Improving the solubility of melanin nanoparticles from apricot kernels is a potent drug delivery system

Abstract

Background: Melanin can be used in biomedical nanomaterials, but its solubility in water and bioavailability are low. Aim: Melanin nanoparticles were prepared and then PEG-natural melanin nanoparticles (NMNP-PEG) were obtained with good performance and optimize their (water solubility, dispersion stability, chelating metal ions, photothermal stability, drug delivery, and biocompatibility), therefore improve the water solubility of melanin and broaden its application scope in biology, medicine, food, and other fields. Methods: MFAK (melanin from apricot kernels) and NMNP-PEG were prepared and characterized using ultraviolet-visible spectrophotometry (UV-Vis), high-performance liquid chromatography (HPLC), Fourier-transform infrared spectroscopy (FTIR), 1H nuclear magnetic resonance (NMR), and electron microscopy. The chelation rate of metal ions, photothermal effect, doxorubicin loading, and cytotoxicity (MCF-7 cells) were examined. Results: UV-Vis, HPLC, FTIR, and NMR indicated that NMNPs contained melanin. NMNPs could be successfully modified using PEG. Under physiological pH conditions (pH 7.4), the metal ion chelation rate of NMNP-PEG increased with time and peaked at 12 h. The photothermal assay showed a temperature enhancement of 26.3°C with 1 mg/mL NMNP-PEG, compared with 1.9℃ with water. The NMNP-PEGs had a typical peak for doxorubicin in the FTIR spectrum, and the peak intensity was proportional to the drug loading. The release of doxorubicin in an acidic buffer was 40.8% at 24 h, almost threefold that in a neutral buffer (11.9%). There was no obvious cytotoxicity from NMNP-PEG. Conclusion: NMNP-PEG displays good stability, high metal ion chelation ability, efficient photothermal conversion potential, drug-retaining capability, sustained controlled drug release, and biocompatibility. This study provides a theoretical basis for NMNP-PEG applications in medicine (targeting specific sites to diagnose and treat diseases), food (extending the shelf life of food), and biology (as metal ion chelating agents to remove heavy metals from wastewater).

Extraction, physicochemical properties, and antioxidant activity of natural melanin from Auricularia heimuer fermentation

“…At the same treatment time, the absorbance of AHM was different in dark, natural light, and strong light conditions, but the differences were not significant (P > 0.05; Figure 4C). Overall, the results showed good thermostability and light resistance of AHM, which is consistent with the literature (38,40) (Table 4).…”

Therapeutic potential of enzymatically extracted eumelanin from squid ink in type 2 diabetes mellitus ICR mice: Multifaceted intervention against hyperglycemia, oxidative stress and depression

“…Among its various species, eumelanin, a black to brown insoluble heteropolymer, has emerged as the most extensively studied form in nature, formed through the oxidative polymerization of 5,6‐dihydroxyindole (DHI) and 5,6‐dihydroxyindole‐2‐carboxylic acid (DHICA) 11 . Its poor solubility poses a challenge for its practical application, as it is slightly soluble in alkaline solutions, insoluble in aqueous and acidic solutions as well as organic reagents, and exhibits unstable dispersion in water 12 . Conventional methods for eumelanin extraction involve alkali solubilization and acid precipitation, which are considered harsh and destructive due to the use of acid and high temperatures 13 .…”

“…11 Its poor solubility poses a challenge for its practical application, as it is slightly soluble in alkaline solutions, insoluble in aqueous and acidic solutions as well as organic reagents, and exhibits unstable dispersion in water. 12 Conventional methods for eumelanin extraction involve alkali solubilization and acid precipitation, which are considered harsh and destructive due to the use of acid and high temperatures. 13 In contrast, enzymatic extraction of eumelanin offers a gentle and purification-oriented approach.…”