EFFECT OF X-RADIATION ON HYALURONIC ACID

Abstract

ABSTRACT

The effects of radiation on tissue have generally been investigated in the context of therapeutic irradiations, radiation protection and exposure to solar radiation. Typically attention has concentrated primarily on cells, less consideration being given to the extracellular matrix (ECM). ECM consists of collagen and elastin fibers immersed in a viscoelastic gel composed principally of hyaluronan (HA) and proteoglycans. The present study examines changes in the physical properties of the principle matrix micromolecules due to exposure to ionizing radiation. Freeze-dried rooster-comb HA (Sigma) were used to give doses of 10-100 Gy for HA, to cover the range of irradiation exposure during radiotherapy. The viscosity of HA (at 1.25% and 0.125% w/v) was measured by both cone and plate and capillary viscometry, the former providing measurement at uniform shear rate and the latter providing a more sensitive indication of changes. The Raman microspectrometry was employed to characterize these changes on ECM molecular conformation. In regard to the viscometry, both techniques (cone and plate and capillary viscometry) reveal a dose-dependent reduction in viscosity (from 340 ± 194 cP for controls to 1500 ± 88 cP at a shear rate of 2 s^-1 and dose of 75 Gy), again suggesting depolymerisation.

ABSTRAK

Kesan sinaran ke atas tisu secara amnya telah dikaji dalam konteks sinaran terapiutik, perlindungan sinaran dan pendedahan kepada sinaran matahari. Lazimnya perhatian lebih tertumpu kepada sel-sel tetapi kurang perhatian terhadap matriks luar sel (ECM). ECM terdiri daripada kolagen dan gentian elastin yang terbenam di dalam gel viskoelastik yang terdiri daripada hyaluronan (HA) dan proteoglikan. Kajian ini mengkaji perubahan dalam ciri-ciri fizikal prinsip matriks mikromolekul yang disebabkan oleh pendedahan kepada sinaran mengion. Freeze-dried rooster-comb HA (Sigma) digunakan untuk memberi dos 10-100 Gy untuk HA, yang merangkumi julat pendedahan penyinaran semasa radioterapi. Kelikatan HA (pada kadar 1.25% dan 0.125% w / v) telah diukur oleh kedua-dua viskometer kon dan plat dan viskometer kapilari, pengukuran terdahulu menyediakan pada kadar ricih yang seragam dan memberikan petunjuk yang lebih peka terhadap perubahan. Raman mikrospektrometri telah digunakan untuk mencirikan perubahan bentuk molekul ECM. Dalam hal berkaitan dengan viskometer, kedua-dua teknik (viskometer kon dan plat dan viskometer kapilari) menunjukkan pengurangan dos bergantung kepada kelikatan (daripada 340 ± 194 cP bagi kawalan kepada 1500 ± 88 cP pada kadar ricih 2 s^-1 dan dos 75 Gy), sekali lagi mencadangkan dipolimerasi.