AFM Investigation of the Influence of Red Light Irradiation on Collagen

Abstract

Low level red laser has a wide range of medical applications over the last decades. However its impact on collagen nanoscale features still remains unknown. Thus, thin collagen films were formed as extracellular matrix (ECM) models and irradiated using low level red laser. The results were recorded using Atomic Force Microscopy (AFM). The research was conducted in two stages. Firstly, collagen fibrils that were not fully formed (i.e. the highly reproducible distance of 67nm between gap and overlapping regions which is defined as D – Band periodicity did not occur in all the regions across the fibrils) were used as a model of damaged fibrils and irradiated for short time periods. The results indicated that red light led to the full creation of the D – Band periodicity. Moreover, a 25.2% reduction of the average width of the fibrils was recorded. In the second stage collagen fibrils with natural occurring characteristics were irradiated using a long period continuous irradiation procedure and the results indicated that red laser altered the dimensions of the fibrils (the reduction of the average width of the fibrils was 14% while the increase in the average height of the fibrils was 5%). More-over, the red laser altered the mechanical properties of the fibrils (the increase of the average Young’s modulus value within the same area on the fibril, post irradiation, was 24.5%). The observed alterations of structural and mechanical properties of collagen fibrils under the influence of low level red laser will provide new insights on the medical applications of red low power irradiation.