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Co-enhancement of fluorescence and singlet oxygen generation by silica-coated gold nanorods core-shell nanoparticle.

Ke X, Wang D, Chen C, Yang A, Han Y, Ren L, Li D, Wang H - Nanoscale Res Lett (2014)

Bottom Line: Metal-enhanced fluorescence (MEF) as a newly recognized technology has been attracting considerable attention and is widely used in fluorescence-based technology.In this paper, we reported a novel distance-dependent MEF and metal-enhanced singlet oxygen generation phenomenon based on silica-coated gold nanorods (AuNRs@SiO2) core-shell structure with tetra-substituted carboxyl aluminum phthalocyanine (AlC4Pc) that serve as both fluorophore and photosensitizer.When the AlC4Pc was linked on the surface of AuNRs@SiO2, the fluorescence intensity and singlet oxygen productivity varied with the thickness difference of silica shell from 2.1 to 28.6 nm.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomaterials, College of Materials, Xiamen University, Xiamen, 361005, People's Republic of China, kcc2691@126.com.

ABSTRACT
Metal-enhanced fluorescence (MEF) as a newly recognized technology has been attracting considerable attention and is widely used in fluorescence-based technology. In this paper, we reported a novel distance-dependent MEF and metal-enhanced singlet oxygen generation phenomenon based on silica-coated gold nanorods (AuNRs@SiO2) core-shell structure with tetra-substituted carboxyl aluminum phthalocyanine (AlC4Pc) that serve as both fluorophore and photosensitizer. When the AlC4Pc was linked on the surface of AuNRs@SiO2, the fluorescence intensity and singlet oxygen productivity varied with the thickness difference of silica shell from 2.1 to 28.6 nm. The co-enhancement effect reached the maximum of 7-fold and 2.1-fold, respectively, when the separation distance was 10.6 nm. These unique characteristics make the prepared core-shell nanoparticles promising for MEF-based biological imaging and photodynamics therapy.

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Photobleaching of ABDA. Photobleaching of ABDA by 1O2 generated by (a) free AlC4Pc as control; (b)-(d) AuNRs@SiO2-AlC4Pc with 2.1, 10.6, and 28.2 nm shell thickness; and (e) time-dependent decrease in ABDA fluorescence (ΔF) as a function of irradiation time, corresponding to (a)-(d).
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Fig6: Photobleaching of ABDA. Photobleaching of ABDA by 1O2 generated by (a) free AlC4Pc as control; (b)-(d) AuNRs@SiO2-AlC4Pc with 2.1, 10.6, and 28.2 nm shell thickness; and (e) time-dependent decrease in ABDA fluorescence (ΔF) as a function of irradiation time, corresponding to (a)-(d).

Mentions: Early studies have indicated that both of the fluorescence and the 1O2 generation would be effectively inhibited by non-radiative decay from the excited PSs to metal when the PSs were close proximity to the metal surface [35]. In our study, three groups of AuNRs@SiO2-AlC4Pc NPs with 2.1, 10.6, and 28.2 nm silica shell were incubated with ABDA to assess the influence of shell thickness on the 1O2 generation. After being exposed in different amount of light exposure, the fluorescence intensity of ABDA was decreased because of the formation of its endoperoxide in the presence of 1O2 (Figure 6a,b,c,d). The decreased amount of ABDA fluorescence at 431 nm can be used to estimate the relative yield of 1O2 produced from AlC4Pc. The time-related fluorescence decline of ABDA in different AuNRs@SiO2-AlC4Pc solutions and free AlC4Pc samples were directly compared in Figure 6e. Among the tested samples, AuNRs@SiO2-AlC4Pc with 10.6 nm silica shell exhibited the highest photo-oxidation efficiency with 2.1-fold higher than that of the free AlC4Pc solution. The accelerated photobleaching of ABDA was mainly affected by the AlC4Pc-AuNRs interaction. As mentioned above, the concentrated electromagnetic field may play a key role in the enhancement of 1O2 generation. 1O2 generation could also be enhanced by the promotion of intersystem crossing and the yield of triplet state, which probably result from the increased population of singlet excited state of AlC4Pc [21, 36] (Figure 4b). Furthermore, a shorter lifetime leads to a less possibility of photobleaching, and then more excitation-emission cycles occur prior to photobleaching of PSs during the excited state [10]. The amplified production of 1O2 and great enhancement of fluorescence intensity of AuNRs@SiO2-AlC4Pc could serve them well as a theranostic agent for fluorescence imaging-guided cancer treatment.Figure 6


Co-enhancement of fluorescence and singlet oxygen generation by silica-coated gold nanorods core-shell nanoparticle.

Ke X, Wang D, Chen C, Yang A, Han Y, Ren L, Li D, Wang H - Nanoscale Res Lett (2014)

Photobleaching of ABDA. Photobleaching of ABDA by 1O2 generated by (a) free AlC4Pc as control; (b)-(d) AuNRs@SiO2-AlC4Pc with 2.1, 10.6, and 28.2 nm shell thickness; and (e) time-dependent decrease in ABDA fluorescence (ΔF) as a function of irradiation time, corresponding to (a)-(d).
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
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Fig6: Photobleaching of ABDA. Photobleaching of ABDA by 1O2 generated by (a) free AlC4Pc as control; (b)-(d) AuNRs@SiO2-AlC4Pc with 2.1, 10.6, and 28.2 nm shell thickness; and (e) time-dependent decrease in ABDA fluorescence (ΔF) as a function of irradiation time, corresponding to (a)-(d).
Mentions: Early studies have indicated that both of the fluorescence and the 1O2 generation would be effectively inhibited by non-radiative decay from the excited PSs to metal when the PSs were close proximity to the metal surface [35]. In our study, three groups of AuNRs@SiO2-AlC4Pc NPs with 2.1, 10.6, and 28.2 nm silica shell were incubated with ABDA to assess the influence of shell thickness on the 1O2 generation. After being exposed in different amount of light exposure, the fluorescence intensity of ABDA was decreased because of the formation of its endoperoxide in the presence of 1O2 (Figure 6a,b,c,d). The decreased amount of ABDA fluorescence at 431 nm can be used to estimate the relative yield of 1O2 produced from AlC4Pc. The time-related fluorescence decline of ABDA in different AuNRs@SiO2-AlC4Pc solutions and free AlC4Pc samples were directly compared in Figure 6e. Among the tested samples, AuNRs@SiO2-AlC4Pc with 10.6 nm silica shell exhibited the highest photo-oxidation efficiency with 2.1-fold higher than that of the free AlC4Pc solution. The accelerated photobleaching of ABDA was mainly affected by the AlC4Pc-AuNRs interaction. As mentioned above, the concentrated electromagnetic field may play a key role in the enhancement of 1O2 generation. 1O2 generation could also be enhanced by the promotion of intersystem crossing and the yield of triplet state, which probably result from the increased population of singlet excited state of AlC4Pc [21, 36] (Figure 4b). Furthermore, a shorter lifetime leads to a less possibility of photobleaching, and then more excitation-emission cycles occur prior to photobleaching of PSs during the excited state [10]. The amplified production of 1O2 and great enhancement of fluorescence intensity of AuNRs@SiO2-AlC4Pc could serve them well as a theranostic agent for fluorescence imaging-guided cancer treatment.Figure 6

Bottom Line: Metal-enhanced fluorescence (MEF) as a newly recognized technology has been attracting considerable attention and is widely used in fluorescence-based technology.In this paper, we reported a novel distance-dependent MEF and metal-enhanced singlet oxygen generation phenomenon based on silica-coated gold nanorods (AuNRs@SiO2) core-shell structure with tetra-substituted carboxyl aluminum phthalocyanine (AlC4Pc) that serve as both fluorophore and photosensitizer.When the AlC4Pc was linked on the surface of AuNRs@SiO2, the fluorescence intensity and singlet oxygen productivity varied with the thickness difference of silica shell from 2.1 to 28.6 nm.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomaterials, College of Materials, Xiamen University, Xiamen, 361005, People's Republic of China, kcc2691@126.com.

ABSTRACT
Metal-enhanced fluorescence (MEF) as a newly recognized technology has been attracting considerable attention and is widely used in fluorescence-based technology. In this paper, we reported a novel distance-dependent MEF and metal-enhanced singlet oxygen generation phenomenon based on silica-coated gold nanorods (AuNRs@SiO2) core-shell structure with tetra-substituted carboxyl aluminum phthalocyanine (AlC4Pc) that serve as both fluorophore and photosensitizer. When the AlC4Pc was linked on the surface of AuNRs@SiO2, the fluorescence intensity and singlet oxygen productivity varied with the thickness difference of silica shell from 2.1 to 28.6 nm. The co-enhancement effect reached the maximum of 7-fold and 2.1-fold, respectively, when the separation distance was 10.6 nm. These unique characteristics make the prepared core-shell nanoparticles promising for MEF-based biological imaging and photodynamics therapy.

No MeSH data available.


Related in: MedlinePlus