Uniform silica coated fluorescent nanoparticles: synthetic method, improved light stability and application to visualize lymph network tracer.
BACKGROUND
The sentinel lymph node biopsy (SLNB) was developed as a new modality in the surgical diagnosis of lymph node metastases. Dye and radioisotope are major tracers for the detection of sentinel lymph nodes (SLN). Dye tends to excessively infiltrate into the interstitium due to their small size (less than several nanometers), resulting in difficulties in maintaining clear surgical fields. Radioisotopes are available in limited number of hospitals. Fluorescent nanoparticles are good candidates for SLN tracer to solve these problems, as we can choose suitable particle size and fluorescence wavelength of near-infrared. However, the use of nanoparticles faces safety issues, and many attempts have been performed by giving insulating coats on nanoparticles. In addition, the preparation of the uniform insulating layer is important to decrease variations in the quality as an SLN tracer.


RESULTS
We herein succeeded in coating fluorescent polystyrene nanoparticles of 40 nm with uniform silica layer of 13 nm by the modified Stöber method. The light stability of silica coated nanoparticles was 1.3-fold greater than noncoated nanoparticles. The popliteal lymph node could be visualized by the silica coated nanoparticles with injection in the rat feet.


CONCLUSIONS
The silica coated nanoparticles in lymph nodes could be observed by transmission electron microscope, suggesting that our silica coating method is useful as a SLN tracer with highly precise distribution of nanoparticles in histological evaluation. We also demonstrated for the first time that a prolonged enhancement of SLN is caused by the phagocytosis of fluorescent nanoparticles by both macrophages and dendritic cells.
Department of Nano-Medical Science, Graduate School of Medicine, Tohoku University, Sendai, Miyagi, Japan.
Liman
L
Cong
Motohiro
M
Takeda
Yohei
Y
Hamanaka
Kohsuke
K
Gonda
Mika
M
Watanabe
Masutaka
M
Kumasaka
Yoshio
Y
Kobayashi
Masaki
M
Kobayashi
Noriaki
N
Ohuchi
D000818:Animals; D046529:Microscopy, Electron, Transmission; D053758:Nanoparticles; D051381:Rats; D021701:Sentinel Lymph Node Biopsy / Q000379:methods*; D012822:Silicon Dioxide
D012822:Silicon Dioxide