Bio-Inspired, Melanin-Like Nanoparticles as a Highly Efficient Contrast Agent for T₁-Weighted Magnetic Resonance Imaging

Abstract

The development of nontoxic and biocompatible imaging agents will create new opportunities for potential applications in clinical MRI diagnosis. Synthetic melanin-like nanoparticles (MelNPs), analogous to natural sepia melanin (a major component of the cuttlefish ink), can be used as contrast agent for MRI. MelNPs complexed with paramagnetic Fe(3+) ions show much higher relaxivity values than existing MRI T1 contrast agents based on gadolinium (Gd) or manganese (Mn); MelNP values at 3T were r1 = 17 and r2 = 18 mM(-1) s(-1) (r2/r1 value of 1.1). With significant enhancement to MRI contrast, this biomimetic approach using MelNPs functionalized with paramagnetic Fe(3+) ions and surface-modified with biocompatible poly(ethylene glycol) units, could provide new insight into how melanin-based bioresponsive and therapeutic imaging probes integrate with their various biological functions.

Intrinsically Mn2+-Chelated Polydopamine Nanoparticles for Simultaneous Magnetic Resonance Imaging and Photothermal Ablation of Cancer Cells

“…38,39 The significant enhancement in relaxivity for T 1 -weighed MRI may be attributed to its characteristic catechol or carboxyl groups, which enable more water molecules to bond to Mn 2+ complex. 21 To be addressed, the use of Mn 2+ rather than Gd 3+ for MRI signal enhancement can avoid the risk of nephrogenic systemic fibrosis in clinical practice. The in vivo MRI experiment was conducted at 9.4 T. The MR images of mouse bearing 4T1 tumor were acquired before and after the intravenous tail injection of PMPDA NPs (0.1 mL, 5 mg/mL).…”

Production of Melanin Pigment by Fungi and Its Biotechnological Applications

“…This strategy may be used to improve nanomaterials with potential applications as efficient catalysts and electrocatalysts. Studies have shown that synthetic melanin-like nanoparticles complexed with paramagnetic Fe 3+ ions have potential as a highly efficient and nontoxic contrast agent for magnetic resonance imaging instead of Gd 3+ -based contrast agents, which can cause nephrotoxicity [136].…”

Evaluation of the Practicality of Melanin as a Photodynamic-Inactivation Photosensitizer by Its Nanonization

“…It is shown that Sepia melanin can be nanonized and dispersed in pure water or biological medium by processing of melanin powder in suspension with a magnetic stirrer running for 48 h. It is also shown that irradiation of Sepia melanin in suspension with femtosecond laser pulses can result in photo-fragmentation, which leads to nanonization and dispersibilization at a rate higher than that with mechanical stir. In this report and our previous work [9] we have demonstrated that both Sepia melanin (natural melanin) and synthetic melanin can be nanonized and dispersed in pure water or biological medium by processing of melanin powder in suspension with a magnetic stirrer running for 48 h. Although water-dispersible melanin processed with the techniques reported herein would not be practical photosensitizer for PDI, we expect it could be utilized in other applications such as adjuvant in radiation therapy [38], antioxidant [4,5,9,39], metal-ion scavenger [40], antidote for acute radiation syndrome [38], antitumor drug [41,42], antivenin drug [43], antivirus [44] and contrast-enhancing agent in magnetic resonance imaging (MRI) [45,46].…”