The problem is that the active molecule itself has a complex structure, and it is very hard to get a high-resolution image of even one of its structures (melanin can be folded in lots of ways). There's some potential for better imaging with fairly recent discoveries in partial-wavelength resolution microscopy using weak-measurement, but it's still a new technology. Melanin's mechanism for absorbing ionizing radiation, if understood, will definitely open up major applications for a perfected, synthesized solution.