3D Bioprinting of an Oral System for Probiotic Delivery to the Colon

Introduction: Inflammatory bowel disease (IBD) affects over 6 million individuals worldwide1. Because patients often show gut dysbiosis, restoring microbial balance through colon targeted delivery of probiotics has been described as a strategy for effective management of these pathologies2. For colon delivery purposes, tableting and coating processes are generally carried out, overall requiring high pressures, temperatures and solvent volumes that may impact bacterial viability3. Hence, 3D bioprinting is here proposed as an innovative technique for manufacturing of a time-dependent L. paracasei colon delivery system. Methods: Disintegrating cores were fabricated from pastes containing paracetamol as an analytical tracer, and either insoluble Kollidon®SR (KSR), with or without superdisintegrants, or soluble Mannogem®XL (MXL) as fillers. Bacterial pellet was added to the latter paste. The functional shell was obtained from hydroxypropyl cellulose (HPC, Klucel®LF). Printing was performed by a 3D Discovery™Gen.5 bioprinter (RegenHU, CH) equipped with extrusion and thermoplastic printheads, followed by mild drying. Core and core-in-shell units underwent physico-technological and release characterization. Bacterial count was conducted in intermediate and final dosage form samples. Results: MXL-containing cores exhibited faster disintegration (15-25min) compared to KSR-based ones (25-40min). The former also showed a rapid tracer dissolution in phosphate buffer pH 6.8. When such cores were embedded in an HPC shell through a simultaneous core and shell printing, as desired, a delay phase was achieved prior to release (Fig.1). Incorporating bacteria into the MXL-based paste, followed by simultaneous printing into a core-in-shell dosage form and subsequent drying, was proved not to negatively affect cell viability. Discussion: Through fine-tuning of formulation and printing parameters, extrudable pastes were attained, resulting in core-in-shell dosage forms with the desired performance. Indeed, a lag phase, brought about by polymer swelling/erosion, was observed followed by a sufficiently prompt release. In this respect, the use of a soluble filler was shown to promote disintegration of the core more efficiently than an insoluble one, even combined with a superdisintegrant. Notably, no processing steps involved impaired viability of L. paracasei. For time-dependent colonic release, an enteric outer shell would be needed, which will be addressed in a future research stage. References: [1] S.C. Ng et al. Lancet 2017, 390 (10114), 2769–2778. [2] J. Ni et al. Nat Rev Gastroenterol Hepatol 2017, 14, 573–584. [3] B. Bosch et al. Eur J Pharm Biopharm 2023, 190, 73-80.