Our objective of this study is to design and develop a polyethylene glycol ( PEG2000)-modified multiwall carbon nanotube (PEGylated MWCNT) formulation for oral controlled metronomic chemotherapeutic drug delivery. Multiwall carbon nanotubes undergo various chemical modifications including oxidation with strong acids, conjugation of polyethylene glycol, and coating with cellulose acetate phthalate which resulted in the formation of aqueous dispersion and prevention of drug degradation in acidic environment. Advanced analytical procedure such as Fourier transform infra-red, X-ray diffraction, differential scanning calorimetry, thermal gravimetric analysis, transmission electron microscopy, and dynamic light scattering techniques were used to evaluate physicochemical characterization. We also performed in vitro cytotoxic study by MTT assay and results revealed that carboplatin-loaded PEGylated MWCNTs did not show significant detrimental effect on the viability of MDA-MB-231 (human breast cancer) cells. The maximum encapsulation and drug-loading capacity were determined to be 71.58 ± 0.04 and 39.62 ± 0.07%, respectively. The release of carboplatin from PEGylated MWCNTs was investigated at simulated intestinal fluid (SIF), pH 6.8, after optimizing at simulated gastric fluid (SGF), pH 1.2, by enteric coating. Enteric-coated PEGylated MWCNTs exhibit pH-responsive drug activity in a sustained manner especially at pH 6.8. This surface modification strongly suggests that PEGylated MWCNTs could be a potential carrier for metronomic chemotherapeutic agent for high drug resistance, drug with maximum adverse effect and poorly oral bioavailable drugs.

    Abstract
    1 Introduction
    2 Experimental
        2.1 Materials
        2.2 Acidic oxidation of MWCNT surface using acid mixture
        2.3 Formation of carbonyl chloride groups on MWCNTs
        2.4 Modification of carbonyl chloride-MWCNTs using PEG2000
        2.5 Preparation and synthesis of CP-loaded PEGylated MWCNTs
        2.6 Enteric coating of CP-loaded PEGylated MWCNTs
        2.7 Characterization
    3 Results and discussion
        3.1 Purification and modification of MWCNTs
        3.2 Zeta potential measurement
        3.3 Dispersion stability
        3.4 MWCNT dispersion as a function of its concentration
        3.5 TGDTA analyses
        3.6 X-ray diffraction analysis
        3.7 TEM analysis for CP-loaded PEGylated MWCNTs
        3.8 In vitro release study
        3.9 Drug release kinetics
        3.10 Cytotoxicity assay
        3.11 Stability study
    4 Conclusions
    Acknowledgements 
    References

• Suraj Sharma(Department of Pharmaceutical Technology, Jadavpur University)
• Sweet Naskar(Department of Pharmaceutical Technology, Jadavpur University)
• Ketousetuo Kuotsu(Department of Pharmaceutical Technology, Jadavpur University)