Purpose: Peptide drugs have been used in therapy various diseases. However, the poor bioavailability of peptide drugs for oral administration has limited their clinical applications, on account of the acidic environment and digestive enzymes inside the human gastrointestinal tract. To enhance stability in the human gastrointestinal tract, bioavailability, and targeted drug delivery of peptide drugs through oral administration, a vitamin B₁₂-modified amphiphilic sodium alginate derivative (CSAD-VB₁₂) was synthesized.
Materials and methods: A vitamin B₁₂-modified amphiphilic sodium alginate derivative (CSAD-VB₁₂) was synthesized via the N,N’-dicyclohexylcarbodiimide active method at room temperature, and then characterized using FTIR and ¹H NMR spectroscopy. Insulin was used as a model peptide drug and the insulin-loaded CSAD-VB₁₂ (CSAD-VB₁₂/insulin) nanoparticles with negative zeta potentials were prepared in PBS (pH=7.4). Scanning electron microscopy was used to observe CSAD-VB₁₂/insulin as spherical nanoparticles. The CSAD-VB₁₂ derivatives and CSAD-VB₁₂/insulin nanoparticles displayed nontoxicity towards the human colon adenocarcinoma (Caco-2) cells by CCK-8 test. Caco-2 cell model was used to measure the apparent permeability (Papp) of insulin, CSAD/insulin and CSAD-VB₁₂/insulin. Furthermore, confocal was used to confirm the endocytosis of intestinal enterocytes. Type 1 diabetes mice were used to evaluate the intestinal absorption and retention effect of test nanoparticles.
Results: They were observed as spherical nanoparticles in the size of 30–50 nm. The CSAD-VB₁₂ derivatives and CSAD-VB₁₂/insulin nanoparticles displayed nontoxicity towards the human colon adenocarcinoma (Caco-2) cells. Comparing with insulin and the CSAD/insulin nanoparticles, the CSAD-VB₁₂/insulin nanoparticles exhibited higher permeation ability through intestinal enterocytes in the Caco-2 cell model. Oral administration of the CSAD-VB₁₂/insulin nanoparticles to Type 1 diabetic mice yields higher intestinal retention effect, targeted absorption, and outstanding efficacy.
Conclusion: CSAD-VB₁₂ derivatives enhance the small intestinal absorption efficacy and retention of peptide by oral administration, which indicated that it could be a promising candidate for oral peptide delivery in the prospective clinical application.
Keywords: nanoparticle, insulin, human colon adenocarcinoma cell, small intestinal absorption efficacy