Albumin-genipin solder for laser tissue-welding

Background. Laser tissue soldering (LTS) is an alternative technique to suturing for tissue repair. One of the major drawbacks of LTS is the weak tensile strength of the solder welds when compared to sutures¹. In this study, the possibility was investigated for a low cytotoxic crosslinker², acting on amino groups, to enhance the bond strength of albumin solders. Materials and Methods. Solder strips were welded onto rectangular sections of sheep small intestine by a diode laser. The laser delivered in CW mode a power of 170 ± 10 mW at 1=808 nm, through a multimode optical fiber (core size=200 mm) to achieve a dose of 10.8 ± 0.5 J/mg. The solder thickness and surface area were kept constant throughout the experiment (thickness = 0.15 ± 1mm, area = 12±2 mm ²). The solder incorporated 62% bovine serum albumin, 0.38% genipin, 0.25% indocyanin green dye (IG) and water. Tissue welding was also performed with a similar solder, which did not include genipin, as a control group. The repaired tissue was tested for tensile strength by a calibrated tensiometer. Pellets of genipin and albumin solders were also heated at 70°C and incubated for 24 hours with EMEM media at 37°C. Mouse fibroblasts (L-929) were subsequently grown in media extracted from both solders to assess cell cytotoxicity (0.18 g/ml). Positive controls used included mixing ethanol with cell media at various concentrations in separate samples (4%, 5%, 7.5%) and negative controls were with no extract or ethanol. Results. The tensile strength of the genipin solder was twice as high as the strength of the BSA solder, as shown in figure 1 (0.21 ± 0.04 N and 0.11 ± 0.04 N respectively; p∼10^-15 unpaired t-test, N=30). Fibroblasts grown for 48 hours with no inhibition in media extracted from both genipin and albumin solders. Discussion. Addition of genipin, a non-toxic crosslinking reagent, significantly increased the tensile strength of adhesive-tissue bonds. A proposed mechanism for this enhanced bond strength is the synergistic action of mechanical adhesion with chemical crosslinking by genipin.