Abstract: 【Objective】The effects of sodium carboxymethyl cellulose (CMC-Na) on the adhesion properties of soybean protein isolate (SPI) onto porcine bone were investigated by studying tensile bond strength, zero shear viscosity, secondary structure, hydrophobicity and scanning electronic microscopy (SEM) images. The aim of the research was to provide a basis for utilization of SPI adhesive in biomedical fields. 【Method】SPI adhesive prepared with/without CMC-Na was used to bond porcine bones in vitro and the effect of CMC-Na on tensile bond strength of SPI adhesive was measured using a tensile strength testing machine. The influence of CMC-Na on zero shear viscosity of the SPI adhesive was measured using a rheometer. The SPI adhesive with CMC-Na secondary structure was measured using circular dichroism spectra to determine the content of α-helix, β-sheet, β-turn and random coil. The influence of CMC-Na on hydrophobicity and surface morphology of SPI adhesive was measured using ANS (1-anilino-8-naphthalene sulfonate) fluorescent probe method and scanning electron microscopy (SEM), respectively. 【Result】 The tensile bond strength of the SPI adhesive increased with the increase of its concentration and reached a peak at a SPI adhesive concentration of 10%, then began to decline. The adhesive strength of 2% SPI with addition of a trace amount of CMC-Na (at 0.01%) was increased 2.4 fold (P<0.01) in comparison with the control. There was a significant positive correlation (r=0.815, P<0.05) between adhesive strength and zero shear viscosity. The addition of trace CMC-Na influenced significantly the secondary structure of the SPI adhesive. The β-sheet and β-turn content increased from 42.2% to 49.1% and from 2.1% to 7.3%, respectively, while the α-helix and random coil content declined from 28.0% to 19.7% and from 27.7% to 23.9%, respectively. The hydrophobicity of the SPI adhesive with CMC-Na was increased significantly; even moderate hydrophobic modification of the SPI adhesive with CMC-Na benefited the increase of its adhesive strength. SEM showed that particles on the surface of the SPI adhesive with addition of CMC-Na arrayed more uniformly and compact than the control, which was beneficial for its adhering to the bones. 【Conclusion】The addition of a trace amount of CMC-Na caused significant changes in the secondary structure of the SPI adhesive, the decline in α-helix content and an increase in β-sheet content, all of which indicated the unfolding of protein molecules and the aggregation of unfolding protein molecules. The increase in the hydrophobicity and zero shear viscosity of the SPI adhesive resulted in the significant increase of bond strength of low concentration SPI adhesive onto porcine bone. Since low concentration SPI might be easier to be absorbed by bodies than at a high concentration, our results after the addition of CMC-Na suggest that SPI adhesive has a great potential to be utilized as an adhesive in medical fields.

Key words: soybean protein isolate (SPI), sodium carboxymethyl cellulose (CMC-Na), adhesion properties