o Commonly used methods (thermal, chemical,
mechanical and ultrasound) cannot offer much
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
o We cannot easily manipulate intercellular mechanisms
with common methods.
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.
o Lasers are commonly used in general and other
o Basic principles behind these applications of lasers are
the following laser-tissue interactions-
o Dermatological applications.
o Ophthalmic applications.
o Laser angioplasty.
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.
o Here tattoo pigment is the target chromophore.
o Laser light causes extremely rapid heating of tattoo
o This fractures these sub micrometer particles and kills
the cells that contain them.
o Based on laser-tissue interactions.
o The 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
810 nm 2.1
2W 20mJ 50-
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.
o Introduced by Jain and Gorisch(1979), who used Nd:YAG
laser light to seal rat arteries.
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.
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.
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).
oUsing laser light to repair tissue damage after
Computer-Aided Tissue Engineering.
New Laser Solders and Dyes to Assist
Mechanism of Tissue Ablation and
Introduction To Biophotonics
Paras N. Prasad
Laser Surgery and Medicine: Principles and Practice,
Cutaneous Laser Surgery,
Mosby, St. Louis