In Vitro Intestinal Uptake And Permeability Of Fluorescently-Labelled Hyaluronic Acid Nanogels

Abstract

Background

Oral administration remains the most common mode of drug delivery. However, orally administered bioactive compounds must first survive digestion and then be absorbed at the intestine in order to reach other tissues or organs. The efficiency of both processes can be improved by encapsulation or conjugation with polymeric nanoparticles. Here we report the synthesis of amphiphilic hyaluronic acid (HyA) nanogels as nanocarriers for drug delivery.

Methods

HyA nanogels were prepared by self-assembly from amphiphilic HyA conjugates produced by grafting hydrophobic alkyl chains to the HyA backbone. The dye Cy5.5 was covalently bonded and used for tracking. The nanogels were characterised according to their structure, size and zeta potential, as well as biocompatibility towards an intestinal epithelial cell line. The uptake and intestinal permeability of the nanogels were assessed using in vitro models, which physiological relevance was verified regarding the morphology of the epithelium, the production of mucus, the expression of occludin and the transepithelial electrical resistance.

Results

The covalent binding of Cy5.5 did not affect significantly the size and surface charge of the nanogels at 125.1 ± 3.2 nm and −57.6 ± 6.2 mV respectively after labelling. Studies of biocompatibility showed that the nanogels were non-toxic to Caco-2 cells up to the concentration of 0.1 mg∙mL⁻¹. The presence of mucus affected the nanogel uptake and highlighted the importance of considering mucus-producing cells in in vitro intestinal models. The uptake or adsorption to a Caco-2/HT29-MTX co-culture (8.1%) was higher than with single Caco-2 cell cultures (4.3%). Interestingly, both models led to minute (<0.5%) permeation of the nanogels across the intestinal barrier.

Conclusion

The HyA nanogels demonstrated to be mucoadhesive and effectively uptaken by intestinal cells. Both are determinant features for sustained release, but if systemic delivery is envisaged further modification with targeting moieties could be important to improve the nanogel permeability.

Keywords:

• oral delivery
• in vitro models
• nanogels
• intestinal permeability
• cellular uptake

Acknowledgements

The authors would like to acknowledge Doctor Andreia Gomes from the University of Minho for providing the HT-29 cells. This work was funded by MICRODIGEST project (grant agreement 037716) co-funded by FCT and ERDF through COMPETE2020, the FODIAC project (grand agreement 778299) funded by the European Commission through H2020-MSCA-RISE-2017 and CVMar+I project (INTERREG V-A España – Portugal – POCTEP 2014–2020, Ref. 0302_CVMAR_I_1_P).

Disclosure

Isabel Amado received funding from the People Programme (Marie Curie Actions) of the European Union’s Seventh Framework Programme (FP7/2007-2013) under REA grant agreement no. 600391. The authors report no other conflicts of interest in this work.