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Feasibility for Creating Self-Illuminating Quantum Dots (QDs) Using Therapeutic Proton Beams

S Bastani

S Bastani1*, R Mangaiyarkarasi2 , Y Chen3 , H Jin4 , S Ahmad5 , J Cho6 , (1) Oklahoma State University, Stillwater, OK, (2) Oklahoma State University, Stillwater, OK, (3) University of Oklahoma Health Science Center, Oklahoma City, OK, (4) University of Oklahoma Health Science Center, Oklahoma City, OK, (5) Oklahoma Univ. Health Science Ctr., Oklahoma City, OK, (6) Oklahoma State University, Stillwater, OK


SU-K-702-15 (Sunday, July 30, 2017) 4:00 PM - 6:00 PM Room: 702

Purpose: Self-illuminating quantum dots (QDs) are being investigated as self-light-emitting optical-probes that do not require external (UV) excitation. Since it does not require an external excitation, they are free from auto-fluorescence and imaging with high signal-to-noise ratio is possible. Various self-illuminating QDs were developed using methods such as labeling/doping with radionuclides or bioluminescent proteins which is rather labor-intensive. In this research, we demonstrated that self-illuminating QDs can be created simply by bombarding commercially available QDs with a therapeutic proton beam.

Methods: 33 mg of QDs (CdSe/ZnS of 590 nm emission maxima (orange-red), NN-Labs, Inc.) were dissolved in toluene and deposited semi-uniformly over the 10-cm diameter on an aluminum foil to dry. This QD sample was placed in a thin plastic bag and sandwiched in a water-equivalent-plastic at a depth of 15.3 cm. The sample was irradiated with a 15-cm range near-monoenergetic proton beam of 10 Gy (dose rate 1 Mu/sec). The beam density was 2 μA over 14 cm diameter area. Following 4 hours of post-irradiation delay, the sample was moved to VersaDoc imaging system for luminescence imaging.

Results: Luminescence imaging acquired for 1000 seconds show non-uniform luminescence. In other words, more photons were recorded at the area where QDs were deposited compared to other areas. On this area, the optical signals of approximately 2000 counts per pixel were recorded. The decent count despite the long (4 hr) post irradiation delay is attributed to long-lived radionuclides ¹¹¹In(T½=2.8 days) and ⁷⁶Br(T½=16.2 hr) created from ¹¹¹Cd(p,n)¹¹¹In and ⁷⁶Se(p,n)⁷⁶Br interactions.

Conclusion: Luminescence imaging show that it is possible to obtain self-illuminating QDs by simply activating commercially available QDs with a therapeutic proton beam. In the next set of measurements, blue and red optical filters will be utilized to separate Cherenkov luminescence and self-excited QD luminescence using a more sensitive luminescence imager (IVIS 200).

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