Infrared active nanoprobes for bio-medical imaging based on inorganic nanocrystals

A. Podhorodecki, M. Banski, A. Noculak, L. Golacki, B. Krajnik, H. Woznica, A. Lesiak, D. Kociolek, B. Sojka
Wroclaw University of Technology,

Keywords: nanocrystals, optical imaging, infrared, lanthanides


Optically active inorganic nanocrystals (NCs) (quantum dots, QDs) are recently widely used in research related to bio-medicine as efficient in vivo and in vitro optical markers but also as building blocks in bio-sensors. However, even if they characterize with much better optical parameters than proteins or molecular markers their clinical use is still only a future perspective. This is mainly due to three disadvantages characterized these markers: low bio-degrabillity, high toxicity and hydrophobic nature of their surface. Some of these drawbacks can be reduced or even eliminated and some of them can be accepted, if we take into account some of unique properties these markers can offer. Among these, the most interesting is their optical activity in near – infrared spectral range (NIR), multi-functionality (simultaneous optical-MRI-CT imaging) and size, shape and surface chemistry control combined with high emission quantum yield and lack of photoblecheing and photoblinking. Thus, the aim of this work was to find the optimal NCs matrix composition which guarantee their efficient emission and/or excitation in infrared spectral range. The second aim of this work was to find the way to control and to change the hydrophobic nature of their surface to hydrophilic form. The third challenge for this work was to develop microscopic techniques enables to image such infrared active nanostructures and benefit from their unique emission properties. To obtain these goals, with use of wet-chemistry approaches we synthesised three types of nanocrystals: NaGdF4:Yb, Er (size control from 3 up to 100 nm) [1], NaGdF4:Eu (size control from 3 up to 20 nm) [2, 3] and PbS/CdS (size control from 2 up to 6 nm). Next, we developed a few ligand exchange protocols and succeed to obtain stable in time and pH hydrophilic NCs. Finally, we build two microscopes enabling optical imaging in NIR spectral range (500-1600 nm) at UV-NIR excitation or using 980 nm excitation wavelength and enabling optical imaging in VIS spectral range. Both microscopes has additional option to stimulate the objects with UV or NIR lasers to modify the object parameters (photochemical activations and temperature increase). In this work, we will present details of our work on optical imaging in NIR and we will show preliminary examples of our nanoprobes in use. This will include experiments which have been done for melanoma cancer cells [1, 2], HeLa cancer cells [3] and macrophages. The examples of results for listed above samples have been shown in Fig.1. Acknowledgment Thank you for Cedars Sinai Medical Center’s International Research and Innovation in Medicine Program, the Association for Regional Cooperation in the Fields of Health, Science and Technology (RECOOP HST Association) for their support of our organization as participating Cedars – Sinai Medical Center - RECOOP Research Center (CRRC).