RESUMO
The near-infrared-IIb (NIR-IIb, 1 500-1 700 nm) window fluorescence with long emission wavelength has reduced light scattering and tissue auto-fluorescent background, achieving deep tissue imaging with high spatial resolution. Herein, we prepared an NIR-IIb fluorescent quantum dots (QDs) composed of lead sulfide (PbS). The fluorescence spectrum of PbS QDs were adjusted by controlling the size of the PbS core. Cadmium sulfide (CdS) shell was synthesized by the cation exchange method to form the core/shelled lead sulfide/cadmium sulfide quantum dots (CSQDs). The surface of CSQDs was modified with polyethylene glycol (PEG) to increase their stability in aqueous solution. The resulting PEG-modified CSQDs (PEG-CSQDs) had the emission peak at ~1 550 nm with quantum yield of 7.2%. The animal procedures were approved by the Institutional Animal Care and Use Committee (IACUC) of Fudan University School of Pharmacy. At 2 h postinjection, PEG-CSQDs clearly delineated the tumor region of mice bearing orthotopic CT26-Luc colon cancer model in the NIR-IIb fluorescence imaging. The fluorescent intensity ratio of primary tumor and adjacent normal tissue was 42.3, and that of metastatic tumor and adjacent normal tissue was 22.3, which allowed to detect the primary tumor of 3.4 mm×2.5 mm in dimension and the metastatic tumor of 1.2 mm×0.9 mm in dimension, and accurately guided the excision of tumors. The PEG-CSQDs prepared in this study provided a new approach for the early diagnosis and guidance of surgical resection of colon cancer.
RESUMO
To investigate factors influencing the intranasal absorption of rivastigmine hydrogen tartrate (RHT), we studied the pharmacokinetics of RHT after intranasal administration and evaluated its brain targeting behavior. In situ rat nasal perfusion model was used in the study and pH impact was examined on the intranasal absorption of RHT. High performance liquid chromatography (HPLC) method was established to measure RHT concentration in the plasma and brain tissue after intranasal and intravenous administration. The pharmacokinetic parameters, drug targeting index (DTI), and nose-to-brain direct transport percentage (DTP) were calculated. It was demonstrated that the intranasal absorption mechanism of RHT was passive diffusion. The absorption rate was highest at pH 6.0. The absolute bioavailability of intranasally administrated RHT was 73.58%. Compared with that of intravenous administration, RHT absorption into the brain was faster and more efficient after intranasal delivery, and the DTI value was 195.27% of intravenous injection. Moreover, 48.79% of the drug can be absorbed directly from the nose into the brain without systematic circulation. Meanwhile, drug elimination half-time in the brain was prolonged by 1.4 fold compared to that of intravenous injection. In conclusion, intranasal administration of RHT not only improves drug absorption into the system, but also enhances drug absorption rate and content in the brain remarkably, which is an advantage in the treatment of central nervous system-related diseases.