Biofunctional Silicon Nanoparticles by Means of Thiol-Ene Click Chemistry

The preparation and characterization of butylene-terminated silicon nanoparticles (SiNPs) and their functionalization using thiol-ene chemistry is described, as well as the coupling of DNA strands. Bromide-terminated SiNPs were prepared by means of the oxidation of magnesium silicide and functionalized with butylene chains through treatment with the corresponding Grignard reagent. The successful coupling was confirmed by NMR and FTIR spectroscopy. TEM measurements revealed a silicon-core diameter of (2.4±0.5) nm. The fluorescence emission maximum is at λmax=525 nm when excited at λexc=430 nm. The conjugation of these alkene-terminated SiNPs by means of thiol-ene chemistry is described for a variety of functional thiols. Efficient coupling was evidenced by NMR and FTIR spectroscopy. Moreover, the characteristic fluorescence properties of the SiNPs remained unaltered, thus demonstrating the value of this approach towards functional oxide-free SiNPs. Activation of the attached carboxylic acid moieties allowed for conjugation of NH2-terminated oligo-ssDNA (ss=single strand) to the SiNPs. Successful coupling was confirmed by a characteristic new UV absorption band at 260 nm, and by the still-present distinctive fluorescence of the SiNPs at 525 nm. Gel electrophoresis confirmed coupling of 2 to 3 DNA strands onto the SiNPs, whereas no uncoupled DNA was observed.