Topical fish scale collagen cream: Formulation, skin permeation, and biocompatibility for cosmetic and therapeutic use

This study aims to develop and characterise fish scale-collagen cream (CoC) intended for topical application. The development of CoC consists of hydrolysed collagen (molecular weight ≈ 1 kDa) dispersed into the aqueous phase of a water-in-oil (w/o) emulsion of Span 60: Tween 60/water/virgin coconut oil (VCO) system. Collagen used in this study has been extracted from Tilapia fish scales using hydrothermal extraction combined with enzymatic hydrolysis treatment. The CoC was developed using a water-in-VCO emulsion medium at water volume fractions (φ w ) of 0.74, 0.83, and 0.94. Up to 20 wt.% of hydrolysed collagen was successfully loaded into the emulsion system via the high shear homogenisation technique. The characterisation of the CoC involved a complex microscopic analysis, including optical polarising microscopy (OPM) and scanning electron microscopy (SEM), complemented by droplet size analysis, differential scanning calorimetry, and rheological evaluation. The physical characteristics of CoC were investigated to evaluate its suitability for administration on the skin. The potential of CoC to be applied on the skin was evaluated using analysis of ex vivo rat skin permeation using the Franz diffusion cell, in vitro fibroblast cell viability and in vivo toxicity to the mice. Franz diffusion cell studies revealed 3466.46 ± 21.70 μg/cm² cumulative collagen permeation over 6 hours (vs. 1750 ± 319.67 μg/cm² control; p < 0.001, 95% CI: 1580–1850 μg/cm²), with 94–97% retention in skin layers. In vitro , 0.02 mg/mL hydrolysed collagen increased fibroblast viability by 34% (p < 0.01, n=3). Furthermore, Sub-acute toxicity tests of 25–50 mg/kg body weight of hydrolysed collagen for 7 days showed no significant weight changes (p > 0.05, 95% CI: −0.5% to +1.2%) or mortality. It was observed that the hydrolysed collagen could pass through the rat skin easily and successfully stimulate the fibroblast cell viability. In conclusion, CoC is a suitable carrier for hydrolysed collagen in topical applications. The use of the designed emulsion-based creams can safely enhance the delivery of the hydrolysed collagen in the skin layers with additional benefits for cosmetic and therapeutic applications.