One-step fabrication of intense red fluorescent gold nanoclusters and their application in cancer cell imaging

Abstract

A one-step method for successfully fabrication of water-soluble and alkanethiol-stabilized Au nanoclusters (NCs) was demonstrated. The novel and facile method was based on simply placing histidine (His), HAuCl4 and 11-mercaptoundcanoic acid (MUA) together at room temperature. The resulting Au NCs were exclusively composed of Au17MUA4His22 (AMH), as demonstrated by the photoluminescence, UV-Vis absorption, electrospray ionization mass and X-ray photoelectron spectroscopy. AMH exhibited intense red fluorescence (λem = 600 nm), a long fluorescence lifetime (7.11 μs), considerable stability, and a large Stoke's shift (320 nm). Based on the excellent properties of the AMH, cell experiments were conducted. Cytotoxicity studies showed that the Au NCs exhibited negligible effects in altering cell proliferation or triggering apoptosis. Cancer cell imaging of HeLa cell lines indicated that the obtained AMH could serve as a promising fluorescent bioprobe for bioimaging. This strategy, based on the one-step method, may offer a novel approach to fabricate other water-soluble and alkanethiol-stabilized metal nanoclusters for application in biolabelling and bioimaging.

Synthesis of water-soluble gold clusters in nanosomes displaying robust photoluminescence with very large Stokes shift

“…Therefore, it is very plausible to think about the formation of inter-charge transfer between the small and large non-close shell configuration clusters in order to achieve the most stable close-shell electronic configurations. From SI Table S2 it is further deduced that such electron transfers should occur among the pairs (Au 6 -Au 16 ) and (Au 5 -Au 14 ). It is to note that such cluster pairs would have an estimated size of 0.5 nm (cluster 5/6) + 0.8 nm (cluster 14/16) = 1.3 nm, which nicely agrees with the averaged TEM particle diameter (1.2 ± 0.2 nm).…”

“…Therefore, only after very inhibited Brownian motion of the (small and large) formed clusters inside the nanosome film by the encounter of small and the corresponding large clusters (i.e. [6][7][8][9][10][11][12][13][14][15][16][5][6][7][8][9][10][11][12][13][14] can be built up stable cluster pairs, as schematically shown in SI Fig. S10.…”

“…Moreover, we will show that these results cannot be explained by the usual LMCT mechanism, but they can be understood assuming the initial formation of two cluster sizes (Au 5,6 and Au 14,16 ), having non-closed shell electronic configurations, due to the difference in bonding strength of the two capping agents, which template the formation of the bimodal cluster size distribution inside the nanosome compartments. Such clusters slowly evolve into very stable, closed-shell Au cluster complexes (Au 6 -Au 16 and Au 5 -Au 14 ) with robust luminescence.…”

“…Shibu et al [13] prepared Au 15 trapped in cyclodextrins showing the maximum emission centered at 690 nm when excited at 375 nm. Biang et al [14] synthesized luminescent Au clusters with a bright red emission and large Stokes shift using both histidine and 11-mercaptoundecanoic acid as stabilizers. Gold clusters were also obtained using ribonuclease A as bio-template showing a large Stokes shift (210 nm) and a high luminescence quantum yield (QY) of 12%, being suitable for cancer targeting and imaging [15].…”

Synthesis of ultrastable and multifunctional gold nanoclusters with enhanced fluorescence and potential anticancer drug delivery application

“…On the other hand, noble metal nanoclusters, consisting of several to several hundred atoms, also have drawn much attention due to their unique physiochemical properties [5][6][7], catalytic activities [8], ion detection capability [9][10][11][12][13] and potential applications in bio-labeling and sensing [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. At the same time, Au NCs can be synthesized using different capping molecules, such as proteins [31][32][33], DNA and nucleotides [34,35], peptides [11,[36][37][38][39], polymers [40][41][42][43][44] and small molecules such as dihydrolipoic acid [10], diphosphine [45], histidine [46,47], purine [48], cytidine [49,…”