Topical gel containing Polysiloxanes and hyaluronic acid for skin scar: Formulation design, characterization, and In vivo activity

Scar formation is undesirable both cosmetically and functionally. It shows that silicone gel is effective in preventing and improving scars formed due to a wound formation after injury.


| INTRODUC TI ON
Scars are wounds caused by burns, injuries, surgery, or skin conditions like acne. 1,2 Both aesthetically and practically, it is unattractive. Scars are frequently considered ugly from a cosmetic standpoint. 3,4 Scar tissue generally lacks many of the functional traits of undamaged skin, such as touch sensitivity and skin integrity. 5,6 Even after surgery or wound injury, it is highly desirable to prevent the formation of scar tissue. 7,8 Scars could be broadly classified as keloid scars, contracture scars, hypertrophic scars, and acne scars. 9,10 Different types of scars vary in their etiology. 11,12 In order to treat or prevent scar formation, numerous methods have been developed which include surgical treatment, pressure treatment, wound collagen implantation and laser ablation, topical application of different materials (such as oils, creams, and greases), aftercare coverings and dressings (such as hydrogel or silicone gel dressings). Table 1. 13 For the treatment of scars in various forms, different approaches have been described in the literature, including topical treatments, 14,15 surgery, [16][17][18] steroid injection, 19 radiotherapy, 20 dermabrasion, 21 microdermabrasion, 22 laser resurfacing, 23 and filler injections and micro-needling. 24,25 Use of silicone gel sheeting is very common for the treatment of scars and keloids. 26,27 There are many clinical studies conducted on its efficacy. In fact, there are many other treatments available for scars, but most of them are not helpful to completely prevent it. 28 Most of the products in market are commonly silicone-based gel formulation. Gels or greases work by coverings and dressing the scar to reduce loss of skin moisture or to actively provide skin hydration. 29 Ninety-one percent of patients surveyed said they would like a better resolution for scarring after surgery. [30][31][32] Silicone gel works by the principle that it forms a skin surface layer on scar and seal it from outside environment. 33 The silicone gel overlying the body surface of scars, the scar body can be significantly reducing surface tension, thereby degrading synthetic collagen fibers against tensile force. 34 However, silicone also has its own problems.

Management for different types of scars was shown in
Water-absorbing property of silicone gel is poor. It uses in the condition of skin redness, itching usually unpleasant. Such gels generally indicated as a preventive measure to stop progress of already developed scar and need to be applied for longer periods to see a visible effect on scar reduction. Hence, it is desirable to design and develop a topical gel formulation which have improved effect in prevention and repair of scars.
Hyaluronic acid is a naturally occurring substance having an important mechanical and structural functions in wound healing process. It is distributed over the connective tissue such as subcutaneous tissue and cartilage tissue and plays an important role in hydration and elasticity of skin. 35,36 However, it decreases in amount and in quality with age, leading to drying out of the skin, which becomes wrinkled. 37 Among the applications of hyaluronic acid as a therapeutic agent are tissue regeneration and wound healing, degenerative and inflammatory joint diseases, synovial fluid replacement, topical cosmetics, and controlled release of drugs through microencapsulation. It is used locally to promote wound healing in the form of cream, gel, or impregnated gauze. 38,39 U.S. Patent discloses that cross-linked hyaluronic acid is useful in treating scars because it facilitates the penetration of bioactive substances through scar tissue. 40 The tolerance of hyaluronic acid is very good, and no immunogenicity has been associated after its use. 41 Silicone gel alone may not be that much effective when aim is to prevent scar formation along with wound healing process. 42,43 Although advances have been made in prior art for the reduction of scar but there remains a need for composition which are operable for reducing the profile of a scar at the same time when wound healing process is progressing. Usually available products are meant for treatment when scar has already formed after wound closure. 44 The present invention provides a gel composition and its process of preparation for the prevention and repair of scars arising due to wound healing. In the wound healing process, the compositions can be used to reduce scarring by aiding in the natural healing process. In this research study, a novel pharmaceutical composition comprising TA B L E 1 Different types of scar, treatment approach, and clinical observation.

Type of scars Treatment approach Observations
Widespread scar Intralesional corticosteroids A course of steroid injections into a scar may help flatten it Atrophic scar Resurfacing, peel, dermabrasion -This treatment involves the removal of the surface of the skin with special equipment. -It is a much less invasive form of dermabrasion but is minimally useful for very superficial scars.
Hypertrophic scar Laser therapy, cryosurgery, bleomycin and fluorouracil injection -These treatments can be used to raise sunken scars to the level of surrounding skin. (eg: Hyaluronic acid serum). -Similar to dermabrasion, removes the surface layers of the skin using different types of lasers.

Keloid
Combination therapy Low-dose, superficial radiotherapy is used to prevent recurrence of severe keloid and hypertrophic scarring.

Scar contractures
Reconstruction possibly with skin grafts, flaps, etc Many small puncture holes are made into the superficial skin to stimulate collagen production and even introduce collagen stimulators or other products to try to reduce the appearance of scars.
of sodium hyaluronate and polysiloxanes was designed and developed for skin scar ( Figure 1).

| Preparation of novel polysiloxane gel formulation
In accordance with Table 2 and the reported method, a gel formulation was prepared by following the composition as described in Table 2. 45 The method of preparation of novel gel formulation comprises following steps: F I G U R E 1 Illustration indicating research design and benefits of developing topical gel containing polysiloxanes and sodium hyaluronate for anti-scar application. Hyaluronic acid on scar treatment.

| Organoleptic characteristics
Various organoleptic characteristics of the novel topical gel were evaluated, such as appearance, homogeneity, washability, consistency, phase separation, and odor through visual observation. The homogeneity and texture characteristics of the gel formulation were evaluated by placing samples between the thumb and index finger. The gel was centrifuged in the REMI centrifugation unit at 5000 rpm for 30 min and the phase separation, creaming or cracking were screened out. Immediate skin feel (including stiffness, grittiness, and greasiness) was also evaluated. 46 2.3.2 | Spreadability 0.5 g of gel samples was compressed under glass plates of known weight to determine the spreadability of the novel topical gel. In a subsequent step, glass plates were placed over the sample one by one at intervals of 1 min. The spreading area was calculated after each glass plate was added, and results were expressed in term of spreading area as a function of applied mass (weight of glass plate).
The slides were fixed to a stand without the slightest disturbance. 47

| Animals
For the in-vivo study, the Wistar rats (180-220 g) were acclimatized to standard laboratory conditions (25 ± 2°C and 55 ± 5%) RH for 7 days with free access to food and water. [53][54][55] The animals were

| Anti-scar activity
The animals were anesthetized prior to wound induction procedures with ketamine (50 mg/kg, i.p) and xylazine (5 mg/kg, i.p). [56][57][58] Following appropriate anesthesia, the dorsum (operative field) of each rat was shaved with depilatory cream (Reckitt Benckiser, Inc), and the shaved areas were cleaned and disinfected with povidoneiodine and alcohol. Under the aseptic condition, a full-thickness skin excision (2 × 2 cm) was made on the dorsum back of the rats using toothed forceps, a surgical blade, and pointed scissors. Two wound areas were created on the dorsum of each rat. Wound were placed at a distance of 3 cm between each other to make sure they would not influence each other's wound healing. After surgery, the animals were monitored for spontaneous breathing efforts and movement.
After surgical recovery, the animals were kept separately to prevent manipulation of the wounds by each other and fed with a standard rat diet and water. [59][60][61] After gross epithelialization, the topical application was randomly applied according to the location of the wound on each of the 24 rats as follows: • Control group (n = 8): No treatment was provided for the scars.
• Standard (Reference Product) group (n = 8): The skin defect site was massaged twice daily for 5 min each time with the reference product.
• Test product group (n = 8): The skin defect site was massaged with test product twice per day for 5 min each day.
In the test and standard groups, the same quantity (0.25 gm) of samples was applied to each site, except in the control group. After 10, 20, and 30 days of the scar treatment, the scar area was measured.

| Histopathology
Rat skin was removed in order to conduct a histological analysis. The

| Statistical analysis
The results were provided as mean standard deviation after each reading was measured in triplicate. p < 0.05 was used as the threshold for statistical significance in the data analysis that was done to compare the experimental results between the groups.

| Preparation of novel topical gel formulation
The formulation development process used only pharmaceuticalgrade components. The gel was created in accordance with the composition layout depicted in Table 2. The method of preparation of novel topical gel formulation comprises the mixing of aqueous phase dispersion and polysiloxanes blend under stirring at room temperature. Finally, a homogenous smooth gel system was formed. The novel topical gel has a smooth texture and white to off-white color translucent and homogeneous.

| Organoleptic characteristics
The Physicochemical evaluation of novel topical gel including appearance, homogeneity, washability, consistency, phase separation, odor, and immediate skin feel was evaluated, and observations were reported in Table 3. The color of the prepared topical gel formulation was off-white, free from grits and lumps, and translucent in appearance. Application of novel gel went smoothly. It was discovered that the gel was uniform/homogenous and washable.

| Spreadability
The capacity of the new gel formulation to spread uniformly on the skin is a unique attribute of the spreadability of the revolutionary topical gel.
Due to its rapid distribution over a short period of time, novel topical gel was thought to have a high spreadability. The distribution of gels affects their therapeutic efficacy. The spreading of the gel aids in its uniform application to the skin, so the prepared topical gel must be well spreadable and meet the requirements for excellent topical application.
According to the study, the gel spread readily in response to the minimal force used (Figure 2). It was calculated that the spreading factor was 0.156 ± 0.001 cm 2 /g. It suggests that when applied at the target site, the formulation could retain a good wet contact time.

| Rheology
In

| Gel morphology
The morphology of novel topical gel formulation was observed under polarized microscope and shown in Figure 4. Spherical droplet of aqueous phase in non-aqueous continuous phase of polysiloxanes indicates that encapsulation of sodium hyaluronate into spherical droplet due to its solubility in aqueous phase. It will be helpful in deeper skin penetrability of enclosed bioactive.

Parameters Observations
Appearance conditions as shown in Figure 5 and Table 4.
Furthermore, stability of product in storage container (gel tube) was observed visually initially at Day -0 and Days − 28 upon storage at condition 40 ± 2°C/75 ± 5% RH. A vertical cut was made through the storage tube from bottom to top. The product was visually evaluated for phase separation, physical appearance changes, and texture changes (e.g., color and lumping). It was observed that sample exhibits no separation or lump appearance in sample ( Figure 6). It indicates stability of developed gel formulation inside storage container system as well.

| In vivo study
The purpose of the animal study was to compare the innovative gel to the marketed product (Kelo-cote scar gel) and see how it affected the healed wound scar. 44 Wound healing with scar formation is an exercise appearing in the organ systems of humans and animals.
This is most obvious in cutaneous wounds, where the injury is often cosmetically damaging. 63 Wound healing were observed on Day 1, Day 7, and Day 15 as shown in Figure 7. Afterward, the scar area was measured.
The scar area was observed and measured at different time intervals up to 30 days to evaluate the progress of anti-scar activity exhibited by the test and standard product as shown in Figure 8.
The test and standard product applied to the scar area showed significant (p < 0.05) improvement in the anti-scar activity as compared to control at different time intervals. A significant difference was observed in the scar area on Day 30 (after full healing) for the standard drug (63.67%) and test drug (75%) as compared to the control ( Figure 9). However, the scar area for the test drug was significantly smaller in comparison with the reference drug. In conclusion, test drug exhibits better anti-scar activity as compared to standard drug.

| Histopathology of treated rat skin
The results of the histopathological examination of skin tissue revealed scar tissue formation in of the control group with no treatment in the form of irregular, slightly thickened epidermis at the healing site (Figure. 10A). The tissue of the standard group (scar treated with reference/marketed product) sections showed thickened epidermis and keratin layer at the healing site ( Figure. 10B).
However, the skin of the test group treated with the novel developed product displayed nearly normal epidermis at the healing site, which means the effectiveness of this novel product in the restoration of normal skin ( Figure 10C).
It was reported that the skin restores the lost tissues by scarring where the new cell population resides in a newly constructed connective tissue with a new vasculature, but the organization of those

| CON CLUS ION
The findings of this study demonstrated that gel significantly reduced scar formation even at the earliest stages of damage. Examination of F I G U R E 8 Progress of anti-scar activity of marketed reference product and developed test product.

F I G U R E 9
Effect of novel topical gel formulation on scar area (n = 6); *p < 0.05, **p < 0.01 and ***p < 0.001 compare with the control and standard group.

ACK N OWLED G M ENTS
This research is owned by the Research and Development at Jamjoom Pharmaceuticals, Jeddah-21442, Kingdom of Saudi Arabia.

CO N FLI C T O F I NTE R E S T
The authors affirm that they have no conflicts of interest.

DATA AVA I L A B I L I T Y S TAT E M E N T
The article contains the information needed to substantiate its findings.

E TH I C A L A PPROVA L
Research Ethics Committee has been examined the application and ap- healed wound compared with reference product" are the base of this research has been approved with reference no: PH-1442-46.