WELCOME

TISSUE ENGINEERING WITH LIGHT

MOHAMED NIJAS VS3ISP

WHY LIGHT?o Commonly used methods (thermal, chemical,

mechanical and ultrasound) cannot offer much accuracy.

o Usage of ultrasound has been found to have some negative impact on tissues.

o Thermal mechanism may produce collateral damage.

o Chemical methods may leave contaminants on the cell surface.

o We cannot easily manipulate intercellular mechanisms with common methods.

TISSUE ENGINEERING AND LIGHT ACTIVATION

Tissue engineering is a field of bioengineering that recently has seen an immense amount of growth.

It is a multidisciplinary field that has resulted in

1) Development of materials.2) Fabrication of engineering tools.3) Determination of biocompatibility and

reduced risk of dysfunction.4) Skills of implementation.

TISSUE ENGINEERINGLASER BASED TISSUE ENGINEERING.

TISSUE CONTOURING AND RESTRUCTURING.

TISSUE WELDING.

TISSUE REGENERATION.

TISSUE CONTOURING

AND RESTRUCTURI

NG.

TISSUE WELDING.

TISSUE REGENERATIO

N.

LASER TISSUE CONTOURING AND RESTRUCTURING

o Lasers are commonly used in general and other surgeries.

o Basic principles behind these applications of lasers are the following laser-tissue interactions-

Thermal effects. Photo Ablation.

Some Applications Of Laser Ablations.

oDermatological applications.oOphthalmic applications.o Laser angioplasty.oOtolaryngology.

DERMATOLOGICAL APLICATIONS OF LASERS.

o Based on the theory of selective photothermolysis.

o Allows highly localized destruction of light absorbing “targets” in skin.

o Minimal damage to surrounding tissue.

o Applications are as follows-

Removal of tattoos.

Treatment of vascular malformations.

Resurfacing.

Hair removal.

DERMATOLOGICAL APPLICATIONS OF LASERS.

Proced ure

Skin Resurfacing.

Hair Removal. Tattoo Removal.

Commonly used lasers

CO2 laser

Er:YAGlaser

Alexandrite laser

Diode laser

Nd:YAGlaser

Ruby laser

Q-switched frequency doubled Nd:YAG

Q-switched alexandrite laser

Wavelen gth

10.6 µm

2.94 µm

0.755 µm

0.81 µm

1.064 µm

0.694 µm

0.53 µm

0.75 µm

Pulse duration

800µsec

0.3-10msec

2-20msec

0.2-1sec

10-50msec

3msec

10-80nsec

50nsec

Fluence(energy)

3.5-6.5J/cm²

5-8J/cm²

25-40J/cm²

23-115J/cm²

90-187J/cm²

10-60J/cm²

6-10J/cm²

2.5-6J/cm²

REMOVAL OF TATTOOS.o Here tattoo pigment is the target

chromophore. o Laser light causes extremely rapid heating of

tattoo pigment granules.o This fractures these sub micrometer particles

and kills the cells that contain them.

OPHTHALMIC APPLICATIONS OF LASERS.o Based on laser-tissue interactions.oThe ophthalmic applications that correct

medical conditions fall into two categories:

1. Use of Visible or Near-Visible Infrared Laser Wavelengths to Treat Retinal Disease or Glaucoma.Example- for the treatment of retinal tears and glaucoma.

2. Use of Invisible Wavelengths for Refractive Surgery to Reshape the Cornea for Vision Correction.Example- Laser in situ keratomileusis(LASIK) and photorefractive keratectomy(PRK) for the treatment of myopia.

OPHTHALMIC APPLICATIONS OF LASERS.

Procedure.

Laser Photocoagulation

LTK LASIK

Commonly used lasers

Argon Ion laser

Krypton ion laser

Laserdiode

Ho:YAG laser

ArF excimer laser

Wavelength

514.5 nm

647 nm

810 nm

2.1µm

193 nm

Pulse duration

CW(.1-1)s

CW up to 10ѕ

CW up to 2s

Pulse(0.25-1)s

Pulse(15-25)ns

Power(energy)

0.05-0.2W

0.3-0.5W

2W 20mJ 50-250mJ

LASIK.o Mainly used for the correction of myopia (near-

sightedness).o Here a pulsed laser beam flattens the cornea by

removing more tissue from the center of the cornea than from its midzone.

o As a result, the focus of the eye moves further back toward its desired spot on the retina and corrects the vision for distance.

LASER TISSUE WELDING.o Introduced by Jain and Gorisch(1979), who used

Nd:YAG laser light to seal rat arteries.

Tissue BondingDirect Welding

of Tissues

Laser Solderin

g

Dye-enhanced Laser Solderin

g

OF TISSUE WELDING.o Microsurgery.o Reduced inflammation.o Faster healing.o Watertight seal.o Ease and speed of application.o Moreover it can be used endoscopically and

laproscopically to extent the range of its applications to cases where sutures or staples cannot be used.

DIRECT WELDING OF TISSUES.

Local heating up to ~60ºC-

80ºC.

Collagen is denatured

and its native triple

helical structure is uncoiled.

Collagen bonding is

formed.

Based on the principle of

photothermolysis.

LASER SOLDERING.o Laser light is utilized to fuse a proteineous

solder to the tissue surface.o It provides greater bond strength with less

collateral damage compared to direct welding.

o Commonly used lasers => CO2,Nd:YAG and CW.

o Solders used => Blood, egg-white albumin, proteins derived from blood fibrinogen and other albumins.

DYE-ENHANCED LASER SOLDERING.o An appropriate dye that will enhance

absorption of the used laser is added to the solder.

o Takes advantage of strong absorption of light by the selected dye and the efficient conversion of light into heat by dye dispersed in the solder.

o Allowed the ability to use more common and relatively inexpensive 808-nm diode laser with the help of a biocompatible dye, indocyanine green(ICG).

LASER TISSUE REGENERATION.oUsing laser light to repair tissue damage after an injury.

LASER

FUTUTRE APPLICATIONS.Computer-Aided Tissue Engineering.New Laser Solders and Dyes to Assist Soldering.Mechanism of Tissue Ablation and Welding.Femtolaser Technology.

REFERENCE.Introduction To Biophotonics

Paras N. Prasad Laser Surgery and Medicine: Principles and

Practice,Wiley-Liss

Cutaneous Laser Surgery,Mosby, St. Louis

Wikipedia

Dfygtruyiopiup[

Tyterwret

yu