Polymeric scaffolds for enhanced stability of melanin incorporated in liposomes

The use of melanin in bioinspired applications is mostly limited by its poor stability in solid films. This problem has been addressed here by incorporating melanin into dipalmitoyl phosphatidyl glycerol (DPPG) liposomes, which were then immobilized onto a solid substrate as an LbL film. Results from steady-state and time-resolved fluorescence indicated an increased stability for melanin incorporated into DPPG liposomes. If not protected by liposomes, melanin looses completely its fluorescence properties in LbL films. The thickness of the liposome-melanin layer obtained from neutron reflectivity data was 4.1 ± 0.2 nm, consistent with the value estimated for the phospholipid bilayer of the liposomes, an evidence of the collapse of most liposomes. On the other hand, the final roughness indicated that some of the liposomes had their structure preserved. In summary, liposomes were proven excellent for encapsulation, thus providing a suitable environment, closer to the physiological conditions without using organic solvents or high pHs.

Graphical abstractMelanin in liposomes (A) and LbL films (B). A much stronger adsorption occurred for the film with immobilized liposomes, denoted by the darker color in PEI/DPPG + melanin.Figure optionsDownload full-size imageDownload high-quality image (51 K)Download as PowerPoint slideResearch highlights► Liposomes protect the melanin in aqueous solution ► Melanin incorporated into liposome may be immobilizated in layer-by-layer films