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Traditional protein solders composed of serum albumin, an optional absorption chromophore, and water, are soluble in physiological fluids before laser irradiation. This can be problematic for application of the solder to the tissue, as some of the material tends to run away before it is bonded to the tissue. In addition, as the solder is subjected to blood dilution during application, the mechanical properties are altered and consequently, the strength of the repair is compromised. This ultimately leads to poor reproducibility and reliability of the repair technique. Enhancement of these protein solders with a synthetic polymer membrane composed of poly(L-lactic-co-glycolic acid) was investigated as a means for increasing the stability of the solders in physiological fluids prior to irradiation. In addition, predenaturation of both the traditional and membrane enhanced solders in a hot water bath at 75°C was investigated as a means to decrease the solubility of the solders, thus improving their handling characteristics, prior to laser irradiation. A Bradford protein assay was used to measure the solubility of the protein solders prior to thermal denaturation with a laser. To compare these results with the final product of laser tissue repairs, the solubility analysis was also performed on similar specimens after laser irradiation with an 805-nm diode laser. Doping of the solder in a polymer membrane and predenaturation of the solders at 75 °C were found to be advantageous for improving their handling characteristics. Alteration of the mechanical properties of the solders prior to laser treatment was also prevented, thus improving the reproducibility and reliability of the repairs. Finally, the solubility of protein solders of varying composition was correlated with the mechanical strength of arterial repairs formed in an in vitro porcine model. The data suggests that there should be an optimal solubility at which solder/tissue contact is maximized and solder runaway minimized, thus resulting in a superior bond.
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