Objective To study the effects of excitation source, intraocular pressure and material parameters on frequency response of human eye under acoustic excitation. Methods Based on the three-dimensional (3D) finite element model of the whole eye, as well as the deformation and stress distribution of human eye, the effects of various parameters on frequency response of human eye were quantitatively analyzed. Results When other parameters were fixed and only the position and size of the excitation source changed, the amplitude at resonance of human eye (the acoustic excitation source was placed directly above the cornea, at an offset of 45°, and at larger excitation) at 134 Hz was 35, 48 and 133 μm, respectively. When only the intraocular pressure changed, the first-order resonance frequency was almost unaffected by the intraocular pressure, and the resonance frequencies of other orders would shift slightly to the left as the intraocular pressure increased. When only the scleral elastic parameters changed, the resonance frequency of eye tissues increased with the increase of the scleral elasticity. Conclusions The position and size of the excitation source have no effects on resonance frequency of human eye, but they have a greater effect on the resonance amplitude. The material parameters of human eye tissues have a greater effect on the frequency response, and there is a linear relationship between the intraocular pressure and resonance frequency. The results provide the theoretical basis for clinical development of high-performance intraocular pressure monitoring technology.

Heparin is a very important anticoagulant drug. Currently, heparin is mainly extracted from porcine mucosa. However, animal-derived heparin shows low anticoagulant activity due to the low proportion of the anticoagulant active unit, the GlcNS6S-GlcA-GlcNS6S3S-Ido2S-GlcNS6S pentasaccharide. In this study we proposed an enzymatic strategy to sulfate the animal-sourced heparin to increase the proportion of anticoagulant pentasaccharide and the anticoagulant activity. First, three sulfotransferases HS2ST, HS6ST, and HS3ST were expressed tentatively in Escherichia coli and Pichia pastoris. After measuring the sulfotransferase activity, we confirmed P. pastoris GS115 is the better host for sulfotransferases production. Then, the maltose binding protein (MBP) and thioredoxin (TrxA) were fused separately to the N-terminal of sulfotransferases to increase enzyme solubility. As a result, the yields of HS2ST and HS6ST were increased to (839±14) U/L and (792±23) U/L, respectively. Subsequent sulfation of the animal-sourced heparin with the recombinant HS2ST, HS6ST and HS3ST increased the anticoagulant activity from (76±2) IU/mg to (189±17) IU/mg.
Animals ; Escherichia coli ; Heparin ; chemistry ; Oligosaccharides ; chemistry ; Pichia ; Sulfotransferases ; biosynthesis ; Swine