Enzyme Mimicking Based on the Natural Melanin Particles from Human Hair

Abstract

Natural enzymes are mainly composed by the protein part and metallic cofactor part, both of which work cooperatively to achieve high catalytic activity. Here, natural melanin particles (NMPs) were extracted from human hair and further bound with metal ions to mimic natural enzymes. The different metal-bound NMPs (M-NMPs) exhibited different enzyme-like activities with great promise in diverse biomedical applications. It was found that Fe-bound NMPs (Fe-NMPs) showed outstanding peroxidase (POD)-like activity that possessed potential in antibacterial applications, and Mn-bound NMPs (Mn-NMPs) displayed catalase (CAT)-like activity with a remarkable radiotherapy sensitization effect in cancer therapy. Besides, Cu-bound NMPs (Cu-NMPs) could serve as combined POD, superoxide dismutase (SOD), and CAT alternatives, which exhibited prominent reactive oxygen species (ROS) scavenging ability, revealing great potential in anti-inflammation. The versatile enzyme-like activities of M-NMPs derived from hair might give extensive perspective for designing biomedical materials and provide a promising tool in solving biomedical problems.

Melanin and Melanin-Like Hybrid Materials in Regenerative Medicine

“…The abundance of metal ions coordination sites in melanins’ structure results in a high affinity for metal cations. This attitude has been extensively exploited to bind different metal ions to improve melanin’s intrinsic features, such as antioxidant and light absorption performance [ 52 , 53 ], but also to confer further non-native contrast properties [ 48 , 49 , 52 ]. Loading strategies include postdoping, predoping, and metal ion-exchange approaches ( Figure 3 ).…”

“…Recently, hair-extracted melanin nanoparticles doped with metal ions demonstrated the ability to mimic natural enzyme activities, revealing potent anti-inflammatory and antibacterial activity, thus opening new scenarios in the design of biomedical materials ( Figure 4 ) [ 53 ]. Metal ions doping enhances significantly light absorption, as well as the photothermal conversion of melanins [ 52 ].…”

“… Enzyme mimicking activity of metal ions-doped melanins for various biomedical applications. Reproduced with permission from [ 53 ]. Copyright Cell Press, 2020.…”

Incorporation of a Biocompatible Nanozyme in Cellular Antioxidant Enzyme Cascade Reverses Huntington’s Like Disorder in Preclinical Model

“…Since the discovery of first iron-containing nanozyme in last decade 4 , numerous nanomaterials have been elucidated to have oxidase 5 , catalase 6 , SOD 7,8 , peroxidase 9 , monooxygenase 10 , hydrolase 11 , laccase 12 mimicking activities and therefore been used in diverse applications like the destruction of biofilm, removal of algal bloom, immunoassay, tissue staining, cancer treatment, and glucose biosensing. However, despite being the most promising candidate as catalytic biomedicine, the clinical translation of nanozymes for therapeutic usage is still lacking [13][14][15] . Inherent toxicity of the materials used in the preparation of contemporary nanozymes, low aqueous solubility, inability to properly function in the physiological milieu, lack of selectivity (towards biological substrate), and incompatibility with other enzymes in catalyzing intracellular cascade reactions are considered to be the confounding factors [15][16][17][18] .…”

“…In contrast, 3-NPA-intoxicated animals were unable to discriminate between the novel and familiar objects, and spent almost similar time with both of them ( Supplementary Figure S6b To changes in the behavioral phenotype and morphometric histological findings indicate toards the retention of GPx mimic activity in vivo. To further confirm its effects, we [14] measured the lipid peroxidation in the brain tissue. Upon 3-NPA administration the lipid peroxidation increased significantly, while the NPs were able to protect the neuronal cells from its.…”