Bromelain Encapsulated in Self Assembly Nanoemulsion Exhibits Better Debridement Effect in Animal Model of Burned Skin

Abstract

Bromelain is a mixture of proteolytic enzymes presence in all tissues of pineapple (Ananas comosus). It is known for clinical use as debridement for burn treatment. However, it is easily degraded by light, high temperature and pH. Nanoemulsion of bromelain is promising to increase its stability. In this study, we investigated the nanoemulsion of bromelain and its formulation into gel preparation in order to increase its efficacy for the burn treatment. Spontaneous or self-nanoemulsifying was applied to form nanoemulsion of bromelain (NEB). Bromelain was incorporated in various types of oil phase i.e virgin coconut oil (VCO), olive oil, vitamin E acetate and combination of both vitamin E acetate and VCO. Cremophor RH 40 was used together with polyethyleneglycol 400 to reduce oil-water interface tension. The stability of NEB in different oil phases was evaluated including particle size, polydispersity index, zeta potential, enzymatic activity and nanoemulsion morphology. Further, the most stable NEB was incorporated into hydrophilic gel matrix. An in vivo evaluation was carried out in hot plate-induced burn skin of New Zealand rabbit. Treatment of wounds was given by applying the preparations: NEB and the nanoemulsion bromelain-CMC gel (GKNB), using a standard protocol. As a control, untreated rabbit burned skin was provided. The efficacy of NEB was evaluated by observing wound contraction, eschar score, erythemic score, pus score and edema. After 14 days of storage, nanoemulsion using vitamin E acetate was found to be the most appropriate formula to encapsulate bromelain with good physical and chemical stabilities. This formula shows clear visual appearance with globule diameter of 74.37 nm, narrow size distribution, high loading efficiency of 97.96 %, and ability to maintain the enzymatic activity of bromelain compared to gel preparation using corresponding bromelain nanoemulsion. The vitamin E acetate nanoemulsion system shows better reduction in wound contraction until the 14th day of observation as well as other relevant parameters for wound healing effects. Taken together, bromelain formulated with the vitamin E acetate nanoemulsion improved the stability of bromelain and showed better activity to heal burnt skin on the animal model tested. The gel matrix retained the release of bromelain resulting in lower wound healing effect but it may have prolonged activity.