Zein-alpha lipoic acid-loaded nanoparticles to enhance the oral bioavailability of dapoxetine: optimization and clinical pharmacokinetic evaluation

Figures & data

Table 1 Independent (X₁–X₃) and dependent (Y₁–Y₄) variables of DPX-Zein-ALA nanoparticles formulations utilized in Box-Behnken design

Independent Variables	Unit	Levels
		−1	0	1
Percentage of ALA in Zein (X1)	%	15	20	25
Percentage of PVA (X2)	%	0.5	1	1.5
Stirring rate (X3)	rpm	800	1000	1200
Dependent variables	Unit	Constraints
Low	High	Goal
Particle size (Y1)	nm	148.6	206.8	Minimize
Zeta potential (Y2)	mV	0.294	19.1	Maximize
Initial DPX release after 1h (Y3)	%	18.09	35.67	Maximize
Cumulative DPX release after 24 h (Y4)	%	79.05	97.65	Maximize

Abbreviations: DPX, dapoxetine; ALA, alpha lipoic acid; PVA, polyvinyl alcohol.

Table 2 Formulation variables (X₁–X₃) of DPX-Zein-ALA nanoparticles and their observed responses (Y₁–Y₄) as suggested by Box-Behnken design

Run #	Independent variables			Dependent variables*
	Percentage of ALA in Zein (X1)	Percentage of PVA (X2)	Stirring rate (X3)	Particle size (Y1)	Zeta potential (Y2)	Initial DPX release after 1h (Y3)	Cumulative DPX release (Y4)
DN-1	15	1.5	1000	155.6	17.3	29.68	97.32
DN-2	15	0.5	1000	159.7	19.1	31.34	97.65
DN-3	20	0.5	800	168.9	15.2	24.34	93.76
DN-4	25	1.0	800	205.7	0.41	19.1	87.61
DN-5	20	1.5	800	163.8	10.6	26.1	96.99
DN-6	25	0.5	1000	206.8	0.41	18.09	79.05
DN-7	20	0.5	1200	150.1	15.1	33.45	96.95
DN-8	15	1.0	1200	148.6	17.9	35.67	97.03
DN-9	25	1.5	1000	194.7	0.29	22.7	88.2
DN-10	25	1.0	1200	196.9	0.39	20.1	89.4
DN-11	20	1.5	1200	160.2	13.6	30.21	96.55
DN-12	15	1.0	800	167.3	18.0	23.54	93.21
DN-13	20	1.0	1000	179.1	14.6	28.48	89.54
DN-14	20	1.0	1000	177.4	14.3	29.36	91.11
DN-15	20	1.0	1000	176.9	14.7	27.12	92.89

Note: *The observed values of Y₁, Y₂, Y₃ and Y₄ represent the means of three determinations; standard deviations were <5% of the mean and thus were omitted from the table.

Abbreviations: DPX, dapoxetine; ALA, alpha lipoic acid; X₁, percentage of alpha lipoic acid in Zein; X₂, percentage of polyvinyl alcohol; X₃, stirring rate; Y₁, particle size (nm); Y₂, zeta potential (mV); Y₃, initial DPX release after 1h (%); Y₄, cumulative DPX release after 24 h (%).

Table 3 Statistical analysis of variance (ANOVA) of the responses (Y₁–Y₄) results

Factors	Particle size (Y1)		Zeta potential (Y2)		Initial DPX release after 1 h (Y3)		Cumulative DPX release after 24 h (Y4)
	Estimate	p-Value	Estimate	p-Value	Estimate	p-Value	Estimate	p-Value
X1	43.225	0.0001*	−17.703	0.0001*	−10.06	0.0001*	−10.238	0.0032*
X2	−2.8	0.3123	−2.002	0.0189*	0.368	0.6257	2.913	0.1923
X3	−12.475	0.0041*	0.693	0.2903	6.588	0.0002*	2.09	0.3290
X1^2	20.275	0.0027*	−9.704	0.0001*	−6.79	0.0013*	−4.875	0.1473
X1X2	−4.0	0.3079	0.842	0.3565	3.135	0.0259*	4.74	0.1435
X1X3	4.95	0.2192	0.041	0.9625	−5.565	0.0026*	−1.015	0.7257
X2^2	−17.475	0.0050*	−0.810	0.3907	1.055	0.3576	3.625	0.2587
X2X3	7.6	0.0836	1.545	0.1214	−2.5	0.0546	−1.815	0.5361
X3^2	−16.625	0.0062*	−1.001	0.2984	−0.645	0.5629	6.14	0.0834
R^2	98.8063		99.529		98.7042		89.9672
Adj. R^2	96.6577		98.6813		96.3719		71.9082
SEE	3.52484		0.828797		1.00074		2.7339
MAE	1.75667		0.409478		0.462667		1.39367

Note: *Significant effect of factors on individual responses.

Abbreviations: DPX, dapoxetine; ALA, alpha lipoic acid; X₁, percentage of alpha lipoic acid in Zein; X₂, percentage of polyvinyl alcohol; X₃, stirring rate; Y₁, particle size (nm); Y₂, zeta potential (mV); Y₃, initial DPX release after 1 h (%); Y₄, cumulative DPX release after 24 h (%); X₁X₂, X₁X₃, X₂X₃, the interaction term between the factors; X₁X₁, X₂X₂, and X₃X₃ are the quadratic terms between the factors; R², R-squared; Adj-R², Adjusted R-squared; SEE, standard error of estimate; and MAE, Mean absolute error.

Figure 1 Standardized Pareto charts showing the significance of X₁, X₂ and X₃ and their combined effects on Y₁ (A); Y₂ (B); Y₃ (C) and Y₄ (D).

Abbreviations: X₁, percentage of alpha lipoic acid in zein; X₂, polyvinyl alcohol % concentration; X₃, stirring rate; Y₁, particle size (nm); Y₂, zeta potential (mV); Y₃, initial permeation after 1 h (%); Y₄, cumulative permeation after 24 h (%).

Figure 2 3D response surface plots showing the effects of X₁, X₂ and X₃ on the investigated dependent variables Y₁ (A and B); Y₂ (C); Y₃ (D and E) and Y₄ (F).

Abbreviations: DPX, dapoxetine; X₁, percentage of alpha lipoic acid in Zein; X₂, polyvinyl alcohol % concentration; X₃, stirring rate; Y₁, particle size (nm); Y₂, zeta potential (mV); Y₃, initial release after 1 h (%); Y_4, cumulative release after 24 h (%).

Figure 3 In vitro release profiles of DPX-loaded NPs formulations: (A) F1-F5; (B) F6-F10; and (C) F11-F15.

Abbreviations: DPX, dapoxetine; ALA, alpha lipoic acid.

Table 4 Optimal calculated variables and observed, predicted and residual values for responses (Y₁–Y₄)

Factor	Optimum	Response	Predicted	Observed	Residual
X1 (%)	15	Y1 (nm)	161.88	159.24	2.64
X2 (%)	0.5	Y2 (mV)	19.49	19.14	0.35
X3 (rpm)	800	Y3 (%)	24.22	25.32	1.10
		Y4 (%)	97.19	95.89	1.29

Abbreviations: X₁, percentage of alpha lipoic acid in zein; X₂, polyvinyl alcohol % concentration; X₃, stirring rate; Y₁, particle size (nm); Y₂, zeta potential (mV); Y₃, initial permeation after 1h (%); Y₄, cumulative permeation after 24 h (%).

Figure 4 Particle size distribution (A), zeta potential (B) measured by particle size analyzer, SEM photomicrographs (C and D) and TEM images (E and F) of optimized DPX-loaded NPs.

Abbreviations: TEM, Transmission electron microscope; DPX, dapoxetine; ALA, alpha lipoic acid.

Table 5 Single dose clinical pharmacokinetic parameters after oral administration of 30 mg of optimized DPX-loaded NPs and DPX marketed tablets

Pharmacokinetic Parameter	Optimized DPX-loaded NPs	DPX Marketed Tablets
Cmax (ng/mL)	197.384±13.153	200.121±44.351
tmax (h)	2.5±0.314*	0.583±0.144
AUC (0–24) (ng.h/mL)	1290.375±262.169*	662.758±116.011
AUC (24-∞)) (ng.h/mL)	85.77±79.191	46.419±31.879
AUC (0-∞) (ng.h/mL)	1376.145±339.592*	709.178±146.307
AUMC (0–24) ng.hr^2/mL	8749.718±2815.176	3324.778±1226.219
AUMC (24-end) ng.hr^2/mL	2058.471±1900.592	1114.068±765.084
AUMC (0-∞) ng.hr^2/mL	10,808.189±4708.753	4438.846±1991.228
Kel (h^−1)	0.135±0.025	0.089±0.032
t1/2 (h)	5.283±1.077	8.452±2.813
MRT (h)	7.637±1.373	6.031±1.826
Relative bioavailability (%)	194.04	–

Notes: Data represent the mean value ± standard deviation (SD) (n=6), *Significant at P<0.05 unpaired t test (two-tailed).

Figure 5 Plasma concentration–time profiles for the optimized DPX-zein-ALA nanospheres and marketed DPX tablets (30 mg) administered orally as a single dose. Data represent the mean value ± standard deviation (n=6). *Significant at P<0.05 (two-way ANOVA, Sidak’s multi-comparison test).