 
effective at targeting and repairing damaged nerve membranes? Borgens teamed up 
with physiologist Riyi Shi and chemist Youngnam Cho, who pointed out that some 
sugars are capable of targeting damaged membranes. Could they find a sugar that 
restored spinal cord activity as effectively as PEG? Borgens and his team 
publish their discovery that chitosan can repair damaged nerve cell membranes in
the April 16 issue of The Journal of Experimental Biology.

Having initially tested mannose and found that it did not repair spinal cord 
nerve membranes, Cho decided to test a modified form of chitin, one of the most 
common sugars that is found in crustacean shells. Converting chitin into 
chitosan, Cho isolated a segment of guinea pig spinal cord, compressed a 
section, applied the modified chitin and then added a fluorescent dye that could
only enter the cells through damaged membranes. If the chitosan repaired the 
crushed membranes then the spinal cord tissue would be unstained, but if the 
chitosan had failed, the spinal cord neurons would be flooded with the 
fluorescent dye. Viewing a section of the spinal cord under the microscope, Cho 
was amazed to see that the spinal cord was completely dark. None of the dye had 
entered the nerve cells. Chitosan had repaired the damaged cell membranes.

Next Cho tested whether a dose of chitosan could prevent large molecules from 
leaking from damaged spinal cord cells. Testing for the presence of the colossal
enzyme lactate dehydrogenase (LDH), Borgens admits he was amazed to see that 
levels of LDH leakage from chitosan treated spinal cord were lower than from 
undamaged spinal cords. Not only had the sugar repaired membranes at the 
compression site but also at other sites where the cell membranes were broken 
due to handling. And when the duo tested for the presence of harmful reactive 
oxygen species (ROS), released when ATP generating mitochondria are damaged, 
they found that ROS levels also fell after applying chitosan to the damaged 
tissue: chitosan probably repairs mitochondrial membranes as well as the nerve 
cell membranes.

But could chitosan restore the spinal cord's ability to transmit electrical 
signals to the brain through a damaged region? Measuring the brain's response to
nerve signals generated in a guinea pig's hind leg, the duo saw that the 
signals were unable to reach the brain through a damaged spinal cord. However, 
30.min after injecting chitosan into the rodents, the signals miraculously 
returned to the animals' brains. Chitosan was able to repair the damaged spinal 
cord so that it could carry signals from the animal's body to its brain.

Borgens is extremely excited by this discovery that chitosan is able to locate 
and repair damaged spinal cord tissue and is even more enthusiastic by the 
prospect that nanoparticles of chitosan could also target delivery of 
neuroprotective drugs directly to the site of injury 'giving us a dual bang for 
our buck,' says Borgens.

Story Source:

Adapted from materials provided by Journal of Experimental Biology, via 
EurekAlert!, a service of AAAS. Original article written by Kathryn Knight.

Journal Reference:
First published online April 16, 2010
Journal of Experimental Biology 213, 1513-1520 (2010)
Published by The Company of Biologists 2010
doi: 10.1242/jeb.035162 This Article


Chitosan produces potent neuroprotection and physiological recovery following 
traumatic spinal cord injury
Youngnam Cho1,*, Riyi Shi1,2 and Richard B. Borgens1,2

1 Center for Paralysis Research, School of Veterinary Medicine, Purdue 
University, West Lafayette, IN 47907, USA

2 Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN
47907, USA
Accepted 10 January 2010

Chitosan, a non-toxic biodegradable polycationic polymer with low 
immunogenicity, has been extensively investigated in various biomedical 
applications. In this work, chitosan has been demonstrated to seal compromised 
nerve cell membranes thus serving as a potent neuroprotector following acute 
spinal cord trauma. Topical application of chitosan after complete transection 
or compression of the guinea pig spinal cord facilitated sealing of neuronal 
membranes in ex vivo tests, and restored the conduction of nerve impulses 
through the length of spinal cords in vivo, using somatosensory evoked potential
recordings. Moreover, chitosan preferentially targeted damaged tissues, served 
as a suppressor of reactive oxygen species (free radical) generation, and the 
resultant lipid peroxidation of membranes, as shown in ex vivo spinal cord 
samples. These findings suggest a novel medical approach to reduce the 
catastrophic loss of behavior after acute spinal cord and brain injury.

Biomed Pharmacother. 2010 Feb 26. [Epub ahead of print]

Potential role of N-Succinyl-Chitosan in immune reconstitution after umbilical 
cord blood transplantation in mice.

Luo H, Li J, Chen X. Department of Pharmacology, Gansu College of Traditional 
Chinese Medicine, No 35, Dingxi East road, Lanzhou 730000, PR China.
Abstract

    How to shorten the immune convalescence required after transplantation in 
    recipients is still an austere medicinal problem. Speed-up recovery means 
    less infection opportunity and high survival. In this study, an 
    immune-deficient mouse model was developed by lethally irradiation to 
    evaluate the immune reconstitution effect of N-Succinyl-Chitosan (NSC), a 
    water soluble low molecular weight chitosan derivative, after umbilical cord
    blood stem cells transplantation, including hematopoiesis parameters 
    detection, T-cell phenotype analysis and pathological comparison; effects of
    NSC on proliferation of umbilical cord blood stem cell has also been 
    evaluated in vitro. By comparison and analysis, we found the combination of 
    NSC and hematopoietic growth factors could dramatically shorten the time 
    required for the recovery of hematopoiesis, T-cell phenotype and injured 
    spleen after transplantation, suggesting that NSC may hasten the immune 
    recovery and therefore may shorten the time of exposure to life-threatening 
    opportunistic infections in transplant recipients. Moreover, we demonstrated
    that NSC was effective on the proliferation and clone of umbilical cord 
    stem cell in vitro, suggesting NSC could speed up the immune reconstitution 
    in umbilical cord blood transplantation by enlarge the number of umbilical 
    cord blood stem cell. Copyright C 2010 Elsevier Masson SAS. All rights 
    reserved.
PMID: 20378302

J Biol Eng. 2010 Jan 29;4(1):2.

Chitosan nanoparticle-based neuronal membrane sealing and neuroprotection 
following acrolein-induced cell injury.

Cho Y, Shi R, Ben Borgens R. Center for Paralysis Research, School of Veterinary
Medicine, Purdue University, West Lafayette, IN 47907, USA. 
Abstract

    ABSTRACT: BACKGROUND: The highly reactive aldehyde acrolein is a very potent
    endogenous toxin with a long half-life. Acrolein is produced within cells 
    after insult, and is a central player in slow and progressive "secondary 
    injury" cascades. Indeed, acrolein-biomolecule complexes formed by 
    cross-linking with proteins and DNA are associated with a number of 
    pathologies, especially central nervous system (CNS) trauma and 
    neurodegenerative diseases. Hydralazine is capable of inhibiting or reducing
    acrolein-induced damage. However, since hydralazine's principle activity is
    to reduce blood pressure as a common anti-hypertension drug, the possible 
    problems encountered when applied to hypotensive trauma victims have led us 
    to explore alternative approaches. This study aims to evaluate such an 
    alternative - a chitosan nanoparticle-based therapeutic system. RESULTS: 
    Hydralazine-loaded chitosan nanoparticles were prepared using different 
    types of polyanions and characterized for particle size, morphology, zeta 
    potential value, and the efficiency of hydralazine entrapment and release. 
    Hydralazine-loaded chitosan nanoparticles ranged in size from 300 nm to 350 
    nm in diameter, and with a tunable, or adjustable, surface charge. 
    CONCLUSIONS: We evaluated the utility of chitosan nanoparticles with an 
    in-vitro model of acrolein-mediated cell injury using PC -12 cells. The 
    particles effectively, and statistically, reduced damage to membrane 
    integrity, secondary oxidative stress, and lipid peroxidation. This study 
    suggests that a chitosan nanoparticle-based therapy to interfere with 
    "secondary" injury may be possible.
PMID: 20205817 [PubMed - in process]PMCID: PMC2824642
Free Text>
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2824642/pdf/1754-1611-4-2.pdf

[Chitosan nanoparticles appear to be quite safe.]

Cornea. 2010 Mar 23. [Epub ahead of print]

Ocular Tolerance to a Topical Formulation of Hyaluronic Acid and Chitosan-Based 
Nanoparticles.

Contreras-Ruiz L, de la Fuente M, Garcia-Vazquez C, Saez V, Seijo B, Alonso MJ, 
Calonge M, Diebold Y.

>From the *Ocular Surface Group-IOBA, University of Valladolid, Valladolid, 
Spain; daggerCIBER de Bioingenieria, Biomateriales y Nanomedicina (CIBER-BBN), 
Valladolid, Spain; and double daggerNANOBIOFAR Group, Department of 
Pharmaceutical Technology, University of Santiago de Compostela, Santiago de 
Compostela, Spain.
Abstract

    PURPOSE:: Hyaluronic acid-chitosan nanoparticles (HA-CS NPs) have the 
    potential to serve as a reliable drug delivery system to topically treat 
    ocular surface disorders. We evaluated the in vivo uptake by ocular 
    structures, the acute tolerance, and possible alterations of tear film 
    physiology in rabbits. METHODS:: Fluorescent HA-CS NPs (fl-HA-CS NPs) were 
    prepared by ionotropic gelation using fluoresceinamine-labeled hyaluronic 
    acid and resuspended in buffer. fl-HA-CS NPs (30 muL, 0.5 mg/mL) and 
    fluoresceinamine-HA conjugate (30 muL) were instilled into rabbit eyes every
    30 minutes for 6 hours. In vivo uptake and acute tolerance were 
    characterized 24 hours after the first instillation and compared with 
    preinstillation measurements. Clinical signs, including tear production, 
    lacrimal drainage system patency and reflux, and ocular surface pathology, 
    were evaluated. RESULTS:: The rabbits showed no signs of ocular discomfort 
    or irritation after exposure to HA-CS NPs. No macroscopic alteration in 
    ocular surface structures was observed. fl-HA-CS NPs were present inside 
    conjunctival and corneal epithelial cells, although the distribution within 
    the cells was different. The fl-HA-CS NPs had no significant effects on 
    tissue morphology and functionality, tear production, or drainage. 
    CONCLUSION:: Taken together, these data demonstrate that HA-CS NPs are a 
    safe drug carrier for ocular surface application.
PMID: 20335805


[With the right nanoparticle, transport of chitosan into the brain is feasible.]

Biomaterials. 2010 Feb;31(5):908-15. Epub 2009 Oct 22.

Trimethylated chitosan-conjugated PLGA nanoparticles for the delivery of drugs 
to the brain.

Wang ZH, Wang ZY, Sun CS, Wang CY, Jiang TY, Wang SL. Department of 
Pharmaceutics, Shenyang Pharmaceutical University, Liaoning, China.
Abstract

    Trimethylated chitosan (TMC) surface-modified poly(d,l-lactide-co-glycolide)
    (PLGA) nanoparticles (TMC/PLGA-NP) were synthesized as a drug carrier for 
    brain delivery. TMC was covalently coupled to the surface of PLGA 
    nanoparticles (PLGA-NP) via a carbodiimide-mediated link. The zeta potential
    of TMC/PLGA-NP was about 20mV with a mean diameter around 150nm. 6-coumarin
    loaded PLGA-NP and TMC/PLGA-NP were injected into the caudal vein of mice, 
    and fluorescent microscopy of brain sections showed a higher accumulation of
    TMC/PLGA-NP in the cortex, paracoele, the third ventricle and choroid 
    plexus epithelium, while no brain uptake of PLGA-NP was observed. There was 
    no pronounced difference in cell viability between TMC/PLGA-NP and PLGA-NP 
    as shown by MTT assay. Behavioral testing showed that the injection of 
    coenzyme Q(10) loaded TMC/PLGA-NP greatly improved memory impairment, 
    restoring it to a normal level, but the efficacy was slight for loaded 
    PLGA-NP, without TMC conjugation. The senile plaque and biochemical 
    parameter tests confirmed the brain-targeted effects of TMC/PLGA-NP. These 
    experiments show that TMC surface-modified nanoparticles are able to cross 
    the blood-brain barrier and appear to be a promising brain drug delivery 
    carrier with low toxicity.
PMID: 19853292


[Disruption of cell membranes by DMSO can occur at low concentrations. I wonder 
what the effect of chitosan nanoparticles would be on hemolysis?]

PDA J Pharm Sci Technol. 2001 Jan-Feb;55(1):16-23.

Comparative hemolytic activity of undiluted organic water-miscible solvents for 
intravenous and intra-arterial injection.

Mottu F, Stelling MJ, Rufenacht DA, Doelker E. School of Pharmacy, University of
Geneva, Switzerland.
Abstract

    In humans, nonaqueous solvents are administered intravascularly in two kinds
    of situations. They have been used in subcutaneous or intramuscular 
    pharmaceutical formulations to dissolve water-insoluble drugs. The need for 
    these vehicles had increased in recent years, since the drug development 
    process has yielded many poorly water-soluble drugs. The use of 
    water-miscible nonaqueous solvents in therefore one of the approaches for 
    administering these products as reference solutions useful in formulation 
    bioequivalence studies. The intravascular use of organic solvents has also 
    gained importance owing to a new approach for the treatment of cerebral 
    malformations using precipitating polymers dissolved in water-miscible 
    organic solvents. At present, the solvent most commonly used for the liquid 
    embolics to solubilize the polymers is dimethyl sulfoxide, which exhibits 
    some local and hemodynamic toxicities. In order to find new, less toxic 
    vehicles for pharmaceutical formulations for the intravenous and 
    intra-arterial routes and for embolic materials, 13 water-miscible organic 
    solvents currently used (diluted with water) for pharmaceutical 
    applications, were evaluated in this study. Their hemolytic activity and the
    morphological changes induced when mixed with blood (1:99, 5:95, 10:90 
    solvent:blood) were estimated in vitro. From these data, the selected 
    organic solvents could be subdivided into four groups depending on their 
    hemolytic activity: very highly hemolytic solvents (ethyl lactate, dimethyl 
    sulfoxide), highly hemolytic solvents (polyethylene glycol 200, acetone), 
    moderately hemolytic solvents (tetrahydrofurfuryl alcohol, 
    N-methyl-2-pyrrolidone, glycerol formal, ethanol, Solketal, glycofurol) and 
    solvents with low hemolytic activity (propylene glycol, dimethyl isosorbide,
    diglyme).
PMID: 11212416

[Could chitosan nanoparticles have prevented this unexplained failure of VS4?]


Snip>"VS4 resulted in cryopreservation damage despite the fact that 
cryoprotectant toxicity was low"

Cryobiology. 2007 Feb;54(1):1-12. Epub 2006 Dec 12.

Cryopreservation of rat precision-cut liver and kidney slices by rapid freezing 
and vitrification.

de Graaf IA, Draaisma AL, Schoeman O, Fahy GM, Groothuis GM, Koster HJ. 
Pharmacokinetics and Drug Delivery, Groningen University Institute for Drug 
Exploration, A. Deusinglaan 1, 9713 AV, Groningen, The Netherlands. I.A.M.
Abstract

    Precision-cut tissue slices of both hepatic and extra-hepatic origin are 
    extensively used as an in vitro model to predict in vivo drug metabolism and
    toxicity. Cryopreservation would greatly facilitate their use. In the 
    present study, we aimed to improve (1) rapid freezing and warming (200 
    degrees C/min) using 18% Me(2)SO as cryoprotectant and (2) vitrification 
    with high molarity mixtures of cryoprotectants, VM3 and VS4, as methods to 
    cryopreserve precision-cut rat liver and kidney slices. Viability after 
    cryopreservation and subsequent 3-4h of incubation at 37 degrees C was 
    determined by measuring ATP content and by microscopical evaluation of 
    histological integrity. Confirming earlier studies, viability of rat liver 
    slices was maintained at high levels by rapid freezing and thawing with 18% 
    Me(2)SO. However, vitrification of liver slices with VS4 resulted in 
    cryopreservation damage despite the fact that cryoprotectant toxicity was 
    low, no ice was formed during cooling and devitrification was prevented. 
    Viability of liver slices was not improved by using VM3 for vitrification. 
    Kidney slices were found not to survive cryopreservation by rapid freezing. 
    In contrast, viability of renal medullary slices was almost completely 
    maintained after vitrification with VS4, however vitrification of renal 
    cortex slices with VS4 was not successful, partly due to cryoprotectant 
    toxicity. Both kidney cortex and medullary slices were vitrified 
    successfully with VM3 (maintaining viability at 50-80% of fresh slice 
    levels), using an optimised pre-incubation protocol and cooling and warming 
    rates that prevented both visible ice-formation and cracking of the formed 
    glass. In conclusion, vitrification is a promising approach to cryopreserve 
    precision-cut (kidney) slices.
PMID: 17166492

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