An anti-angiogenic reverse thermal gel as a drug-delivery system for age-related wet macular degeneration

Abstract

Reverse thermal gels have numerous biomedical implications, as they undergo physical gelation upon temperature increases and can incorporate biomolecules to promote tissue repair. Such a material is developed for the sustained release of bevacizumab (Avastin), a drug used to treat age-related macular degeneration. The polymer, poly(ethylene glycol)-poly(serinol hexamethylene urethane) (ESHU), forms a physical gel when heated to 37 °C and shows good cytocompatibility with ocular cells. ESHU is capable of sustaining bevacizumab release over 17 weeks in vitro, and the release kinetics can be altered by changing the drug dose and the ESHU concentration. These results suggest that ESHU is biologically safe, and suitable for ocular drug delivery.

Figure 1

Representative fluorescence micrograph images of bovine CE cells exposed to control (A, B) and ESHU (C, D) at 24 h. Both groups show comparable intense nuclei staining (A, C) with scarce red stained cells (B, D) indicating little cell death.

Figure 2

In vitro cytotoxicity of ESHU against bovine CE cells after 1, 12, and 24 h incubation. The number of dead CE cells was determined by counting the number of PI+ cells, and was expressed as a function of the total number of cells labeled by Hoechst staining. Values are expressed as the means ± SD (n = 3).

Figure 3

Representative fluorescence micrograph images of human ARPE-19 cells exposed to control (A, B) and ESHU (C, D) at 72 h. There was no difference between experimental groups in the total number of viable cells (A, C) and dead cells (B, D).

Figure 4

In vitro cytotoxicity of ESHU against human ARPE-19 cells after 24, 48, and 72 h incubation. The percentage of dead ARPE-19 cells was determined by expressing the number PI+ cells over the total number of cells labeled by Hoechst staining. Values are the means ± SD (n = 3).

Figure 5

Thermal behavior of bevacizumab-loaded ESHU formulated with 20 wt% ESHU and 1.25 mg bevacizumab. The steep increase in G′ from 33 to 39 °C indicated a sol–gel phase transition. The phase transition behavior is similar to pure ESHU.^[18]

Figure 6

The release profile of bevacizumab from (A) 15 and (B) 20 wt% ESHU systems. The release was sustained over the 17-weeks period with burst releases at the beginning. The 20 wt% ESHU systems resulted in slower release rates, and smaller burst releases due to its higher concentration.