Cancer poses a major global health burden, cases predicted to increase to 28.4 million per year by 2040. While conventional treatments like surgery, chemotherapy, and radiation have led to gradual improvements, they have significant limitations. Nitric oxide (NO) delivered under control has the potential to completely transform cancer treatment but faces challenges regarding stability of traditional NO donors, ability to target tumor sites, and biocompatibility. Hydrogels offer unique advantages that could address these hurdles through their biocompatibility, controllable degradation, and capacity for localized drug loading and release. Specifically, hydrogels have potential to enhance efficacy of standard interventions like chemotherapy, radiotherapy, immunotherapy, magnetic hyperthermia, and photothermal/photodynamic therapy. They can also improve drug penetration into tumors, retention at tumor sites, and reduce side effects, thereby improving patient tolerance. Furthermore, in situ forming hydrogels enable minimally invasive administration, precise delivery to target sites, and enhanced patient convenience. Magnesium peroxide (MgO2) allows controlled NO release from hydrogels, increasing bioavailability at tumors and easing administration demands. This study aims to create an in situ hydrogel that can release NO for cancer treatment. A gelatin-hydroxyphenyl propionic acid (GH) polymer precursor was synthesized using EDC/NHS chemistry. The hydrogel, incorporating MgO2, was formed through HRP enzyme-catalyzed crosslinking, minimizing cytotoxicity. Key physicochemical properties were characterized, including gelation time, mechanical strength, degradability, porosity, and swelling. The hydrogel was also investigated for the release of molecules like H2O2, Mg2+ ions, and NO. The cytotoxicity against various cancer cell lines and biocompatibility with normal cells were evaluated based on the amount of NO released. As a result, by adjusting HRP and Mg2+ concentration, the hydrogels' physicochemical characteristics, such as gelation time, mechanical strength, microstructure, swelling ratio, and degradation rate, could be controlled. The amount of NO released over a 24-hour period, ranging from 23.84 to 37.99 µM depending on MgO2 loading, resulted in selective cytotoxicity towards various cancer cell lines including cervical cancer, breast cancer, prostate cancer, lung cancer, and colon cancer while sparing normal cells. In summary, this in situ NO-releasing GH/Mg hydrogel is expected to be a promising material for effective cancer therapy. _x000D_
<br>Keywords: gelatin; in situ forming hydrogel; nitric oxide; cancer therapy.
