A self-healable and injectable hydrogel for pH-responsive doxorubicin drug delivery in vitro and in vivo for colon cancer treatment

Hydrogels are three-dimensional solid-like structures with a wide range of applications in drug trans-port, tissue engineering, wound dressing, etc. We developed herein a new hydrogel by mixing 5'-gua-nosine monophosphate (5'-GMP) disodium salt (16 mM) and 1,4,5,8-naphthalene tetracarboxylic acid tetra potassium salt (NAP) (4 mM) in 4:1 (GMP:NAP) stoichiometry in aqueous media (pH similar to 4 at 25 degrees C). The mechanical properties of the resulting hydrogel were investigated by rheological studies, which showed that the hydrogel formed at pH 4 is the most stable [storage modulus (G ') of similar to 4000 Pa] and has higher endurance for the oscillatory strain (20% strain). Spectroscopic investigations provided insights into the unique self-assembly of 5'-GMP and NAP. Further, the composite exhibited pH-responsive hydrogelation over the pH range of 3-6, and the gel was transformed into a sol form at pH > 5. This stimuli-sensitive nature of the hydrogel was then exploited for the encapsulation and efficacious delivery of an anticancer drug, doxorubicin (DOX), specifically toward the colorectal cancer. Microscopic studies revealed the presence of a regular entangled fibrillar network for the hydrogels, which allowed for its exceptionally high drug loading capacity. The controlled release of DOX from the hydrogel was then studied at the physiological pH of the gastrointestinal tract, i.e. pH similar to 7.4. The DOX-loaded hydrogel (DOX-Gel) exhibited a similar to 82% release of DOX over 100 h at pH similar to 7.4. The enhanced cellular toxicity of DOX was observed in CT-26 murine colorectal carcinoma cell lines treated with the DOX-loaded hydrogel compared to DOX only as manifested from the fluorescence-activated cell sortinganalyses and fluores-cence microscopic studies. The fluorescence-activated cell sorting analysis showed a similar to 4.5-fold increase in the drug internalization for the DOX-Gel as compared to DOX only formulations. The co-localization of DOX into the cell nucleus was confirmed from confocal microscopy. The in vivo drug delivery efficacy of this pH-responsive hydrogel was further assessed on an animal tumor model, Balb/c mice (n = 9). A significant regression of similar to 87.5% in the tumor volume was observed after 21 days of DOX-gel adminis-tration, in contrast to DOX only formulation, which showed only a similar to 46.0% regression in the tumor vol-ume. The blood reports of the non-treated control mice and the mice treated with DOX only indicated a metastatic behavior in comparison with the mice treated with the DOX-Gel. This, the present system, is a self-healable, injectable hydrogel, which makes it an ideal drug delivery vehicle with stimuli-responsive controlled drug release capabilities even in vivo. (c) 2023 Elsevier Ltd. All rights reserved.