Abstract
Purpose :
Intravitreal injection (IVI) to treat retinal diseases affords high drug bioavailability, but is among the most invasive treatment modality. Frequent injections especially can exacerbate complications of direct injections such as retinal detachment and infection. To address the problem of achieving high drug bioavailability but reducing frequent IVI risks, we synthesized an injectable hydrogel drug delivery formulation for the sustained release of the chemotherapeutic melphalan for the treatment of retinoblastoma as a proof of concept model. We hypothesize that the resulting burst and sustained release mechanisms of the dendrimer hydrogel (DH) will maintain an effective mode of action on Y79 cells relative to free melphalan.
Methods :
The DH was synthesized starting with a surface modified generation 5 (G5) polyamidoamine dendrimer to chemical conjugate melphalan onto its surface via a pH cleavable linker. The G5-melphalan then crosslinks with polyethylene glycol-diacrylate in the presence of free melphalan to form a drug encapsulated hydrogel network (Fig 1). The DH was characterized via proton nuclear magnetic resonance (1H NMR), high pressure liquid chromatography (HPLC), rheology, in vitro drug release, and cell viability in Y79 retinoblastoma and HCE-2 corneal cells.
Figure 1. Experiment schematic.
Results :
1H NMR and HPLC data confirmed the conjugation of melphalan onto the surface of generation 5 polyamidoamine dendrimer via a pH liable linker. UV-Vis spectrometry data indicates the enhanced aqueous solubility of DH physically encapsulated melphalan (Melphalan Cs = 0.2 mM; G5/Melphalan Cs = 1.5 mM). Cell viability data concluded the IC50 values of melphalan on Y79 and HCE-2 cells as that a concentration of 10 µM and 16 µM, values which are easily reached within the formulation.
Conclusions :
The enhanced solubility of melphalan in the DH formulation are expected due to the sequestering ability of spaces within the dendrimer structure and gel network. The sensitivity of the Y79 cells to the chosen drug make it feasible for this formulation to deliver the required dosage in the burst of physically encapsulated melphalan and sustained release of chemically conjugated drug. The next steps are to determine the drug release kinematics of the DH formulation relative to free drug and test the formulation in a xenograft model of retinoblastoma.
This is a 2020 ARVO Annual Meeting abstract.