Chemical engineering of a lipid nano-scaffold for the solubility enhancement of an antihyperlipidaemic drug, simvastatin; preparation, optimization, physicochemical characterization and pharmacodynamic study

Figures & data

Table 1. Coded independent and dependent variables with their lower and higher limit.

	Level used, actual (coded)
Factor	Low (−1)	Medium (0)	High (+1)
Independent variables
X1 = Lipid mix (7:3%w/v)	2	2.5	3
X2 = Surfactant (%)	0.5	1	1.5
X3 = sonication time (min)	3	5	7
Dependent variables
Y1 = Particle size	Minimize
Y2 = PDI	Minimize
Y3 = Entrapment efficiency (%)	Maximize

Table 2. Box–Behnken experimental design of SMV-loaded NLC and evaluated response parameters (n = 3).

					Dependent variables
	Independent variables				Observed response		Predicted response
Formulation code	X1	X2	X3	Y1	Y2	Y3	Y1	Y2	Y3
NLC1	+1	0	+1	126.7 ± 14.52	0.300 ± 0.036	88.10 ± 6.26	127.591	0.287	88.17
NLC2	0	0	0	117.4 ± 8.10	0.214 ± 0.028	85.31 ± 5.89	115.57	0.209	85.38
NLC3	−1	−1	0	106.3 ± 6.10	0.192 ± 0.018	80.34 ± 4.74	106.54	0.187	80.45
NLC4	+1	+1	0	139.47 ± 12.54	0.261 ± 0.021	92.12 ± 6.23	138.85	0.252	92.07
NLC5	0	0	0	118.34 ± 13.18	0.220 ± 0.023	85.25 ± 5.78	115.57	0.209	85.38
NLC6	+1	−1	0	142.73 ± 12.30	0.236 ± 0.019	95.15 ± 6.88	142.36	0.228	95.31
NLC7	0	+1	+1	120.22 ± 5.80	0.245 ± 0.040	82.74 ± 4.67	119.01	0.237	82.83
NLC8	0	−1	−1	136.85 ± 10.90	0.172 ± 0.028	92.80 ± 4.87	137.62	0.165	92.76
NLC9	0	0	0	113.63 ± 9.50	0.220 ± 0.027	85.61 ± 5.38	115.57	0.209	85.38
NLC10	0	−1	+1	122.98 ± 11.64	0.278 ± 0.037	86.90 ± 6.10	121.53	0.269	86.78
NLC11	−1	0	−1	110.4 ± 12.20	0.181 ± 0.019	81.20 ± 4.23	109.07	0.178	81.18
NLC12	−1	0	+1	89.45 ± 5.10	0.222 ± 0.020	72.60 ± 4.98	89.73	0.212	72.70
NLC13	0	0	0	114.10 ± 10.65	0.210 ± 0.024	85.20 ± 4.98	115.57	0.209	85.38
NLC14	0	0	0	115.3 ± 11.89	0.216 ± 0.019	85.40 ± 4.90	115.57	0.209	85.38
NLC15	−1	+1	0	105.23 ± 8.26	0.197 ± 0.029	78.49 ± 3.98	105.23	0.191	78.39
NLC16	+1	0	−1	141.36 ± 15.17	0.209 ± 0.028	94.30 ± 6.97	140.65	0.205	94.25
NLC17	0	+1	−1	134.32 ± 12.18	0.231 ± 0.023	91.25 ± 5.98	135.33	0.225	91.41

X₁: Lipid-mix (%); X₂: Surfactant (%); X₃: Sonication time (minute); Y₁: Particle size (nm); Y₂: PDI (unit less); Y₃: EE (%).

Figure 1. Solubility of simvastatin in (A) liquid lipids (B) solid lipids.

Table 3. Transmittance of NLC formulations produced by different surfactants (n = 3).

Surfactant	% transmittance ± SD
Tween 80	91.1 ± 2.8
Tween 40	81.4 ± 2.1
Tween 20	79.6 ± 1.7
Poloxamer 188	93.8 ± 2.5
Labrasol	86.91 ± 3.2
Capryol	88.5 ± 1.8

Table 4. ANOVA Results for responses Y₁, Y₂ and Y₃ obtained from experimental design response.

Response	Source	F value	p Value prob > F	Inference	Adj. R^2	Predicted R^2	Adequate precision
Particle size (Y1)	Quadratic	105.55	<.0001	Significant	.9833	.9541	36.170
	Lack of fit	0.65	.6250	Not significant
PDI (Y2)	Quadratic	147.39	<.0001	Significant	.9880	.9750	46.180
	Lack of fit	0.38	.7739	Not significant
Entrapment efficiency (Y3)	Quadratic	2096.69	<.0001	Significant	.9992	.9967	169.82
	Lack of fit	1.39	.3682	Not significant

Figure 2. 3 D-response surface plots showing effect of independent variables on (A) Particle size, (B) PDI and (C) entrapment efficiency.

Figure 3. Linear correlation plots (A, C, E) between actual and predicted values and the corresponding residual plots (B, D, F) for particle size, PDI and entrapment efficiency.

Table 5. Optimized levels of independent variables and their corresponding predicted and observed responses.

Optimized formula	Optimized level	Responses	Predicted value	Observed value
Lipid mix (%)	2.5	Particle size	115.57	114.62 ± 5.65
Surfactant (%)	1.0	PDI	0.209	0.210 ± 0.034
Sonication time (min)	5.0	EE	85.38	85.20 ± 7.98

Figure 4. Representative particle size distribution graph of optimized SMV-NLC.

Figure 5. (A) TEM image and (B) SEM image of optimized drug-loaded NLC formulation.

Figure 6. DSC thermogram of (A) SMV (B) blend of GMS and poloxamer 188 (C) Lyophilized SMV-NLC.

Figure 7. FT-IR spectra of (A) SMV, (B) physical mixture (SMV, poloxamer 188, GMS) and (C) SMV-loaded optimized NLC formulation.

Figure 8. Comparative in vitro release profile of API suspension and SIM-NLC.

Figure 9. (A) Percentage change in total serum cholesterol level at different time intervals. (B) Percentage change in serum TG level at different time intervals. (C) Percentage change in HDL level at different time intervals.