SKIN CARE 53
TABLE 4: CONCENTRATION-DEPENDENT STABILIZATION OF ZNO SUSPENSIONS BY SURFACTIN ZnO (F1)
ZnO+0.1 %SF (F2) ZnO+0.2 %SF (F3) ZnO+0.3 %SF (F4)
ZnO+0.4 %SF (F5)
ZnO+0.5 %SF (F6)
ZnO+1% SF (F7)
The surfactin-containing TiO2
formulation
(Formula 20) was compared with its control (Formula 19) with respect to spreadability, light texture, absorption rate, white cast, and non- sticky afterfeel. Sensory attributes were scored on a 10-point scale, with higher scores indicating superior performance.
Results Powder dispersibility test in aqueous solution The stabilizing effect of surfactin on ZnO particle dispersion is presented in Table 4. The 10% ZnO formulation in aqueous medium showed limited dispersion capability, with particles accumulating at the air-liquid interface and exhibiting persistent phase separation upon standing. In contrast, the incorporation of surfactin substantially improved the suspension stability. As the surfactin concentration increased,
a progressive enhancement in dispersion homogeneity was observed. A complete and stable suspension was achieved at a surfactin concentration of 1% (w/w), with no visible sedimentation over 24 hours. This finding indicates that surfactin effectively functions as a dispersion stabilizer for ZnO in aqueous systems.
Particle size analysis As shown in Table V, surfactin incorporation significantly reduced the particle size of both TiO2 and ZnO suspensions, as reflected by their median diameters (D50). The D50 of TiO2
decreased from 84.8 μm to
50 40 30 20 10 0
0 0.2
Surfactin concentration (%) 0.6
0.4 Figure 1: Modulation of ZnO particle size by surfactin concentration
www.personalcaremagazine.com 0.8 1
TABLE 5: REDUCTION IN PARTICLE SIZE OF PHYSICAL SUNSCREEN SUSPENSIONS BY SURFACTIN INCORPORATION
Groups
20%ZnO (F8)
20%ZnO +0.1%SF (F9)
20%ZnO +0.5%SF (F10)
20%ZnO +1%SF (F11)
20%TiO2 (F12)
20%TiO2 +1%SF (F13)
D10 (µm) 0.215 0.132 0.13 0.091 1.64 1.48 D50 (µm) 45.2 1.01 0.249 0.276 84.8 8.07 D90 (µm) 180 12.6 0.881 1.44 1.79 37.8
8.07 μm, representing a 90% reduction, while that of ZnO was reduced from 45.2 μm to 0.276 μm, corresponding to a 99% decrease. These results demonstrate that surfactin effectively disrupted the large aggregates of the physical sunscreens, particularly transitioning ZnO into a sub-micron dispersion. The corresponding fitting curve is provided in Figure 1.
In vitro SPF assessment The demonstrated capacity of surfactin to enhance dispersion stability and reduce particle size of physical sunscreens prompted further investigation into its effects on sunscreen performance. As shown in Figure 2, the
formulation protocol significantly influenced SPF enhancement. Co-dispersing ZnO and surfactin in the aqueous phase (Formula 16) yielded the highest SPF value of 31.7, representing a 25% improvement over the surfactin-free ZnO formulation (Formula 14, p < 0.001). This improvement substantially exceeded that achieved with the commercial dispersant SG (Formula 18), which yielded only a 1.6% SPF increase under identical conditions. In contrast, alternative incorporation methods — adding both ZnO and surfactin to the oil phase (Formula 17) or placing them in the oil and aqueous phases, respectively (Formula 15) — yielded only marginal or no SPF improvement. Similarly, addition of surfactin to TiO2
-based
formulations also significantly increased SPF by 12%.
These findings demonstrate that pre-
dispersing both surfactin and physical sunscreen agents in the aqueous phase prior to formulation represents the most effective strategy for maximizing SPF enhancement.
Sensory evaluation Sensory evaluation results are presented in Figure 3. The study demonstrated that surfactin incorporation enhanced the skin-feel characteristics of micronized physical sunscreens. Compared with the formulation containing
the commercial dispersant SG, surfactin-based systems exhibited a lighter texture, faster absorption, superior spreadability (score 8.0 in ZnO formulations), and substantially reduced stickiness and white cast.
Discussion This study demonstrates that surfactin serves as a multifunctional performance enhancer for micron- sized physical UV filters, effectively addressing the long-standing challenges of dispersion instability, inadequate UV protection, and undesirable sensory properties. Our findings reveal that surfactin not only functions as a dispersion stabilizer but also significantly improves sunscreen efficacy and user experience. Surfactin incorporation yielded remarkable
improvement in suspension stability, preventing the particle aggregation and sedimentation that commonly plague micron-sized physical filters formulations, attributable to the amphiphilic molecular structure of surfactin that promotes effective adsorption onto particle surfaces and generates strong electrostatic and steric repulsion
March 2026 PERSONAL CARE MAGAZINE
D50 (µm)
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104
