Electronic Thesis and Dissertation Repository

Degree

Master of Science

Program

Surgery

Supervisor

Dr.Hutnik

Abstract

Background: Glaucoma is the leading cause of irreversible blindness. The last decade has seen the emergence of minimally invasive glaucoma surgical procedures, with the most recent utilizing implantable devices. The first generation of micro-incisional devices has been made of titanium. Since then other materials have also been introduced. In each case, the presence of a permanent foreign body has been associated with undesirable wound healing responses characterized by fibroblast proliferation and surgical failure. Magnesium alloys have attracted much attention as biodegradable implantable materials due to their excellent biodegradable and biocompatibility properties. The purpose of this research was to evaluate the in vitro biocompatibility and anti-proliferative properties of differently coated magnesium alloys in a primary culture of human Tenon’s capsule fibroblasts (HTCFs). The goal of the research was to establish a proof of principle for further exploration of this novel material as a potential adjunct to glaucoma surgery.

Materials and Methods: Pure magnesium was cut into discs measuring 14.5 mm in diameter and 1 mm thick. These were coated with Hydroxyapatite (HA), Dicalcium phosphate dehydrate (DCPD) and Dicalcium phosphate dehydrate + Stearic acid (DCPD+SA), respectively. Coated magnesium alloys were immersed in simulated aqueous humor to examine the corrosive properties, the released ions, and the variation of pH. The primary HTCFs were seeded on DCPD, DCPD+SA and HA disks in 24-well culture and incubated at 37 degrees for 2-7 days.. Glass disks were used as control. The MTT and LDH assays were used to determine cellular metabolic activity and cytotoxicity during the logarithmic phase of HTCFs, respectively. The BrdU assay was used to evaluate cellular proliferation. Western blot was used to assess the expression of alpha-smooth muscle actin (α-SMA).

Results:A total of 453 coated magnesium alloy disks were evaluated. Corrosion was observed in 67 disks (14.8%). The corrosion rate of HA (12.6%) was lower than other two coatings (DCPD 15.9%, DCPD+SA 15.9%, respectively), but the difference was not statistically significant different (p=0.851). The immersion test showed that the HA coating had better ability to prevent the coating dissolution and corrosion. The cellular metabolic activity of different coated magnesium alloys gradually declined during the logarithmic phase of HTCFs, and each type of coated magnesium alloy demonstrated significant decreased metabolic activity of HTCFs when compared to the control (p

Chemical coatings are able to affect the corrosive properties of magnesium. HA was the most resistant to corrosion. No significant difference was found in metabolic activity or necrosis at different times during the logarithmic phase of HTCFs. DCPD+SA demonstrated a stronger ability to reduce metabolic activity while its cytotoxic profile was the same as the titanium and glass controls. In comparison to titanium, coated magnesium alloys attenuated HTCFs proliferation. Coated magnesium alloys reduced the expression of α-SMA. The expression of α-SMA was significantly decreased in cells exposed to the HA coated magnesium

Conclusions: Different chemical coatings on magnesium were able to affect the corrosive properties which, in turn, influenced the morphology and function of human Tenon’s capsule fibroblasts. These results support the further study of coated magnesium for its potential modulatory role in Tenon’s capsule wound healing.


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