Alkyl Passivation and Amphiphilic Polymer Coating of Silicon Nanocrystals for Diagnostic Imaging

• Published in: Small (Weinheim an der Bergstrasse, Germany) Vol. 6; no. 18; pp. 2026 - 2034
• Main Authors: Hessel, Colin M., Rasch, Michael R., Hueso, Jose L., Goodfellow, Brian W., Akhavan, Vahid A., Puvanakrishnan, Priyaveena, Tunnel, James W., Korgel, Brian A.
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 20.09.2010; WILEY‐VCH Verlag; Wiley Subscription Services, Inc
• Subjects: Alkylating Agents - chemistry; Alkylating Agents - pharmacology; amphiphilic polymers; Coated Materials, Biocompatible - chemical synthesis; Coated Materials, Biocompatible - chemistry; Diagnostic Imaging - instrumentation; Diagnostic Imaging - methods; Humans; Hydrophobic and Hydrophilic Interactions - drug effects; Hydroxylation - drug effects; Hydroxylation - physiology; imaging; Models, Biological; Nanoparticles - chemistry; Nanotechnology; Nanotechnology - methods; Polymers - chemistry; Polymers - pharmacology; Silicon - chemistry; silicon nanocrystals; surface passivation; Surface Properties; Surface-Active Agents - chemistry; Surface-Active Agents - pharmacology; X-Ray Diffraction
• ISSN: 1613-6810; 1613-6829
• DOI: 10.1002/smll.201000825

A method to produce biocompatible polymer‐coated silicon nanocrystals for medical imaging is shown. Silica‐embedded Si nanocrystals are formed by HSQ thermolysis. The nanocrystals are then liberated from the oxide and terminated with Si–H bonds by HF etching, followed by alkyl monolayer passivation by thermal hydrosilylation. The Si nanocrystals have an average diameter of 2.1 nm ± 0.6 nm and photoluminesce with a peak emission wavelength of 650 nm, which lies within the transmission window of 650–900 nm that is useful for biological imaging. The hydrophobic Si nanocrystals are then coated with an amphiphilic polymer for dispersion in aqueous media with the pH ranging between 7 and 10 and an ionic strength between 30 mM and 2 M, while maintaining a bright and stable photoluminescence and a hydrodynamic radius of only 20 nm. Fluorescence imaging of polymer‐coated Si nanocrystals in biological tissue is demonstrated, showing the potential for in vivo imaging. Luminescent silicon (Si) nanocrystals are formed from the thermolysis of hydrogen silsesquioxane and passivated with a dodecane monolayer via thermal hydrosilylation. The nanocrystals are rendered hydrophilic for biological imaging by coating with an amphiphilic polymer. The polymer‐coated nanocrystals are imaged in biological tissue, highlighting the potential of Si nanocrystals for in vivo diagnostic imaging.