Cellular internalisation, bioimaging and dark and photodynamic cytotoxicity of silica nanoparticles doped by {Mo₆I₈}⁴⁺ metal clusters

Abstract

Silica nanoparticles (SNPs) doped by hexanuclear molybdenum cluster complexes [{Mo6X8}L6] n (X = Cl, Br, or I; L = various inorganic or organic ligands) have been recently suggested as materials with a high potential for biomedical applications due to both the outstanding photoluminescent properties and the ability to efficiently generate singlet oxygen upon photoirradiation. However, no studies were undertaken so far to prove this concept. Therefore, here we examined the potential of photoluminescent SNPs doped by {Mo6I8} 4+ for such applications as bioimaging and photodynamic therapy using human epidermoid larynx carcinoma (Hep-2) cell line as a model. Our results demonstrated both: (i) significant luminescence from cells with internalised molybdenum cluster-doped SNPs combined with the low cytotoxicity of particles in the darkness and (ii) significant cytotoxicity of the particles upon photoirradiation. Thus, this research provides strong experimental evidence for high potential of molybdenum-cluster-doped materials in such biomedical applications as optical bioimaging, biolabeling and photodynamic therapy.

Superior performance of macroporous over gel type polystyrene as a support for the development of photo-bactericidal materials

“…The hexanuclear molybdenum complex 1 has the valuable property of bright-red room temperature phosphorescence. [24][25][26][27][28][29][30][31][32][33][34][35] In our case solid powder of 1 emitted phosphorescence at λ max = 678 nm, 1@P gel emitted at λ max = 671 nm and 1@P mp displayed emission at λ max = 676 nm. The intensity of both emissions are quenched by oxygen upon exposure of the samples to air.…”

“…22 Recently we have proposed a hexanuclear molybdenum cluster complex (1: [Mo 6 I 8 Ac 6 ] 2-, Ac is acetate; see structure in Figure 1) as photoactive agent for aPDI, 23 owing to its notable photochemical properties. [24][25][26][27][28][29][30][31][32][33][34][35] Regarding the supports for the photoactive agents, a variety of materials have been described in the literature, like polyurethane, cellulose, nylon, chitosan, silica and polystyrene. [13][14][15][16][17][18][19][20] This last polymer is one of the most popular supports employed so far, dating back to the pioneering works of Schaap and Neckers.…”

Time-gated luminescence bioimaging with new luminescent nanocolloids based on [Mo6I8(C2F5COO)6]2−metal atom clusters

“…Owing to the ionic nature of the interaction between the cluster units and the countercations (K + , Cs + , tetrabutylammonium…), the solid state powder can be dispersed at nanosized level in solution. 30 Even after high dispersion in organic or inorganic matrix, Mo6 or Re6 metal atom clusters exhibit a characteristic broad emission band in the red and NIR (550-900 nm), 30,34,40 which is particularly interesting for biotechnology applications as it corresponds to a low human tissues absorption at these wavelengths. Moreover, some of these MC could generate singlet oxygen under irradiation, which is of particular interest for photodynamic therapy (PDT) applications.…”

“…[10][11][12] Functional silica nanoparticles with magnetic and/or optical properties have attracted much attention for numerous applications not only in the fields of biotechnologies but also photonics. 13,14 They are usually achieved through the encapsulation of superparamagnetic nanocrystals such as ferrites 15 or photonic nanocrystals such as metal nanoparticles 16,17 or luminescent nanophosphors such as organic dyes, 18,19 semi-conductor quantum dots, [20][21][22][23][24][25][26][27] organometallic complexes, 28,29 metal atom cluster (MC) [30][31][32][33][34] or doped nanocrystals. [35][36][37] Thus, since 2006, some of us developed a simple, versatile, highly reproducible and efficient method based on microemulsion process to prepare large amount of silica nanoparticles incorporating luminescent nanosized inorganic Mo6 or Re6 metal atom clusters based on octahedra.…”

“…[35][36][37] Thus, since 2006, some of us developed a simple, versatile, highly reproducible and efficient method based on microemulsion process to prepare large amount of silica nanoparticles incorporating luminescent nanosized inorganic Mo6 or Re6 metal atom clusters based on octahedra. [30][31][32][33][34] These MC salts are generally synthesized by a solid state chemistry route at high 8 I 8X ] 2-nano-sized cluster units (M = Mo, W or Re) wherein the M6 cluster is face-capped by eight inner ligands (X i ) and additionally bonded to six apical ligands (X a ). Owing to the ionic nature of the interaction between the cluster units and the countercations (K + , Cs + , tetrabutylammonium…), the solid state powder can be dispersed at nanosized level in solution.…”