Engineering of Naproxen Loaded Polymer Hybrid Enteric Microspheres for Modified Release Tablets: Development, Characterization, in silico Modelling and in vivo Evaluation

Figures & data

Figure 1 Chemical structure of naproxen.

Table 1 Process Parameter and Compositions of NP Loaded PHE-Ms

Formulation Code	EUD-L100: NP	NP %(w/V)	SLS %(w/V)	HPMC %(w/V)	Stirring (Rpm)	Temp (°C)	Stirring Time (Hrs)
NP-M1TT	1:1	3	0.2	0.5	1200	35	8
NP-M2T	1:2	3	0.2	1	1200	35	8
NP-M3	1:3	3	0.2	1.5	1200	35	8
NP-M4	1:4	3	0.2	2	1200	35	8
NP-M5T	1:5	3	0.2	2.5	1200	35	8

Abbreviations: NP, Naproxen; SLS, Sodium Lauryl Sulphate; EUD-L100, Eudragit grade L100; HPMC-E5, Hydroxypropyl methylcellulose grade E5.

Figure 2 Minimized structures of polymers, surfactants, and NP.

Table 2 Composition of NP Loaded PHE-Ms Based Tablets Formulations (MT1-MT5)

Formulation Code	Microspheres Containing(250 Mg) of NP (mg)	Avicel pH-101 (Mg)	Kolidone-30 (Mg)	Talcam Powder (Mg)	Mg. Stearate (Mg)	Total Weight (Mg)
NP-MT1	330.6	269.4	30	5	15	650
NP-MT2	356.6	240.4	33	5	15	650
NP-MT3	370.6	223.4	36	5	15	650
NP-MT4	400.6	190.4	39	5	15	650
NP-MT5	427.6	160.4	42	5	15	650

Abbreviations: NP, Naproxen; NP-MT, Naproxen loaded microspheres based tablet; Mg.Stearate, Magnesium Stearate.

Table 3 Particle Size (μm) and Span Index of NP Loaded PHE-MS of Formulations (M1–M5)

Formulation Code	D (0. 1) 10th	D (0.5) 50th	D (0.9) 90th	Span Index	Particle Size (μm) (Volume-Weighted Mean)
NP-M1	21.6	29.4	36.2	0.49	29.06 ± 0.5
NP-M2	32.3	49.5	66.7	0.69	49.03 ± 0.14
NP-M3	41.2	59.4	72.6	0.52	57.73 ± 0.32
NP-M4	49.8	68.9	87.5	0.54	68.74 ± 0.35
NP-M5	58.2	71.3	93.4	0.50	74.31 ± 0.26

Note: All values were represented in mean±SD.

Abbreviations: NP, Naproxen; NP-M, Naproxen loaded microspheres; D, Volume mean Diameter.

Figure 3 (A) FTIR spectra for NP (Unprocessed) and (B) NP-M1 optimized formulation.

Figure 4 (A) Unprocessed NP at magnification of 500× and (B) NP-M1 optimized formulation (2000×).

Figure 5 P-XRD pattern of NP (Unprocessed), NP-PM, NP-M1, EUD, and HPMC.

Figure 6 DSC Thermograms of NP (Unprocessed) and NP-M1.

Table 4 Impact of Formulation Variables on (%) Yield, Drug Loading, and Encapsulation Efficiency on Formulations (M1-M5)

Formulations Code	Entrapment Efficiency (%)	Yield(%)	Theoretical Drug Loading (%)	Actual Drug Loading (%)
NP-M1	73.12±0.31	72.55±0.42	16.67±0.05	12.1±0.03
NP- M2	78.09±0.63	77.45±0.37	18.5±0.03	9.3±0.01
NR-M3	84.67±0.37	83.31±0.33	21.3±0.01	8.1±0.01
NR-M4	89.4±0.77	87.99±0.41	25.34±0.04	6.3±0.03
NR-M5	91.73±0.72	90.01±0.53	29.6±0.02	5.6±0.05

Note: All the values represent Standard Error Mean (SEM), n=3.

Abbreviations: NP, Naproxen; NP-M, Naproxen loaded Microspheres.

Table 5 Binding Energies Calculations for Different Co-Polymeric Systems of SLS, Eudragit (EUD), HPMC and Naproxen (NP)

Co-Polymer Complex	Binding Energies (Kcal/Mol)
SLS- EUD	−2.0
SLS- HPMC	−1.5
SLS-NP	−3.2
EUD-NP	−3.1
EUD-SLS	−1.8
EUD-HPMC	−1.4
HPMC-EUD	−1.8
HPMC-SLS	−1.5
HPMC-NP	−2.5
SLS- EUD-HPMC	−2.1
SLS- EUD-HPMC-NP	−3.9

Note: The bold text indicates the combination of polymers and surfactants showing highest binding energy with NP 

Figure 7 3D surface and structure representation of SLS and Eudragit complex (A). 3D surface and structure representation of SLS-Eudragit (host) and HPMC (guest) complex structure (B). 3D surface and structure representation of SLS-Eudragit-HPMC host) and Naproxen (guest) complex structure (C).

Figure 8 (A) Drug release from formulations of NP (MT1-MT5) at pH 6.8. (B) Drug release from formulations of NP (MT1-MT5) at pH 1.2. (C) Comparative drug release profile of NP (Marketed Drug), NP (Unprocessed) and NP-MT1 at pH1.2 and pH 6.8.

Table 6 Modulation and the Model Equations Applied to the in- Vitro Release Kinetics of PHE-Ms Based Tablets Respectively; the Correlation Coefficient (R²); the Release Exponent (n) of the Korsmeyer–Peppas Model

Formulation Code	Zero Order (R^2)	First Order(R^2)	Higuchi (R^2)	Kors Meyers Peppas (R^2)	Release Exponent (N)
NP-MT1	0.9349	0.9915	0.9926	0.9524	0.68570971
NP-MT2	0.9464	0.9921	0.9927	0.9487	0.70322459
NP-MT3	0.9499	0.9909	0.9914	0.9594	0.7299674
NP-MT4	0.9366	0.9839	0.9852	0.9442	0.70337142
NP-MT5	0.9384	0.9777	0.9801	0.9433	0.70515446

Abbreviations: NP, Naproxen; NP-MT, Naproxen loaded microspheres based tablets.

Table 7 Pharmacokinetics Parameters for NP (Unprocessed), NP (Marketed Drug), and NP MT1 Formulation in Rats

Treatments	tmax (h)	Cmax (µg/mL)	AUC0-t (µg h/mL)	t1/2 (h)
NP(Unprocessed)	2.39 ± 0.21	16.01 ± 3.05	81.01 ± 31.31	6.385 ± 1.788
NP (Marketed drug)	1.65 ± 0.16	31.01 ± 3.21*	259.1 ± 49.77	13.97 ± 1.664
NP-MT1 Formulation	4.31 ± 0.26**	44.41 ± 4.43**	444.9 ± 76.41**	17.22 ± 2.853*

Notes: Values were expressed as mean ± SEM. One-way repeated-measures ANOVA followed by post hoc Dunnett’s test. *P < 0.05, **P < 0.01 as compared to NP (Unprocessed).

Figure 9 Pharmacokinetic profile of NP (Unprocessed), NP (Marketed drug) and NP-MT1 in rats. The plot of plasma concentration (µg/mL) versus time (h). Data represented as mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001 in contrast to NP (Unprocessed) treated animals group at respective time-period; two-way repeated-measures ANOVA followed by post hoc Bonferroni’s analysis was used.