Biomolecule-Based Optical Metamaterials: Design and Applications

Abstract

Metamaterials are broadly defined as artificial, electromagnetically homogeneous structures that exhibit unusual physical properties that are not present in nature. They possess extraordinary capabilities to bend electromagnetic waves. Their size, shape and composition can be engineered to modify their characteristics, such as iridescence, color shift, absorbance at different wavelengths, etc., and harness them as biosensors. Metamaterial construction from biological sources such as carbohydrates, proteins and nucleic acids represents a low-cost alternative, rendering high quantities and yields. In addition, the malleability of these biomaterials makes it possible to fabricate an endless number of structured materials such as composited nanoparticles, biofilms, nanofibers, quantum dots, and many others, with very specific, invaluable and tremendously useful optical characteristics. The intrinsic characteristics observed in biomaterials make them suitable for biomedical applications. This review addresses the optical characteristics of metamaterials obtained from the major macromolecules found in nature: carbohydrates, proteins and DNA, highlighting their biosensor field use, and pointing out their physical properties and production paths.

Keywords: biomolecule-based metamaterials; crystals; hydrogel; lattices; nanoparticles; nanostructure.

Figure 3

Schematic diagram of protein based metamaterials. (a) Protein films of silk fibroin nanopatterned 2D lattices that exhibit different colors as a function of varying lattice spacing [98], (b) Protein affinity interactions direct the self-assembly of metamolecules integrated by NPs tightly packed around a single dielectric core [115], (c) Protein amyloid fibrils induction by chemical and thermal denaturation, site directed adsorption and subsequent reduction of precursor salt inducing the growth of NP´s nanoparticles aligned regularly into amyloids fibrils [132], (d) Formation of protein amyloid based hydrogel by reduction, concentration variation and thermal denaturation process [138], (e) Coated Protein based self-assembly of metal/metal plasmonic core/satellite nanoclusters [143].

Figure 1

(a) One dimensional (1D), 2D, and 3D organization of photonic crystals, found in nature through the wings of several insects such as butterflies and cicadas. (b) Natural opals, an instance of periodic crystals, display a colorful aspect as a consequence of periodic systems with spheres substantially packed, which form a face-centered cubic lattice. (c) When nematic liquid crystals are doped with chiral molecules they can form supramolecular helix structures, conferring them remarkable features as diffraction grating, and selective light reflection. It is important to mention that the helix pitch is determined by the chemical structures of molecules forming the cholesteric phase, as well as the concentration of chiral moieties present in the dopant component. (d) Cellulose, the major component of cell wall plants, is organized in nanofibers (CNFs) possessing chiral nematic structures and 1D nanostructures with crystalline and amorphous regions.

Figure 2

Major natural polysaccharides used in biomedical applications, highlighting their main sources, and the wide range of processes to isolate them.

Figure 4

Protein extraction or production process alternatives and methods of synthesis.

Figure 5

One dimensional (1D) DNA nanostructures.(a) Quantum dots attached to functionalized DNA origami nanotubes, (b) DNA gold nanorods films, (c) construction of DNA nanowires through the assembly of DNA origami and DNA coated AuNPs, (d) Electrospin fibers made of DNA-CTMA, (e) Formation of NP chains with the interaction between ssDNA strands and AuNPs functionalized with DNA binding peptides.

Figure 6

Main aspect of RNA and the construction of nanostructures. (a) Basic interactions between RNA motifs that are relevant for the assembly of RNA nanostructures. (b) Main RNA structural motifs. (c) Examples of molecules that are used for functionalization of RNA nanostructures. (d) Examples of 2D RNA nanostructures. (e) Main 3D RNA nanostructures. (f) Different kind of materials that have been created with RNA.

Figure 7

DNA and RNA sources from nature and methods of synthesis.