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Dynamics of T-Junction Solution Switching Aimed at Patch Clamp Experiments.

Auzmendi JA, Smoler M, Moffatt L - PLoS ONE (2015)

Bottom Line: The exchange time was found to increase quadratically with the delay, although a sizeable variability remains unexplained by this relationship.This effect would be present in all tubing based devices.Present results might be of fundamental importance for the adequate design of serial compound exchangers which would be instrumental in the discovery of drugs that modulate the action of the physiological agonists of ion channels with the purpose of fine tuning their physiology.

View Article: PubMed Central - PubMed

Affiliation: Instituto de Química Física de los Materiales, Medio Ambiente y Energía. Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina.

ABSTRACT
Solutions exchange systems are responsible for the timing of drug application on patch clamp experiments. There are two basic strategies for generating a solution exchange. When slow exchanges are bearable, it is easier to perform the exchange inside the tubing system upstream of the exit port. On the other hand, fast, reproducible, exchanges are usually performed downstream of the exit port. As both strategies are combinable, increasing the performance of upstream exchanges is desirable. We designed a simple method for manufacturing T-junctions (300 μm I.D.) and we measured the time profile of exchange of two saline solutions using a patch pipette with an open tip. Three factors were found to determine the timing of the solution switching: pressure, travelled distance and off-center distance. A linear relationship between the time delay and the travelled distance was found for each tested pressure, showing its dependence to the fluid velocity, which increased with pressure. The exchange time was found to increase quadratically with the delay, although a sizeable variability remains unexplained by this relationship. The delay and exchange times increased as the recording pipette moved away from the center of the stream. Those increases became dramatic as the pipette was moved close to the stream borders. Mass transport along the travelled distance between the slow fluid at the border and the fast fluid at the center seems to contribute to the time course of the solution exchange. This effect would be present in all tubing based devices. Present results might be of fundamental importance for the adequate design of serial compound exchangers which would be instrumental in the discovery of drugs that modulate the action of the physiological agonists of ion channels with the purpose of fine tuning their physiology.

No MeSH data available.


Related in: MedlinePlus

Time course of the forward exchange at different distances (horizontal panels) and pressures (line color) at the optimal position.Experimental data is indicated on black; fits to the equation (same as in Fig 2) are indicated on color. (A) The delay between the time of valve activation (arrow, ton) and the exchange increased with both distance and pressure. (B) Expanded time scales showed that the fit covered the data in all cases. The correlation coefficients for 1 mm were the following: 0.986, 0.980 and 0.974 for 0.1, 0.2 and 0.4 bar respectively. For 20 mm, they were: 0.984; 0.988 and 0.987 while for 51 mm: 0.985, 0.975 and 0.982. Finally for 70 mm were: 0.983, 0.982 and 0.980.
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pone.0133187.g003: Time course of the forward exchange at different distances (horizontal panels) and pressures (line color) at the optimal position.Experimental data is indicated on black; fits to the equation (same as in Fig 2) are indicated on color. (A) The delay between the time of valve activation (arrow, ton) and the exchange increased with both distance and pressure. (B) Expanded time scales showed that the fit covered the data in all cases. The correlation coefficients for 1 mm were the following: 0.986, 0.980 and 0.974 for 0.1, 0.2 and 0.4 bar respectively. For 20 mm, they were: 0.984; 0.988 and 0.987 while for 51 mm: 0.985, 0.975 and 0.982. Finally for 70 mm were: 0.983, 0.982 and 0.980.

Mentions: To characterize the changes that occur at this transient interface along its way we placed the T-junction at 1, 20, 51, 70 mm of the tip and measured the exchange dynamics (Fig 3). We also studied the effect of the velocity of the fluid on the interface by applying different propellant pressures (Fig 3, trace color indicates pressure). A delay between the time of valve activation and the time when changes in concentration were detected at the measuring tip was always clear; this delay increased both with increasing distance (Fig 3A, compare different panels) and with decreasing propellant pressure (Fig 3A, compare different plots at each panel). The exchange time increased in a similar way (Fig 3B). The colored fit lines covered the black data traces in Fig 3; the correlation coefficient indicated a good fit (R2 > 0.97) in all cases. For the same pressure, an increase in the distance traveled decreased α, the fraction of the response that is described by an error function, at the same propelled pressure (Table 1). Furthermore, the increased flow rate increased α (Table 1).


Dynamics of T-Junction Solution Switching Aimed at Patch Clamp Experiments.

Auzmendi JA, Smoler M, Moffatt L - PLoS ONE (2015)

Time course of the forward exchange at different distances (horizontal panels) and pressures (line color) at the optimal position.Experimental data is indicated on black; fits to the equation (same as in Fig 2) are indicated on color. (A) The delay between the time of valve activation (arrow, ton) and the exchange increased with both distance and pressure. (B) Expanded time scales showed that the fit covered the data in all cases. The correlation coefficients for 1 mm were the following: 0.986, 0.980 and 0.974 for 0.1, 0.2 and 0.4 bar respectively. For 20 mm, they were: 0.984; 0.988 and 0.987 while for 51 mm: 0.985, 0.975 and 0.982. Finally for 70 mm were: 0.983, 0.982 and 0.980.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4503516&req=5

pone.0133187.g003: Time course of the forward exchange at different distances (horizontal panels) and pressures (line color) at the optimal position.Experimental data is indicated on black; fits to the equation (same as in Fig 2) are indicated on color. (A) The delay between the time of valve activation (arrow, ton) and the exchange increased with both distance and pressure. (B) Expanded time scales showed that the fit covered the data in all cases. The correlation coefficients for 1 mm were the following: 0.986, 0.980 and 0.974 for 0.1, 0.2 and 0.4 bar respectively. For 20 mm, they were: 0.984; 0.988 and 0.987 while for 51 mm: 0.985, 0.975 and 0.982. Finally for 70 mm were: 0.983, 0.982 and 0.980.
Mentions: To characterize the changes that occur at this transient interface along its way we placed the T-junction at 1, 20, 51, 70 mm of the tip and measured the exchange dynamics (Fig 3). We also studied the effect of the velocity of the fluid on the interface by applying different propellant pressures (Fig 3, trace color indicates pressure). A delay between the time of valve activation and the time when changes in concentration were detected at the measuring tip was always clear; this delay increased both with increasing distance (Fig 3A, compare different panels) and with decreasing propellant pressure (Fig 3A, compare different plots at each panel). The exchange time increased in a similar way (Fig 3B). The colored fit lines covered the black data traces in Fig 3; the correlation coefficient indicated a good fit (R2 > 0.97) in all cases. For the same pressure, an increase in the distance traveled decreased α, the fraction of the response that is described by an error function, at the same propelled pressure (Table 1). Furthermore, the increased flow rate increased α (Table 1).

Bottom Line: The exchange time was found to increase quadratically with the delay, although a sizeable variability remains unexplained by this relationship.This effect would be present in all tubing based devices.Present results might be of fundamental importance for the adequate design of serial compound exchangers which would be instrumental in the discovery of drugs that modulate the action of the physiological agonists of ion channels with the purpose of fine tuning their physiology.

View Article: PubMed Central - PubMed

Affiliation: Instituto de Química Física de los Materiales, Medio Ambiente y Energía. Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina.

ABSTRACT
Solutions exchange systems are responsible for the timing of drug application on patch clamp experiments. There are two basic strategies for generating a solution exchange. When slow exchanges are bearable, it is easier to perform the exchange inside the tubing system upstream of the exit port. On the other hand, fast, reproducible, exchanges are usually performed downstream of the exit port. As both strategies are combinable, increasing the performance of upstream exchanges is desirable. We designed a simple method for manufacturing T-junctions (300 μm I.D.) and we measured the time profile of exchange of two saline solutions using a patch pipette with an open tip. Three factors were found to determine the timing of the solution switching: pressure, travelled distance and off-center distance. A linear relationship between the time delay and the travelled distance was found for each tested pressure, showing its dependence to the fluid velocity, which increased with pressure. The exchange time was found to increase quadratically with the delay, although a sizeable variability remains unexplained by this relationship. The delay and exchange times increased as the recording pipette moved away from the center of the stream. Those increases became dramatic as the pipette was moved close to the stream borders. Mass transport along the travelled distance between the slow fluid at the border and the fast fluid at the center seems to contribute to the time course of the solution exchange. This effect would be present in all tubing based devices. Present results might be of fundamental importance for the adequate design of serial compound exchangers which would be instrumental in the discovery of drugs that modulate the action of the physiological agonists of ion channels with the purpose of fine tuning their physiology.

No MeSH data available.


Related in: MedlinePlus