Abstract
Purpose: :
To study the biocompatibility and degradation of two different compositions of biodegradable microfilms in the rabbit.
Methods: :
Two types of biodegradable microfilms were cast from either poly (d,l-lactide-co-glycolide) (PLGA) 53/47 or poly (d, l-lactide-co-caprolactone) (PLC) 70/30. Each film was sized at 0.5 x 5.0 x 10.0 mm. 18 eyes (9 rabbits) were surgically implanted with one type of microfilm in each eye. The implant was inserted in the subconjunctival space and sutured with 10/0 nylon. The eyes were regularly assessed for clinical signs of inflammation or implant-related complications with slit-lamp photography and anterior-segment optical coherence tomography (AS-OCT). Rabbits were sacrificed at 1, 3 and 6 months (n=3) and the eyes were histologically analyzed for sign of inflammation, foreign body reaction and implant encapsulation.
Results: :
All PLGA53/47 (n=9) and PLC70/30 (n=9) microfilms remained within the subconjunctival space with no evidence of implant migration or erosion through the conjunctiva over the 6 months. Clinical assessment showed both microfilms to degrade gradually. PLGA53/47 microfilms were softer and more gel-like in consistency compared to PLC70/30, and degraded at a faster rate. The mean degradation rate for the PLGA53/47 microfilms was 1.47 (95% confidence interval [CI] 0.55-2.35) while that of PLC70/30 microfilm was 1.28 (95% CI 0.72-1.85). All the implanted PLGA54/37 microfilms had completely degraded by 4 months. In contrast, PLC7030 microfilms remained visible even at 6 months. Minimal conjunctival inflammation and vascularisation were clinically observed during the study period, even after the onset of degradation of both the microfilms. Implant encapsulation was observed with only PLGA70/30.
Conclusions: :
Biodegradable microfilms composed of PLGA53/47 and PLC70/30 are non-toxic and well tolerated for potential use as ocular drug delivery platforms via the subconjunctival route. PLGA53/47 degraded at a faster rate than PLC70/30. These properties may be used to vary the duration of drug delivery in the eye.
Keywords: drug toxicity/drug effects