Researchers created self-assembling nanoparticles that combine semaglutide with engineered bile acids, enabling the drug to hitch a ride on the gut's bile acid transport system for improved oral delivery and better efficacy in obese mice.
~279 nm self-assembling nanocomplexesSemaglutide spontaneously formed stable nanoparticles with engineered bile acids through charge-based interactions, enabling bile acid transporter-driven intestinal absorption for improved oral delivery
What the researchers found
Researchers engineered positively charged bile acid-peptide conjugates (PCBs) that self-assemble with negatively charged semaglutide through electrostatic interactions, forming stable nanoparticles approximately 279 nm in size. The best candidate, PCB4, created 'PBSG nanocomplexes' that significantly enhanced semaglutide's absorption through the intestinal wall via bile acid transporter-driven endocytosis.
In a high-fat diet mouse model, oral PBSG nanocomplexes improved semaglutide's therapeutic efficacy compared to unformulated semaglutide. The nanocomplexes also elevated GLP-1 expression in vivo through a dual mechanism: directly delivering semaglutide and simultaneously modulating bile acid metabolism. This approach hijacks the body's own bile acid transport system to shuttle peptide drugs across the intestinal barrier.
Why it matters
Semaglutide's biggest limitation is its delivery: the injectable form (Ozempic/Wegovy) requires needles, while the current oral form (Rybelsus) has very low bioavailability (~1%) and requires strict fasting before taking it. A nanoparticle delivery system that dramatically improves oral peptide absorption could make semaglutide — and potentially other peptide drugs — much more effective when taken by mouth. Using bile acid transporters as a natural uptake pathway is elegant because these transporters are specifically designed to absorb bile acids from the gut, providing a pre-built highway for drug delivery.
The numbers in context
PBSG nanocomplexes: ~279 nm average size · bile acid transporter-driven endocytosis · improved GI permeation and oral absorption · enhanced efficacy in HFD mouse model · dual action: semaglutide delivery + bile acid metabolism modulation · GLP-1 expression elevated in vivo
How the study worked
The researchers synthesized a series of positively charged peptide-engineered bile acids (PCBs) and screened them for ability to form stable nanocomplexes with semaglutide. Intestinal permeability was tested in Caco-2 cells and intestinal tissue. In vivo efficacy was evaluated in C57BL mice fed a high-fat diet, comparing oral PBSG nanocomplexes to controls. Bile acid transporter activity and GLP-1 expression were measured to characterize the mechanism.
Who was studied
C57BL mice on high-fat diet; Caco-2 intestinal cell line and intestinal tissue
What this study cannot tell us
This is a preclinical study in mice and cell cultures. The critical metric — oral bioavailability improvement as a percentage — is not quantified in the abstract. Long-term safety of repeatedly administering bile acid-modified nanoparticles is unknown. Manufacturing scalability and stability under storage conditions are not addressed. Comparison to the existing commercial oral semaglutide formulation (Rybelsus with SNAC enhancer) was not reported.
How to read the evidence
This study is graded as preliminary. While published in Biomaterials (a top-tier journal) and showing promising results, all data comes from mouse models and cell cultures. No human pharmacokinetic or clinical data exists for this delivery system.
When this study was published
Published in 2026, this is a brand-new study representing the cutting edge of oral peptide delivery technology.
The bigger picture
Oral delivery of peptide drugs is arguably the biggest unsolved challenge in pharmaceutical science. Current oral semaglutide (Rybelsus) uses the absorption enhancer SNAC but still has ~1% bioavailability. This bile acid transporter-hijacking approach represents a fundamentally different strategy that could achieve much higher absorption. If successful, it could transform not just semaglutide delivery but potentially the entire field of oral peptide therapeutics — making injectable-only drugs like insulin, GLP-1 agonists, and other peptides available as efficient oral medications.
Questions still open
- How does the oral bioavailability of PBSG nanocomplexes compare quantitatively to the current commercial oral semaglutide formulation (Rybelsus)?
- Could this bile acid transporter delivery system be adapted for other peptide drugs like insulin or tirzepatide?
- What are the long-term effects of repeatedly engaging bile acid transporters for drug delivery on normal bile acid metabolism?
Common questions
Why is it so hard to take peptide drugs like semaglutide as a pill?
How do these nanoparticles improve oral absorption?
Read the original research
Charge-based supramolecular peptide nanocomplexes for oral delivery via transporter-driven endocytosis.
Biomaterials, 329, 123903
Citation
Park, So-Hyeon; Ma, Gaeun; Park, Seong Jin; Yang, Seong-Bin; Seo, Minho; Lee, Jun-Hyuck; Kweon, Seho; Park, Jooho. (2026). Charge-based supramolecular peptide nanocomplexes for oral delivery via transporter-driven endocytosis.. Biomaterials, 329, 123903. https://doi.org/10.1016/j.biomaterials.2025.123903