Abstract
Hypertrophic scars are pathogenic scars caused by abnormal healing of a wound. Excessive deposition of collagen in extracellular matrix increases the size of scar by protrusion. These scars are cosmetically disfiguring and unappealing which leads to lack of confidence in appearance. Social stigma related to the scars has been reported to cause mental health
diseases like depression. It occurs in genetically predisposed patients from African, Asian, and, Mediterranean decent. It develops following a deep dermal injury from burns, acne, or surgery. A few treatment options available are not that effective to effectively treat hypertrophic scars. Papain is a proteolytic enzyme traditionally used as a meat tenderizer. It breaks peptide
bonds in peptides and proteins. Papain can be used in the treatment of hypertrophic scars to break down excess collagen. However, high molecular weight (23.4 kD), of papain limits its transport through the stratum corneum barrier of the skin when applied topically. To deliver papain across the stratum corneum barrier, lipid vesicles like liposomes can be used.
Liposomes are spherical phospholipid vesicles which can entrap both hydrophilic and hydrophobic agents. They can deliver the entrapped substance by fusing with the lipids in the stratum corneum. Although, liposomes are utilized in topical delivery, there are studies which show that liposomes localize in the upper layer of stratum corneum and fail to deliver the payload deeper into the skin. Transfersomes on the other hand, are also phospholipid vesicles which have edge activators that make them more flexible as compared to liposomes and allow them to pass intact through narrower pores than the diameter of the vesicles. This is possible due to the accumulation of edge activators in the stress site which allows vesicles to bend instead of breaking. We hypothesize that both liposomes and transfersomes would effectively encapsulate and deliver papain across the stratum corneum barrier when applied topically. Three specific aims were designed to test the hypothesis. Three specific aims are: development and validation of an HPLC (High-pressure liquid chromatography) method for the quantification of papain, formulation, and characterization of papain liposomes and transfersomes, and, in vitro evaluation of permeability and cytotoxicity of papain loaded liposomes and transfersomes on HeLa cells. Liposomes and transfersomes were found to be negatively charged spherical nano-sized particles. Drug load for liposomes and transfersomes were 7.69±0.02 % and .28±0.05 %, respectively. They were found to have retained enzymatic activity of papain 77.55±1.34 % and 79.15±1.83 %, respectively, compared to papain solution. In vitro permeation studies showed that transfersomes were able to deliver papain across shed snakeskin which indicated it may cross the stratum corneum barrier whereas papain solution and papain in liposomes were not able to deliver papain across the stratum corneum barrier at 1 mg/ml concentration. However, liposomes, transfersomes and papain in solution were not able to deliver papain across the full thickness Sprague Dawley rat skin. Permeation of papain loaded transferosomes across stratum corneum can be a step closer towards the treatment of hypertrophic scars.