Students Bucky Ball_ as Novel Nano Material

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Publication Ref No.: IJPRD/2009/PUB/ARTI/VOL-8/OCT/009 ISSN 0974 – 9446

International Journal of Pharma Research and Development – Online

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(Review Article)

BUCKY BALL: AS NOVEL NANOMATERIAL

Anju Goyal*, Neeraj Kumar Trivedi, Arvind Arora

Department of Pharmaceutical Chemistry,B. N. P.G. College of Pharmacy, Udaipur-313002, India

ABSTRACT:

Buckyball as a novel nanomaterial was discovered by Scientist Fuller, hence termed as Fullerenes. Thisnew allotrope forms an extensive series of polyhedral cluster molecules, Cn (n even), comprising fusedpentagonal and hexagonal rings of C atoms, which becomes base of nanotechnology. Pure fullerenes,derived fullerenes, metal endohedral fullerenes and carbon nanotube fullerenes are available fornanoscience. They have different shapes showing surprising physical and chemical characteristic. Thenatural sources and synthetic sources are available for their production. They show many biomedical,therapeutic, diagnostic and miscellaneous applications. Enviromental toxicity and biological toxicity arealso reported. The global market for fullerenes in 2005 worth over $60 million. Fullerenes are the futurefor nanomedicine and nanosurgery.

Key Words: Buckyball, Fullerene, nanomaterial, allotrope.





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INTRODUCTION AND MATERIALS AND METHODS

Introduction

The notion of nanotechnology has evolved since its inception as a fantastic conceptual idea to its currentposition as a mainstream research initiative with broad application among all division of science. As thename indicate the nanoparticle form the base of nanotechnology and nanosciences. These minute particles

about 100A° to 2000A° in diameter were introduced by Krenter and Speiser in the 1970s as a controlledrelease drug carrier.[1] The nanomaterials currently being employed in pharmaceuticals includes:Micelles, Liposomes, Dendrimers, Fullerenes, Hydrogels, Nanoshells, Smart Surfaces, Quantum Dots,Colloidal Gold, Polymeric nanoparticles etc. Buckyballs are an integral and newly emerging part of nanomaterials. This new allotrope forms an extensive series of polyhedral cluster molecules, Cn (n even),comprising fused pentagonal and hexagonal rings of C atoms. The first member to be characterized wasC60, which features 12 pentagons separated by 20 fused hexagons. It has full icosahedral symmetry and

was given the name buckminsterfullerene in honour of the architect R. Buckminster Fuller whosebuildings popularized the geodesic dome, which uses the same tectonic principle. [2] Fuller, who is shown on the cover of Time Magazine of January 10, 1964, was renowned for his geodesicdomes that are based on hexagons and pentagons. The group actually tried to understand the absorptionspectra of interstellar dust, which they suspected to be related to some kind of long-chained carbonmolecules. Initially, C60 could only be produced in tiny amounts. So there were only a few kinds of experiments that could be performed on the material. Things changed dramatically in 1990, whenWolfgang Krätschmer, Lowell Lamb, Konstantinos Fostiropoulos, and Donald Huffman discovered howto produce pure C60 in much larger quantities. This opened up completely new possibilities forexperimental investigations and started a period of very intensive research. Nowadays it is relativelystraightforward to mass-produce C60. It opened up the new branch of Fullerene-Chemistry, which studies

the new families of molecules that are based on Fullerenes. Knowledge of chemical modification,biological significance and materials application of functionalized fullerenes is growing rapidly and thesecompounds are emerging as new tools in the pharmaceutical field. . [3]

Classification Fullerenes can be classified into following ways [4] –

A. Pure Fullerenes:1. Fullerene C60 or Buckminsterfullerene:

Molecular wt: 720.66, Appearance: Granular, dark-brown powder. Sublimed appears as deep blue-black needle-like crystals. The diameter of a C60 molecule is about 1 nanometer. The C60 moleculehas two bond lengths. The 6:6 ring bonds (between two hexagons) can be considered "double bonds" andare shorter than the 6:5 bonds (between a hexagon and a pentagon) given in Figure 1.2. Fullerene C70: Molecular wt: 840.77, Appearance: Granular, Sublimed black powder (Figure 2).3. Fullerene C76: Molecular wt: 912.84, Appearance: Granular, dark-brown powder.4. Fullerene C78: Molecular wt.: 936.86, Appearance: Granular, black powder (Figure 3).5. Fullerene C84 : Molecular wt.:1008.92, Appearance: Granular, brown-black powder (Figure 4).

B. Derived fullerenes (functionalized fullerenes):





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Chemical groups can be attached to a fullerene carbon atom and this process is called functionalization,used for modifying the properties. The number of carbon atoms available to do this had led to the epithet“molecular pincushion”, especially within the context of medical application such as those being

developed by the company C60. Ferrocenes are compounds containing iron and organic groups that haveattracted much interest in the decades since their discovery. The hybrids might create vesicles for drugdelivery.

C. Metal Endohedrals:An area of research that has been as active as functionalization of fullerenes is that of putting atoms insidethem. The results are called endohedral fullerenes (Figure 5). A huge number of elements have beenencapsulated in fullerenes, including the noble gases, which have no desire to bond with surroundingcarbon atoms but can be used in application such as magnetic resonance imaging (MRI). [5]

D. Carbon Nanotubes:

Nanotubes are cylindrical fullerenes. These tubes of carbon (Figure 6) are usually only a few nanometreswide, but they can range from less than a micrometre to several millimetres in length.

Description

Shapes of Fullerenes:The structural motif of the fullerenes is a sequence of polyhedral clusters, Cn, each with 12 pentagonalfaces and (1/2 n-10) hexagonal faces. C60 itself has 20 hexagonal faces. C70 has 25 hexagonal faces with 5types of carbon atoms and 8 types of C-C bonds.

Systematic Names:

Systematic names for the icosahedral C60 and the D5h (6) C70 fullerenes are (C60-Ih) [5,6] fullerene and(C70-D5h (6))[5,6] fullerene. Systematic Numbering is given in both 3-D and Schlegel format (Figure 7).[6]

Physical Characteristics:

Physically, buckyballs are extremely strong molecules, able to resist great pressure-they bounce back tothe original shape after being subjected to over 3000 atmospheres. This gives buckyballs, graphite likepotential as a lubricant. Fullerenes have interesting electrical properties, which have led to suggestions foruse in number of electronics related areas. The same properties offer potential use in photo detectors forX-rays. The purified fullerenes have very attractive colors. Thin films of C 60 are mustard colored (dark

brown in bulk) and solutions in aromatic hydrocarbons are a beautiful magenta. Thin films of C70 arereddish brown (grayish-black in bulk) and solutions are port-wine red. C76, C78 and C84 are yellow incolour.

Solubility: Fullerenes are sparingly soluble in many solvents. Common solvents for the fullerenes includearomatics such as toluene and carbon disulfide. Solutions of pure Buckminsterfullerene have a deep purplecolor. Solutions of C70 are a reddish brown. The higher fullerenes C76 to C84 have a variety of colors. C76 has two optical forms, while other higher fullerenes have several structural isomers. Fullerenes are theonly known allotrope of carbon that can be dissolved in common solvents at room temperature.





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Chemical stability: Fullerenes are stable and the characteristic reaction of fullerenes is electrophilicaddition at 6, 6-double bonds, which reduces angle strain by changing sp2-hybridized carbons into sp3-hybridized ones. Other atoms can be trapped inside fullerenes to form inclusion compounds known as

endohedral fullerenes.

Chemical reactions : Fullerenes undergo following chemical reactions : Hydrogenation, Addition,Functionalization , Oxidation, Reduction. [7]

Production

I. Natural sources :C60 and C70 have been detected in several naturally occurring minerals e.g. In carbon-rich semi-anthracitedeposits from the yarrabee mine in Queens land, Australia. In Shungite, a highly metamorphosed meta-anthracite from Shunga, Kerelia, Russia. Most recently, significant findings of naturally occurring

fullerenes have been made in Sudbury (Canada) and New Zealand.II. Synthetic Sources

:

They were first produced by man (at least knowingly) in the soot resulting from vaporizing graphite with alaser. The earliest bulk production process is the arc discharge (or Krätschmer-Huffman) method, usinggraphite electrodes, developed in 1990.Other Routes:Heating naphthalene vapor (C10H8) in argon at about 1000oC followed by extraction with CS2. Burningsoot in a benzene/oxygen flame at about 1500oC with argon as diluent. [8, 9]

Applications

A. Biomedical Applications:Fullerenes unique qualities have promise for certain type of drug design. The small size, spherical shape

and hollow interior all provide therapeutic opportunities. Moreover, a cage of 60 carbon atoms has 60places at which chemical groups can attach in almost any configuration. Such opportunity has led to thedevelopment of not only drug candidates for treating diseases including HIV, cancer and neurologicalconditions but also new diagnostic tools.

B.Therapeutic Applications:

The relatively high tolerance of biological systems to carbon is one of the reasons for the potential of buckyballs in medical applications, in addition buckyballs are small enough to pass through kidneys andbe excreted. The ability to chemically modify the sidewalls of buckytubes also leads to biomedicalapplications such as neuron growth and regeneration. [10]

Self Assembled DNA Buckyballs for drug deliveryTiny geodesic spheres that could be used for drug delivery and as containers for chemical reactions havebeen developed. About 70% of the volume of the DNA buckyball is hollow and drugs can be encapsulatedin it to be carried into cells, where natural enzymes break down the DNA, releasing the drug. They mightalso be used as cages to study chemical reactions on the nanoscale. [11] Buckyballs to fight allergy

The buckyballs are able to interrupt the allergy/immune response by inhibiting a basic process in the cellthat leads to release of an allergic mediator. Essentially, the buckyballs are able to prevent mast cells fromreleasing histamine. These findings advance the emerging field of medicine known as nanoimmunology. [12]





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Buckyballs as antioxidants:

The unique structure of buckyballs enable it to bind to free radicals dramatically better then anyantioxidant currently available, such as vitamin E. Free radicals are molecules that cause oxidative stress,

which experts believe may be the basis of aging therefore finds use in cosmetics.Buckyballs as Passkey into Cancer cells

Drugs are far more effective if they are delivered through membrane, directly into the cells. The passkeydeveloped contain a molecule called Bucky amino acid based on phenylalanine that are strung togetherlike a beads on a necklace to build all proteins The peptides were found effective at penetration thedefenses both liver cancer cells and neuroblastoma cells.

Buckyballs are the first targeted antibiotic ( New Defense Against Bioterrorism)

A new variant of vancomycin that contains buckyballs -- tiny cage-shaped molecules of pure carbon couldbecome the world's first targeted antibiotic, creating a new line of defense against bioweapons like

anthrax.

Buckyball as HIV Protease Inhibitor:

C Sixty's drug targets the human immunodeficiency virus (HIV) that causes AIDS by latching onto theenzyme necessary for viral reproduction. The fullerenes deactivate both the HIV-1 and HIV-2 types of virus, and don't seem to harm cells or organs, which is a problem with some other HIV inhibitors. Since aC60 molecule has approximately the same radius as the cylinder that describes the active site of HIVP andsince C60 and its derivatives are primarily hydrophobic, an opportunity exists for a strong hydrophobicVander Waals interaction between the nonpolar active-site surface and the C60 surface (Figure 8). Inaddition, however, there is an opportunity for increasing binding energy by the introduction of specific

electrostatic interactions. One obvious possibility involves salt bridges between the catalytic aspartic acidson the floor of the HIVP active site and basic groups such as amines introduced on the C60 surface. Thekey to exploiting this promising system will be the development of organic synthetic methodology toderivatize the C60 surface in highly selective ways.

Buckyballs as Neuroprotectants:

Buckyball act as neuroprotectants-a drug that prevents or repair neurological damage. Diseases such asamyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease and Parkinsonism are under trial.[13]

Buckyball as Cytoprotective agent

The Water-soluble Buckyball derivative Radical Sponge exerts cytoprotective action against UVirradiation without visible light catalyzed cytotoxicity toward human skin keratinocytes. [14]

Buckyball C60 α Alanine Adduct As Radical Scavenging Agent

Water-soluble C60 α Alanine Adduct has been synthesized and scavenging ability for super oxide anion O-2 (-) and hydroxyl radical has been demonstrated. It shows excellent efficiency in eliminating these anionsand radicals and will be useful in radical related biomedical field. [15, 16]





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C. Diagnostic Applications

Buckyballs may be especially useful for shuttling metal contrast agents through the body for magneticresonance imaging (MRI) scans. Bolskar, Lon Wilson of Rice University in Houston, and otherresearchers have designed carbon-60 and other fullerene molecules with an atom of gadolinium inside andwith chemical appendages that make them water-soluble. In typical MRI contrast agents, the metalgadolinium is linked to a non fullerene molecule. For most diagnostic tests, this molecule is excreted fromthe body quickly. However, fullerene-encapsulated gadolinium might one day be a safer option for certaindiagnostic tests in which doctors leave the contrast agent in longer time. Trimetaspheres are a larger version of the buckyball, with 80 carbons caging up to three metal or rareearth atoms, such as scandium, lanthanum or yttrium, which are covalently bonded to nitrogen. Intrimetaspheres the nitrogen complex spins freely within the larger cage of carbons.They have potentialuses as contrast agents for medical magnetic resonance imagining, as light emitting diodes, and potentially

for molecular electronics and computing. [17]

D. Miscellaneous Application

There is a wealth of other potential applications for Buckytubes, such as solar collection; nanoporousfilters; and coatings of all sorts. Following are certain example:1) Data storage devices: fullerene have interesting electrical properties’, which have led to the suggestionfor use in a number of electronics related areas from data storage devices to solar cells.2) Fuel cells: another use of electrical property of fullerene is in fuel cells exploiting their ability to helpproton move around.3) Memory devices: fullerene have been inserted into nanotube, the result sometime referred to as

‘peapods’, the properties can be modified by moving the location of the enclosed fullerens and researchhas even suggested using this to create memory devices.4) Photonic devices

5) Telecommunication devices

6) Supreconducting devices7) Fullerene can also be used as precursor for other materials such as diamond coating or nanotubes.8) Liquid crystal display these have potential in liquid crystal application which goes beyond Liquidcrystal displays as there is growing interest in there use in areas such as non linear optics, photonics andmolecular electronics.Fullerenes are effective at mopping up free radicals, which damage liver tissue. This had led to thesuggestion that they might protect the skin in cosmetics, or health hinder neural damage caused by radicals

in certain diseases, research on which on rats has already shown promise.The size of C60 is similar to many biologically acting molecules, including drugs, such as Prozac andsteroid hormone. This gives it potential as a foundation for creating a variety of biologically activevariants. Buckyballs have a high physical and chemical affinity for the active site on an important enzymefor HIV, called HIV protease, and block the action of enzyme. Buckyballs target HIV protease differentlyso their effect should not be subject to resistance already developed. [18]

The neuroprotective potential for C60 has already been demonstrated, and vesicles made out of them couldbe used to deliver drugs. Applications for buckyballs with other atoms trapped inside them, referred to asendohedral fullerenes. [19]





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Toxicities

Although C60 has been thought in theory to be relatively inert, the studies suggest the molecule may prove

injurious to organisms.

I. Environmental ToxicityAn experiment by Eva Oberdörster at Southern Methodist University, which introduced fullerenes intowater at concentrations of 0.5 parts per million, found that largemouth bass suffered a 17-fold increase incellular damage in the brain tissue after 48 hours. The damage was of the type lipid peroxidation, which isknown to impair the functioning of cell membranes. There were also inflammatory changes in the liverand activation of genes related to the making of repair enzymes. The overwhelming evidence of theessential non-toxicity of C60 (not nC60) in previously peer-reviewed articles of C60 and many of itsderivatives indicates that these compounds are likely to have little (if any) toxicity, especially at the verylow concentration at which it is≈ used (~1-10 µM).[20]

Desorption behavior of carbon nanotubes shows that high adsorption capacity and reversible adsorption of

poly aromatic hydrocarbons on nanotubes imply the potential release of PAHs. If PAH-adsorbed CNTsare inhaled by animal and human beings it may lead to a high environmental and public health risk. [21]

II. Biological Toxicity

A study published in December 2005 in Biophysical Journal raises a red flag regarding the safety of C60when dissolved in water. It reports the results of a detailed computer simulation that finds C60 binds to thespirals in DNA molecules in an aqueous environment, causing the DNA to deform, potentially interferingwith its biological functions and possibly causing long-term negative side effects in people and otherliving organisms.Despite of the hydrophobic behavior fullerenes strongly bound to the nucleotides. C60 bind singlestranded DNA and deform the nucleotides significantly.unexpectedly,when double stranded DNA is in Aform ,fullerene penetrate into the double helix from the end, form stable hybrids, and frustrate the

hydrogen bond between endgroup basepair in the nucleotide. The simulation results suggest the C60molecules have potentially negative impact on the structure, stability and biological functions of DNAmolecule. [22]

Economics

The Global Market for FullerenesBased on the research's structured market analysis, the $60 million 2005 market should grow to $92million in 2006, and $1.312 million by 2011, an average annual growth rate (AAGR) of 70%. The annualglobal fullerene market could be worth over $4.7 billion by 2016. The U.S. and Japan will remain the

predominant Tier I fullerene countries in terms of both technology and production. South Korea and thePeople's Republic of China should move to Tier I in the next few years. [23]

Future Aspects

Even though the fullerene drug candidates and diagnostic products now at various points along thedevelopment pipeline excite them, the researchers caution that more toxicity tests in animals and varioushuman trials are needed to prove the safety and efficacy of these newcomers to the biomedical arena. Forsome of the potential molecules, these tests might take a couple years; for others, much longer.





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Drugs in the Pipeline

Research groups worldwide are developing fullerene drug candidates for a variety of diseases and testing

them in animals. C Sixty reports that some of these candidates have moved well beyond the chemistryphase of drug development and that it plans to conduct human trials of fullerene-based molecules in abouta year for two diseases.The company first expects to begin these trials on a modified fullerene that combats HIV. In lab andanimal studies, the protease inhibitor that C Sixty plans to test on patients has proven both nontoxic andeffective against several strains of HIV. C Sixty plans to conduct its next set of human trials againstamyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease. In this case, the fullerene acts asa neuroprotectant—a drug that prevents or repairs neurological damage. Molecules built from thebuckyball framework are efficient at eliminating so-called free radicals from cells. Free radicals appear todamage neurons in diseases such as ALS and Parkinson's disease. In rat studies, one of the fullerene-basedmolecules that C Sixty is developing has both stopped the degeneration of nerves and caused some motor

activity to return. [24]

SUMMARY AND CONCLUSION

The geodesic structure of buckyball is so unique and symmetric that it has been referred by some scientistas The Most Beautiful Molecule. Their physical and chemical properties have been a hot topic in the fieldof research and development for the past decade and are likely to continue for a long time. Their small,hollow interiors, spherical shape, high physical and chemical affinity for active sites in some importantenzymes provide therapeutic opportunities. More over a cage of 60 carbons has 60 places at whichchemical groups can be attached in almost any configuration. Such opportunity has led to the developmentof not only drug candidates for treating diseases including HIV, cancer and neurological conditions but

also new diagnostic tool. Field and clinical trials are required to define the risk/benefit ratio of fullerenes.Apart from pharmaceuticals there is a wealth of other potential applications for buckyballs electronics,communication, chemicals and defense etc. The results are such that the world market of fullerene isgrowing at an enormous rate day by day and it is expected that the global market could be worth over $4.7 billion by 2016. Thus it can be concluded that although at an early stage of development, thebuckyballs are likely to become the future of mature nanomedicine and nanosurgery.





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REFERENCES

1.Alferd, M.; Bustamnate, A.H. Physical Pharmacy; Lippincott Williams and Wilkins, 2005. 2.Greenwood, N. N; Earnshaw, Chemistry of Elements; Bullerworth Henemann, 2003.3.Aldersley, H.; Williams ; The Most Beautiful Molecules; Auram Press London, 1995.4.www.wikipedia.com5.www.cientifica.com6.Taylor, R. The Chemistry of the Fullerenes; World Scientific, Singapore, 1995.7.www.cnanotech.com8.Wilson, M.A.; Pang, L.S.K.; Vassalo, A.M. Nature, 1992. 9.Bilogical abstract, 2006, 114, Article Reference No. 110959.10. Biological Abstract, 2006, 113, Article Reference Number 240946.11. http:www.sciencedaily.com/releases/2005/08/050829074441.htm

12. Anya, M.; Hillery, A.; Lloyd, W.; Swarbrick, J. Drug Ddelivery and TargetingGluenberg Press Ltd,Malta, 1999.13. http://www.nanotechfoundation.com14. Biological Abstract, 2006, 113, Article Reference Number 158676.15. Biological Abstract, 2006, 113, Article Reference Number 22920616. Biological Abstract, 2007, 114, Article Reference Number 72964.17. Dorn, H.C.; Iezzi, E.B; 223rd American Chemical Socitey National Meeting, 2002.18. www.azonano.com19. http://www.cnanotech.com20. Biological Abstract, 2006, 113, Article Reference Number 243225.21. Biological Abstract, 2006, 113, Article Reference Number 196828.

22. Biological Abstract, 2006, 113, Article Reference Number 67406.23. www. azojono.com24. Sagman, U.; 223rd American Chemical Society National Meeting, 2002.

FIGURES AND DIAGRAMS:

Figure 1: Fullerene C 60 or Buckminsterfullerene





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Figure 2: Fullerene C 70







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Figure 5: Metal endohedral

Figure 6: Carbon Nanotube

Figure 7: 3-D Representation Schlegel Representation





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Figure 8: Buckyball as HIV Protease Inhibitor

Figure 9: A schematic illustration showing how buckyballs might be used to treat cancer

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