Drinkable in situ-forming tough hydrogels for gastrointestinal therapeutics

Abstract

Pills are a cornerstone of medicine but can be challenging to swallow. While liquid formulations are easier to ingest, they lack the capacity to localize therapeutics with excipients nor act as controlled release devices. Here we describe drug formulations based on liquid in situ-forming tough (LIFT) hydrogels that bridge the advantages of solid and liquid dosage forms. LIFT hydrogels form directly in the stomach through sequential ingestion of a crosslinker solution of calcium and dithiol crosslinkers, followed by a drug-containing polymer solution of alginate and four-arm poly(ethylene glycol)-maleimide. We show that LIFT hydrogels robustly form in the stomachs of live rats and pigs, and are mechanically tough, biocompatible and safely cleared after 24 h. LIFT hydrogels deliver a total drug dose comparable to unencapsulated drug in a controlled manner, and protect encapsulated therapeutic enzymes and bacteria from gastric acid-mediated deactivation. Overall, LIFT hydrogels may expand access to advanced therapeutics for patients with difficulty swallowing.

Fig. 1. Overview of LIFT hydrogels.

a, LIFT hydrogels form within the stomach after oral administration of (1) a 200-ml crosslinker solution comprising CaCl₂ and a dithiol-containing molecule, followed by (2) a 20–40-ml polymer solution comprising alginate and four-arm PEG–maleimide. These two solutions (3) mix within the stomach to form a tough double-network hydrogel (4) within the stomach. b, Schematic of the polymers and reagents used to facilitate crosslinking. Materials were selected due to their established safety profiles. Both PEG–dithiol and dimercaptosuccinic acid (DMSA) were investigated as a dithiol crosslinker. c, Left: LIFT hydrogels may act as controlled release depots through encapsulation of water-insoluble drug that gradually dissolves and diffuses from the hydrogel. Middle and right: LIFT hydrogels enable co-encapsulation and co-localization of therapeutic microbes or enzymes and excipient (for example, CaCO₃) that modulate local pH and protect against proteases.

Fig. 2. In vitro characterization of LIFT hydrogels.

a, Representative load–strain curves of LIFT hydrogels comprising 0%, 5% or 10% w/v four-arm PEG–maleimide crosslinked in CaCl₂/PEG–dithiol for 20 min, 37 °C, 50 RPM. b, Load at 90% strain of the different hydrogel compositions; n = 4 hydrogels were tested. Statistical analysis was performed by one-way ANOVA with post-hoc Tukey’s multiple comparisons test, n = 4 independent experiments. Data are presented as mean ± standard deviation. c, Images of various compositions of hydrogels before and after 90% strain. Scale bars, 5 mm. d, Load–strain curves of LIFT hydrogels formed in various % v/v mixtures of real porcine gastric fluid (rGF) and water containing CaCl₂/PEG–dithiol. e, Gelation kinetics of LIFT hydrogels immersed in a crosslinker bath comprising CaCl₂/PEG–dithiol at 37 °C, as characterized by rheology. f, Cumulative release of 155 kDa dextran and 20- or 100-nm nanoparticles from alginate and LIFT hydrogels. Hydrogels were incubated in SGF or SIF for the indicated time periods. Shown is the average of n = 3 independent experiments. Source data

Fig. 3. In vivo characterization of LIFT hydrogels.

a, Hydrogel geometries after in vivo formation in female Yorkshire pigs. LIFT hydrogels were formed by endoscopic administration of crosslinker solution (200 mM CaCl₂/10 mM PEG–dithiol) followed by polymer solution (0.5% alginate/5% w/v four-arm PEG–maleimide). Scale bar, 5 cm. b, X-ray imaging of LIFT hydrogels in female Yorkshire pigs throughout time. Shown is representative of n = 3 independent pig experiments. c, Load–strain curves of alginate or LIFT hydrogels after retrieval from Yorkshire pig stomachs. Hydrogels were characterized by five cycles of 90% strain. d, Maximum loads experienced by alginate or LIFT hydrogels throughout five cycles of 90% strain. Statistical analysis was performed by two-way ANOVA with post-hoc Šidák’s multiple comparisons test, n = 3 (alginate) or 4 (LIFT) independent experiments. Data are presented as mean ± standard deviation. e, Images of retrieved alginate or LIFT hydrogels before and after 90% strain. Source data

Fig. 4. Pharmacokinetics of various oral lumefantrine formulations.

a, Plasma lumefantrine concentration over time of free lumefantrine and lumefantrine encapsulated in alginate or LIFT hydrogel. For each treatment, n = 3 female Yorkshire pigs were tested. b, Lumefantrine AUC of each formulation. c, Maximum observed lumefantrine concentration (C_max) of each formulation. For b and c, statistical analysis was performed by one-way ANOVA with post-hoc Tukey’s multiple comparisons test, n = 3 Yorkshire pigs per treatment. All data are presented as mean ± standard deviation. Source data

Fig. 5. LIFT hydrogel co-encapsulation of CaCO₃ protects lactase activity after oral delivery.

a, Lactase activity, as measured by ONPG assay, after 15 min incubation in PBS or SGF at 37 °C. Absorbances were normalized to that of lactase incubated in PBS. Statistical analysis was performed by two-tailed Student’s t-test, n = 3 independent experiments. b, Lactase activity after hydrogel encapsulation with or without CaCO₃ co-encapsulation and incubation in SGF for 1 h. Absorbances were normalized to that of alginate/CaCO₃. Statistical analysis was performed by two-way ANOVA with post-hoc Šidák’s multiple comparisons test, n = 3 independent experiments. c, Lactase activity of various treatments after trypsin treatment. Absorbances were normalized to that of treatment without trypsin. Statistical analysis was performed by one-way ANOVA with post-hoc Tukey’s multiple comparisons test, n = 3 independent experiments. d, Activity of lactase encapsulated in LIFT hydrogels after 1 h in male Sprague–Dawley rats. CaCO₃ was administered separately (LIFT + CaCO₃) or co-encapsulated (LIFT/CaCO₃). Absorbances were normalized by hydrogel mass. Statistical analysis was performed by one-way ANOVA with post-hoc Tukey’s multiple comparisons test, n = 5 rats per treatment. e, Activity of lactase encapsulated in LIFT hydrogels after 2 h in male Sprague–Dawley rats. Absorbances were normalized by hydrogel mass. Statistical analysis was performed by one-way ANOVA with post-hoc Tukey’s multiple comparisons test, n = 4 (LIFT) or 5 rats (LIFT+CaCO₃, LIFT/CaCO₃). f, Activity of lactase encapsulated in LIFT hydrogels after 6 h in female Yorkshire pigs. Hydrogels were retrieved from porcine stomach and randomly sampled. Absorbances were normalized by hydrogel mass and to control hydrogels without CaCO₃. Statistical analysis was performed by two-tailed Student’s t-test, n = 3 independent pig experiments. All data are presented as mean ± standard deviation. Source data

Fig. 6. LIFT hydrogel co-encapsulation of CaCO₃ protects bacterial activity.

a, L. lactis viability, as measured by a luminescent ATP quantification assay, after 10 min incubation in PBS or SGF at 37 °C. Luminescence was normalized to that of bacteria incubated in PBS. Statistical analysis was performed by two-tailed Student’s t-test, n = 3 independent experiments. b, Viability of L. lactis encapsulated in LIFT hydrogels with or without CaCO₃ and incubated in SGF for 3 h. Statistical analysis was performed by two-tailed Student’s t-test, n = 3 independent experiments. c, Viability of L. lactis encapsulated in LIFT hydrogels after 6–7 h in female Yorkshire pigs. Hydrogels were retrieved from porcine stomach and randomly sampled. Luminescence values were normalized by hydrogel mass and to control hydrogels without CaCO₃. Statistical analysis was performed by two-tailed Student’s t-test, n = 3 independent pig experiments. All data are presented as mean ± standard deviation. Source data