Characterization of Thermo-Responsive Hydrogel Drug Delivery System by Spectral Domain Optical Coherence Tomography and Scanning Laser Ophthalmoscope(oct)

Abstract

Purpose: : Recently developed thermo-responsive hydrogel has been shown to be effective in encapsulating and releasing protein. It has been also demonstrated that it can be utilized as an ocular drug delivery system. The main objective of this study was to utilize spectral domain optical coherence tomography (SD-OCT) and scanning laser ophthalmoscope (SLO) to characterize the hydrogel in vivo.

Methods: : All experiments were performed on anesthetized adult pigmented rats. Thermo-responsive hydrogel was synthesized using poly(N-isopropylacrylamide) (PNIPAAm) and crosslinked with polyethylene glycols-diacrylate (PEG-DA). Approximately 3 µl of sterile hydrogel was injected into the vitreous cavity via a 30 gauge needle. SD-OCT was used to measure the thickness of the retina and injected hydrogel. SLO was used to assess the size and location of the hydrogel. Data were acquired prior to the injection and weekly up to 4 weeks post injection.

Results: : Both the retina and hydrogel can be imaged at the same time with SD-OCT. The retinal thickness near the hydrogel was determined to be 259 ± 15 µm compared to the non-exposed area of 247 ± 19 µm. The cross-sectional thickness of the hydrogel was ~400 µm. Using 2-deminsional SLO infrared reflectance (IR) images, the area of the hydrogel was estimated to be ~4 mm². The location of the hydrogel and the size of the hydrogel were remained constant throughout the investigated period.

Conclusions: : SD-OCT and SLO can be useful tools to characterize the hydrogel in vivo. The analysis allows in vivo chacterization of hydrogel as well as any potential impacts it may have on the retina. As various drug delivery systems are being investigated, it is important to establish tools to evaluate the potential effects.

Keywords: retina • imaging/image analysis: non-clinical