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Polyethyleneimine-functionalized boron nitride nanospheres as efficient carriers for enhancing the immunostimulatory effect of CpG oligodeoxynucleotides.

Zhang H, Feng S, Yan T, Zhi C, Gao XD, Hanagata N - Int J Nanomedicine (2015)

Bottom Line: Furthermore, the positively charged surface of the BNNS-PEI complexes greatly improved the loading capacity and cellular uptake efficiency of CpG ODNs.Class B CpG ODNs loaded on the BNNS-PEI complexes enhanced the production of interleukin-6 and tumor necrosis factor-α from peripheral blood mononuclear cells compared with CpG ODNs directly loaded on BNNS.Therefore, BNNS-PEI complexes can be used to enhance the immunostimulatory effect and therapeutic activity of CpG ODNs and the treatment of diseases requiring interleukin-6, tumor necrosis factor-α, and interferon-α.

View Article: PubMed Central - PubMed

Affiliation: The Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, People's Republic of China.

ABSTRACT
CpG oligodeoxynucleotides (ODNs) stimulate innate and adaptive immune responses. Thus, these molecules are promising therapeutic agents and vaccine adjuvants against various diseases. In this study, we developed a novel CpG ODNs delivery system based on polyethyleneimine (PEI)-functionalized boron nitride nanospheres (BNNS). PEI was coated on the surface of BNNS via electrostatic interactions. The prepared BNNS-PEI complexes had positive zeta potential and exhibited enhanced dispersity and stability in aqueous solution. In vitro cytotoxicity assays revealed that the BNNS-PEI complexes with concentrations up to 100 μg/mL exhibited no obvious cytotoxicity. Furthermore, the positively charged surface of the BNNS-PEI complexes greatly improved the loading capacity and cellular uptake efficiency of CpG ODNs. Class B CpG ODNs loaded on the BNNS-PEI complexes enhanced the production of interleukin-6 and tumor necrosis factor-α from peripheral blood mononuclear cells compared with CpG ODNs directly loaded on BNNS. Contrary to the free CpG ODNs or CpG ODNs directly loaded on BNNS, class B CpG ODNs loaded on the BNNS-PEI complexes induced interferon-α simultaneously. PEI coating may have changed the physical form of class B CpG ODNs on BNNS, which further affected their interaction with Toll-like receptor 9 and induced interferon-α. Therefore, BNNS-PEI complexes can be used to enhance the immunostimulatory effect and therapeutic activity of CpG ODNs and the treatment of diseases requiring interleukin-6, tumor necrosis factor-α, and interferon-α.

No MeSH data available.


Characterizations of the BNNS and BNNS–PEI complexes.Notes: (A) Dispersed BNNS and BNNS–PEI complexes in PBS after statically placed for 24 hours. (B) Hydrodynamic diameters distribution of BNNS and BNNS–PEI complexes in PBS.Abbreviations: BNNS, boron nitride nanospheres; PBS, phosphate-buffered saline; PEI, polyethyleneimine.
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f4-ijn-10-5343: Characterizations of the BNNS and BNNS–PEI complexes.Notes: (A) Dispersed BNNS and BNNS–PEI complexes in PBS after statically placed for 24 hours. (B) Hydrodynamic diameters distribution of BNNS and BNNS–PEI complexes in PBS.Abbreviations: BNNS, boron nitride nanospheres; PBS, phosphate-buffered saline; PEI, polyethyleneimine.

Mentions: BNNS were synthesized through chemical vapor deposition.35 The as-prepared BNNS showed a uniform spherical shape with an average diameter of approximately 150 nm (Figure 2A). In addition, well-ordered channels were clearly observed from the high-resolution transmission electron micrograph of the BNNS (Figure 2B). We used PEI to functionalize the surface of BNNS and obtain a positively charged surface that facilitates the loading of CpG ODNs onto the BNNS. Figure 1 shows the schematic of the synthesis route. BNNS were first noncovalently functionalized by PEI polymers, forming positively charged BNNS–PEI complexes. Then, the negatively charged CpG ODNs were loaded onto the BNNS–PEI complexes via electrostatic interactions. FTIR results show the PEI coating on BNNS. Figure 3A shows the FTIR spectra of BNNS, PEI, and the BNNS–PEI complexes. Two distinct peaks at 2,700–2,900 cm−1 assigned to the C–H vibrations in PEI were clearly observed in the BNNS–PEI complexes compared with pure BNNS. This result suggests that PEI has been functionalized on the surface of BNNS. Zeta potential measurements further confirmed the successful functionalization of the BNNS with PEI (Figure 3B). The coating of PEI greatly increased the zeta potential of BNNS from −5 mV to +40 mV for the BNNS–PEI complexes. In addition, the surface charge of the BNNS–PEI complexes increased when the initial concentration of the PEI solution was increased during the functionalization of the BNNS. This phenomenon was probably due to the increased amino groups coated on the surface of BNNS. PEI concentrations were optimized to 5% to achieve the highest positive zeta potential and were used in the following studies. Therefore, the positive charge of the BNNS–PEI complexes facilitated the loading of the negatively charged CpG ODNs through electrostatic interactions and enhanced the cellular uptake of the complexes. Thermogravimetric analysis is a convenient technique that reveals the composition and change in the thermal stability of complexes. This process was used to determine the amount of PEI coated on the surface of BNNS. Figure 3C shows that BNNS only exhibited slight mass loss (<5%) because of their superb structural stability and anti-oxidation ability. By contrast, a high weight loss (22%) was observed for the BNNS–PEI complexes. Thus, the weight ratio of PEI in the BNNS–PEI complexes was calculated to be approximately 17%, which possibly facilitated the loading of the CpG ODNs on the BNNS. The dispersity and stability of nanoparticles are crucial for their application as carriers in drug delivery systems. PEI coating enhanced these characteristics of BNNS in physiological solutions (Figure 4A) mainly through the interaction of the amino functional group in PEI with BNNS. PEI coating on the surface can trigger electrostatic and steric repulsion among the highly positively charged BNNS–PEI complexes in solutions and stabilize the dispersion. Further measurement of the size distributions showed that PEI coating did not significantly increase the mean particle size of the BNNS–PEI complexes, which exhibited a relatively narrow size distribution in PBS compared with BNNS (Figure 4B). This phenomenon also indicates that the BNNS–PEI complexes may have favorable dispersity in PBS. Thus, the BNNS–PEI complexes can be used as carriers for CpG ODNs delivery.


Polyethyleneimine-functionalized boron nitride nanospheres as efficient carriers for enhancing the immunostimulatory effect of CpG oligodeoxynucleotides.

Zhang H, Feng S, Yan T, Zhi C, Gao XD, Hanagata N - Int J Nanomedicine (2015)

Characterizations of the BNNS and BNNS–PEI complexes.Notes: (A) Dispersed BNNS and BNNS–PEI complexes in PBS after statically placed for 24 hours. (B) Hydrodynamic diameters distribution of BNNS and BNNS–PEI complexes in PBS.Abbreviations: BNNS, boron nitride nanospheres; PBS, phosphate-buffered saline; PEI, polyethyleneimine.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4554408&req=5

f4-ijn-10-5343: Characterizations of the BNNS and BNNS–PEI complexes.Notes: (A) Dispersed BNNS and BNNS–PEI complexes in PBS after statically placed for 24 hours. (B) Hydrodynamic diameters distribution of BNNS and BNNS–PEI complexes in PBS.Abbreviations: BNNS, boron nitride nanospheres; PBS, phosphate-buffered saline; PEI, polyethyleneimine.
Mentions: BNNS were synthesized through chemical vapor deposition.35 The as-prepared BNNS showed a uniform spherical shape with an average diameter of approximately 150 nm (Figure 2A). In addition, well-ordered channels were clearly observed from the high-resolution transmission electron micrograph of the BNNS (Figure 2B). We used PEI to functionalize the surface of BNNS and obtain a positively charged surface that facilitates the loading of CpG ODNs onto the BNNS. Figure 1 shows the schematic of the synthesis route. BNNS were first noncovalently functionalized by PEI polymers, forming positively charged BNNS–PEI complexes. Then, the negatively charged CpG ODNs were loaded onto the BNNS–PEI complexes via electrostatic interactions. FTIR results show the PEI coating on BNNS. Figure 3A shows the FTIR spectra of BNNS, PEI, and the BNNS–PEI complexes. Two distinct peaks at 2,700–2,900 cm−1 assigned to the C–H vibrations in PEI were clearly observed in the BNNS–PEI complexes compared with pure BNNS. This result suggests that PEI has been functionalized on the surface of BNNS. Zeta potential measurements further confirmed the successful functionalization of the BNNS with PEI (Figure 3B). The coating of PEI greatly increased the zeta potential of BNNS from −5 mV to +40 mV for the BNNS–PEI complexes. In addition, the surface charge of the BNNS–PEI complexes increased when the initial concentration of the PEI solution was increased during the functionalization of the BNNS. This phenomenon was probably due to the increased amino groups coated on the surface of BNNS. PEI concentrations were optimized to 5% to achieve the highest positive zeta potential and were used in the following studies. Therefore, the positive charge of the BNNS–PEI complexes facilitated the loading of the negatively charged CpG ODNs through electrostatic interactions and enhanced the cellular uptake of the complexes. Thermogravimetric analysis is a convenient technique that reveals the composition and change in the thermal stability of complexes. This process was used to determine the amount of PEI coated on the surface of BNNS. Figure 3C shows that BNNS only exhibited slight mass loss (<5%) because of their superb structural stability and anti-oxidation ability. By contrast, a high weight loss (22%) was observed for the BNNS–PEI complexes. Thus, the weight ratio of PEI in the BNNS–PEI complexes was calculated to be approximately 17%, which possibly facilitated the loading of the CpG ODNs on the BNNS. The dispersity and stability of nanoparticles are crucial for their application as carriers in drug delivery systems. PEI coating enhanced these characteristics of BNNS in physiological solutions (Figure 4A) mainly through the interaction of the amino functional group in PEI with BNNS. PEI coating on the surface can trigger electrostatic and steric repulsion among the highly positively charged BNNS–PEI complexes in solutions and stabilize the dispersion. Further measurement of the size distributions showed that PEI coating did not significantly increase the mean particle size of the BNNS–PEI complexes, which exhibited a relatively narrow size distribution in PBS compared with BNNS (Figure 4B). This phenomenon also indicates that the BNNS–PEI complexes may have favorable dispersity in PBS. Thus, the BNNS–PEI complexes can be used as carriers for CpG ODNs delivery.

Bottom Line: Furthermore, the positively charged surface of the BNNS-PEI complexes greatly improved the loading capacity and cellular uptake efficiency of CpG ODNs.Class B CpG ODNs loaded on the BNNS-PEI complexes enhanced the production of interleukin-6 and tumor necrosis factor-α from peripheral blood mononuclear cells compared with CpG ODNs directly loaded on BNNS.Therefore, BNNS-PEI complexes can be used to enhance the immunostimulatory effect and therapeutic activity of CpG ODNs and the treatment of diseases requiring interleukin-6, tumor necrosis factor-α, and interferon-α.

View Article: PubMed Central - PubMed

Affiliation: The Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, People's Republic of China.

ABSTRACT
CpG oligodeoxynucleotides (ODNs) stimulate innate and adaptive immune responses. Thus, these molecules are promising therapeutic agents and vaccine adjuvants against various diseases. In this study, we developed a novel CpG ODNs delivery system based on polyethyleneimine (PEI)-functionalized boron nitride nanospheres (BNNS). PEI was coated on the surface of BNNS via electrostatic interactions. The prepared BNNS-PEI complexes had positive zeta potential and exhibited enhanced dispersity and stability in aqueous solution. In vitro cytotoxicity assays revealed that the BNNS-PEI complexes with concentrations up to 100 μg/mL exhibited no obvious cytotoxicity. Furthermore, the positively charged surface of the BNNS-PEI complexes greatly improved the loading capacity and cellular uptake efficiency of CpG ODNs. Class B CpG ODNs loaded on the BNNS-PEI complexes enhanced the production of interleukin-6 and tumor necrosis factor-α from peripheral blood mononuclear cells compared with CpG ODNs directly loaded on BNNS. Contrary to the free CpG ODNs or CpG ODNs directly loaded on BNNS, class B CpG ODNs loaded on the BNNS-PEI complexes induced interferon-α simultaneously. PEI coating may have changed the physical form of class B CpG ODNs on BNNS, which further affected their interaction with Toll-like receptor 9 and induced interferon-α. Therefore, BNNS-PEI complexes can be used to enhance the immunostimulatory effect and therapeutic activity of CpG ODNs and the treatment of diseases requiring interleukin-6, tumor necrosis factor-α, and interferon-α.

No MeSH data available.