Solubilization and protection of curcumin by mixed surfactants / 药学学报

The solubilization and protection of curcumin (Cur) by mixed surfactants were studied through the determination about the critical micellar concentration (CMC) of the mixed surfactants of Tween 80 and dodecyl trimethyl ammonium bromide (DTAB), molar solubilization ratio (MSR), degradation rate (k) of Cur in pH 13 solution and mixed surfactant solutions prepared at pH 13. The results showed that when Tween 80 was used alone, it exhibited high solubilization ability but poor stability. DTAB was used alone, it showed strong stability but poor solubilization ability. When DTAB was mixed with Tween 80 at different mole fractions, the stability of Cur was enhanced, and the best stability was observed when the mole fraction of DTAB was 0.4, although the solubilization ability was not the best at this mole fraction, but MSR was increased by 1.7 times compared to DTAB used alone. Mixed surfactant not only increased the solubility but also improved the stability of Cur. In addition, mixed surfactant has the advantages of less dosage and low toxicity, which is worth popularizing in application.

Determination of contact angle of pharmaceutical excipients and regulating effect of surfactants on their wettability / 药学学报

To study the effects of surfactants on wettability of excipients, the contact angles of six types of surfactants on the surface of two common excipients and mixture of three surfactants with excipients were measured using hypsometry method. The results demonstrated that contact angle of water on the surface of excipients was associated with hydrophilcity of excipients. Contact angle was lowered with increase in hydrophilic groups of excipient molecules. The sequence of contact angle from small to large was starch < sodium benzoate < polyvinylpyrrolidone < sodium carboxymethylcellulose < sodium alginate < chitosan < hydroxypropyl methyl cellulose <magnesium stearate. In addition, surfactants both in droplets and mixed in excipients significantly reduced the contact angle of excipients, and their abilities to lower contact angle varied. The results of the present study offer a guideline in the formulation design of tablets.

Changes of IA and IK from the pyramidal neurons at hippocampal CA1 during the early development of rats / 生理学报

Brain growth spurt (BGS) is the critical period of neuronal growth and synaptic connection. The voltage-gated K(+) channel is the key channel for maintenance of cell excitability and information transfer among neurons. The purpose of the present study is to investigate the critical period of voltage-gated K(+) channel development in hippocampal CA1 neurons during the BGS. Changes of voltage-gated K(+) currents in neurons from acutely isolated hippocampal CA1 brain slices of rats at different ages (0-4 weeks after birth) were recorded by the whole-cell patch-clamp technique. The depolarization voltage was set at +90 mV, and 0 week was set as the control group. The experimental results showed that, with increasing ages (1-4 weeks), the maximum current densities of IA increased by (16.14 ± 0.51)%, (81.73 ± 10.71)%, (106.72 ± 5.29)%, (134.58 ± 8.81)% (n = 10, P < 0.05), and the maximum current densities of IK increased by (16.75 ± 3.88)%, (134.01 ± 2.85)%, (180.56 ± 8.49)%, (194.5 ± 8.53)% (n = 10, P < 0.05), respectively, compared with those in 0 week. During 0-4 weeks after birth, the activation kinetics of IA shifted to left, and the half activation voltages of IA were 14.67 ± 0.75, 13.46 ± 0.64, 8.39 ± 0.87, 4.60 ± 0.96, 0.54 ± 0.92 (mV, n = 10, P < 0.05), respectively; The activation kinetics of IK shifted to left and the half activation voltages of IK were 8.94 ± 0.85, 6.65 ± 0.89, 0.47 ± 1.15, -1.80 ± 0.89, -8.56 ± 1.08 (mV, n = 10, P < 0.05) respectively. The inactivation kinetics of IA also shifted to left, and the half inactivation voltages were -45.68 ± 1.26, -46.81 ± 0.78, -48.64 ± 0.81, -51.96 ± 1.02, -58.31 ± 1.35 (mV, n = 10) respectively at 0, 1, 2, 3 and 4 weeks after birth, which showed no significant changes between 0 and 1 week, but significant decreases during 1-4 weeks after birth (P < 0.05). These results indicate that the current densities of IA and IK increase and the kinetic characteristics of the voltage-gated K(+) channels change with increasing ages during 0-4 weeks after birth, and the differences are especially significant between the 1st week and the 2nd week after birth. These changes may be related to the maturation of hippocampal neurons and the progress of their functions.

Changes of Na(+) channels in rat hippocampal CA1 neurons in early development after birth / 生理学报

The purpose of this research is to investigate the critical period of voltage-gated Na(+) channel development in hippocampal CA1 neurons. Changes of Na(+) currents in acutely isolated hippocampal CA1 neurons of rats at different ages (0-4 weeks after birth) were recorded using the whole-cell patch-clamp technique. The results indicated that the maximum current density of Na(+) channels was increasing with age, and the amplitudes in 1, 2, 3 and 4 weeks respectively grew by (42.76 ± 4.91)%, (146.80 ± 7.63)%, (208.79 ± 5.28)% and (253.72 ± 5.74)% (n = 10, P < 0.05) compared with that in 0 week. The current density in CA1 neurons of 1-2 weeks after birth increased more significantly than those of other groups. The activation curve of Na(+) channel shifted to the left. The half-activation voltages (mV) in 0-2 weeks were -39.06 ± 0.65, -43.41 ± 0.52, -48.29 ± 0.45 (n = 10, P < 0.05), respectively, showing significant age-dependent decrease, and there were no significant changes in other groups. The slope factors of activation curve for each group did not change significantly. There were no regular changes in inactivation curve and no significant changes in half-inactivation voltage. The slope factors of inactivation curve in 1-2 weeks were: 5.77 ± 0.56, 4.42 ± 0.43 (n = 10, P < 0.05). The inactivation rate of the second week after birth was faster than that of the first week, and there were no significant changes during 0-1 week and 2-4 weeks. The recovery from inactivation curve of Na(+) channel shifted to the left. The recovery time declined in 1-3 weeks. Changes of action potential properties were consistent with Na(+) current. These results suggest that the period of 1-2 weeks after birth may be the critical development period of voltage-gated Na(+) channel in hippocampal CA1 neurons. During this time, the distribution of Na(+) channel increases significantly; the activation curve of Na(+) channel shifts to the left; inactivation rate increases as well as recovery time shortens.