Synthesis, staining properties, and biocompatibility of a new cyanine dye for ILM peeling

The aim of this work is to investigate the biocompatibility and staining properties of DSS: 3,3'-Di-(4-sulfobutyl)-1,1,1',1'-tetramethyl-di-1H-benz[e]indocarbocyanine (DSS).

Dye concentrations of 0.5, 0.25, and 0.1% were evaluated (290 and 295 mOsm). Toxicity was assessed using a colorimetric test measuring the inhibition of ARPE 19 cell, human primary RPE cell, and human Müller cell proliferation. Exposure time was 30, 60, 120, and 300 s. Indocyanine green (ICG) (0.5, 0.25, and 0.1%) served as a control. Cells were also illuminated with plain white light (750 mW/cm(2)) for 10 min to assess phototoxic effects. Besides staining of porcine and human lens capsule, internal limiting membrane (ILM)-staining was assessed by applying 0.25 and 0.5% DSS over the macula in two human post-mortem eyes.

DSS of 0.25 and 0.1% showed no toxic effect on primary RPE cells and MIO-M1cells, and 0.5, 0.25, and 0.1% for ARPE-19 cells. In MIO-M1cells, 0.5% dye showed a significant reduction of mitochondrial dehydrogenase activity only following an exposure time of 300 s. Following illumination, ICG showed a significantly more pronounced effect on cell viability in primary RPE cells and MIO-M1cells compared to DSS. The absorption maximum is found at 591 nm; the even more bathochromic fluorescence proceeds with a common Stokes' shift where maxima at 620 and 660 nm with a quantum yield of 32% were found. The fluorescence is sufficiently hypsochromic and the fluorescence quantum yield high enough for an easy visual detection. The contrast and staining properties at the ILM were excellent and allowed for a controlled removal of the ILM during surgery. No penetration into deeper retinal layers was noted.

Our results indicate that this new cyanine dye DSS may represent an alternative for ILM staining due to its matched absorption concerning visibility and fluorescence qualities as well as its good biocompatibility.