Herein is presented a proof-of-concept study of protease sensing that combines nontoxic silicon quantum dots (SiQDs) with Förster resonance energy transfer (FRET). The SiQDs serve as the donor and an organic dye as the acceptor. The dye is covalently attached to the SiQDs using a peptide linker. Enzymatic cleavage of the peptide leads to changes in FRET efficiency. The combination of interfacial design and optical imaging presented in this work opens opportunities for use of nontoxic SiQDs relevant to intracellular sensing and imaging.
In this paper we present recent advances in Förster resonance energy transfer (FRET) sensing and bioimaging using nontoxic silicon quantum dots. (SiQDs) In our work, we prepare SiQDs-dye conjugates, with SiQDs serving as the donor which are covalently attached to organic dye acceptors via self-assembled monolayer linkers. Enzymatic cleavage of the peptide leads to changes in FRET response which was monitored using fluorescence lifetime imaging microscopy (FLIM-FRET). The combination of interfacial design and optical imaging presented in this work opens new opportunities for bio-applications using nontoxic silicon quantum dots.
In this paper we demonstrate the possibility of modifying porous silicon (PSi) particles with surface chemistry and
immobilizing a biopolymer, gelatin for the detection of protease enzymes in solution. A rugate filter, a one-dimensional
photonic crystal, is fabricated that exhibits a high-reflectivity optical resonance that is sensitive to small changes in the
refractive index. To immobilize gelatin in the pores of the particles, the hydrogen-terminated silicon surface was first
modified with an alkyne, 1,8-nonadiyne <i>via </i>hydrosilylation to protect the silicon surfaces from oxidation. This
modification allows for further functionality to be added such as the coupling of gelatin. Exposure of the gelatin
modified particles to the protease subtilisin in solution causes a change in the refractive index, resulting in a shift of the
resonance to shorter wavelengths, indicating cleavage of organic material within the pores. The ability to monitor the
spectroscopic properties of microparticles, and shifts in the optical signature due to changes in the refractive index of the
material within the pore space, is demonstrated.
Mesoporous silicon (PSi) photonic crystals have attracted interest as biosensing transducers owing to their high quality
optics and sensitivity in optical characteristics to changes in refractive index. We describe progress our group has made
derivatizing PSi towards devices for biology and medicine. PSi rugate filters display a high reflectivity resonant line in
the reflectance spectrum. As an example for biosensing, immobilization of peptides and biopolymers within the PSi is
demonstrated for detecting protease enzymes. Secretion of matrix metalloproteases from live cells was detected as a
blue shift in the photonic resonance within hours, demonstrating the promise of this biosensor.