electrospun nanofibres

Submitted by:

Nikita Gupta

Mtech-NST

01140801014

Electrospun nanofibres

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Introduction Nanofabrics are composed of non-woven Nano fibers. Nano fibers are created by a process called electrospinning. Electrospinning is a major way to engineer (without self-assembly)

nanostructures that vary in: Fiber Diameter Mesh Size Porosity Texture Pattern Formation

Burger, Christian, et. al. Nanofibrous Materials and Their Applications. 2006.

http://en.wikipedia.org/wiki/File:Taylor_cone_photo.jpg

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Electrospinning Setup

1. A high voltage power supply (normally working in a range between 10 and 30kV);

2. A polymer reservoir that can maintain a constant flow rate of solution, commonly a syringe connected to either a mechanical or a pneumatic syringe pump;

3. A conductive dispensing needle as polymer source connected to the high voltage power supply;

4. A conductive substrate, normally grounded, which serves as a collector for the electrospun fibers.

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Electrospinning – Parameters

Polymer precursor material. Solvent and solution additives. Polymer concentration. Needle-to-collector distance. Voltage. Flow rate.

10kV 15kV 20kV

To optimize material properties, fiber thickness, homogeneity, density, and distribution.

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Electrospinning - Procedure An electrostatic potential is applied between a spinneret and a collector A fluid is slowly pumped through the spinneret. The fluid is usually a solution where the solvent can evaporate during the

spinning. The droplet is held by its own surface tension at the spinneret tip, until it gets

electrostatically charged. The polymer fluid assumes a conical shape (Taylor cone). When the surface tension of the fluid is overcome, the droplet becomes

unstable, and a liquid jet is ejected


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Types of Solvent Stream Ejections

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Electrospinning Polymers

The small size between the fibers allows the capture of particles in the 100- to 300- nanometer range

That is the same size of viruses and bacteria Used as air-filter: Airplanes, office, etc.


Polymer Solvent Concentration Potential ApplicationNylon 6,6 Formic Acid 10 wt% Protective Clothing

Polyurethanes Dimethylformamide 10 wt% Protective Clothing

Polycarbonate Dichloromethane 15 wt% Sensor, FilterPolylactic Acid Dichloromethane 14 wt% Drug Delivery

System

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Applications


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Applications

Ultrafiltration in water treatment

High flux, low-fouling membrane The top layer provides the actual filtration, and the middle and bottom

layer provide sting support and are very porous Increased efficiency Able to filter without top layer.



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Recent Research on Electrospinning

Surface-functionalized Elecrospun Nanofibers for Tissue Engineering and

Drug Delivery

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Electrospun Nanofibers High surface area to volume ratio Versatile method for preparing nanofibrous meshes Potential applications:

Biomedical devices

Tissue engineering scaffolds

Drug delivery carriers

Done through Surface Modification Plasma treatment

Wet chemical method

Surface graft polymerization

Co-electrospinning of surface active agents and polymers

Creates bio-modulating microenvironments to contacting cells and tissues

"Surface-functionalized Electrospun Nanofibers for Tissue Engineering and Drug Delivery."

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Surface Modification Techniques Synthetic polymers vs. natural polymers

a. Synthetic: easier processing for electrospinning and more controllable nanofibrous morphology

b. Natural: difficult to directly process into nanofibers because of unstable nature and weak mechanical properties

Natural polymers can be immobilized onto the surface of synthetic polymers without compromising bulk properties


http://www.animate4.com/nanotech/nanotechnology/nanomedicine/nano/nanoscale/nanotech-nanotechnology-nano-nanomedicine-moleculare-nanotech-nanoscale.jpg

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Modification – Plasma Treatment Changes the surface chemical composition Selection of plasma source – introduce diverse functional groups on surface

a. Plasma treatments with oxygen, ammonia, or air – generates carboxyl groups or amine groups

b. Air or argon treatments When nanofibers were soaked in a simulated body solution – calcium

mineralization occurred on surface

a. Improved wettability

b. Potential with bone grafts


http://www.devicedaily.com/wp-content/uploads/2008/11/fortross-02.jpg

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Modification – Wet Chemical Method

Films and scaffolds under acidic or basic conditions – modify surface wettability

Plasma treatment can not modify surface of nanofibers deep in the mesh Wet chemical etching methods can modify thick meshes


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Modification – Surface Graft Polymerization Synthetic biodegradable polymers retain hydrophobic surface – need hydrophilic

surface modification for desired response Introduce multi-functional groups on the surface

Enhanced cell adhesion, proliferation, and differentiation

Initiated with plasma and UV radiation treatment to generate free radicals for polymerization


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Modification – Co-electrospinning

Nanoparticles and functional polymer segments can be directly exposed on surface of nanofibers Co-electrospinning with bulk polymers

Any combination of electrospinnable polymer and polymer conjugate can be used


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Target Molecule Loading on Surface

Simple physical adsorbtion Nanopoarticle assembly on surface Layer by layer multilayer assembly Chemical immobilization


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Applications – Drug Delivery Superior adhesiveness to biological surfaces Variety of structures containing drug molecules Drug release mechanism – polymer degradation and diffusion pathway Can tailor drug release profiles by varying polymer properties, surface coating,

combination of polymers Has been successful in laboratory trials – controlled topical release


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Applications – Tissue Engineering Various cells cultivated on nanofibrous meshes

Embryonic stem cells, mesenchymal stem cells Better than other tissue engineering methods

Coronary artery cells Collagen Limited to in vitro studies because cells could not be loaded within the

nanofibrous meshes in large quantities 3D nanofibrous scaffolds


http://pcsl.mit.edu/images/nano.jpg

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Improvements and Further Research Develop more precise electrospinning techniques Mechanisms of electrospinning Growth rates Bending Instability Producing nanofabrics with specific mechanical

properties. Creating 3-dimensional shapes Capable of being used in controlled release of drugs.


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Improvements and Further Research

Optimization of parameters Intrinsic properties of solution Polarity, surface tension of solvent Controlling nanofiber alignment Electric field Modifying type of collector Better control of fiber alignment

"Electrospin Nanofibers for Neural Tissue Engineering."

http://www.rsc.org/ejga/NR/2010/b9nr00243j-ga.gif

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Improvements and Further Research

Reduce Cost of Production Make economically viable Increase production rate Incorporate the use of an array of

spinnerets Safety Solvents Dangerous to health and environment Polymers


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References

Burger, Christian, Benjamin S. Hsiao, and Benjamin Chu. "Nanofibrous Material and Their Applications." Review. 25 Apr. 2006. Web. 14 Feb. 2010.

Hunley, Matthew T., and Timothy E. Long. "Electrospinning Functional Nanoscale Fibers: a Perspective for the Future." Polymer International 57 (2008): 385-89. Web. 7 Mar. 2010.

Theron, J. P., J. H. Knoetze, R. D. Sanderson, R. Hunter, K. Mequanint, T. Franz, P. Zilla, and D. Bezuidenhout. "Modification, Crosslinking and Reactive Electrospinning of a Thermoplastic Medical Polyurethane for Vascular Graft Applications." Acta Biomaterialia (2010). 27 Jan. 2010. Web. 05 Feb. 2010.

Xie, Jingwei, Matthew R. MacEwan, Andrea G. Schwartz, and Younan Xia. "Electrospin Nanofibers for Neural Tissue Engineering." Nanoscale 2 (2010): 35-44. Print.

Yoo, Hyuk S., Taek G. Kim, and Tae G. Park. "Surface-functionalized Electrospun Nanofibers for Tissue Engineering and Drug Delivery." Advanced Drug Delivery Reviews 61 (2009): 1033-042. Print.

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Thank you!!