The use of nanoencapsulation to decrease human skin irritation caused by capsaicinoids

Figures & data

Table 1 Composition of hydrogels

Formulations	Components
	Chitosan (2.5%)	Lactic acid (1%)	Nanocapsule suspension	Hydroalcoholic solution	Capsaicinoids
CH-NC-CP	x	x	x		x
CH-NC	x	x	x
CH-ET-CP	x	x		x	x
CH-ET	x	x		x

Note: x, used in the formulation preparation.

Abbreviations: CH, chitosan gel; NC, nanocapsules; CP, capsaicinoids; ET, ethanolic solution.

Figure 1 Viscosity as a function of shear rate of (A) chitosan hydrogels containing nanocapsules and (B) chitosan hydrogels containing ethanol and a commercial formulation of capsaicinoids.

Abbreviations: CH, chitosan gel; NC, nanocapsules; CP, capsaicinoids; ET, ethanolic solution; Commercial, commercial formulation.

Figure 2 Size distribution analyses of chitosan hydrogels containing nanocapsules.

Abbreviations: CH, chitosan gel; NC, nanocapsules; CP, capsaicinoids.

Figure 3 Skin erythema measured by electronic probe. The results indicate a ratio between the initial values (before application of formulation) and the final value at every measuring time point.

Notes: Significant differences observed (P<0.05): *CH-ET-CP versus no formulation; **commercial formulation versus no formulation.

Abbreviations: CH, chitosan gel; NC, nanocapsules; CP, capsaicinoids; ET, ethanolic solution; Commercial, commercial formulation.

Figure 4 Skin erythema measured by a visual scale.

Notes: Significant differences observed (P<0.05): *CH-ET-CP versus no formulation; **commercial formulation versus no formulation.

Abbreviations: CH, chitosan gel; NC, nanocapsules; CP, capsaicinoids; ET, ethanolic solution; Commercial, commercial formulation.

Figure 5 Arm of a volunteer 90 minutes after application of the formulations. The photograph is representative of the entire experiment.

Abbreviations: CH, chitosan gel; NC, nanocapsules; CP, capsaicinoids; ET, ethanolic solution; Commercial, commercial formulation.

Figure 6 Skin pH (A) and transepidermal water loss (B) measured by electronic probe. The results indicate a ratio between the initial values (before application of formulation) and the final value at every measuring time point.

Note: No significant differences (P<0.05) are observed between areas with and without application of the formulations.

Abbreviations: CH, chitosan gel; NC, nanocapsules; CP, capsaicinoids; ET, ethanolic solution; Commercial, commercial formulation.

Table 2 Sensory analyses of skin irritation

Formulations and degree of irritation	Time (minutes)
	30	60	90	120	180
CH-NC-CP
Negligible	69	69	92	100	100
Slight irritation	23	31	8	0	0
Moderate irritation	8	0	0	0	0
Severe irritation	0	0	0	0	0
CH-NC
Negligible	100	92	100	100	100
Slight irritation	0	8	0	0	0
Moderate irritation	0	0	0	0	0
Severe irritation	0	0	0	0	0
CH-ET-CP
Negligible	46	8	15	54	62
Slight irritation	46	38	69	31	38
Moderate irritation	8	46	8	15	0
Severe irritation	0	8	8	0	0
CH-ET
Negligible	77	85	92	100	100
Slight irritation	23	15	8	0	0
Moderate irritation	0	0	0	0	0
Severe irritation	0	0	0	0	0
Commercial formulation
Negligible	8	0	0	38	92
Slight irritation	15	8	38	54	8
Moderate irritation	54	23	62	8	0
Severe irritation	23	69	0	0	0

Note: Number represents percentages of volunteers who felt slight, moderate, or severe irritation.

Abbreviations: CH, chitosan gel; NC, nanocapsules; CP, capsaicinoids; ET, ethanolic solution.

Table 3 Skin permeation parameters of capsaicinoids from different semi-solid formulations

Formulations	AUC0–30 (μg/cm^2/hour)	Total amount permeated (μg/cm^2)	Lag time (hours)	Flux (μg/cm^2/hour)
CH-NC-CP	40.80±12.15a,b	4.23±0.97a	9.01±1.04a,b	0.19±0.04a
CH-ET-CP	343.84±87.54	29.41±7.17	5.91±0.69	1.19±0.29
Commercial formulation	114.92±16.11	9.39±1.34	5.34±1.50	0.38±0.07

Notes:

a Significant differences (P<0.05) between CH-NC-CP and CH-ET-CP;

b significant differences (P<0.05) between CH-NC-CP and commercial formulation.

Abbreviations: CH, chitosan gel; NC, nanocapsules; CP, capsaicinoids; ET, ethanolic solution.

Figure 7 Skin permeation of capsaicinoids incorporated in different semisolid formulations.

Note: Significant differences are described in Table 3.

Abbreviations: CH, chitosan gel; NC, nanocapsules; CP, capsaicinoids; ET, ethanolic solution; Commercial, commercial formulation.