A PRELIMINARY DOUBLE BLIND CONTROLLED STUDY ON FREE AMINO ACID ANALYSIS IN BURN WOUNDS IN THE MOUSE FOLLOWING 830 nm DIODE LASER THERAPY

Abstract

A double-blind controlled study is presented on the amino acid analysis of levels of a selected group of 26 free amino acids (FAA) in CO₂ laser generated standardized burn wounds on the bilateral dorsum in the ddy mouse model. Four groups of ddy white mice (male, 5 weeks old, average weight 20 g), 6 animals per group, were anaesthetized with ether. The hair on the bilateral dorsum of all animals was carefully removed with a depilatory cream, and in three of the groups standardized burn injuries were inflicted using the defocused beam of the CO₂ laser (25 W, continuous wave, 1.45 cm diameter spot, 0.99 sec/shot). The injuries were made bilaterally 1 cm laterally from the dorsal midline, 1.5 cm caudally from the line drawn between the base of the ears. The 4th group was the unburned control group for assessing base FAA levels. In experimental group A (LLLT group), the centre of the right hand burn injury was irradiated daily on days 0, 1, 2, 3, 4, and 5 with an 830 nm GaAlAs diode laser system (60 mW continuous wave). The left hand injury was unirradiated. The laser was held 1 mm from the surface of the wound, giving a spot size of approximately 0.03 cm², 20 sec per exposure per day, energy density per exposure of 40 J/cm². Group B (sham irradiation group) was handled in exactly the same way, but a non-emitting probe was used. Group C (unirradiated burned controls) was not handled at all. The animals were killed (ether overdose) on post-burn day 10. The size of the burn injury and the degree of wound healing were measured macroscopically on days 2, 5 and 7 and 10. The LLLT group A demonstrated better wound healing than groups B and C, between which there was no difference. On days 0, 1, 3, 5, 7 and 10, sample tissue was collected from both burned sites in the burned animals and from the unburned controls and subjected to automated AA analysis. The unburned controls were used as standards. On day 7 specimens were taken from the burn wounds in groups A, B and C and routinely processed for histological assessment with haematoxylin and eosin and elastica van Giesen’s stains. Automated AA analysis in general revealed higher levels of total FAA in group A, with no statistical difference between groups B and C. When looked at individually as spider graphs, the 26 AA isolated in this study at fell into 6 typical patterns. At day 10 histology revealed more advanced wound healing between the LLLT group and groups B and C, between which there was no difference. although the present study was only designed to isolate patterns in FAA associated with healing burns, the authors conclude that 830 nm diode LLLT certainly appears to accelerate wound healing, and there is a higher level of those FAA associated with protein synthesis.