Laser-assisted end-to-end BioWeld anastomosis in an ovine model

Improving the strength of sutureless laser-assisted vessel repair using preloaded longitudinal compression on tissue edge

BACKGROUND AND OBJECTIVE

Little is known about the approximation of coapted edges in sutureless laser-assisted vessel welding. Tissue shrinkage by laser irradiation may cause coapted edges to separate, reducing strength of welding. This may be avoided by preloaded longitudinal compression on the tissue edges to be welded. This study compared welding strength with and without preloaded compression in ex vivo animal experiments.

MATERIALS AND METHODS

This study evaluated 24 samples of harvested porcine carotid arteries, each having a length of 3 cm and an inner diameter of 1.0-2.0 mm. A half circumferential incision was made at the center of each sample. A steel shaft 2.0 mm in diameter was inserted into each sample to approximate the incised edges. The samples were longitudinally compressed to 6 mm. Incision sites were repaired by irradiation with a 970-nm diode laser. No glue or die was used. The repair strength was evaluated by measuring the bursting point (BP) of all samples. In a pilot study, the welding conditions, including power, duration, and interval of the laser spots, were tested by trial and error in 18 samples, including six treated under optimum conditions. As a control group, six samples were welded under optimum conditions, but without compression.

RESULTS

Optimum conditions, consisting of 2.4 W power, 30-second duration, and 1-mm intervals of laser spots, yielded the highest BP (623 ± 236 mmHg), which was significantly higher than in the control group without compression (204 ± 208 mmHg, P = 0.009). Defining BP > 400 mmHg as successful repair, the success rates in the compression and control groups were 83% and 17%, respectively.

CONCLUSION

Preloaded longitudinal compression on the coapted edges may be important for sutureless laser-assisted vessel repair and anastomosis and may affect the strength of welding. Lasers Surg. Med. 49:533-538, 2017. © 2017 Wiley Periodicals, Inc.

Photochemical tissue bonding with chitosan adhesive films

Background

Photochemical tissue bonding (PTB) is a promising sutureless technique for tissue repair. PTB is often achieved by applying a solution of rose bengal (RB) between two tissue edges, which are irradiated by a green laser to crosslink collagen fibers with minimal heat production. In this study, RB has been incorporated in chitosan films to create a novel tissue adhesive that is laser-activated.

Methods

Adhesive films, based on chitosan and containing ~0.1 wt% RB were manufactured and bonded to calf intestine 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, tested the bonding strength. K-type thermocouples recorded the temperature (T) at the adhesive-tissue interface during laser irradiation. Human fibroblasts were also seeded on the adhesive and cultured for 48 hours to assess cell growth.

Results

The RB-chitosan adhesive bonded firmly to the intestine with adhesion strength of 15 ± 2 kPa, (n = 31). The adhesion strength dropped to 0.5 ± 0.1 (n = 8) kPa when the laser was not applied to the adhesive. The average temperature of the adhesive increased from 26°C to 32°C during laser exposure. Fibroblasts grew confluent on the adhesive without morphological changes.

Conclusion

A new biocompatible chitosan adhesive has been developed that bonds photochemically to tissue with minimal temperature increase.

Heat denatured/aggregated albumin-based biomaterial: effects of preparation parameters on biodegradability and mechanical properties

Albumin-based biomaterials prepared using heat-aggregation or cross-linking agents have been used in various biomedical applications such as solder materials for laser-assisted tissue welding, anti-bacterial coatings and drug carriers. In this study, solid albumin-based materials were prepared via heat aggregation of albumin solution. The study aimed to determine the influences of the preparation parameters such as albumin concentration in solution, solution pH and temperature, on the mechanical properties as well as the biodegradation rate of heat-aggregated albumin-based materials. The results demonstrated that the materials prepared from the albumin solution with the pH of 8.5 had the highest mechanical strength. Augmenting the albumin concentration in solution led to an increase in mechanical strength, and the materials prepared from the solution with isoelectric albumin pH (pH 4.8) possessed the lowest biodegradation rate and those prepared at pH 12 showed the highest biodegradation rate.