RESUMEN
A sensitive electrochemical sensor for the detection of semicarbazide ( SEM ) based on the glassy carbon electrode modified with carboxylated multi-walled carbon nanotube ( CMWCNTs ) was constructed in this work. The modified materials were characterized by Fourier transform infrared spectroscopy, transmission electron microscopy and electrochemical impedance spectroscopy. The results showed that the CMWCNTs exhibited a certain degree of changes, such as the appearance of the characteristic peaks of carbon oxygen double bonds in carboxyl group, a decrease in diameter and length and a remarkable reduction of the impedance value. The electrochemical behavior of SEM on CMWCNTs/GCE was investigated by cyclic voltammetry and amperometric i-t curve in 1 mol/L HAc-NaAc buffer solution. An irreversible oxidation peak of SEM appeared at CMWCNTs/GCE. Compared to the bare electrode, the current of the oxidation peak was significantly increased. Under the optimal conditions such as HAc-NaAc solution ( pH 7 ) and scan rate of 0. 1 V/s, the obtained sensor presented linear response to SEM concentration in the range of 5. 0 × 10-6 mol/L-1. 09×10-3 mol/L, the linear regression equation was Ip(μA)=-0. 472+0. 0599C (μmol/L) with linear correlation coefficient of 0. 997. The detection limit was 1. 88×10-7 mol/L. At the same time, the recovery was from 92. 8% to 98. 0% in the test of pork liver samples.
RESUMEN
A sensitive electrochemical sensor for the detection of semicarbazide ( SEM ) based on the glassy carbon electrode modified with carboxylated multi-walled carbon nanotube ( CMWCNTs ) was constructed in this work. The modified materials were characterized by Fourier transform infrared spectroscopy, transmission electron microscopy and electrochemical impedance spectroscopy. The results showed that the CMWCNTs exhibited a certain degree of changes, such as the appearance of the characteristic peaks of carbon oxygen double bonds in carboxyl group, a decrease in diameter and length and a remarkable reduction of the impedance value. The electrochemical behavior of SEM on CMWCNTs/GCE was investigated by cyclic voltammetry and amperometric i-t curve in 1 mol/L HAc-NaAc buffer solution. An irreversible oxidation peak of SEM appeared at CMWCNTs/GCE. Compared to the bare electrode, the current of the oxidation peak was significantly increased. Under the optimal conditions such as HAc-NaAc solution ( pH 7 ) and scan rate of 0. 1 V/s, the obtained sensor presented linear response to SEM concentration in the range of 5. 0 × 10-6 mol/L-1. 09×10-3 mol/L, the linear regression equation was Ip(μA)=-0. 472+0. 0599C (μmol/L) with linear correlation coefficient of 0. 997. The detection limit was 1. 88×10-7 mol/L. At the same time, the recovery was from 92. 8% to 98. 0% in the test of pork liver samples.
RESUMEN
BACKGROUND:In senile osteoporosis patients, capacity of pedicle screw fixation is relatively poor due to fragile bone substance. Currently, augmentation of pedicle screw fixation with bone cement can improve the ability of screw fixation, but bone cement leakage and difficulties in screw removal become the problem to be solved. OBJECTIVE:To develop a novel pourable pedicle bone cement and to investigate its biomechanical properties, safety and practicality, thus providing the basis for clinical treatment of osteoporosis and spinal diseases. METHODS:Six cases of complete wetting spines were colected at the Affiliated Hospital of Nanjing University of Traditional Chinese Medicine from December 2013 to January 2015, including 42 vertebrae. Pedicle screw fixation with X-ray assisted bone cement injection (2 mL) was performed unilateraly as experimental group, and conventional pedicle screw fixation was done contralateraly as control group. Bone cement dispersion was observed in the two groups. RESULTS AND CONCLUSION:It was 3-4 minutes for bone cement to agglomerate. Injection of bone cement paste into the infusion cylinder using a syringe was more convenient. The cylinder was connected tightly with the tail-end of the screw with no leakage. The push bar could provide sufficient perfusion force. Bone cement dispersion was found in the holow part and side holes of the screw. Side holes arranged regularly, and the hole pitch was equal. Compared with the control group, the yield load and yield displacement were significantly higher in the experimental group (P < 0.05), but the ultimate strength and ultimate displacement were significantly lower in the experimental group (P < 0.05). Bone cement around the pourable cement screw dispersed regularly, which was diffused into the surround cancelous bone and integrated with adjacent bone cement mass. The axial withdrawal force was increased by 114% in the experimental group compared with the control group (P < 0.05). The maximum rotary torque was significantly higher in the experimental group than the control group (P< 0.05). These finding suggest that the new pourable cement screw combined with bone cement putter and infusion cylinder is applied more convenient, can effectively control the leakage of bone cement, and can improve the stability of the pedicle in osteoporosis patients, which has been widely used.