Carbon dots (C-dots) were used to detect UV-induced DNA damage. C-dots are small carbon nanoparticles less than 10nm in size with surface passivation that gives them fluorescent properties. In this study, C-dots were modified with amine groups to give them a positive charge and ability to interact with negatively charged DNA. Genomic DNA was isolated from human cells and exposed to UV radiation for varying times. C-dots were incorporated into both native and UV-exposed DNA. Fluorescence energy transfer between the C-dots and ethidium bromide (EtBr) showed that the intensity of EtBr emission decreased more for DNA exposed to UV, indicating the C-dots method could more sensitively detect

1. Carbon Dots are used for the detection of
UV-DNA Damage
Bio-Analytical chemistry and High performance
Ahmad Ali
University of Camerino

2. Outlines
1. What is C-dots:
2. Nature of C-dots
3. Size of C-dots
4. How can be c-dots modified for the detection
5. Genomics DNA isolation and damage experiment
6. Interaction of C-dots and DNA and Fluorescence energy
Transfer
7. conclusion

3. Introduction
C-Dots:
C’dots (or CD’s)are small carbon nanoparticle(less than10nm in size )
with same form of surface passivation.( Creation of Outer Layer)
• C’dots were First discovered by XU et al., in 2004 accidently during the
purification of single walled carbon nanotubes .
• This discovery achieved much progress in the florescence property of c-dots in
various sector of biological, analytical chemistry and their Applications.

4. Cont’d
• C’dots are Biocompatible , have small size with relatively large
surface area , photostable and having photoluminescence properties.
• Fluorescent carbon dots- carbon dots (C’dots)are currently emerging
as a class of promising fluorescent probe on account of their low photo
bleaching ,versatile surfaces and excellent biocompatibility.
• That’s why fluorescent carbon Dots (C’dots ) have attracted increasing
attention due to their potential application in sensing ,catalysis and
biomedicine.

5. Merits of C-Dots:
• C-dots, in contrast to other’s semiconductor quantum dots,
possess several merits such as;
• low cost, versatile surface modifications, excellent photo stability,
small size, chemical inertness, water solubility, etc.
• These extraordinary properties, together with biocompatibility and low
toxicity, make them an ideal candidate for biomedical, biochemical
and chemical applications.

6. Chemistry of C-dots and how it can be modified?
• The chemistry of c-dots consist of an amorphous to non crystalline
core with mostly SP2 carbons and highly abundant oxygen.

7. Cont’d
• The size and surface passivation of c-dots influence the absorption and
fluorescent characteristics. however, they harvest light in the
ultraviolet (UV) region.

8. Modification of carbon Dots : for the
Detection Of Damage DNA
• The c-dots were modified with their surface amine moieties, using the
microwave assisted pyrolysis of CA (Citric acid), in the presence of
DETA (diethylenetriamine).
• Amine moiety rich molecule such as 1,2-ethylenediamine,
polyethyleneimine were previously used to stabilize the C-dots
surface.
• DETA was chosen as the surface passivation agent in order to obtain
C-dots with a positive surface charge and to promote their interaction
with the negatively charged backbone of the DNA.

9. Genomics DNA isolation and damage
experiment:
• Actually in this experiment genomics DNA were taken, and control
condition were applied:
• Native DNA
• UV Exposed DNA
• Condition
Isolation of genomic DNA from human prostate cancer cell lines (PC-3)
and exposed to UV at 254 nm for 1 and 5 min.
• Damaged DNA was prepared using UV irradiation at 254 nm and was
monitored using UV/Vis spectrophotometry.

10. Cont’d
• C-dots incorporated in both Native and UV exposed DNA.
• Similarly in the next step EtBr incorporated to detect the Fluorescence
resonance energy transfer between these two molecule.
• At the very last step fluorescence readout will be noticed for samples
containing melanoma and non-melanoma DNA detection.

11. (A) The procedure for the preparation of samples for the detection of UV damage on PC-3 cell line
genomic DNA; (B) the fluorescence spectra of the C-dots solution containing EtBr and DNA isolated
from the PC-3 cells damaged by UV radiation (254 nm) for 1 and 5 min (C) the comparison of EtBr
emissions at 612 nm for samples containing melanoma and non-melanoma DNA

12. First Case:
• In the First case, when EtBr was taken alone for both DNA, and was
damaged by UV radiation for 20 min (λ=254 nm).
• which show 33% lower emission intensity, than the control sample
containing non-damaged DNA.
• The decrease is due to total amount of canonical base pairs, which are
partially replaced by UV photoproducts.

13. Cont’d
2nd Case:
• The FRET between the C-dots and EtBr took place (λex=360 nm).
• In this case, the EtBr emission intensity decreased by 50%.
• In the first case photoproducts are not able to accommodate EtBr or
shield the intercalated EtBr from quenching.
• Now in this case the non-canonical base pair are completely replaced
by the UV Photoproduct.

14. Conclusion:
• The FRET between the C-dots and EtBr was used to quantify the UV
damage to the DNA and show how we distinguish native DNA from
DNA Damaged by UV.
• C-dots with a positive surface charge were attached to DNA and
served as a donor of excitation energy.
• suggested that the FRET-based mechanism between C-dots and EtBr is
more sensitive to UV-induced damage to DNA than EtBr alone.

15. Thank you so much