Thermosensitive hydrogel containing liposomal nanoparticles of deferoxamine and curcumin: In vitro evaluation and diabetic wound healing effect in rats.

Diabetic wound as a serious complication of diabetes remains a major clinical challenge. Excessive chronic inflammation, recurrent infection and impaired angiogenesis are the main causes of the complex diabetic wound microstructure. Therefore, developing a multifunctional hydrogel-based wound dressing incorporating various modalities to restore the tissue function and accelerate the healing process could offer a promising strategy. To this goal, curcumin (CUR, as an anti-inflammatory agent) and deferoxamine (DFO, as an angiogenesis stimulant) were simultaneously loaded into liposomal nanoparticles and further incorporated into thermosensitive hydrogel made of PEG-PCL-PEG copolymer. Particle size, zeta potential, encapsulation efficiency (EE) and release pattern of liposomal nanoparticles were evaluated. Liposomal nanoparticles (DPPC/DPPGG/CUR/DEF: 80/10/10) incorporating DFO in the core and CUR in the shell were 160.5 ± 0.44 nm in size and negatively charged (-19.4 ± 0.21). EE for CUR and DFO were 88.37 % and 97.15 %, respectively. CUR release reached 14 % and DFO was released 100 % from liposomal formulation after 5 days. To determine the optimal concentration of curcumin and deferoxamine in induction of angiogenesis, chicken chorioallantoic membrane (CAM) test was conducted. The results indicated that liposomal formulation containing both curcumin (90 μM) and deferoxamine (100 μM) demonstrated the highest angiogenic effect. Afterwards, thermosensitive hydrogel (PEG-PCL-PEG) was synthesized. The finally optimized hydrogel was made of 30 % (Wt %) polymer solution of PCL:PEG (4:1 wt ratio). Thereafter, liposomal nanoparticles were incorporated into the hydrogel and the release pattern of curcumin and deferoxamine from liposome incorporated hydrogel was studied. Hydrogel to liposomal volume ratio was 70:30. The swelling ratio of the designed hydrogel reached 0.7 of its initial weight in 28 days. Moreover, stability study revealed that about 50 % of hydrogel's initial weight was degraded in 28 days. Rheology study showed that the synthesized hydrogel was pseudoplastic as the viscosity was decreased by increasing the shear rate. The release pattern of CUR and DFO from the liposome loaded hydrogel platform occurred in a gentler slope and more uniformly due to the hydrogel resistance although the final release rate was approximately the same as the liposomal formulation. In the final step, the effect of the developed hydrogel on an animal model of diabetic ulcer in rats was evaluated. Tissue morphology, collagen deposition, angiogenesis (CD31 and vimentin) were also evaluated. The results of histological studies showed that the hydrogel platform incorporating CUR-DEF coloaded liposomes performed better in terms of collagen deposition and re-epithelialization than other groups (hydrogel loaded with either liposomal CUR or liposomal DEF). Immunohistochemistry tests for CD31 and Vimentin in newly formed vessels also showed that angiogenesis occurred earlier in the group received the mentioned formulation. Therefore, the multifunctional thermosensitive hydrogel platform incorporation liposomes co-loaded with CUR&DEF can be used in diabetic wounds with promising potential for further clinical research.