Study type: Medical/biological study (experimental study)

Effect of microwave radiation on the biophysical properties of liposomes med./bio.

By: Gaber MH, Abd El Halim N, Khalil WA
Published in: Bioelectromagnetics 2005; 26 (3): 194-200
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Aim of study (acc. to author)

To study the changes in lipid bilayer permeability in egg lecithin multilamellar vesicles after exposure to 900 MHz microwave irradiation.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 900 MHz
Modulation type: CW
Exposure duration: continuous for 5 h
  • SAR: 12 W/kg average over mass (1 g) (± 1 W/kg)

Exposure 1

Main characteristics
Frequency 900 MHz
Type
Charakteristic
  • guided field
Exposure duration continuous for 5 h
Modulation
Modulation type CW
Exposure setup
Exposure source
  • coaxial line, magnetron
Chamber The samples were placed inside a 13-mm diameter soda glass, round bottomed test tube with a Teflon bottom. The tube was held vertically and covered from the top with a Teflon cover. A Teflon container enclosed the sample to minimize the heat loss to the surrounding.
Setup The electric field was created between two conductors in coaxial arrangement with the outer conductor on the wall of the tube.
Additional info Another identical sample was placed in a special thermostated place and exposed to the same temperature rise as that resulting from the microwave radiation.
Parameters
Measurand Value Type Method Mass Remarks
SAR 12 W/kg average over mass measured and calculated 1 g ± 1 W/kg
Measurement and calculation details

The output power was monitored with a power meter connected to a waveguide directional coupler situated between the magnetron and the antenna. SAR was determined in a separate experiment by exposing the test solution (1 ml of the PBS buffer) in the sample container for about 5 h and recording the temperature of the sample as a function of time [Saalman et al., 1991].

Reference articles

  • Saalman E et al. (1991): Effect of 2.45 GHz microwave radiation on permeability of unilamellar liposomes to 5(6)-carboxyfluorescein. Evidence of non-thermal leakage

Exposed system:

Methods Endpoint/measurement parameters/methodology

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

Main outcome of study (acc. to author)

Optical anisotropy of the liposome sample decreased dramatically upon microwave exposure, indicating structural changes in hydrocarbon acyl chain packing. Infrared and NMR studies showed an increased damage upon exposure to microwave. The changes found in the 1H NMR spectrum of the microwave exposed samples indicated hydrolysis of carboxylic and phosphoric esters. Infrared study showed conformational changes in the acyl chains of the lipids upon exposure to microwave irradiation. However, both infrared and 31P NMR did not show any appreciable changes in the head group part of the phospholipid forming membranes.
In conclusion, this study provides no physical basis to assume that exposure of animals/humans to microwave irradiation may be associated with other hazards than those due to heating of tissue.

Study character:

Study funded by

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