(652i) Carbon Nanotube-Based Microdevices for Tracking Single Macrophages By Raman Scattering

Carbon
Nanotube-Based Microdevices for Tracking Single Macrophages by Raman Scattering

Zhibin Wang¹,
Junfei Xia¹, Li Sun², Phong Tran³, Sida Luo³,
Yi Ren², Tao Liu³, Jingjiao Guan^1,4

¹ Dept. of Chemical and Biomedical
Engineering, FAMU-FSU College of Engineering, Florida State University.

² Dept. of Biomedical Sciences,
College of Medicine, Florida State University.

³ Dept. of Industrial &
Manufacturing Engineering, FAMU-FSU College of Engineering, Florida State
University.

⁴ Integrative NanoScience Institute, Florida
State University

Introduction: The ability to track therapeutic
cells in vivo is useful for developing effective cell therapies. Existing cell-tracking
techniques such as magnetic resonance imaging and positron emission tomography suffer
from the need for ionizing radiation or limited capability for multiplex
labelling. In contrast, Raman imaging does not involve ionizing radiation; are
highly material dependent and can be excited by NIR, which permits a
tissue-penetration depth at the centimeter scale. Carbon nanotubes exhibit
strong resonance-enhanced Raman modes and have a unique Raman spectrum. On the
other hand, we developed a low-cost, highly versatile technique for fabricating
microdevices and preparing the complexes of the microdevices and live cells. We
thus extended this method to produce carbon nanotube-based microdevices for
tracking single macrophages by Raman scattering.

Materials and Methods: A polydimethylsiloxane stamp carrying
an array of 7 ¦Ìm-diameter circular pillars was coated a trilayer of poly(allylamine
hydrochloride) (PAH), and poly (sodium 4-styrenesulfonate) (PSS) and PAH. An
aqueous solution of surfactant-stabilized single walled carbon nanotubes dispersed
were sprayed on the stamp by using a self-made automatic spraying machine
operated by a computer numerical control system. After spraying, poly(lactic-co-glycolic
acid) (PLGA) containing a fluorescence dye octadecyl rhodamine B chloride (R18)
was spin-coated on carbon nanotubes film surface. The microdevices were transferred
onto a poly(vinyl alcohol) (PVA) -coated glass surface and released by dissolving
PVA with water. Raman scattering of 785 nm laser by single microdevices was overserved.
The microdevices were incubated with mouse bone marrow-derived macrophages to
study interactions between the microdevices and the macrophages using
fluorescence microscopy and flow cytometry. The viability of macrophages
carrying microdevices were investigated by staining the macrophages with
calcein AM. Raman scattering of single microdevices were characterized using a
Raman microscope and a 5¡Á objective lens.

Results and Discussion: Fig. A1 shows released carbon
nanotube-based microdevices loaded with R18 were d in. Fig. A2 shows
microdevices were associated to the macrophages after 24 h incubation.
Moreover, viability of the cells was not significantly affected by the
microdevices. Figs. B1 and B2 show a single macrophage generated the
characteristic Raman spectrum of the carbon nanotubes.

Conclusions: We have developed a novel method
for fabricating carbon nanotube-based microdevices for tracking single
macrophage by Raman scattering. The microdevices are composed of a polyelectrolyte
trilayer, carbon nanotubes and PLGA. The Raman signals generated by carbon
nanotubes in the microdevices can be detected at a centimeter-scale sample-lens
distance under NIR excitation, suggesting this technique may be used in vivo. Moreover,
the microdevices can be engulfed by the primary macrophages without affecting viability
and phagocytic ability of the cells. Single macrophages carrying the
microdevices can be detected by Raman scattering. The microdevices promise to
be useful for non-invasive multiplex tracking of single macrophages in vivo.