Development and characterization of floating spheroids of atorvastatin calcium loaded NLC for enhancement of oral bioavailability

Figures & data

Table I. Experimental protocol for in vivo studies.

Groups	Formulations	No. of animals in each group (n)	Oral dose
I	marketed formulation of atorvastatin calcium	6	10 mg/kg
II	Nanolipid carriers of atorvastatin calcium	6	10 mg/kg
III	spheroids of NLCs loaded atorvastatin calcium	6	10 mg/kg

Table II. Optimization of homogenization time, sonication time, and ratio of solid lipid:liquid lipid.

Formulation	Homogenization time (min)	Sonication time (min)	Surfactant (w/v)	Ratio of solid lipid to liquid lipid	Particle size (nm)	PDI
NLC1	4	1	0.1%	6:4	521.2 ± 2.3	0.284
NLC2	6	1	0.1%	6:4	485.3 ± 2.5	0.267
NLC3	8	1	0.1%	6:4	362.4 ± 1.6	0.216
NLC4	10	1	0.1%	6:4	546.5 ± 1.7	0.305
NLC5	8	2	0.1%	6:4	256.6 ± 3.4	0.236
NLC6	8	3	0.1%	6:4	182.1 ± 0.9	0.208
NLC7	8	4	0.1%	6:4	217 ± 4.8	0.225
NLC8	8	3	0.2%	6:4	156.8 ± 2.7	0.124
NLC9	8	3	0.3%	6:4	182.3 ± 5.1	0.153
NLC10	8	3	0.2%	7:3	143.6 ± 3.8	0.104
NLC11	8	3	0.2%	8:2	243.1 ± 1.4	0.126

Table III. Optimization of amount of atorvastatin calcium with respect to lipids ratio.

Formulation	Homogenization time (min)	Sonication time (min)	Surfactant (w/v)	Ratio of solid lipid to liquid lipid	Drug (mg)	Particle size (nm)	PDI	EE (%)
NLC12	8	3	0.2%	7:3	10	162.3 ± 2.2	0.103	35.63 ± 3.4
NLC13	8	3	0.2%	7:3	20	155.8 ± 1.9	0.066	58 ± 3.2
NLC14	8	3	0.2%	7:3	30	185.2 ± 2.7	0.128	46 ± 3.1
NLC15	8	3	0.2%	7:3	40	210.8 ± 3.4	0.138	41 ± 2.7
NLC16	8	3	0.2%	6:4	20	312.7 ± 1.1	0.146	48 ± 2.6
NLC17	8	3	0.2%	8:2	20	346.2 ± 2.9	0.165	52.20 ± 3.5

Figure 1. (A) DSC thermogram of pure atorvastatin calcium. (B) DSC thermogram of final optimized atorvastatin NLCs formulation.

Figure 2. % Drug release of optimized atorvastatin NLCs formulation.

Table IV. Kinetics modeling of atorvastatin calcium NLC13.

Release kinetic model	Linear (R2)	Correlation	Coefficient
Zero order		0.714
First order		0.781
Higuchi model		0.877
Peppas model		0.720

Table V. Influence of spheronization speed on the size and shape of floating atorvastatin calcium spheroids.

Formulation	Speed (rpm)	Sieve No.	Shape
Fl	200–500	12	Irregular
F2	500–800	16	Spherical
F3	800–1000	20	Very fine particles

Table VI. Influence of sizes of extruder die and spheronization plate on the properties of floating atorvastatin calcium spheroids.

Extruder die size	Spheronization plate size	Conclusion
1 mm	0.5 mm	Avg. Pellet size: 1.2 mm
0.5 mm	0.5 mm	Avg. Pellet size: 0.4 mm (Spherical)

Table VII. Optimization of HPMC-K4M with respect to lag floating time and floating time of spheroid.

Ingredients	F1	F2	F3
HPMC K4M (gm)	2.5	5	7
Carbopol 934 (mg)	200	200	200
Sod. Bicarbonate (gm)	1	1	1
Citric acid (mg)	500	500	500
Avicel – 101 (gm)	q.s. up to 8	q.s. up to 8	q.s. up to 8
Lag time (min)	3	2	Burst
Floating time (hours)	10	12.5	14

Table VIII. Optimization of Carbopol 934 with respect to lag floating time and floating time of spheroid.

Ingredients	Fl	F2	F3
HPMC K4M (gm)	5	5	5
Carbopol 934 (mg)	300	400	500
Sod. Bicarbonate (gm)	1	1	1
Citric acid (mg)	500	500	500
Avicel – 101 (gm)	q.s. up to 8	q.s. up to 8	q.s. up to 8
Lag time (min)	3	2	1
Floating time (hours)	12	16	20

Table IX. Optimization of concentration of sodium bicarbonate of spheroid.

Ingredients	FI	F2	F3
HPMC K4M (gm)	5	5	5
Carbopol 934 (mg)	500	500	500
Sod. Bicarbonate (gm)	1.5	2	3
Citric acid (mg)	500	500	500
Avicel – 101 (gm)	q.s. up to 8	q.s. up to 8	q.s. up to 8
Shape	Spherical	Spherical	Lump formation
Lag time (min)	2	1.5	60 s
Floating time (hours)	26.5	28	29

Table X. Optimization of concentration of citric acid of spheroid.

Ingredients	F1	F2	F3
HPMC K4M (gm)	5	5	5
Carbopol 934 (mg)	500	500	500
Sod. Bicarbonate (gm)	2	2	2
Citric acid (gm)	1	2	3
Avicel – 101 (gm)	q.s. up to 8	q.s. up to 8	q.s. up to 8
Shape	Spherical	Spherical	Lump formation
Lag time (seconds)	80	20	60
Floating time (hours)	29	> 32	34

Table XI. Evaluation parameters for spheroids of atorvastatin calcium.

S. No	Parameter	Value
1	Bulk density	0.76 ± 0.64 g/cm^3
2	Tapped density	0.84 ± 0.84 g/cm^3
3	Carr’s Index (%)	9.52 + 0.35%
4	Hausner’s Ratio	1.10 ± 0.76
5	Angle of repose (θ°)	26 ± 0.88
6	Friability (%)	0.72 ± 0.2 l

Figure 3. Motic image of floating spheroid.

Figure 4. Photographic images of stages of spheroid formation during spheronization at (a) 0 s, (b) 15 s, and (c) 30 s.

Figure 5. In vitro release profile of final optimized floating atorvastatin calcium spheroid NLCs.

Table XII. In vitro release kinetic of floating atorvastatin calcium spheroids-loaded NLCs.

Release kinetic model	Linear (R2)	Correlation	Coefficient
Zero order		0.870
First order		0.912
Higuchi model		0.931
Peppas model		0.811

Figure 6. Plasma concentration–time curve following oral administration of atorvastatin calcium MF, atorvastatin calcium-loaded NLC formulations (NLC), and floating atorvastatin calcium spheroids-loaded NLC (NLC-S) groups of Wistar rats.

Table XIII. Pharmacokinetic parameters of control and test sample calculated using plasma concentration–time data using software Kinetica.

Parameters	NLC	NLC-S	MF
AUC0–t (ug/ml*min)	1156 ± 0.12	436 ± 0.27	151 ± 0.12
AUC0–∞ (ng/ml*min)	1123272 ± 0.23	458483 ± 0.72	1399891 ± 0.34
t1/2 (hour)	22.469 ± 2.48	29.36 ± 1.35	17.79 ± 3.57
Cmax (ng/ml)	53437 ± 2.68	60426 ± 1.53	48582 ± 2.37
Tmax (hr)	38.68 ± 3.51	48.5 ± 2.31	32.6 ± 3.47
AUMCo–t (ng/ml*min^2)	16422123 ± 0.82	5368267 ± 0.25	738220 ± 0.64