Characteristics and useful effects for human health of antioxidant carbon nanodots contained in microwave-assisted Opuntia humifusa extract (MA-OHE(CD)) were investigated in this work. MA-OHE(CD) was characterized using transmission electron microscopy, dynamic light scattering analysis, X-ray diffraction, UV–vis spectroscopy, X-ray photoelectron spectroscopy, and Fourier transform-infrared spectroscopy. Besides, total phenolic content and antioxidant activity of MA-OHE(CD) were measured. It was revealed that the MA-OHE(CD) increases aquaporin-3 expression in human epidermal keratinocytes cell with hydrophilic characteristics. Moreover, the bio-active compound extraction efficacy and antioxidant activity of microwave-assisted extraction were great when compared to maceration.

Microwave-assisted Opuntia humifusa extract containing multifunctional antioxidant carbon nanodots
    Abstract
    1 Introduction
    2 Materials and methods
        2.1 Reagents
        2.2 Extraction of O. humifusa
        2.3 Transmission electron microscopy (TEM)
        2.4 Dynamic light scattering (DLS)
        2.5 X-ray diffraction spectroscopy (XRD)
        2.6 UV–vis spectroscopy
        2.7 X-ray photoelectron spectroscopy (XPS)
        2.8 Fourier transform-infrared (FT-IR) spectroscopy
        2.9 Mass spectroscopy (UPLC-MSMS)
            2.9.1 Total phenolic content assay
            2.9.2 ABTS radical scavenging assay
    3 SDS-PAGE
        3.1 Cell culture
            3.1.1 SDS-PAGE
            3.1.2 Statistical analysis
    4 Results and discussion
        4.1 Extraction of O. humifusa
        4.2 TEM image analysis
        4.3 Dynamic light scattering (DLS)
        4.4 X-ray diffraction spectroscopy
        4.5 UV–vis spectroscopy
        4.6 X-ray photoelectron spectroscopy (XPS)
        4.7 Fourier transform-infrared (FT-IR) spectroscopy
        4.8 Mass spectroscopy (UPLC–MSMS)
        4.9 Total phenolic content assay
            4.9.1 ABTS radical scavenging assay
            4.9.2 SDS-PAGE
    5 Conclusion
    Anchor 33
    Acknowledgements 
    References

• Seong‑Hyeon Kim(Department of BioNano Technology, Gachon University, 1342 Seongnam‑Daero, Sujeong‑Gu, Seongnam‑Si 13120, Gyeonggi‑Do, Korea)
• In‑Sun Bae(Swsonaki Inc., Gwangyang Frontier‑Valley 3Rd, 30 Gaseok‑Ro, Seo‑Gu, Incheon, Korea)
• Hyun Uk Lee(Research Center for Materials Analysis, Korea Basic Science Institute (KBSI), Daejeon 34133, Korea)
• Ju‑Young Moon(Department of Beauty Design Management, Hansung University, 116 Samseongyoro‑16Gil, Seoul 02876, Korea)
• Young‑Chul Lee(Department of BioNano Technology, Gachon University, 1342 Seongnam‑Daero, Sujeong‑Gu, Seongnam‑Si 13120, Gyeonggi‑Do, Korea)