Study type: Medical/biological study (experimental study)

Permeability changes induced by 130 GHz pulsed radiation on cationic liposomes loaded with carbonic anhydrase. med./bio.

Published in: Bioelectromagnetics 2007; 28 (8): 587-598

Aim of study (acc. to author)

Cationic liposomes loaded with carbonic anhydrase were used to analyze the influence of 130 GHz irradiation pulse modulated at low frequencies, on the diffusion rate of the substrate p-nitrophenyl acetate across the lipid bilayer.

Background/further details

Additionally, changes on kinetic parameters, such as the Michaelis-Menten constant and maximum reaction rate of both free carbonic anhydrase and loaded in liposome were examined to address the possible effects of 130 GHz irradiation on the enzyme activity of carbonic anhydrase itself. The effect of 130 GHz exposure on carbonic anhydrase reaction rate was also studied before and after proteolytic digestion of carbonic anhydrase sticking onto external surface of liposomes.
Thermal effects are also investigated.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 130 GHz
Modulation type: pulsed
Exposure duration: continuous for 30 s plus 2 min
Exposure 2: 150 GHz
Modulation type: CW
Exposure duration: continuous for 30 s plus 2 min

Exposure 1

Main characteristics
Frequency 130 GHz
Type
Exposure duration continuous for 30 s plus 2 min
Modulation
Modulation type pulsed
Pulse width 50 ps
Additional info

trains of triangular pulses with 330 ps spacing, a train duration of 4 µs, and a train repetition rate of 5, 7, or 10 Hz

Exposure setup
Exposure source
Chamber The exposure system was located in a temperature-controlled room (~22 °C). The temperature at the bottom of the cuvette containing the liposome suspension was continuously monitored and recorded during the irradiation time.
Setup The sample cell of a CARY 50 spectrophotometer was modified to directly deliver the radiation to one side of the cuvette (1 cm wide x 3 cm high x 0.5 cm thick) containing the liposomes in a final volume of 1.5 ml. The radiation generated by the FEL was sent through a copper light-pipe with 2.5 cm diameter. An electroformed copper horn was used to match the circular cross-section of the light-pipe to the rectangular cross-section of the cuvette focussing the beam to a spot size of 0.5 cm². The radiation was strongly attenuated while passing through the liposome suspension, and the reflection from the opposite wall of the cuvette was negligible.
Sham exposure A sham exposure was conducted.
Additional info The radiation was turned on and, after 30 s, the p-NPA was added and stirred before carrying out the kinetic measurement over 2 min. The initial stirring of the liposomes maintained them in suspension and avoided any sedimentation during irradiation.
Parameters
Measurand Value Type Method Mass Remarks
power density 5 mW/cm² average over time calculated - min
power density 17 mW/cm² average over time calculated - max

Exposure 2

Main characteristics
Frequency 150 GHz
Type
Exposure duration continuous for 30 s plus 2 min
Modulation
Modulation type CW
Exposure setup
Exposure source
  • Impact Avalanche Transit Time (IMPATT) diode
Setup The IMPATT diode was connected to the exposure system by means of an additional focusing cone.
Sham exposure A sham exposure was conducted.
Additional info For comparison purposes, CW irradiation at 150 GHz was performed under identical experimental conditions.
Parameters
Measurand Value Type Method Mass Remarks
power density 6.2 mW/cm² average over time calculated - -

Reference articles

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Time of investigation:
  • during exposure
  • after exposure

Main outcome of study (acc. to author)

The data indicate that interactions can take place between lipid bilayer and 130 GHz pulsed irradiation affecting its permeability, and that this is not simply caused by heating. 130 GHz expsoure pulse modulated at low frequencies (5, 7, or 10 Hz) can enhance the permeability of cationic enzyme-containing liposomes.

Study character:

Study funded by

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