Orally administered covalently-assembled antioxidative peptide nanoparticles for inflammatory bowel disease therapy.

Hypothesis: Inflammatory bowel disease (IBD) is a chronic inflammation disease and still faces many therapeutic challenges, such as ineffective treatments, antibiotic resistance, and systematic toxicity. In order to improve the therapeutic efficacy of IBD, it is thus urgent to develop efficient, non-toxic and conveniently-administrated nanoagents to replace the currently used medicines. Casein phosphopeptide (CPP) has been found capable of chelating transition metal ions to suppress reactive oxygen species (ROS) generation, showing the potential for the treatment of IBD. However, CPP easily suffers from hydrolysis and enzymatic degradation, which limits its further clinical application. Covalent assembly of CPP to form nanoparticles (GCPP NPs) may be an efficient way to enhance the CPP stability in physiological environment and finally improve its capability of in vivo antioxidation and IBD treatment.

Experiments: We synthesized GCPP NPs through covalent assembly of Genipin and CPP, followed by characterizing their physicochemical properties. GCPP NPs were incubated under different physiological conditions including phosphate buffered saline, cell culture media, simulated gastrointestinal fluid for evaluation of stability. Cytotoxicity and antioxidation activities of GCPP NPs were tested in vitro under the 3T3 cell line using the ABTS and MTT assays, respectively. Finally, a DSS-induced mouse colitis model was established to assess specific accumulation and good therapeutic efficacy of GCPP NPs via an oral administration strategy.

Findings: GCPP NPs are robust and stable to overcome easy degradation of CPP even under the harsh gastrointestinal environments, which are adapted for oral administration. As-prepared GCPP NPs show benign antioxidant activity to scavenge ROS. Meanwhile, nanoscale GCPP NPs can passively accumulate and maintain at inflamed sites. The body weight and colon length of DSS-induced colitis mice treated by GCPP NPs perform a rehabilitation trend. These results indicate that GCPP NPs, as peptide-based therapeutic nanoagents, have great potential in the anti-inflammatory treatment of IBD by oral administration.