Marwa Mahmoud Bedier

NANOTECHNOLOGY

Presented by : marwa bedier

             lecturer in endodontic departement

 NANOSCIENCE:

Is the study of phenomena and mainpulation of materials at the nanoscale (1-100 nanometers)

NANOTECHNOLOGY :

    sometimes shortened to "nanotech" is the manipulation of matter on an atomic and molecular scale.

    It’s the production of functional materials and structures in the range of   1-100nm

Nanoscale

                      









       Nanomaterials

categorized according to their dimensions as:

1- All three dimensions less than 100nm.

              e.g., Nanoparticles.

2- Two dimensions less than 100nm.

             e.g., Nanotubes.

 3-  One dimension less than 100nm.

                  e.g., thin films. 

What makes “ nano “ special ??

A-Quantum effect: 

       AT THE NANOMETER SCALE, the properties of matter, like   

            electrical conductivity, color, strength or weight change.

     This is consequence of the small size of the nanomaterials 

                        physicaly explained as Quantum effect.

                ex: - Bulk of silver is toxic, whereas Nanosilver has    

                                        antibacterial properties.

B- Surface to volume ratio:

   Nanomaterials have an increased surface to volume ratio compared to bulk materials; this means that for a given volume of a material, the external surface is greater if it’s made of nanomaterials sub-units than of bulk material.

C-Moreover Nanoparticles possess an extremly  large surface free energy so, often agglomerate to form either clusters or larger particles to minimize the total surface or interfacial energy of the system.

 
1- Fullerenes:
 
          Fullerene is any molecule composed entirely of carbon,
              in the form of a hollow sphere, ellipsoid, tube, and many other shapes.


A- Spherical fullerenes are also called buckyballs,
and they resemble the balls used in football (soccer).

B -Cylindrical carbon nanotubes or buckytubes.

Single-walled nanotubes (SWNTs) are a single pipe with a diameter in the range of 1–5 nm, while multi-walled tubes (MWNTs) have several nested tubes with lengths varying from 100 nm up to several tens of micrometers.

Shapes of Nanoparticles
 
       a-Nanorods
 
       Typically 1-100 nm in length, and used in nanomedicine as   
                                        imaging agents.

    
       Nanorods are of particular interest in a restorative context.
 
            
              Chen et al, have synthesized enamel-prism-like  
                            hydroxyapatite (HA) nanorods

B-Dendrimers and dendritic copolymers


Dendrimers are hyper-branched polymers with
 
 precise nano-architecture. “Hooks” on their

surfaces that can be used to attach the cell-

identification tags or  fluorescent dyes or  enzymes
and other molecules.
 
 
 
 

c-Quantum dots

Also known as nanocrystals, quantum dots are nanosized semiconductors that, can emit light in all colours of the rainbow.

 
They have been applied in biotechnology for cell labelling and imaging, particularly in cancer imaging studies.

D-Nanoshells

Also referred to as core-shells, nanoshells are spherical cores of a particular compound surrounded by a shell or outer coating of another, which is a few nanometers thick.

 *  Upon absorbing infrared light, release a lethal dose of intense heat.


*    Linking nanoshells to antibodies that recognize cancer cells has successfully allowed researchers to kill cancer cells without harming neighboring non-cancerous tissue.
 

E-Liposomes

   Liposomes are lipid-based liquid crystals

     used in the  pharmaceutical and cosmetic industries

 because of their capacity for breaking down inside cells.

               Liposomes were the first engineered nanoparticles used for drug delivery

F-Nanocapsules

Are 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.

Two different approaches to nanofabrication

Top –down approach:

Starting material is reduced in size

produce very small structures from large pieces

of materials

Bottom-up or self-assembly approach:

Construction of structure atom-by-atom   or

molecule-by-molecule

Methods of synthesis of nanoparticles.

Methods of synthesis of nanoparticles.

A- physical:

1- Attrition: macro or micro scale particles are ground  in a ball mill or

                                other size  reducing mechanism..

2-Pyrolysis:  thermochemical decomposition of organic material at elevated temperatures

                                      then  condensation on substrate surface.

Thermal plasma tourch : Delivery of the energy necessary to cause decomposition and 

                                                                    vaporization of the material through

Chemical vapour deposition , Hot wire CVD (HWCVD) – also known as catalytic CVD (Cat-CVD) or hot filament CVD (HFCVD), this process uses a hot filament.

 laser pyrolysis

Methods of synthesis of nanoparticles.

B- chemical method:

Sol-Gel:

     The sol-gel process is a wet-chemical technique (also known as chemical solution deposition) widely used recently in the fields of materials science and ceramic engineering.

    starting from a chemical solution (sol) which acts as the precursor for an integrated network (or gel)

The precursors are metal alkoxides

( compounds in which a metal is bonded to organic radical by oxygen atom)

Ex. Metal alkaloids of silica is tetraethyl orthosilicate ( Si (OC2H5) 4 )

            undergo hydrolysis and condensation reactions to form siloxane bond

( Si-O-Si ) then particles aggregate into a network.

                 Drying of the gel occurs when water are removed from the gel network.

                                       Grinding into powder or sintered into dense ceramic

                               They determine the in vivo distribution, biological fate, toxicity and the targeting ability of nanoparticle systems. In addition, they influence the drug loading, drug release and stability of nanoparticles.

           Generally nanoparticles have higher intracellular uptake due to their   

         small   size and relative mobility.

           Smaller particles also have greater risk of aggregation of particles  

         during  storage and transportation of nanoparticle dispersion.

As the surface electrical charges are formed,

an unequal charge distribution always exists

between a particle surface and the solvent,

The charge density at any distance from the surface is equal to the difference in concentration of positive and negative ions . Charge density is greatest near the colloid and gradually diminished toward zero as the concentration of positive and negative ions equal each other.

The  surface potential is related to the surface charge . As we leave the surface, the potential drops off, The potential measured at the interface of Stern layer and the diffuse layer is defined as zeta potential.

When the potential is low, attraction exceeds repulsion and the dispersion will aggregate.

Change in electrolyte concentration destroy the electric double layer, which results in particle agglomeration.

So Nanoparticles with a zeta potential above (+/-) 30 mV have been shown to be stable in suspension, as the surface charge prevents aggregation of the particles.

Characterization of Nanoparticles

* Stabilization of nanoparticale  achieved by:

(a) Surfacecoating:  of nanoparticles with hydrophilic polymers/surfactants

 (b) Formulation of nanoparticles with biodegradable copolymers with hydrophilic segments such as polyethylene glycol (PEG), polyethylene oxide, polyoxamer.

Applications of nanotechnology in various fields

 Computers

 Military Applications

 Solar cells

MEDICAL SCIENCE

NANODENTISTRY

Nanoparticles

 used as a physical approach to alter and improve the pharmacokinetic and pharmacodynamic properties of various types of drug molecules.

     They have been used in vivo to protect the drug entity in the systemic circulation, restrict access of the drug to the choosen sites and to deliver the drug at a controlled and sustained rate to the site of action.

A-Drug Delivery System:

                          Biodegradable polymeric nanoparticles,

Nanoparticles coated with hydrophilic polymer such as poly(ethylene glycol) (PEG) is known as long-circulating particles, have been used as potential drug delivery devices because of :

✓ Achieving the site-specific action of the drug at the therapeutically

optimal rate and dose regimen.

APPLICATION IN MEDICAL SCIENCE

Nanobots

   -  Drug carriers robots have walls that are just 5-10 nm thick and the inner drug-filled cell is usually 50-100 nanometers wide.

   - When they detect signs of the disease, thin wires in their walls emit an electrical pulse which causes the walls to dissolve and the drug to be released.

   - The drug  target a precise location which make the drug much more effective , reduce the chances of possible side-effects and the  time of drug release can be easily controlled  (Harry, 2005)

                                              Special sensor nanobots can be inserted into the blood under the

                                          skin where they check blood contents and warn of any possible diseases.  

                                                                                              (Harry, 2005) .

                             Nanobots can also be used to prevent heart-attacks by  removing fat deposits

                                                                  blocking the blood vessels.  (Harry, 2005).

Bone-like nanoparticles form an ordered structure which later becomes part of the bone

         (Adhikari, 2005).

 Nano-fibers called amphiphiles for  treatment of injured nerves (Weiss, 2005).

Nanoparticles made of a metal such as magnesium oxide, coated with antibodies.

Nanoparticles become localized around cancer cells; MRI shows a more detailed image of where the cancer is.

NANODENTISTRY

Orthodontic nanorobots could directly manipulate the periodontal tissues, allowing rapid and painless tooth straightening, rotating and vertical repositioning within minutes to hours.

Precisely and restricted to demineralized enamel and dentin

                                                  thus providing maximum conservation of the the tooth structure.                                       tooth structure.

        Colloidal suspension containing millions of active   
       analgesic dental  nanorobot particles  instaled  on the  
                                      patient’s gingiva.

          Moving nanorobots reach dentin by migrating into the  
        gingival sulcus, passing painlessly through the lamina.
   

        On reaching the dentin, the nanorobots enter dentinal    
      tubular and proceed towards the pulp, all under the control of   the   
                    onboard nanocomputer, as directed by the dentist.

  
           Nanorobots commanded to shut down all sensitivity in the tooth
                                            that requires treatment

 

         Nanorobots complete the journey into the pulp chamber in  

                                                        100 sec.

                                                                                        Formed of   silica  nanoparticles of size

20-75 nm that   are homogeneously  distributed in resins

         Advantages:

        • Superior hardness

        • Superior flexural strength, modulus of elasticity and

        • Translucency

        • 50% reduction in polymerization  shrinkage

        • Excellent handling properties

A-

Nanotechnology in dental Adhesive  (Bonding agents)

The aim of nanoparticles filler addition to dentin adhesives are to increase the mechanical properties and elastic modulus of adhesive layer, to improve the distribution of the stresses induced by resin composite polymerization shrinkage and occlusal loading, and consequently to increase the dentin bonding strength.

 B-

Intracanal irrigant :

Liquid (L)-form of Nanosilver particles.

The idea of Nano-featured scaffolds was based on the belief that they may create more favorable environment for, cells growth, nutrition and waste removal. since they mimic the nano-sized components of normal tissues.
   

Fioretti et al 2010  reported the first use of nanostructured multilayered films containing   a-MSH (melanocortin peptides)  as a new active biomaterial for endodontic regeneration.

     They showed that a-MSH possess anti-inflammatory properties:

Antimicrobial mechanisms of nanomaterials include:

1) Photocatalytic production of reactive oxygen species (ROS) that damage cellular and viral components.

2) Compromising the bacterial cell wall/membrane.

3) Interruption of energy transduction.

4) Inhibition of enzyme activity and DNA synthesis.

Different types of nanomaterials like copper, zinc, titanium, magnesium, gold and silver have come up …………………………

but silver nanoparticles have proved to be most effective as it has good antimicrobial efficacy against bacteria, viruses and other micro-organisms.

A-Silver Nanoparticles

1-The silver nanoparticles show extremely large surface area, which provides better contact with microorganisms. Doty et al.

2-The nanoparticles get attached to the cell membrane and also penetrate inside the bacteria. The silver nanoparticles interact with proteins in the bacterial cell as well as with the phosphorus containing compounds like DNA. Ghandour et al 1988.

3- In an aqueous microenvironment, silver nano-particles continuously release silver ion (Lok et al., 2007).

B-Chitosan Nanoparticles

Chitosan is a partially deacetylated chitin

               (a long biopolymer chain of N-acetylglucosamine).

The main sources exploited are marine crustaceans, shrimp

and crabs.

Chitin and chitosan are effective materials for biomedical applications because of their biocompatibility, biodegradability and non-toxicity.

These  biopolymers can be easily processed into gels, sponges, membranes, beads and scaffolds forms.

1-Binding to the negatively charged bacterial surface to cause agglutination, increasing the permeability of the microbial wall, which eventually induces a leakage of intracellular components.

2-chitosan chelates trace metals and thereby inhibits enzyme activities and the microbial growth.

3- It was also proposed that chitosan penetrates to the nucleus of fungi and inhibits RNA and protein syntheses.

 N.B yeasts and moulds are the most sensitive group, followed by Gram-positive bacteria and finally Gram-negative bacteria.

4-The lower molecular weight chitosans  have greate antimicrobial activity than native chitosans..

5-The Low pH increases the antimicrobial activity of chitosan

6-The temperature also has an effect, as higher temperature (37°C) has been shown to enhance antimicrobial activity compared to refrigeration temperatures.

7-The zeta potential of chitosan nanoparticulates can greatly influence its stability in suspension through the electrostatic repulsion between particles.

8- When positively charged chitosan nanoparticulates in an aqueous suspension are allowed to settle onto a substrate surface, the positive charge of the nanoparticles allows adherence to negatively charged dentin surface

NANO CARE PLUS

Based on the silver and gold nano particles

Used  during the final rinsing of root canal treatment.

It leaves the layer of long lasting nanoparticles on the canals surface,

which has a strong bacteriostatic effect and prevents the re-colonization of canal system by bacteria and fungi

NANO CARE PLUS

Low surface tension of the NANOCARE PLUS allows

    nanoparticles to get to the smallest fissures and dental

    ducts of the system.

Eliminate Enterococcus Faecalis

Nanoparticles of gold and silver does not undergo corrosion process, and their minimum concentration in the liquid allows the avoidance of any problems during the final canals filling followed by tooth filling.

D-Nanoparticles containing photosensitizers

Photodynamic Therapy

PDT is well-established for targeting various gram-positive

and gram-negative oral bacteria

Studies have shown incomplete destruction of oral biofilms

using PDT.(Soukos NS et al. 2007,Tegos GP & Hamblin MR 2006)

attributed to:

1-Reduced penetration of the photosensitizer

2-Photosensitizers, including MB and toluidine blue O, are substrates of  multidrug resistance pumps in bacteria, thus decreasing the effectiveness of the photosensitizer (Pagonis TC et al  2010)

Overcoming Deficiencies :

Developing Drug Delivery System that improve the pharmacological characteristics

   

 
E-Root canal filling material :

* Nanoseal

Recently experimental endodontic sealer (Nanoseal) has been prepared. This sealer is similar to various epoxy resin-based sealers, but with a calcium phosphate HA nanofiller.

Reactive nano particles can slow down the growth of bacteria and this in turn accelerates the process of recovery of infected teeth.

The size of the active nano particles can enter the accessory canals to ensure that all the spaces have been sealed effectively.

The similarity between the structure of the material with that of the teeth also increases the bio-compatibility between the material and the teeth, thereby increasing its adhesive strength.

 
E-Root canal filling material

 * (EndoSequence® BC Points™).

Unlike traditional points, EndoSequenceBC Points™ are subjected to a patented process of impregnating and coating each cone with bioceramic nanoparticles.

The bioceramic particles found in BC Sealer bond with the bioceramic particles in BC Points™ to form a true gap-free seal. A recent study showed that BC Sealer, when used in conjunction with our impregnated and coated cones, actually increased the fracture resistance to a level comparable to that of teeth that have not undergone root-canal therapy.

 
E-Root canal filling material

 * Novel Nano-Calcium Carbonate polyurethane based   
     R.C.F

 
F-Root–end filling material

 * DiaRoot BioAggregate Root Canal Repair Material

DiaRoot BioAggregate Root Canal Repair Material is a biocompatible pure white powder composed of ceramic nano-particles.

Upon mixing DiaRoot with  Liquid, the hydrophilic BioAggregate Powder promotes cementogenesis .

Its effectiveness to clinically block off bacterial infection, ease of material manipulation and superior quality make DiaRoot the most innovative and unique root canal repair material

Problems with using Nanotechnology

a- Environmental Problems

nanoparticles have a tendency to form aggregates that are very water soluble and bacteriocidal (capable of killing bacteria) and can be catastrophic as bacteria are the foundation of the ecosystem (Balbus et al-2005).

b-  Health Problems

1-Risk to Lungs  :worsen existing air disease such as asthma and bronchitis and can be fatal. (Donaldson, Stone, 2004)

2-Effects on Brain : nanoparticles that are inhaled can move upward into the base of the brain.  This may damage the brain and the nervous system and could be fatal. (Donaldson, Stone, 2004)

3-Problems in Blood : Nanoparticles flowing thorough the bloodstream may affect the clotting system which    may result  in a heart-attack

C. Feasibility Problems  

1-Expense

2-Lack of knowledge and research

d. Ethical Dilemma

   Nanotechnlogy gives  man a better quality of life, power to prevent diseases, speed up tissue reconstruction and alter his genetic sequence (Silva, 2004)

 People are using this technology to modify their unborn children to have the right hair or eye color….. In doing this people risk losing their individuality.