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Surface engineering of macrophages with nanoparticles to generate a cell-nanoparticle hybrid vehicle for hypoxia-targeted drug delivery.

Holden CA, Yuan Q, Yeudall WA, Lebman DA, Yang H - Int J Nanomedicine (2010)

Bottom Line: Nanoparticles immobilized on the cell surface provide numerous new sites for anticancer drug loading, hence potentially minimizing the toxic effect of anticancer drugs on the viability and hypoxia-targeting ability of the macrophage vehicles.Further, a reducing agent, sodium cyanoborohydride, was applied to reduce Schiff bases to stable secondary amine linkages.The distribution of nanoparticles on the cell surface was confirmed by fluorescence imaging, and it was found to be dependent on the stability of the linkages coupling nanoparticles to the cell surface.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering, School of Engineering, Virginia Commonwealth University, Richmond, VA 23284, USA.

ABSTRACT
Tumors frequently contain hypoxic regions that result from a shortage of oxygen due to poorly organized tumor vasculature. Cancer cells in these areas are resistant to radiation- and chemotherapy, limiting the treatment efficacy. Macrophages have inherent hypoxia-targeting ability and hold great advantages for targeted delivery of anticancer therapeutics to cancer cells in hypoxic areas. However, most anticancer drugs cannot be directly loaded into macrophages because of their toxicity. In this work, we designed a novel drug delivery vehicle by hybridizing macrophages with nanoparticles through cell surface modification. Nanoparticles immobilized on the cell surface provide numerous new sites for anticancer drug loading, hence potentially minimizing the toxic effect of anticancer drugs on the viability and hypoxia-targeting ability of the macrophage vehicles. In particular, quantum dots and 5-(aminoacetamido) fluorescein-labeled polyamidoamine dendrimer G4.5, both of which were coated with amine-derivatized polyethylene glycol, were immobilized to the sodium periodate-treated surface of RAW264.7 macrophages through a transient Schiff base linkage. Further, a reducing agent, sodium cyanoborohydride, was applied to reduce Schiff bases to stable secondary amine linkages. The distribution of nanoparticles on the cell surface was confirmed by fluorescence imaging, and it was found to be dependent on the stability of the linkages coupling nanoparticles to the cell surface.

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pH-dependent viability of RAW264.7 macrophages. Cells were incubated for two hours at the indicated pH, and then assessed by the Trypan blue assay 48 hours later. Nontoxicity of 0.1 mM sodium cyanoborohydride in DMEM at pH 7.4 was confirmed.Note: Bar = SD.Abbreviations: DMEM, Dulbecco’s modified Eagle’s medium; SD, standard deviation.
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f2-ijn-5-025: pH-dependent viability of RAW264.7 macrophages. Cells were incubated for two hours at the indicated pH, and then assessed by the Trypan blue assay 48 hours later. Nontoxicity of 0.1 mM sodium cyanoborohydride in DMEM at pH 7.4 was confirmed.Note: Bar = SD.Abbreviations: DMEM, Dulbecco’s modified Eagle’s medium; SD, standard deviation.

Mentions: A number of methods have been developed to enable the chemical modification of cell surfaces. In this project, we employed a simple and well-documented methodology to immobilize nanoparticles to the macrophage cell surface. In particular, sialic acid residues embedded on the cell surface were converted to aldehydes with sodium periodate. Our results showed that the toxicity of NaIO4 was negligible at the concentration of 0.1 mM. This was supported by the work of Ong and coworkers.15 Aldehydes reacte with primary amine end groups of PEG on the nanoparticle surface to form Schiff bases. Schiff base linkage is labile and can be cleaved in aqueous solution by hydrolysis. Accordingly, the macrophage– T-nanoparticle hybrids constructed are expected to readily release nanoparticles through the cleavage of the transient Schiff base linkages. We also applied a reducing agent sodium cyanoborohydride to reduce Schiff bases to stable secondary amine linkages.29 It has been reported that sodium cyanoborohydride has high specificity toward the Schiff base. According to our cell viability studies (Figure 2), sodium cyanoborohydride at 0.1 mM was nontoxic to RAW264.7 macrophages. As the reaction proceeds more efficiently at basic pH,30 the viability of RAW264.7 macrophages at high pH (8–10) was evaluated to determine whether the immobilization chemistry can be performed at high pH. As shown in Figure 2, pH affects the cell viability. The viability of RAW264.7 macrophages remains intact at pH 8 or pH 7.4 with 0.1 mM sodium cyanoborohydride. The cell viability dropped slightly to 88% at pH 9. By contrast, the viability was reduced drastically to 52% at pH 10. The results suggest that mild basic pH has a minimal impact on the viability of RAW264.7 macrophages and the optimum pH within that range can be explored for increasing the immobilization efficiency.


Surface engineering of macrophages with nanoparticles to generate a cell-nanoparticle hybrid vehicle for hypoxia-targeted drug delivery.

Holden CA, Yuan Q, Yeudall WA, Lebman DA, Yang H - Int J Nanomedicine (2010)

pH-dependent viability of RAW264.7 macrophages. Cells were incubated for two hours at the indicated pH, and then assessed by the Trypan blue assay 48 hours later. Nontoxicity of 0.1 mM sodium cyanoborohydride in DMEM at pH 7.4 was confirmed.Note: Bar = SD.Abbreviations: DMEM, Dulbecco’s modified Eagle’s medium; SD, standard deviation.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2819902&req=5

f2-ijn-5-025: pH-dependent viability of RAW264.7 macrophages. Cells were incubated for two hours at the indicated pH, and then assessed by the Trypan blue assay 48 hours later. Nontoxicity of 0.1 mM sodium cyanoborohydride in DMEM at pH 7.4 was confirmed.Note: Bar = SD.Abbreviations: DMEM, Dulbecco’s modified Eagle’s medium; SD, standard deviation.
Mentions: A number of methods have been developed to enable the chemical modification of cell surfaces. In this project, we employed a simple and well-documented methodology to immobilize nanoparticles to the macrophage cell surface. In particular, sialic acid residues embedded on the cell surface were converted to aldehydes with sodium periodate. Our results showed that the toxicity of NaIO4 was negligible at the concentration of 0.1 mM. This was supported by the work of Ong and coworkers.15 Aldehydes reacte with primary amine end groups of PEG on the nanoparticle surface to form Schiff bases. Schiff base linkage is labile and can be cleaved in aqueous solution by hydrolysis. Accordingly, the macrophage– T-nanoparticle hybrids constructed are expected to readily release nanoparticles through the cleavage of the transient Schiff base linkages. We also applied a reducing agent sodium cyanoborohydride to reduce Schiff bases to stable secondary amine linkages.29 It has been reported that sodium cyanoborohydride has high specificity toward the Schiff base. According to our cell viability studies (Figure 2), sodium cyanoborohydride at 0.1 mM was nontoxic to RAW264.7 macrophages. As the reaction proceeds more efficiently at basic pH,30 the viability of RAW264.7 macrophages at high pH (8–10) was evaluated to determine whether the immobilization chemistry can be performed at high pH. As shown in Figure 2, pH affects the cell viability. The viability of RAW264.7 macrophages remains intact at pH 8 or pH 7.4 with 0.1 mM sodium cyanoborohydride. The cell viability dropped slightly to 88% at pH 9. By contrast, the viability was reduced drastically to 52% at pH 10. The results suggest that mild basic pH has a minimal impact on the viability of RAW264.7 macrophages and the optimum pH within that range can be explored for increasing the immobilization efficiency.

Bottom Line: Nanoparticles immobilized on the cell surface provide numerous new sites for anticancer drug loading, hence potentially minimizing the toxic effect of anticancer drugs on the viability and hypoxia-targeting ability of the macrophage vehicles.Further, a reducing agent, sodium cyanoborohydride, was applied to reduce Schiff bases to stable secondary amine linkages.The distribution of nanoparticles on the cell surface was confirmed by fluorescence imaging, and it was found to be dependent on the stability of the linkages coupling nanoparticles to the cell surface.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering, School of Engineering, Virginia Commonwealth University, Richmond, VA 23284, USA.

ABSTRACT
Tumors frequently contain hypoxic regions that result from a shortage of oxygen due to poorly organized tumor vasculature. Cancer cells in these areas are resistant to radiation- and chemotherapy, limiting the treatment efficacy. Macrophages have inherent hypoxia-targeting ability and hold great advantages for targeted delivery of anticancer therapeutics to cancer cells in hypoxic areas. However, most anticancer drugs cannot be directly loaded into macrophages because of their toxicity. In this work, we designed a novel drug delivery vehicle by hybridizing macrophages with nanoparticles through cell surface modification. Nanoparticles immobilized on the cell surface provide numerous new sites for anticancer drug loading, hence potentially minimizing the toxic effect of anticancer drugs on the viability and hypoxia-targeting ability of the macrophage vehicles. In particular, quantum dots and 5-(aminoacetamido) fluorescein-labeled polyamidoamine dendrimer G4.5, both of which were coated with amine-derivatized polyethylene glycol, were immobilized to the sodium periodate-treated surface of RAW264.7 macrophages through a transient Schiff base linkage. Further, a reducing agent, sodium cyanoborohydride, was applied to reduce Schiff bases to stable secondary amine linkages. The distribution of nanoparticles on the cell surface was confirmed by fluorescence imaging, and it was found to be dependent on the stability of the linkages coupling nanoparticles to the cell surface.

Show MeSH
Related in: MedlinePlus