Formulation development and evaluation of the anti-malaria properties of sustained release artesunate-loaded solid lipid microparticles based on phytolipids

Figures & data

Table 1. Formulation compositions of the SLMs.

Batch	LM ratio (Soy bean: dika wax)	Tween® 80 (% w/w)	LM (% w/w)	Sorbitol (% w/w)	Thiomersal (% w/w)	Artesunate (% w/w)	Distilled water q.s (% w/w)
A1	1:19	1.0	10	4	0.002	1.0	100
A2	1:19	1.0	10	4	0.002	1.5	100
A3	1:19	1.0	10	4	0.002	2.0	100
A4	1:19	1.0	10	4	0.002	2.5	100
A5	1:19	1.0	10	4	0.002	0.0	100
B1	1:6	1.0	10	4	0.002	1.0	100
B2	1:6	1.0	10	4	0.002	1.5	100
B3	1:6	1.0	10	4	0.002	2.0	100
B4	1:6	1.0	10	4	0.002	2.5	100
B5	1:6	1.0	10	4	0.002	0.0	100
C1	1:3	1.0	10	4	0.002	1.0	100
C2	1:3	1.0	10	4	0.002	1.5	100
C3	1:3	1.0	10	4	0.002	2.0	100
C4	1:3	1.0	10	4	0.002	2.5	100
C5	1:3	1.0	10	4	0.002	0.0	100

Batches A₁–A₄, B₁–B₄ and C₁–C₄ contain various ratios of artesunate while, batches A₅, B₅, and C₅ contain no drug, LM: Lipid matrix.

Figure 1. DSC thermograms of: (a) dika wax, (b) lipid matrix 1:19, (c) lipid matrix 1:9, (d) lipid matrix 1:6, (e) lipid matrix 1:4, and (f) lipid matrix 1:3.

Table 2. DSC results of the lipid matrices.

Material	Melting peak (°C)	Enthalpy (mW/mg)
Dika wax	44.3	−7.29
LM 1:19	44.7	−8.63
LM 1:9	44.7	−16.14
LM 1:6	47.0	−21.73
LM 1:4	46.3	−36.41
LM 1:3	44.8	−20.04

LM: lipid matrix (Soybean oil: Dika wax).

Figure 2. SAXD differactograms of different batches of structured lipid matrices formulated with different ratios of soybean oil and dika wax. S:D = soybean oil: dika wax.

Figure 3. WAXD diffractograms of different batches of structured lipid matrices formulated with different ratios of soybean oil and dika wax. S:D = soybean oil: dika wax.

Figure 4. Photomicrographs (at day 1) of SLMs formulated with lipid matrices 1:19, 1:6 and 1:3 and containing 2.5 g of artesunate, A₄, B₄ and C₄.

Figure 5. Particle size of artesunate-loaded and unloaded SLMs over time (a): A₁ – A₅ were formulated with LM 1:19, (b): B₁ – B₅ were formulated with LM 1:6 and (c): C₁ – C₅ were formulated with LM 1:3 and different concentrations of artesunate, while A₅, B₅, and C₅ contain no API; □, day 1; ▪, 30 days and ▪, 90 days for a, b and c, respectively.

Figure 6. The pH of unloaded and artesunate-loaded SLMs (a): A₁ – A₅ were formulated with LM 1:19, (b): B₁ – B₅ were formulated with LM 1:6 and (c): C₁ – C₅ were formulated with LM 1:3 and different concentrations of artesunate, while A₅, B₅ and C₅ contain no API; □, day 1; ▪, 30 days and ▪, 90 days for a, b and c, respectively.

Table 3. Some properties of artesunate-loaded SLMs.

Batch	TDC (%)	ADC (% ± SD)^a	EE (%)	LC (mg API/100 mg lipid)
A1	1.0	0.52 ± 0.51	52.40	15.90
A2	1.5	0.63 ± 0.52	42.30	21.40
A3	2.0	1.42 ± 0.95	71.00	27.90
A4	2.5	2.02 ± 1.18	80.60	32.80
A5	0.0	–	–	–
B1	1.0	0.46 ± 0.98	46.10	15.80
B2	1.5	0.96 ± 0.30	64.30	23.00
B3	2.0	1.49 ± 0.40	74.60	27.90
B4	2.5	2.00 ± 0.10	79.90	32.78
B5	0.0	–	–	–
C1	1.0	0.47 ± 1.82	47.10	15.80
C2	1.5	0.99 ± 1.73	66.00	15.37
C3	2.0	1.49 ± 1.00	74.50	28.00
C4	2.5	1.98 ± 1.00	79.00	32.79
C5	0.0	–	–	–

SD, standard deviation; TDC, theoretical drug concentration; ADC, actual drug concentration; LC, loading capacity; API, active pharmaceutical ingredient; A₁–A₄, contain LM 1:19; B₁–B₄, contain LM 1:6; C₁–C₄, contain LM 1:3 and different concentrations of artesunate, while A₅, B₅ and C₅ contain no API.

^an = 5.

Figure 7 In vitro release profile of artesunate from SLMs; ♦ - A₄, □-B₄, ▴ – STD, batches A₄ and B₄ were formulated with lipid matrices 1:19 and 1:6 and contain 2.5% artesunate, respectively; STD is the artesunate tablet (reference).

Table 4. Drug release kinetics of artesunate-loaded SLMs.

	Zero order		First order		Higuchi			Ritger-Peppas
Batch	r^2	k (h^−1)	r^2	k (h^−1)	r^2	n	k (h^−1)	r^2	n	k (h^−1)
A4	0.990	4.141	0.976	2.000	0.995	0.734	10.023	0.995	0.736	0.149
B4	0.981	7.680	0.965	1.994	0.985	0.578	15.630	0.985	0.578	0.211

A₄ and B₄ were formulated with lipid matrices 1:19 and 1:6, respectively, and contain 2.5% artesunate.

r², regression coefficient; n = slope; k, release rate constant.

Figure 8. Percent parasitaemia of mouse treated with artesunate-loaded SLMs. Significant at p < 0.05 compared to control. Values shown are mean ± SD (n = 5). □, STD; ▪, TARF; ▪, CTL; TARF representents group that received the artesunate-loaded SLMs the artesunate-loaded SLMs; STD received the standard artesunate tablet, while group CTL (control) received normal saline.

Figure 9. Rectal temperature of mouse treated with artesunate-loaded SLMs. Significant at p < 0.05 compared to control. Values shown are mean ± SD (n = 5). □, STD; ▪, TARF; ▪, CTL; TARF representents group that received the artesunate-loaded SLMs the artesunate-loaded SLMs; STD received the standard artesunate tablet, while group CTL (control) received normal saline.