Repairing wounds with a light stitch
Senior editor Charles T. Troy reported in the September issue
that laser radiation can be used effectively to bond wounds on the battlefield in
combination with dyes to heat the tissue (“Treating battlefield injuries with light,” p. 16). The article covered the work of Dr. Irene Kochevar at Harvard
Medical School in Boston and Massachusetts General Hospital’s Wellman Center,
and of Dr. Robert Redmond, also at Wellman.
An approach known as laser tissue welding (LTW) uses laser energy
at a certain wavelength, bypassing foreign materials or agents, to muster wound
welding. A team at the Institute for Ultrafast Spectroscopy and Lasers (IUSL) at
The City College of New York (CCNY), led by professor Robert R. Alfano, has spent
10 years researching the use of lasers to bond wounds without foreign molecules
– first with in vitro pig tissue and arteries1 and, later, with live piglets
using laser radiation in the near-IR.2
The magic of LTW was achieved by photoexciting the vibrations
of the native molecules that exist in the tissue, primarily water. The researchers
used a tunable forsterite laser for the bonding, covering 1150 to 1350 nm, which
revealed that the tensile strength followed the spectral shape of the absorption
of water. The water absorption in this near-IR spectral range results from the combination
of the three primary vibrational modes of water molecules. The mechanism that produces
almost-scar-free results arises from the rapid energy transfer from the water surrounding
the collagen fibers to the collagen, the building block that gives tissue its structure.
The team also has achieved satisfactory welding on pig aorta and
in guinea pigs (quality-/functionally wise: histology/tensile strength) using fiber
laser pulses near 1450 nm without the need for foreign binding material. The tensile
strength of the welded tissue is very similar to original tissue samples and shows,
histologically, very little or no evidence of scarring in the welded area. Currently,
the limiting factor is the speed of the welding, which may be addressed in a variety
As for the mechanism of action of laser stitch, the laser energy
delivered to water molecules – in abundance around the disrupted collagen
fibers – is transferred to the collagen fibers, which undergo a number of
molecular transformations, resulting in the creation of hydrogen and covalent bonds.
Robotic surgery using systems such as the da Vinci from Intuitive
Surgical Inc. of Sunnyvale, Calif., is gaining considerable interest in every field,
from intracavitary (intracranial, thoracic and abdominal) to nonintracavitary (peripheral
vessels, nerves, cosmesis) procedures for reasons including greater precision, blood
sparing and faster recovery. The incorporation of LTW into robotic surgery will
be a further advance without the addition of foreign agents into the surgical field.
Laser technology in surgery currently is used to incise, to excise,
to induce scarring, to coagulate or to destroy. The IUSL team intends to add another
constructive dimension for tissue welding in structures that require closure, such
as blood vessels, nerves, viscera and skin. The benefits will include fast closure
and healing, liquid tight and low probability of breakdown because of the very low
risk of infection without foreign materials. CCNY’s patented LTW method3 should
be excellent for the battlefield as well as for the operating room.
The tissue welding methodology of using water as the native bonder
agent with the near-IR lasers offers a novel, simple and efficient way to close
any incision. CCNY has achieved welding without any adjuvant material, and this
will become the preferred method used by surgeons in the operating room and on the
Stephane Lubicz, M.D.IUSL
The City College of New York
1. A. Alimova et al (2009). In vivo molecular evaluation of guinea
pig skin incisions healing after surgical suture and laser tissue welding using
Raman spectroscopy. J Photochem and Photobiol B: Biology, Vol. 96, pp. 178-183.
2. J. Tang et al (2000). A comparison of cunyite and forsterite
NIR tunable laser tissue welding using native collagen fluorescence imaging. J Clin
Laser Med and Surg, Vol. 18, pp. 117-123.
3. R.R. Alfano et al (April 25, 2006). Gelatin based on power-gel
as solders for Cr4+ laser tissue welding and sealing of lung air leak and fistulas
in organs. #7,033,348 B2.
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