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Tag: Nanoscience

Why should we learn Nanoscience? Impact to our Society

In 1959, Professor Richard Feynman in a public lecturer at California Institute of Technology shared his thought about the strange behaviour of small particles. His lecturer was entitles as: “There’s plenty of room at the bottom”. Professor Feynman actually gave us the idea to enter into a new field of Physics, today it is known as Nanoscience. Professor Feynman in his lecture also talked about “How do we write small”, “Information on a small scale” and the importance of developing better electron microscope. All his novel ideas have created breakthroughs in the field of nanoscience.  

Nanoscience enables us to study the properties of system at nanoscale and Nanotecgnology enables us to organize and manipulate the properties and behaviour of a system in atomic or molecular level. Nanoscience has wide prospect and finds application in various different fields. Here I describes application of nanoscience and the scope and prospect in this field.   

What is nanoparticle?  

A particle has dimension of nanometer size. The question is how small one nonometer is. The 1 nm (1 nm = 10-9 meter) is one billionth of a meter or equivalent to 10 Å (1 Å = 10-8 cm). Nanosized particles of a substance exhibit different properties and behaviours than larger particles of the same substance. Carbon is very common also very abundant material in nature. We are aware of its two different forms; graphite and diamond. During 1985 to 2004, scientists have discovered three new allotropes of carbon. They are known as fullerene (known as Buckminsterfullerene: C60), carbon nanotube and graphene.     

Fullerene: In 1985 a group of scientists lead by Prof. Harry Kroto had discovered a small structure in which 60 Carbon atoms are joined together in one unit. The structure is quite similar like a football. In this fullerene structure we could see hexagon + pentagon pattern. Prof. Kroto and his collaborators were awarded the 1996 Nobel Prize in Chemistry. With the advancement of technology various different structures like fullerenes with larger number of carbon atoms (C70, C76, C80, etc.) were synthesized.   

Graphene: Graphene is 2-dimensional nano-structure. It is a 2D sheet of single layered carbon atoms arranged in hexagonal lattice. Graphite is actually made of millions of layers of graphene. In 2004 at the University of Manchester, Andre Geim and K. Novoselov produce graphene from graphite using a scotch tape in laboratory. Professor Geim and his co-workers were awarded Nobel Prize for Physics in 2010. Graphene is the most useful and thinnest 2D nanomaterial due to its extremely high electrical conductivity, transparency and tensile strength.     

Carbon nanotube (CNT): CNTs are cylindrical nanostructure consists of one or more layer of graphene sheet. Diameter of single-wall CNT (SWCNT) and multi-wall CNTs (MWCNT) may vary from 0.8 to 2 nm and 5 to 20 nm respectively. A single-wall CNTs can be realize as cut-outs from a 2D hexagonal graphene sheet rolled up along one of the Bravais lattice vectors and thereby form a hollow cylinder. CNTs exhibit remarkable electrical conductivity. Single-wall CNTs are metallic but multi-wall CNTs are having small band-gap. CNTs exhibit exceptionally high tensile strength and thermal conductivity. These properties of CNT make them valuable and are used in electronics, optics, biological and biomedical research. 

Exciting Properties of Nanoparticles

Super surface activity: Nanoparticles exhibit strong reactivity due to much higher surface to volume ratio. With decrease of particle size the number of particles at the surface increases. This leads to a significant energy contribution to the system from the unsatisfied bonds of the surface atoms. Hence, the surface becomes extremely ‘active’ due to the high available surface energy. This effect finds applications in: adsorption of toxic gases, catalysis, etc.

Superparamagnetism: A ferromagnetic particle behaves like a paramagnet when particle size is made very small. Ferromagnetic solid consists of small magnetic domains and spins are aligned inside the domain. If particle size is reduced to very small size (typically < 20 nm) the entire particle becomes a single domain. With further reduction in particle size (< 5 nm) ferromagnetic property is lost. Therefore in the absence of external field the particle behaves like a paramagnet and in the presence of a field spins are getting aligned leading to a large magnetization, also known as super-paramagnetic behavior.

Super-hydrophobicity: If surfaces are highly hydrophobic (super-hydrophobic) then they are difficult to wet. The contact angle of water droplet may exceed 150o on a super-hydrophobic surface. Surface roughness is increased at nano-scale therefore actual contact area of the surface decreases and hence the surface becomes non-wetting. The super-hydrophobic coating is used in vehicle windshields and maritime industry.

Why nano-scale become so Important?

Nanoparticles exhibits some unique mechanical, optical, magnetic, and electrical properties that are distinctly different from that of bulk materials. It was found that nanoparticles exhibits enhanced activity when subjected to similar applications. A few are discussed below.

  • Nano-crystals have lower melting point and has reduced lattice constant (difference can be as large as 1000oC).
  • Due to high surface to volume ratio nano-crystals are used for catalysis, drug delivery and energy storage.
  • Semiconductor nanocrystals have larger band gap than that of bulk semiconductors.
  • Ferroelectric and ferromagnetic materials lost their ferroelectricity and ferromagnetic property at the nano scale.
  • A system composed of nano-particles can conducts electricity better.

Applications:

Use of nanotechnology includes sports equipment, vehicle parts, storage of power in batteries, cosmetics, drug delivery and many more. Scientists are working with nonomaterials with a hoped that nanoscience will control our health-care system in future. We all use sunscreens; it contains ZnO or TiO2 nano powder to avert sunburns. Nano-science is combined with bio-science naturally because in general the bio-molecules that we are dealing with (e.g; DNA, RNA, proteins, enzymes) are all within the nanoscale range from 1-100 nm. In November 2012, Scientists at NIST (American National Institute of Standard and Technology) demonstrate that SW-CNTs can protect DNA molecules from oxidation.  Here I illustrate some more applications of CNTs in bio-medical research.

  • CNTs are bio-compatible and having low-level of toxicity.
  • CNTs are elastic cylindrical tubes with both ends open and therefore can be used in intracellular delivery.
  • Due to high tensile strength, CNTs filled with calcium and grouped in the structure of bone can act as a bone substitute.
  • For biomedical application, functionalization is required and it is possible for CNTs. Functionalization may improve biocompatibility and also reduce the toxicity level.

CNTs can enter into cells by binding their tips to the cell membrane receptors. This actually helps in drug delivery. 

THE NANO SCIENCE AND ITS CONTRIBUTION IN TREATING CANCER

Nanoscience involves the study of the control of matter on an atomic and molecular scale. This molecular level investigation is at a range usually below 100 nm. In simple terms, a nanometer is one billionth of a meter and the properties of materials at this atomic or subatomic level differ significantly from properties of the same materials at larger sizes. Although, the initial properties of nano materials studied were for its physical, mechanical, electrical, magnetic, chemical and biological applications, recently, attention has been geared towards its pharmaceutical application, especially in the area of drug delivery. According to the definition from NNI (National Nanotechnology Initiative), nanoparticles are structures of sizes ranging from 1 to 100 nm in at least one dimension. However, the prefix “nano” is commonly used for particles that are up to several hundred nanometers in size. Nanocarriers with optimized physicochemical and biological properties are taken up by cells more easily than larger molecules, so they can be successfully used as delivery tools for currently available bioactive compounds.

Cell-specific targeting can be achieved by attaching drugs to individually designed carriers. Recent developments in nanotechnology have shown that nanoparticles (structures smaller than 100 nm in at least one dimension) have a great potential as drug carriers. Due to their small sizes, the nanostructures exhibit unique physicochemical and biological properties (e.g., an enhanced reactive area as well as an ability to cross cell and tissue barriers) that make them a favorable material for biomedical applications. It is difficult to use large size materials in drug delivery because of their poor bioavailability, in vivo solubility, stability, intestinal absorption, sustained and targeted delivery, plasma fluctuations, therapeutic effectiveness etc. To overcome these challenges nanodrug delivery have been designed through the development and fabrication of nanostructures. Nanoparticles have the ability to penetrate tissues, and are easily taken up by cells, which allows efficient delivery of drugs to target site of action. Uptake of nanostructures has been reported to be 15–250 times greater than that of microparticles in the 1–10 um range. Nanoparticles can mimic or alter biological processes (e.g., infection, tissue engineering, de novo synthesis, etc. These devices include, but not limited to, functionalized carbon nanotubes, nanofibers, self-assembling polymeric nano constructs, nanomembranes, and nano-sized silicon chips for drug, protein, nucleic acid, or peptide delivery and release, and biosensors and laboratory diagnostics. Various polymers have been used in the design of drug delivery system as they can effectively deliver the drug to a target site and thus increase the therapeutic benefit, while minimizing side effects. The controlled release (CR) of pharmacologically active agents to the specific site of action at the therapeutically optimal rateand dose regimen has been a major goal in designing such devices. The drug is dissolved, entrapped, encapsulated or attached to a NP matrix and depending upon the method of preparation, nanoparticles, nanospheres or nanocapsules can be obtained. Nanocapsules are vesicular systems in which the drug is confined to a cavity surrounded by a unique polymer membrane, while nanospheres are matrix systems in which the drug is physically and uniformly dispersed. Biodegradable polymeric nanoparticles have attracted considerable attention as potential drug delivery devices in view of their applications in the controlled release of drugs, their ability to target particular organs/tissues, as carriers of DNA in gene therapy, and in their ability to deliver proteins, peptides and genes through a per oral route of administration. Recent advances in the application of nanotechnology in medicine, often referred to as nanomedicine, may revolutionize our approach to healthcare. Cancer nanotechnology is a relatively novel interdisciplinary area of comprehensive research that combines the basic sciences, like biology and chemistry, with engineering and medicine. Nanotechnology involves creating and utilizing the constructs of variable chemistry and architecture with dimensions at the nanoscale level comparable to those of biomolecules or biological vesicles in the human body. Operating with sub-molecular interactions, it offers the potential for unique and novel approaches with a broad spectrum of applications in cancer treatment including areas such as diagnostics, therapeutics, and prognostics.

Nanotechnology also opens pathways to developing new and efficient therapeutic approaches to cancer treatment that can overcome numerous barriers posed by the human body compared to conventional approaches. Improvement in chemotherapeutic delivery through enhanced solubility and prolonged retention time has been the focus of research in nanomedicine. The submicroscopic size and flexibility of nanoparticles offer the promise of selective tumor access. Formulated from a variety of substances, nanoparticles are configured to transport myriad substances in a controlled and targeted fashion to malignant cells while minimizing the damage to normal cells. They are designed and developed to take advantage of the morphology and characteristics of a malignant tumor, such as leaky tumor vasculature, specific cell surface antigen expression, and rapid proliferation.

Nanotechnology offers a revolutionary role in both diagnostics (imaging, immune-detection) and treatment (radiation therapy, chemotherapy, immunotherapy, thermotherapy, photodynamic therapy, and anti-angiogenesis). Moreover, nanoparticles may be designed to offer a multifunctional approach operating simultaneously as an effective and efficient anticancer drug as well as an imaging material to evaluate the efficacy of the drug for treatment follow-up. In recent years, nanomedicine has exhibited strong promise and progress in radically changing the approach to cancer detection and treatment.

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