Figure 4. SiRNA delivery in PBI with CAQK-conjugated PSiNPs.

(a) Schematic of the experimental design for siRNA delivery. (b) Gated luminescence imaging of PSiNPs under pulsed laser excitation (λex=410 nm). PBI mice expressing GFP were injected with vehicle alone (PBS) or PSiNPs conjugated with CAQK (CAQK-PSiNPs) or CGGK (CGGK-PSiNPs). Brains and other organs were isolated 72 h after PBI and analysed for gated luminescence. (c) Signal-to-noise ratio (SNR) calculated for the peptide-conjugated PSiNPs in each mouse tissue (relative to PBS control) as described in the Methods section. CAQK-PSiNP showed significantly higher SNR in PBI brains than the control peptide-conjugated group (mean±s.d., *P<0.05, two-tailed Student's t test, NS, not significant, n=3). (d) Microscopic analysis of GFP expression (green) in coronal sections from the animals from panel A counterstained with 4,6-diamidino-2-phenylindole (DAPI; blue). CAQK-PSiNP-injected brains exhibited a large void of GFP in injured area of PBI brain (inset). Scale bar, 500 μm. (e) Higher magnification fluorescent images of GFP expression in PBI brain from d. Scale bar, 50 μm. (f) Mean GFP intensity in injured hemisphere was normalized to corresponding contralateral hemisphere and plotted as percentage GFP expression (y axis; ***P<0.001, ANOVA analysis, n=3). DAPI (DAPI signal (plotted) showed similar total cell number. Mean±s.e.m., NS, not significant.