Effects of Carbopol^® 934 proportion on nanoemulsion gel for topical and transdermal drug delivery: a skin permeation study

Figures & data

Figure 1 Pseudoternary phase diagrams of four cosurfactants combined with EL-40 at fixed mass ratio (1:1).

Notes: (A) 1,2-Propylene glycol; (B) glycerin; (C) ethanol; and (D) n-butyl alcohol.

Abbreviations: EL-40, Cremophor EL-40; Smix, mix of surfactant and cosurfactant.

Figure 2 Pseudoternary phase diagrams of various K_m ratios of EL-40 and 1,2-propylene glycol.

Notes: (A) K_m: 1:0; (B) K_m: 1:2; (C) K_m: 1:3; (D) K_m: 2:1; (E) K_m: 3:1; and (F) K_m: 4:1.

Abbreviations: EL-40, Cremophor EL-40; K_m, surfactant–cosurfactant; Smix, mix of surfactant and cosurfactant.

Figure 3 Droplet size distribution immediately after production.

Notes: (A) NE; (B) NG1; (C) NG2; and (D) NG3. NG1, NG2, NG3: NE gels containing 1%, 2%, and 3% (w/w) Carbopol^® 934, respectively.

Abbreviations: d, diameter; NE, nanoemulsion; NG, NE gel.

Figure 4 Zeta potential diagrams.

Notes: (A) NE; (B) NG1; (C) NG2; (D) NG3. NG1, NG2, NG3: NE gels containing 1, 2, and 3% (w/w) Carbopol^® 934, respectively.

Abbreviations: NE, nanoemulsion; NG, NE gel.

Figure 5 TEM images of the formulations.

Notes: (A) NE; (B) NG1; (C) NG2; (D) NG3. NG1, NG2, NG3: NE gels containing 1%, 2%, and 3% (w/w) Carbopol^® 934, respectively.

Abbreviations: NE, nanoemulsion; NG, NE gel; TEM, transmission electron microscopy.

Table 1 Stability of the NE and NGs treated with either extreme gravity (ie, centrifugation) or high temperature

Treatment methods	Formulation	Droplet size distribution (nm)	Polydispersity index	Zeta potential (mV)
No treatment	NE	15.53±3.32^a	0.074±0.009^a	−7.4±1.8^a
Centrifugation
12,000 rpm, 30 min	NE	16.32±4.86^a	0.069±0.013^a	−6.2±2.3^a
	NG1	12.83±5.43^a	0.075±0.015^a	−5.4±1.7^a
	NG2	15.61±5.52^a	0.076±0.006^a	−7.1±3.1^a
	NG3	17.78±3.51^a	0.076±0.005^a	−6.1±0.42^a
5,000 rpm, 30 min	NE	12.32±4.80^a	0.063±0.025^a	−6.1±1.9^a
	NG1	15.23±4.40^a	0.071±0.023^a	−6.2±3.1^a
	NG2	17.37±2.03^a	0.078±0.013^a	−6.4±3.2^a
	NG3	17.41±3.09^a	0.064±0.02^a	5.2±1.9^a
High temperature
65°C, 30 min	NE	93.68±25.06^c,C	0.307±0.045^b,c,B,C	−3.2±0.5^a
	NG1	72.53±20.49^c,C	0.329±0.033^c,C	−3.9±0.8^a
	NG2	41.71±11.30^b,B	0.261±0.014^b,B	−4.2±0.4^a
	NG3	20.52±6.46^a,A,B	0.058±0.010^b,A	−4.1±0.9^a
95°C, 30 min	NE	–	–	–
	NG1	1,062.53±105.09^c,C	0.369±0.041^d,D	1.3±0.2^b,B
	NG2	390.05±27.15^b,B	0.273±0.055^c,C	1.6±0.2^b,B
	NG3	89.20±18.57^a,A	0.17±0.055^b,B	1.4±0.5^b,B

Notes: Within the same line and treatment, values with different lowercase and uppercase letters differ significantly at the 0.05 and 0.01 levels, respectively. NG1, NG2, NG3, NE gels containing 1%, 2%, and 3% (w/w) Carbopol^® 934, respectively. Data is presented as mean ± SD.

Abbreviations: NE, nanoemulsion; NG, NE gel.

Figure 6 Influence of pH on the (A) DSD and (B) zeta potential of the NE and NGs.

Notes: NG1, NG2, NG3: NE gels containing 1%, 2%, and 3% (w/w) Carbopol^® 934. Error bars represent mean ± SD.

Abbreviations: DSD, drop size distribution; NE, nanoemulsion; NG, NE gel.

Table 2 Mean erythema/edema scores 24, 48, and 72 h after application

Formulations	Intact skin			Abraded skin
	Erythema/edema scores (n =5)			Erythema/edema scores (n =5)
	24 h	48 h	72 h	24 h	48 h	72 h
NE	2	5.4	6	5	6.6	7
NG1	2.5	5	7	5.6	6.8	7.2
NG2	1	2.4	3.2	3	4.4	6.8
NG3	0	0.2	2	1	2.4	2.6
BNE	0	0.33	0.5	0.17	0.33	0.5
Gel base	0	0	0	0.17	0.17	0.17
PBS	0	0	0	0	0	0
1% formalin	6.67	8	8	8	8	8

Note: NG1, NG2, NG3, NE gels containing 1%, 2%, and 3% (w/w) Carbopol^® 934, respectively.

Abbreviations: BNE, blank NE; NE, nanoemulsion; NG, NE gel; PBS, phosphate- buffered saline.

Figure 7 HPLC diagrams of different formulations.

Notes: (A) NE and NGs, the specific peaks of TER and CIT; (B) BNE; (C) standard TER; (D) standard CIT. NG1, NG2, NG3: NE gels containing 1%, 2%, and 3% (w/w) Carbopol^® 934, respectively.

Abbreviations: BNE, blank NE; CIT, citral; HPLC, high-performance liquid chromatography; NE, nanoemulsion; NG, NE gel; TER, terbinafine.

Table 3 Ex vivo skin permeation parameters over 24 h

Formulations	Drug	Jss (μg/cm^2/h)	ER
NE	TER	11.30±0.56^a,A	7.64
NG1		11.50±0.43^a,A	7.77
NG2		7.45±0.23^b,B	5.03
NG3		4.45±0.28^c,C	3.01
CG		1.48±0.34^d,D	1
NE	CIT	54.71±1.34^a,A	5.19
NG1		55.01±1.67^a,A	5.21
NG2		31.92±2.14^b,B	3.03
NG3		20.59±1.22^c,C	1.95
CG		10.55±0.87^d,D	1

Notes: Within the same line and drug, Jss values with different lowercase and uppercase letters differ significantly at the 0.05 and 0.01 levels, respectively. NG1, NG2, NG3, NE gels containing 1%, 2%, and 3% (w/w) Carbopol^® 934, respectively. Data presented as mean ± SD.

Abbreviations: CG, conventional gel; CIT, citral; ER, enhancement ratio; Jss, steady state flux; NE, nanoemulsion; NG, NE gel; TER, terbinafine.

Figure 8 Cumulative permeation of (A) TER and (B) CIT through guinea pig abdominal skin in vitro.

Note: NG1, NG2, NG3: NE gels containing 1%, 2%, and 3% (w/w) Carbopol^® 934, respectively.

Abbreviations: CG, conventional gel; CIT, citral; NE, nanoemulsion; TER, terbinafine.

Table 4 Temporal changes in the deposition of TER and CIT3

Model drug	Formulation	Stratum corneum			Epidermis/dermis
		2 h	6 h	12 h	2 h	6 h	12 h
TER (μg/cm^2)	NE	0.63±0.32^a,A	0.73±0.26^a,A	1.65±0.29^a,A	27.18±4.99^a,A	44.54±6.06^a,A	73.5±8.23^a,A
	NG1	6.32±1.52^c,C	6.58±2.02^c,C	6.27±1.03^c,C	28.54±4.29^a,A	41.69±4.86^a,A	75.25±9.52^a,A
	NG2	4.45±0.61^b,B	3.53±0.89^b,B	3.40±0.74^b,B	12.87±3.63^b,B	24.67±5.22^b,B	36.88±8.25^b,B
	NG3	3.52±0.46^b,B	5.85±1.05^c,C	2.92±0.69^b,B	9.21±1.82^b,B	16.47±7.69^c,B	25.26±5.51^c,B,C
	CG	1.18±0.23^a,A	3.56±0.59^b,B	5.63±0.76^c,C	3.08±1.70^c,C	5.74±2.01^d,C	17.42±5.63^d,C
CIT (μg/cm^2)	NE	1.28±0.98^a,A	1.62±0.34^a,A	0.95±0.52^a,A	79.88±8.24^a,A	121.25±10.58^a,A	210.71±12.38^a,A
	NG1	12.74±6.40^c,C	12.50±4.23^c,D	10.88±5.80^c,C,D	75.17±10.91^a,A	130.56±10.91^a,A	214.64±8.92^a,A
	NG2	9.58±3.71^c,B,C	5.65±2.18^b,B	5.81±1.64^b,B,C	46.68±9.15^b,B	73.61±9.23^b,B	123.58±11.20^b,B
	NG3	5.41±1.17^b,A,B	9.55±1.60^c,C,D	3.94±1.21^a,b,B	19.75±6.76^c,C	46.99±7.79^c,C	68.1±9.71^c,C
	CG	2.79±1.13^a,b,A	7.28±0.64^b,B,C	13.68±1.91^c,D	8.51±2.22^d,C	28.82±6.32^d,C	39.47±5.51^d,D

Notes: Within the same line and skin layer, values with different lowercase and uppercase letters differ significantly at the 0.05 and 0.01 levels, respectively. NG1, NG2, NG3, NE gels containing 1%, 2%, and 3% (w/w) Carbopol^® 934, respectively. Data presented as mean ± SD.

Abbreviations: CG, conventional gel; CIT, citral; NE, nanoemulsion; NG, NE gel; TER, terbinafine.

Figure 9 Visualization of drug traces in the abdominal skin of guinea pigs 2, 6, and 12 h after application of NE, NGs, and CG.

Notes: NG1, NG2, NG3: NE gels containing 1%, 2%, and 3% (w/w) Carbopol^® 934, respectively. (A–C) The trace of drugs in skin layers treated with NE, (D–F) NG1, (G–I) NG2, (J–L) NG3, and (M–O) CG at time intervals 2, 6 and 12 h, respectively.

Abbreviations: CG, conventional gel; NE, nanoemulsion; NG, NE gel.

Figure 10 Skin histological cross sections 2, 6, and 12 h after application of the NE and NGs.

Notes: NG1, NG2, NG3: NE gels containing 1%, 2%, and 3% (w/w) Carbopol^® 934, respectively. All figures were magnified 200 fold. (A) Normal structure of skin, (B–D) the structure of skin treated with NE, (E–G) NG1, (H–J) NG2, and (K–M) NG3 at time intervals 2, 6 and 12 h, respectively.

Abbreviations: NE, nanoemulsion; NG, NE gel.