Apoferritin fibers: a new template for 1D fluorescent hybrid nanostructures

Abstract

Recently, research in the field of protein amyloid fibers has gained great attention due to the use of these materials as nanoscale templates for the construction of functional hybrid materials. The formation of apoferritin amyloid-like protein fibers is demonstrated herein for the first time. The morphology, size and stiffness of these one-dimensional structures are comparable to the fibers formed by β-lactoglobulin, a protein frequently used as a model in the study of amyloid-like fibrillar proteins. Nanometer-sized globular apoferritin is capable of self-assembling to form 1D micrometer-sized structures after being subjected to a heating process. Depending on the experimental conditions, fibers with different morphologies and sizes are obtained. The wire-like protein structure is rich in functional groups and allows chemical functionalization with diverse quantum dots (QD), as well as with different Alexa Fluor (AF) dyes, leading to hybrid fluorescent fibers with variable emission wavelengths, from green to near infrared, depending on the QD and AFs coupled. For fibers containing the pair AF488 and AF647, efficient fluorescence energy transfer from the covalently coupled donor (AF488) to acceptor tags (AF647) takes place. Apoferritin fibers are proposed here as a new promising template for obtaining hybrid functional materials.

Hybrid Nanoscopy of Hybrid Nanomaterials

“…Figure A shows an AFM image in which the quantum dots are clearly observed attached to the fiber. The labeling density is not homogeneous along the fiber, with some sections where the QDs seem to overlap, while others are not functionalized, consistent with previous observations using high‐resolution transmission electron microscopy (HR‐TEM) . The height of the QDs is about 8 nm and that of the fiber is slightly above 3 nm.…”

“…In previous work, we showed that βLG can be readily functionalized with AlexaFluor 488 after amyloid‐like fiber formation to yield fluorescent fibers that appear homogeneously fluorescent at the spatial resolution provided by standard fluorescence microscopy . In the present study, correlative AFM and localization‐based super‐resolution fluorescence microscopy was used to gain information about the labeling properties at nanoscale spatial resolution both with dyes and QDs.…”

“…Preparation of the Dye‐Labeled βLG Fibrils : βLG fibril formation was described previously . Briefly, amyloid‐like protein fibers were formed after heat treatment of protein purified solutions at 80 °C and pH 2 for 24 h. Solutions of protein fibers (2 mL) in aqueous solution at pH 8.0 were incubated for 24 h with AlexaFluor488 succinimidyl ester derivative (Life Technologies).…”

Amyloid β-Sheet Secondary Structure Identified in UV-Induced Cataracts of Porcine Lenses using 2D IR Spectroscopy

“…The 2D IR spectra exhibit the 1621 cm −1 peak and the corresponding cross peaks of amyloid β-sheets. Short amyloid morphologies are not uncommon and are observed in TEM images of other proteins with fibrillary, 41; 42 prefibrillar, 43; 44 oligomeric, 45 or amorphous morphologies. 46 These images and spectra are shown to illustrate the diversity in length that crystallin amyloids can adopt, as measured by TEM, and that 2D IR spectra exhibit characteristic amyloid β-sheet secondary structure even for lengths that are difficult to resolve with TEM.…”

Development and characterization of folic acid-functionalized apoferritin as a delivery vehicle for epirubicin against MCF-7 breast cancer cells

“…The HsAFr surface can be modified with antibodies [14], peptides [15], aptamers [16] or small molecules such as folic acid (FA) [17]. Covalent modification of HsAFr lysine residues with the carboxyl functional group of targeting molecules can be used in the surface modification of HsAFr [18].…”