Generally applicable procedure for in situ formation of fluorescent protein-gold nanoconstructs

Abstract

Small noble metal nanoclusters can be formed in situ by direct reduction and stabilization of a metal precursor by biomolecules such as proteins. Considering the diversity in amino acid composition of proteins, and hence their reductive ability, a general method for synthesis of gold nanoclusters using proteins is presented here. A range of proteins (bovine serum albumin, fibrinogen, a-lactalbumin, lysozyme, cytochrome c, myoglobin, b-lactoglobulin and a-chymotrypsin) have been studied, based on size, isoelectric point, flexibility and 3-dimensional structure. Results show protein-gold nanoconstructs with complex protein-specific photophysical properties. The effect on the 3-dimensional conformation of the proteins upon formation of gold nanoclusters and/or nanoparticles within the protein structure is also shown to be highly protein-dependent. A general mechanism for the formation of protein-gold nanoconstructs is proposed, based on charge density matching, yielding a high local concentration of the metal precursor on the protein structure which in turn can nucleate, grow and be stabilized by amino acid residues in the protein.

Self-assembly and characterization of transferrin–gold nanoconstructs and their interaction with bio-interfaces

“…In samples where only AuNCs are present, the AuNCs can be detected with fluorescence spectroscopy. [15][16][17] While the LSPR feature is prominent in the Tf-AuXH system, the band observed for Tf-AuINT has lower absorbance and occur at shorter wavelengths, indicating smaller AuNPs. 16 When AuNPs and AuNCs are in close proximity, the AuNPs can quench the emitted fluorescence from AuNCs.…”

“…16 When AuNPs and AuNCs are in close proximity, the AuNPs can quench the emitted fluorescence from AuNCs. [15][16][17] Steady-state emission spectra of the Tf-AuNCs upon excitation at 370 nm are shown in Figure 1b. UV-visible spectra of the different Tf-AuNCs studied here, as well as the reference systems (Tf only and Tf treated with NaBH 4 ), are shown in Figure 1a.…”

“…[15][16][17][18][19] The average changes in trough area upon injection of Tf and Tf-AuINT under a precompressed phospholipid film are shown in Figure 4b. Consequently, only Tf and Tf-AuINT results are shown here.…”

Luminescent gold nanoclusters as biocompatible probes for optical imaging and theranostics

“…Advantage of protein templated synthesis is the possibility of directly including biological active moieties in the GNCs. Xie and co-workers, for example, [62] synthesized protected red emissive luminescent GNCs, using as templating and reducing agents Bovine Serum Albumine (BSA) (figure 3), [63][64][65][66] Insuline [67], Lisozyme, [68][69][70] Apo-Ferritin, [53] Transferrine, [71] DNase 1, [72] RNase-A, [73] Pepsine, [74] cytochrome c, myoglobin, milk holo α-lactalbumin (type I), milk β-lactoglobulin and pancreas α-chymotrypsin. [66] Despite evidences of protein unfolding have been reported during clusters synthesis in some of these cases, [66] clusterprotecting proteins have been proved to retain their biological function both in-vivo [53,67] and in-vitro.…”

Functionalized nanomaterials: their use as contrast agents in bioimaging: mono- and multimodal approaches

“…Regardless of composition, surface functionalization of the nanomaterial is required to enable targeting and stealth for long circulation times with minimal nonspecific binding [239]. There is a plethora of entities that can be incorporated onto a NP's surface, with covalent bonding preferred over electrostatic interactions: DNA, RNA, [472] oligonucleotides (aptamers), [29,434,[473][474][475][476] peptides, [36,175,201,[477][478][479][480][481][482] proteins, [483][484][485][486][487] enzymes, [488][489][490][491] antibodies [492]. No matter what the surface moiety, its activity must not be altered once anchored to the NP surface ( Figure 13).…”