Methacrylic acid-co-butylmethacrylate copolymers: design, characterization and evaluation as encapsulating material for colon targeted formulations

Figures & data

Figure 1. Synthesis of copolymer of methacrylic acid and butylmethacrylate.

Figure 2. Percentage weight gain (swelling) of polymer membranes in buffers of increasing pH. Each bar represents mean ± SD (n = 3).

Figure 3. Percentage erosion of polymer membranes in buffers of increasing pH (− sign indicates weight loss). Each bar represents mean ± SD (n = 3).

Figure 4. FTIR spectra of monomers (methacrylic acid and butyl methacrylate) and selected copolymers MAA:BMA (3:7 and 4:6).

Figure 5. ¹H NMR spectra of monomers (methacrylic acid and butyl methacrylate) and selected copolymers MAA:BMA (3:7 and 4:6).

Table 1. Average molecular weights of copolymers MAA:BMA (3:7 and 4:6).

	MAA:BMA (3:7)	MAA:BMA (4:6)
Weight average molecular weight	39,022	41,482
Number average molecular weight	6831	8800
Z-average molecular weight	107,716	107,996

Figure 6. SEM images of microparticle formulation M3 (a) and (b); and M4 (c).

Table 2. Microspheres characterization.

	M3	M4
Drug loading (%)	5.33 ± 0.30*	6.26 ± 0.22*
Drug loading efficiency (%)	26.65 ± 1.876*	31.33 ± 1.30*
Zeta potential	−25.9 mV	−29.9 mV
Mucoadhesion time (stomach mucosa)	57 ± 08 s*	65 ± 11 s*
Mucoadhesion time (intestinal mucosa)	26 ± 3 min*	30 ± 6 min*

* Values are mean ± SD of three observations.

Figure 7. Overlay showing PXRD diffractograms of aceclofenac, MAA:BMA (3:7 and 4:6), and formulation M3 and formulation M4.

Figure 8. Overlay showing DSC thermograms of formulation M4 (A), copolymer MAA: BMA (4:6) (B), copolymer MAA:BMA (3:7) (C), formulation M3 (D), and aceclofenac (E).

Figure 9. In vitro drug release profile of microparticle formulations M3 and M4. Each point represents mean ± SD (n = 3).

Table 3. Release kinetics of aceclofenac from microparticles using different kinetic equations.

Formulation	r^2				n	Release mechanism
	Zero-order	First-order	Higuchi	Korsmeyer–Peppas
M3	0.94	0.81	0.85	0.71	0.61	Anomalous
M4	0.95	0.82	0.87	0.72	0.65	Anomalous

Notes: Where r² is the correlation coefficient; and n is the diffusion exponent in Korsmeyer–Peppas model.

Figure 10. Clinical activity scores during induction of colitis (from day 1 to day 9) and colon-to-body weight ratios (day 3, 5, 7 and 9) after TNBS administration. *Statistically significant (p < 0.05) compared with group I (healthy), as determined by one-way ANOVA followed by Dunnett’s test. Each bar represents the mean ± SD (n = 5).

Figure 11. Clinical activity scores, colon-to-body weight ratio, and myeloperoxidase activity of group I (healthy group), group II (colitis group), group III (formulation treatment group), and group IV (standard treatment group). *Statistically significant (p < 0.05) compared with group II (colitis group), as determined by one-way ANOVA followed by Dunnett’s test. Each bar represents the mean ± SD (n = 5).

Figure 12. Microscopic image of the colon of rat belonging to group I (healthy group), group II (colitis group), group III (formulation treatment group), and group IV (standard treatment group).