Effects Of Sodium Carboxymethyl Cellulose On Adhesion Properties Of Soybean Protein Isolate Onto Porcine Bones

Soybean protein is one of the most abundant and renewable plant proteins in the world.Enhancing and exploring utilization of soybean protein for adhesive applications could help to alleviate environmental problems and add value to agricultural products.Soy protein-based adhesives have become the popular and hot research target.In this study,safe,efficient,non-toxic medical soy protein-based adhesives have been studied.Effects of degreasing solvents on the extraction rate and purity of the soybean protein isolate(SPI)were investigated.The results showed that there were the significant differences in the residual amount of lipids of SPI and the extraction rate of 7S(P<0.01)between three different degreasing solvents: hexane-ethanol(V/V=2:1),hexane andethyl ether,but no significant differences in the extraction rate and purity of SPI(P>0.05).Compared to the other two degreasing solvents,ethyl ether had higher efficiency in decreasing,the residual amount of lipids of defatted soy flour and SPI at 0.3% and 0.2%,respectively,increasing the extraction rate and purity of 7S and11 S at 73.5%,84.8% and 77.3%,90.2%,respectively.The results indicated that ethyl ether was the best degreasing solvent for preparation of high-quality 7S and 11 S from soybean.The influence of pH,concentration,and curing time on the adhesive strength of soybean protein isolate(SPI)onto porcine bones was explored.The bonding performance parameters of SPI adhesive were optimized through orthogonal experiments.The results of single factor test showed that SPI concentration,pH(at6.5 and 8.5),and curing time(at 12 h and 36 h)had significant effects on the adhesive strength(P<0.05).The results of orthogonal experiments indicated that the optimal bonding performance of the adhesive was obtained at SPI concentration of 10%,pH of 6.5 and curing time of 48 h.Under the optimal condition the bonding strength of the SPI adhesive was 380 KPa,suggesting that SPI has a potential to be utilized as an adhesive in medical fields.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.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 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 ?-helix,?-sheet,?-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.The tensile bond strength of SPI adhesive increased with the increase of its concentration and reached a peak at 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 significant positive correlation(r=0.815,P<0.05)between adhesive strength and zero shear viscosity.Addition of trace CMC-Na influenced significantly the secondary structure of SPI adhesive.The ?-sheet and ?-turn content increased from 42.2% to 49.1%and from 2.1% to 7.3%,respectively,while the ?-helix and random coil content declined from 28.0% to 19.7%and from 27.7% to 23.9%,respectively.The hydrophobicity of SPI adhesive with CMC-Na was increased significantly,even moderate hydrophobic modification of SPI adhesive with CMC-Na benefited the increase of its adhesive strength.SEM showed that particles on the surface of SPI adhesive with addition of CMC-Na arrayed more uniformly and compact than the control,which was beneficial for its adhering to bones.Therefore,addition of a trace amount of CMC-Na caused significant changes in the secondary structure of SPI adhesive,decline in ?-helix content and an increase in?-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 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 high concentration,our results after addition of CMC-Na suggest that SPI adhesive has a great potential to be utilized as an adhesive in medical fields.Therefore,this study will provide insightful theoretical basis for developing the high-value processing and utilization of soybean protein as new medical bio-adhesives.