Genetically Programmable Thermoresponsive Plasmonic Gold/Silk-Elastin Protein Core/Shell Nanoparticles

Abstract

The design and development of future molecular photonic/electronic systems pose the challenge of integrating functional molecular building blocks in a controlled, tunable, and reproducible manner. The modular nature and fidelity of the biosynthesis method provides a unique chemistry approach to one-pot synthesis of environmental factor-responsive chimeric proteins capable of energy conversion between the desired forms. In this work, facile tuning of dynamic thermal response in plasmonic nanoparticles was facilitated by genetic engineering of the structure, size, and self-assembly of the shell silk-elastin-like protein polymers (SELPs). Recombinant DNA techniques were implemented to synthesize a new family of SELPs, S4E8Gs, with amino acid repeats of [(GVGVP)4(GGGVP)(GVGVP)3(GAGAGS)4] and tunable molecular weight. The temperature-reversible conformational switching between the hydrophilic random coils and the hydrophobic β-turns in the elastin blocks were programmed to between 50 and 60 °C by site-specific glycine mutation, as confirmed by variable-temperature proton NMR and circular dichroism (CD) spectroscopy, to trigger the nanoparticle aggregation. The dynamic self-aggregation/disaggregation of the Au-SELPs nanoparticles was regulated in size and pattern by the β-sheet-forming, thermally stable silk blocks, as revealed by transmission electron microscopy (TEM) and dynamic light scattering (DLS). The thermally reversible, shell dimension dependent, interparticle plasmon coupling was investigated by both variable-temperature UV–vis spectroscopy and finite-difference time-domain (FDTD)-based simulations. Good agreement between the calculated and measured spectra sheds light on design and synthesis of responsive plasmonic nanostructures by independently tuning the refractive index and size of the SELPs through genetic engineering.

Tunable Thermoresponsiveness of Resilin via Coassembly with Rigid Biopolymers

“…This observation is consistent with previous reports of RSF solutions that display negative minima in this region and indicates the protein has a random-coil conformation in solution. 30,31 The coassembled Rec1-resilin/RSF solutions at days 1 and 6 also showed negative bands in the same region (∼196 nm); however, the intensity of this peak decreased with increasing incubation time. In addition, the negative intensity in the 210 to 220 nm region increased with time.…”

Silk-elastin-like protein biomaterials for the controlled delivery of therapeutics

“…SELP nanoparticles, which have potential to serve as stimuli responsive drug delivery vehicles, can be prepared using a variety of methods, including direct self-assembly [25], and gold nanoparticle triggered [69] or hydrophobic drug triggered self-assembly [23] in aqueous solution. The self-assembly of SELPs in aqueous solution is based on hydrogen bonding between the silk blocks, and the hydrophobicity differences between silk and elastin blocks.…”

“…Lin et al . utilized nickel-chelate-nitrilotriacetate (NTA-Ni 2+ ) functionalized gold nanoparticles to trigger the formation of core/shell gold/SELP nanoparticles based on the nickel affinity of the polyhistidine tag fused at the N-terminus of SELP [69]. Xia et al .…”

Sortase A-mediated multi-functionalization of protein nanoparticles

“…3A). 36,37 To ligate ELP to E2, an LPETG motif was added to the C-terminus of the ELP polymer; the resulting ELP-LPETG fusion proteins were purified by two cycles of precipitation/solubilization by taking advantage of the thermally induced phase transition property (Fig. S1, ESI †).…”