Fabrication and Application of Rose Bengal-chitosan Films in Laser Tissue Repair

Summary

Sutures are usually needed to repair tissue during surgical procedures. However, their application can be problematic as they are invasive and may damage tissue. The fabrication and application methods of a novel tissue adhesive are here reported. This adhesive film is laser-activated and does not require the use of sutures.

Abstract

Photochemical tissue bonding (PTB) is a sutureless technique for tissue repair, which is achieved by applying a solution of rose bengal (RB) between two tissue edges^1,2. These are then irradiated by a laser that is selectively absorbed by the RB. The resulting photochemical reactions supposedly crosslink the collagen fibers in the tissue with minimal heat production³. In this report, RB has been incorporated in thin chitosan films to fabricate a novel tissue adhesive that is laser-activated. Adhesive films, based on chitosan and containing ~0.1 wt% RB, are fabricated and bonded to calf intestine and rat tibial nerves by a solid state laser (λ=532 nm, Fluence~110 J/cm², spot size~0.5 cm). A single-column tensiometer, interfaced with a personal computer, is used to test the bonding strength. The RB-chitosan adhesive bonds firmly to the intestine with a strength of 15 ± 6 kPa, (n=30). The adhesion strength drops to 2 ± 2 kPa (n=30) when the laser is not applied to the adhesive. The anastomosis of tibial nerves can be also completed without the use of sutures. A novel chitosan adhesive has been fabricated that bonds photochemically to tissue and does not require sutures.

Protocol

1. Chitosan Adhesive Preparation

1. The chitosan powder is soluble in acetic acid solution; for the preparation of a stock solution of acetic acid (2% v/v), add 10 ml glacial acetic acid to 490 ml deionized water (DI-H₂O).
2. For the preparation of a stock solution of Rose Bengal (RB) (0.01% w/v) in acetic acid, weigh 5 mg of RB in a vial wrapped with aluminum foil to avoid photobleaching. Add 0.5 ml of DI-H₂O to dissolve the powder then add 49.5 ml of the acetic acid stock solution (described in section 1.1).
3. For the preparation of chitosan solution (1.7% w/v), weigh 0.85 g of chitosan powder (medium MW, 85% degree of a....

Discussion

The rose adhesive fabrication is based on a simple dry-cast process, though the dissolution of RB in acidic pH requires prolonged stirring of the chitosan solution. It is important to let the solution dry up until it becomes a water-insoluble film. This happens when the weight water content is ~10% in the dried film⁶. Insoluble films are usually obtained 2 weeks after dry-casting at standard conditions of temperature and pressure (~25 °C and ~1 atm). The mechanism of tissue bonding is not clear yet, althou.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Rose Bengal	Sigma-Aldrich	632-69-9
Chitosan (medium MW)	Sigma-Aldrich	10318AJ
Glacial acetic acid	Sigma-Aldrich	08050051	2% v/v in DI water
Magnetic stirrer	Heidolph	MR Hei-Mix S
Centrifuge	Beckman Coulter Inc.	Allegra X-12R
Spectrophotometer	Varian Inc., Agilent	Cary 4000 UV-Visible
Laser	CNI Laser	MGL-532
Micrometer	Mitutoyo	Series 227
Surgical microscope	Carl Zeiss, Inc.	OPMI