Dual-functional Nanofibrous Enzyme For Biochemical Protection

Nowadays, as the increasing use of organophosphates(OPs), an effective method for the human body protection from OP poisoning in both civilian and military domains is urgent for research. The organophosphorus hydrolase(OPH) is widely used for OP degradation, for example organic phosphorus pesticide. While, OPs usually combine with moisture or dust in the air to transform into OPs-adhesive aerosol particles. Electrostatic nanofibers with high specific surface area and porosity can used for the filtration of OPs-adhesive aerosol particles. But, OPH or nanofibers used alone is difficult to effectively protect human body from OPs. This paper firstly prepared polyamide 66(PA-66) nanofibrous membrane carriers by nanospider electrospinning. OPH was immobilized on the PA-66 nanofibers for the preparation of dual-functional enzyme membrane. The model system of practical application was further built up for OP filtration and degradation dual-functional enzyme membrane realizing. The details in this study were summarized as follows:Firstly, PA-66 nanofibers with 14%w/w were prepared by nanospider electrospinning. The solvents of formic acid and acetic acid was 1:2 by weight. The PA-66 nanofibrous membrane with a uniform diameter of 250-300 nm were electrostatic spinning at 80 kV, 170 cm of electrode spacing and 8 r/min of electrode speeds. The electrospinning time changed from 2 to 8 min with the membrane thicknesses from 15 to 70 ?m, and the pore size was 95 nm. The PA-66 nanofibrous membrane was tested to 0.3 ?m Na Cl aerosols by TSI-8130 with a high filtration efficiency of over 99%.Secondly, the PA-66 nanofibrous membrane carrier immobilized with OPH and the dual-functional PA-66 nanofibrous enzyme membrane was prepared. The specific activity of native OPH was 0.24 U/mg with the OPH protein content of 309.7 ?g/mL and the molecular weight of 45 k D. The PA-66 nanofibrous membrane was activated in 3 mol/L HCl for 2 h. The nanofibrous membrane was then transferred into 25%v/v OPH solution after washing, and was subsequently cross linked by 0.5%v/v GA for 3 h. The PA-66 nanofibrous enzyme with 20 ?m thickness exhibited a specific activity of 41 U/g with the OPH loading of 16.5 ?g/mg; the enzyme activity recovery was 53.3%; the methyl parathion(MP) degradation efficiency was 40%; the particle filtration efficiency was over 99%. The dual-functional enzyme membrane contact angle reduced to 69.82 o from 92.59 o after immobilization, and the strain-stress increased from 3 MPa to 3.5 MPa. The nanofibrous enzyme kept 35% of its initial activity after stored at 60 oC for 24 h and the residual activity was 40% after being stored for 30 d at 25 oC. After 10 repeated uses, the residual activity of the nanofibrous enzyme was 37%, and 70% of its initial activity was retained after incubation in xylene solvent for 24 h.Thirdly, modified PA-66 nanofiber was compared with PA-66 nanofiber in immobilization methods and results. The modified PA-66 nanofiber was easier for immobilization and expressed better immobilization results. OPH was further immobilized in dry method on the modified PA-66 nanofiber with pp spunbonded nonwoven fabric. The pp/modified dual-functional nanofibrous enzyme exhibited high mechanical strength, good hydrophilic modification, air permeability and moisture permeability, and inhalation and exhalation resistance with excellent filtration efficiency of over 99.9%. The model system of practical application was set up; the pressure drop was-20 KPa; the OPH concentration was 1100 ?g/mL; MP concentration was 0.1 mg/mL. The penetration time of reaction system was 14 min and the degradation efficiency was 29%, which realized the filtration-degradation dual-functional enzyme membrane. 45% of its initial activity was retained after stored 45 d at 4oC; the residual activity of the dual-functional nanofibrous enzyme was 30% after 5 repeated uses. This research demonstrated the great application potentials of dual-functional nanofibrous enzyme as protecting materials in biochemical protection, aimed at military and civilian applications.