Preparation, characterization, and optimization of altretamine-loaded solid lipid nanoparticles using Box-Behnken design and response surface methodology

Figures & data

Table I. Comparison of the observed and predicted values in the SLN prepared under predicted optimum conditions.

Response Variable	Predicted values	Observed values	% Bias *
Entrapment Efficiency (%)	95.77	93.21	2.67
Drug Loading (%)	1.22	1.15	5.73
Particle Size (nm)	106.54	100.6	5.57

*Bias was calculated as (predicted value−observed value)/predicted value × 100%.

Table II. Independent variables, along with their coded and actual values, along with their respective responses for different batches of ALT-SLNs.

		Coded value variables			Actual value variables			Response values
Std.	Run	X1	X2	X3	X1	X2	X3	% EE	%DL	PS (nm)	ZP (mV)	PDI
13	1	0	0	0	0.05	2	1:2	94.32 ± 4.17	0.19 ± 0.017	82.16 ± 1.23	20.32 ± 0.51	0.12
10	2	0	1	− 1	0.05	3	1:1	86.24 ± 0.26	1.06 ± 0.003	121.08 ± 0.17	23.21 ± 0.39	0.23
1	3	− 1	− 1	0	0.025	1	1:2	81.24 ± 1.12	0.31 ± 0.026	102.94 ± 0.04	16.24 ± 0.06	0.34
9	4	0	− 1	− 1	0.05	1	1:1	83.49 ± 0.07	0.24 ± 0.002	134.31 ± 0.36	19.21 ± 0.41	0.15
2	5	1	− 1	0	0.075	1	1:2	92.16 ± 2.31	1.18 ± 0.203	126.34 ± 0.51	21.36 ± 0.24	0.28
6	6	1	0	− 1	0.075	2	1:1	89.31 ± 1.03	1.48 ± 0.124	109.42 ± 0.02	18.31 ± 0.39	0.21
11	7	0	− 1	1	0.05	1	1:3	87.13 ± 0.24	0.28 ± 0.210	124.61 ± 1.05	25.04 ± 0.21	0.27
14	8	0	0	0	0.05	2	1:2	92.18 ± 0.09	0.16 ± 0.159	85.34 ± 0.22	22.31 ± 0.47	0.24
12	9	0	1	1	0.05	3	1:3	84.39 ± 3.14	0.48 ± 0.102	106.52 ± 0.49	24.29 ± 0.11	0.41
15	10	0	0	0	0.05	2	1:2	91.29 ± 1.52	0.21 ± 0.006	84.62 ± 0.63	20.45 ± 0.48	0.29
5	11	− 1	0	− 1	0.025	2	1:1	88.29 ± 3.29	0.94 ± 0.237	116.32 ± 0.49	21.34 ± 0.17	0.18
4	12	1	1	0	0.075	3	1:2	96.24 ± 1.10	1.39 ± 0.410	139.54 ± 1.01	27.17 ± 0.73	0.25
16	13	0	0	0	0.05	2	1:2	95.46 ± 0.18	0.16 ± 0.012	82.19 ± 0.01	21.19 ± 0.22	0.31
3	14	− 1	1	0	0.025	3	1:2	89.24 ± 2.49	0.65 ± 0.172	119.46 ± 0.19	20.31 ± 0.18	0.25
8	15	1	0	1	0.075	2	1:3	95.29 ± 1.50	0.36 ± 0.015	114.62 ± 0.13	23.26 ± 0.41	0.37
7	16	− 1	0	1	0.025	2	1:3	89.14 ± 2.16	1.26 ± 0.312	108.43 ± 0.28	24.62 ± 0.38	0.41
17	17	0	0	0	0.05	2	1:2	93.26 ± 3.29	0.19 ± 0.019	86.27 ± 0.19	21.15 ± 0.25	0.32

Table III. Summary of the results of regression analysis for responses, and analysis of variance for particle size, EE and DL.

Parameters	DF	SS	MS	F	P value	R^2	SD	C. V %
% Entrapment efficiency
Model	9	267.85	29.76	4.45	0.0309 SIGNIFICANT	0.8512	2.59	2.88
Residual	7	46.83	6.69
Total	16	314.68
% Drug loading
Model	9	3.23	0.36	4.81	0.0252 SIGNIFICANT	0.8608	0.27	44.09
Residual	7	0.52	0.075
Total	16	3.75
Mean particle size (nm)
Model	9	168.89	4825.01	4.80	0.0253 SIGNIFICANT	0.8605	10.57	9.74
Residual	7	1.64	781.92
Total	16	170.53

Figure 2. (A) DSC thermogram of altretamine (ALT), Compritol ATO 888, physical mixture and ALT-SLNs. (B) TEM image of optimized ALT-SLNs.

Figure 3. Release profile of the optimized ALT-SLN dispersion in 6.8 pH phosphate buffer at 37°C.

Table IV. Model-fit for optimized ALT-SLNs.

Models	Slope	R^2
Zero order	1.913	0.610
First order	− 0.01	0.915
Higuchi	0.050	0.986
Hixson- Crowell	− 0.347	0.820
Korsmeyer-Peppas	0.159	0.719

Figure 4. (A) Effect of storage conditions on the particle size of SLNs. (B) Effect of storage conditions on the percentage of entrapment efficiency of SLNs.