title: Characterization and application of single fluorescent nanodiamonds as cellular biomarkers.
abstract: Type Ib diamonds emit bright fluorescence at 550-800 nm from nitrogen-vacancy point defects, (N-V)(0) and (N-V)(-), produced by high-energy ion beam irradiation and subsequent thermal annealing. The emission, together with noncytotoxicity and easiness of surface functionalization, makes nano-sized diamonds a promising fluorescent probe for single-particle tracking in heterogeneous environments. We present the result of our characterization and application of single fluorescent nanodiamonds as cellular biomarkers. We found that, under the same excitation conditions, the fluorescence of a single 35-nm diamond is significantly brighter than that of a single dye molecule such as Alexa Fluor 546. The latter photobleached in the range of 10 s at a laser power density of 10(4) W/cm(2), whereas the nanodiamond particle showed no sign of photobleaching even after 5 min of continuous excitation. Furthermore, no fluorescence blinking was detected within a time resolution of 1 ms. The photophysical properties of the particles do not deteriorate even after surface functionalization with carboxyl groups, which form covalent bonding with polyL-lysines that interact with DNA molecules through electrostatic forces. The feasibility of using surface-functionalized fluorescent nanodiamonds as single-particle biomarkers is demonstrated with both fixed and live HeLa cells.
authors.affiliation: Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 106, Taiwan.
authors.forename: Chi-Cheng
authors.initials: CC
authors.lastname: Fu
authors.forename: Hsu-Yang
authors.initials: HY
authors.lastname: Lee
authors.forename: Kowa
authors.initials: K
authors.lastname: Chen
authors.forename: Tsong-Shin
authors.initials: TS
authors.lastname: Lim
authors.forename: Hsiao-Yun
authors.initials: HY
authors.lastname: Wu
authors.forename: Po-Keng
authors.initials: PK
authors.lastname: Lin
authors.forename: Pei-Kuen
authors.initials: PK
authors.lastname: Wei
authors.forename: Pei-Hsi
authors.initials: PH
authors.lastname: Tsao
authors.forename: Huan-Cheng
authors.initials: HC
authors.lastname: Chang
authors.forename: Wunshain
authors.initials: W
authors.lastname: Fann
mesh_terms: D015415:Biomarkers / Q000032:analysis / Q000737:chemistry; D004247:DNA / Q000737:chemistry; D018130:Diamond / Q000032:analysis* / Q000737:chemistry*; D005453:Fluorescence; D006367:HeLa Cells; D006801:Humans; D015336:Molecular Probe Techniques; D015335:Molecular Probes / Q000032:analysis* / Q000737:chemistry*; D049329:Nanostructures / Q000032:analysis* / Q000737:chemistry*; D011107:Polylysine / Q000737:chemistry; D055672:Static Electricity
chemical_list: D015415:Biomarkers; D015335:Molecular Probes; D011107:Polylysine; D018130:Diamond; D004247:DNA