Gated Luminescence Imaging of Silicon Nanoparticles

Abstract

The luminescence lifetime of nanocrystalline silicon is typically on the order of microseconds, significantly longer than the nanosecond lifetimes exhibited by fluorescent molecules naturally present in cells and tissues. Time-gated imaging, where the image is acquired at a time after termination of an excitation pulse, allows discrimination of a silicon nanoparticle probe from these endogenous signals. Because of the microsecond time scale for silicon emission, time-gated imaging is relatively simple to implement for this biocompatible and nontoxic probe. Here a time-gated system with ~10 ns resolution is described, using an intensified CCD camera and pulsed LED or laser excitation sources. The method is demonstrated by tracking the fate of mesoporous silicon nanoparticles containing the tumor-targeting peptide iRGD, administered by retro-orbital injection into live mice. Imaging of such systemically administered nanoparticles in vivo is particularly challenging because of the low concentration of probe in the targeted tissues and relatively high background signals from tissue autofluorescence. Contrast improvements of >100-fold (relative to steady-state imaging) is demonstrated in the targeted tissues.

Antibiotic-loaded nanoparticles targeted to the site of infection enhance antibacterial efficacy

“…Time-gated luminescence imaging of the long-lived photoluminescence signal from the pSiNPs 23 (Fig. 5e and f) showed that intravenously injected CARG-conjugated pSiNPs (CARG-pSiNPs) accumulated in infected lungs at markedly higher levels than control-pSiNPs (Fig.…”

“…The time-gated method images the intrinsic, long-lived photoluminescence from the pSiNP carrier and eliminates tissue autofluorescence, 23 and allows the payload to be reliably quantified in intact organs. The quantitation of %ID/g of elemental silicon in different organs measured by ICP-OES showed a significantly higher accumulation of CARG-pSiNPs in the infected lungs than of control pSiNPs (> 4-fold).…”

“…The amine-terminated nanoparticles were rinsed with ethanol and water, and then further functionalized by either MAL-PEG-SCM (maleimide-polyethylene glycol-succinimidyl carboxy methyl ester, MW: 5000) or mPEG-SCM (methoxy PEG-succinimidyl carboxy methyl ester, MW: 5000). 23 The maleimide-activated nanoparticles were then mixed with the CARG peptide solution (0.5 mg/ml in water, 1 mL) and vortexed for 2 hr to conjugate the peptide via the free cysteine residue at the terminal group of the peptide (Supplementary Fig. S14).…”

Porous silicon–graphene oxide core–shell nanoparticles for targeted delivery of siRNA to the injured brain

“…Grafting of the PEG linkers and targeting peptides slightly increased the mean hydrodynamic diameter of the nanocarriers to ~190 nm (measured by DLS, polydispersity index < 0.2). 53 When incubated with Neuro-2a cells, confocal microscopy indicated significant uptake of the RVG peptide-conjugated pSiNPs (Fig. 3a).…”

Nanoparticle Technologies in the Spinal Cord

“…Nanoparticles can be fab-ricated from a wide variety of materials, including polymers, liposomes, inorganics, and metals [Gurny, 1981;Park et al, 2009;Papastefanaki et al, 2015;Saxena et al, 2015]. Due to the vast differences among these materials, there is a broad range of functions and applications for nanoparticles; they are utilized for imaging, cell identification, cell targeting, and drug delivery [Sun et al, 2008;Ruoslahti et al, 2010;Chan et al, 2013;Joo et al, 2015;Accomasso et al, 2016]. Advances in chemistry, biology, engineering, materials science, pharmaceutics, and physics have allowed for the development of innovative nanoparticles with different shapes, sizes, surface chemistries, and cargoes.…”