In this article, a new type of mesoporous carbon nanoparticles (MCN) was fabricated as a potential oral delivery system of insulin to reduce the adverse reactions by hypodermic injection. The mesoporous carbon nanoparticles-carried insulin (MCNI) was studied using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FT-IR) compared with the blank MCNs. The Brunauer–Emmett–Teller (BET) method was utilized to calculate the specific surface area. The pore volume and pore size distribution (PSD) curves were calculated by Barrett–Joyner–Halenda (BJH) model. The entrapment efficiency (EE%) and loading content (LC%) of insulin onto the MCNs were determined by RP-HPLC. In vitro insulin release from MCNI was determined in simulated intestinal fluid. To evaluate the pharmacodynamics of MCNIs orally, the variation of glycemia of diabetic rats after oral administration of MCNIs was compared with the rats receiving hypodermic injection of insulin. Besides, the absorption of FITC-labeled MCNs in HCT-116 cells was tested. The results showed that there is significant difference between MCNs and MCNIs through SEM, TEM, and FT-IR. The entrapment efficiency, loading content and in vitro insulin release met the requirements of the pharmacodynamic study. The specific surface area, pore volume and pore size of MCNIs were significantly decreased compared to that of MCNs. The pharmacodynamics study showed that the blood sugar level was significantly decreased after the oral administration of MCNIs. The FITC-labeled MCNs showed significant absorption in HCT-116 cells. The MCNIs were successfully synthesized with commendable entrapment efficiency and loading content which preferably decreased the blood sugar in diabetes rats via oral administration.

Oral delivery of insulin via mesoporous carbon nanoparticles for colonic release allows glycemic control in diabetic rats
    Abstract
    1 Introduction
    2 Materials and methods
        2.1 Materials
            2.1.1 Reagents
            2.1.2 Instruments
        2.2 Synthesis of insulin-containing mesoporous carbon nanoparticles (MCNIs)
        2.3 Characterization of insulin-containing mesoporous carbon nanoparticles (MCNIs)
        2.4 Determination of the entrapment efficiency (EE%) and loading content (LC%) of insulin into the mesoporous carbon nanoparticles
        2.5 In vitro release of Insulin
        2.6 In vivo studies
            2.6.1 Diabetic rat model
            2.6.2 Administration of insulin formulations to diabetic rats
        2.7 Uptake assay of MCNs in HCT-116 cell
    3 Results and discussion
        3.1 The characterization of MCNIs
        3.2 The loading content and in vitro release study of MCNIs
        3.3 In vivo pharmacodynamics of MCNIs
        3.4 HCT-116 cell uptake assay of MCNs
        3.5 Discussions
    4 Conclusion
    Acknowledgements 
    References

• Haorong Lin(College of Pharmacy, Guangdong Pharmaceutical University)
• Jia Zhang(College of Pharmacy, Guangdong Pharmaceutical University)
• Chaochang Yu(College of Pharmacy, Guangdong Pharmaceutical University)
• Yan Lu(College of Pharmacy, Guangdong Pharmaceutical University)
• Jie Ning(College of Pharmacy, Guangdong Pharmaceutical University)
• Sixian Le(College of Pharmacy, Guangdong Pharmaceutical University)
• Yue Li(College of Pharmacy, Guangdong Pharmaceutical University)
• Lin‑quan Zang(College of Pharmacy, Guangdong Pharmaceutical University/Guangdong Provincial Key Laboratory for Biotechnology Drug Candidate, Guangdong Pharmaceutical University)