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Hydrogel-based matrix prepared using biopolymers is a new frontier of emerging platforms for enzyme immobilization for biomedical applications. Catalase (CAT) delivery can be effective in inhibiting reactive oxygen species (ROS)-mediated prolongation of the wound healing process. In this study, to improve CAT stability for effective application, gelatin(Gel)–alginate (Alg) biocompatible hydrogel (Gel–Alg), as immobilization support, was prepared using calcium chloride as an ionic cross-linker. High entrapment efficiency of 92% was obtained with 2% Gel and 1.5% Alg. Hydrogel immobilized CAT (CAT–Gel–Alg) showed a wide range of pH from 4 to 9 and temperature stability between 20 to 60 °C, compared to free CAT. CAT–Gel–Alg kinetic parameters revealed an increased Km (24.15 mM) and a decreased Vmax (1.39 µmol H2O2/mg protein min) × 104. CAT–Gel–Alg retained 52% of its original activity after 20 consecutive catalytic runs and displayed improved thermal stability with a higher t1/2 value (half-life of 100.43 vs. 46 min). In addition, 85% of the initial activity was maintained after 8 weeks’ storage at 4 °C. At 24 h after thermal injury, a statistically significant difference in lesion sizes between the treated group and the control group was reported. Finally, our findings suggest that the superior CAT–Gel–Alg stability and reusability are resonant features for efficient biomedical applications, and ROS scavenging by CAT in the post-burn phase offers protection for local treatment of burned tissues with encouraging wound healing kinetics.

Nigella sativa L. has been used in folk medicine for treatment of many diseases. Thymoquinone (TQ), a main constituent of its oil and seeds, has shown promising medicinal properties in the treatment and prevention of various diseases. The present study aims to investigate the potential effect of TQ on airway-induced hypersensitivity. Ovalbumin (OVA) sensitization and challenge in guinea pig tracheal muscle preparation were used in order to investigate the anti-asthmatic activity of TQ. To study the effect of TQ on acute lung injury, lipopolysaccharide (LPS)-induced lung injury method was used. In addition, rat peritoneal mast cells (RPMCs) were collected to investigate the release of histamine from these cells. Furthermore, to study the anti-allergic activity of TQ, the systemic anaphylactic shock technique induced by compound 48/80 was performed. Pretreatment with TQ (3 mg/kg, i.p.) for 5 days prior to ovalbumin sensitization showed a marked decrease in the response of the tracheal spirals to acetylcholine and histamine, as spasmogens in a cumulative dose response-curve. TQ (8mg/kg, i.p.) prevented most of the pathological detrimental changes that occurred in response to the endotoxin LPS as the inflammatory cells infiltration, lipid peroxidation (LP), glutathione depletion (GSH), tumor necrosis factor-alpha (TNF-α) and interlukin-1 beta (IL-1β) levels in both boronchoalevolar lavage fluid (BALF) and lung tissue homogenates. Sensitization of rats induced a significant increase in the histamine release from RPMCs which is inhibited by pretreatment with TQ (8 mg/ kg, i.p.). Similarly, pretreatment of mice with TQ (50 and 100 mg/kg), 1hr prior to injection of compound 48/80 (8mg/kg, i.p.) significantly inhibited the % of mortality of mice following the systemic anaphylactic reaction. Considering the anti-asthmatic, anti-inflammatory, antioxidant and anti-allergic activities of TQ reported in this study, one can conclude that TQ could be of therapeutic potentials in treating various diseases associated with airway-induced hypersensitivity.

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