Insulin paired with a modified cell-penetrating peptide (GET) formed nanocomplexes that crossed intestinal barriers 22-fold better and controlled blood sugar in diabetic mice when given orally over several days.
>22-fold increased translocationInsulin-GET nanocomplexes crossed intestinal cell barriers more than 22 times better than free insulin in Caco-2 assays
What the researchers found
Insulin-GET nanocomplexes (140 nm, +27.10 mV charge) enhanced insulin transport across differentiated Caco-2 intestinal epithelium by more than 22-fold compared to free insulin. The nanocomplexes accumulated inside cells and were progressively released from both the apical and basal surfaces, effectively turning gut cells into sustained-release depots.
The complexes showed enhanced proteolytic stability (resisting enzymatic destruction) and retained significant biological activity. In streptozotocin-induced diabetic mice, serial oral dosing of Insulin-GET nanocomplexes controlled elevated blood glucose levels over several days without compromising intestinal barrier integrity or cell viability.
Why it matters
Millions of people with diabetes inject insulin multiple times daily. An oral insulin pill would dramatically improve quality of life and treatment adherence, but the gut's harsh environment and poor absorption have prevented it. This cell-penetrating peptide approach solves multiple problems at once — protecting insulin from digestion, shuttling it across the intestinal wall, and creating intracellular depots for sustained release. The simplicity of the complexation platform also makes it potentially applicable to other peptide drugs.
The numbers in context
140 nm NCs; +27.10 mV; >22-fold translocation increase; blood glucose control over several days in STZ mice
How the study worked
Insulin was complexed with GET cell-penetrating peptide via electrostatic interaction to form nanocomplexes. In vitro: transport tested in differentiated Caco-2 intestinal epithelium monolayers; biological activity confirmed via insulin-responsive reporter assays; proteolytic stability assessed. In vivo: oral delivery tested in streptozotocin-induced diabetic mice with serial dosing and blood glucose monitoring.
Who was studied
In vitro: Caco-2 intestinal epithelial cells. In vivo: streptozotocin-induced diabetic mice
What this study cannot tell us
Mouse model only; Caco-2 model doesn't fully replicate human intestine; oral bioavailability not quantified; long-term safety unknown; STZ model represents type 1 diabetes only.
How to read the evidence
This is a well-designed preclinical study with both in vitro (Caco-2 cells) and in vivo (diabetic mice) validation. The results are promising but remain animal-stage, with no human data. Rated moderate-preclinical.
When this study was published
Published in 2023, this is recent research using a novel cell-penetrating peptide platform for oral insulin delivery. The findings are current and the approach is in early development.
The bigger picture
Oral peptide delivery is one of the biggest unsolved problems in drug development. While oral semaglutide (Rybelsus) cracked the code for GLP-1 using an absorption enhancer, insulin is a larger and more fragile molecule that has resisted similar approaches. Cell-penetrating peptide nanocomplexes represent a different strategy — actively transporting insulin through cells rather than just enhancing passive absorption. If this translates to humans, it could transform diabetes management and serve as a platform for oral delivery of other injectable peptide drugs.
Questions still open
- What is the oral bioavailability of insulin from these nanocomplexes compared to injected insulin?
- Do the cell-penetrating peptide nanocomplexes accumulate in gut tissue with chronic use, and is this safe long-term?
- Can this GET platform deliver larger or more complex peptide therapeutics beyond insulin?
Common questions
Why can't you just swallow an insulin pill?
How does the cell-penetrating peptide help insulin get absorbed?
Read the original research
Orally-delivered insulin-peptide nanocomplexes enhance transcytosis from cellular depots and improve diabetic blood glucose control.
Journal of controlled release : official journal of the Controlled Release Society, 360, 93-109
Citation
Rehmani, Sahrish; McLaughlin, Christopher M; Eltaher, Hoda M; Moffett, R Charlotte; Flatt, Peter R; Dixon, James E. (2023). Orally-delivered insulin-peptide nanocomplexes enhance transcytosis from cellular depots and improve diabetic blood glucose control.. Journal of controlled release : official journal of the Controlled Release Society, 360, 93-109. https://doi.org/10.1016/j.jconrel.2023.06.006