Abstract
Phase contrast and epifluorescence microscopy were utilized to monitor morphological changes in human astrocytoma cells during a time-course exposure to single-walled carbon nanotube (SWCNT) conjugates with different surfactants and to investigate sub-cellular distribution of the nanotube conjugates, respectively. Experimental results demonstrate that cytotoxicity of the nanotube/surfactant conjugates is related to the toxicity of surfactant molecules attached on the nanotube surfaces. Both sodium dodecyl sulfate (SDS) and sodium dodecylbenzene sulfonate (SDBS) are toxic to cells. Exposure to CNT/SDS conjugates (0.5 mg/mL) for less than 5 min caused changes in cell morphology resulting in a distinctly spherical shape compared to untreated cells. In contrast, sodium cholate (SC) and CNT/SC did not affect cell morphology, proliferation, or growth. These data indicate that SC is an environmentally friendly surfactant for the purification and dispersion of SWCNTs. Epifluorescence microscopy analysis of CNT/DNA conjugates revealed distribution in the cytoplasm of cells and did not show adverse effects on cell morphology, proliferation, or viability during a 72-h incubation. These observations suggest that the SWCNTs could be used as non-viral vectors for diagnostic and therapeutic molecules across the blood–brain barrier to the brain and the central nervous system.
Highlights
In recent years, increasing attention is being directed to the structure, maintenance, and pathological disturbance of the blood–brain barrier (BBB), with regard to enlarging a conceptual understanding of the signaling pathways that exist between and among the constituent cells of the BBB [1]
We report here an attempt to assess the cytotoxicity of singlewalled carbon nanotube (SWCNT) conjugates for human astrocytoma cells by extending our previous observations to the sub-10 min reaction time, by direct observation with phase contrast light microscopy, and to confirm penetration and localization of an SWCNT conjugate in astrocytoma cell cytoplasm
The morphology of human astrocytoma cells exposed to the SWCNT/surfactant conjugates, CNT/sodium cholate (SC), CNT/sodium dodecylbenzene sulfonate (SDBS), or CNT/sodium dodecyl sulfate (SDS), was similar to the cellular morphology demonstrated by exposure to the corresponding surfactant solution cargoes SC, SDBS, or SDS, respectively (Fig. 1)
Summary
In recent years, increasing attention is being directed to the structure, maintenance, and pathological disturbance of the blood–brain barrier (BBB), with regard to enlarging a conceptual understanding of the signaling pathways that exist between and among the constituent cells of the BBB (i.e., endothelial cells, astrocytes, perivascular cells, and pericytes) [1]. A tight BBB can effectively protect the brain from many common bacterial and selected, non-tissue specific viral infections, but can hinder the delivery of many effective diagnostic and therapeutic agents to the brain. Defeating this latter capability of the BBB has been a particular interest of the pharmaceutical industry, especially with regard to delivery of successful chemotherapy against central nervous system (CNS) tumors and other CNS neuropathologies [2]. An increasing number of observations have demonstrated that nanoscale materials can be used as nonviral vectors to deliver therapeutic drugs and other small molecules across the plasma membrane [3] or putatively across the BBB [4,5,6,7]. A critical evaluation of the potential cytotoxicity of nanoscale materials on the brain must be executed before we can safely use nanomaterials as drug vectors or Nanoscale Res Lett (2009) 4:1517–1523 in the manufacture of nanoscale electronics and optoelectronic devices
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