Localized rosuvastatin via implantable bioerodible sponge and its potential role in augmenting bone healing and regeneration

Figures & data

Table 1. Composition and evaluation of rosuvastatin sponge formulae prepared adapting a 4¹.3¹ full factorial design.

	Variables		Response parameters
Formula	X1	X2	MDT (h)^a		RE8h (%)^b
F1	−2	−1		0.436 ± 0.034			75.3 ± 3.96
F2	−2	0	0.391 ± 0.042			83.4 ± 4.10
F3	−2	+1		0.345 ± 0.042			65.1 ± 4.24
F4	−1	−1		0.450 ± 0.057			69.5 ± 4.24
F5	−1	0	0.552 ± 0.056			65.3 ± 6.01
F6	−1	+1		0.635 ± 0.049			46.3 ± 3.18
F7	+1	−1		0.533 ± 0.053			66.3 ± 4.53
F8	+1	0	0.485 ± 0.063			53.3 ± 3.18
F9	+1	+1		0.695 ± 0.057			37.7 ± 3.82
F10	+2	−1		0.552 ± 0.049			62.1 ± 4.24
F11	+2	0	0.545 ± 0.049			41.3 ± 4.59
F12	+2	+1		0.655 ± 0.034			39.2 ± 4.24
Independent variables	Very low	Low	Medium	High	Very high
X1 = Anionic polymer type	Xanthan gum	Polycarbophil	…….	Carbopol®	Na alginate
X2 = Chitosan: polymer ratio	…….	1:3	1:1	3:1	…….
Transformed values	−2	−1	0	+1	+2

All values are mean of three readings ± S.D.

^aMedian dissolution time calculated as follows: .

^bRelease efficiency calculated as follows: .

Table 2. Release kinetics and mechanism of the release data of rosuvastatin from the prepared sponges analyzed using DDsolver software.

	Mathematical model
	Higuchi			Korsmeyer–Peppas		Baker–Lonsdale
Formula	Best fitted equation	R^2adjusted	F0 (%)	R^2adjusted	n	R^2adjusted	Release mechanism
F1	^aHiguchi with F0	0.9498	20.67	–	–	–	Diffusion
F2	Higuchi with F0	0.9667	41.502	–	–	–	Diffusion
F3	Higuchi with F0	0.9318	42.133	–	–	–	Diffusion
F4	Higuchi	0.9773	–	0.9963	0.650	0.8004	Anomalous diffusion
F5	Higuchi	0.9816	–	0.9971	0.527	0.8511	Anomalous diffusion
F6	Higuchi	0.9571	–	0.9991	0.316	0.9794	Fickian diffusion
F7	Higuchi with F0	0.9681	24.74	0.9837	0.507	0.8009	Anomalous diffusion
F8	Higuchi with F0	0.9666	2.97	0.9888	0.115	0.9763	Fickian diffusion
F9	Higuchi	0.9630	–	0.9421	0.610	0.8327	Anomalous diffusion
F10	Higuchi with F0	0.9863	8.65	0.9550	0.434	0.9609	Fickian diffusion
F11	Higuchi with F0	0.9874	3.06	0.9819	0.347	0.9800	Fickian diffusion
F12	Higuchi	0.9345	–	0.9929	0.716	0.8917	Anomalous diffusion

Composition of the formulae is shown in Table 1.

^aHiguchi with F₀ model: . where F is the cumulative quantity of drug released at time t and F₀ is burst effect.

Figure 1. Photographic presentation of the surgical procedure (1) making an incision on the proximal anterior part of the femur, (2) Removing a 2-mm segment of the fractured femur and (3) fixing femur using an intramedullary K-wire.

Figure 2. Photographs of (a) xanthan gum-based, (b) polycarbophil-based, (c) Carbopol®-based and (d) Na alginate-based sponges at magnifications of 4×, all at 1:1 chitosan to anionic polymer ratio.

Figure 3. DSC thermograms of rosuvastatin, chitosan, anionic polymer, chitosan/anionic polymer physical mixtures and drug laoded sponges for (a) xanthan gum-based, (b) polycarbophil-based, (c) Carbopol®-based and (d) Na alginate-based formulae.

Figure 4. FT-IR of rosuvastatin, chitosan, anionic polymer, chitosan/anionic polymer physical mixtures and drug laoded sponges for (a) xanthan gum-based, (b) polycarbophil-based, (c) Carbopol^®-based and (d) Na alginate-based formulae.

Figure 5. In vitro release profiles of rusovastatin from (a) xanthan gum-based, (b) polycarbophil-based, (c) Carbopol®-based and (d) Na alginate-based sponges prepared adapting a 4¹.3¹ full factorial design (n = 3, Error bars indicate SD).

Figure 6. Effect of anionic polymer type and chitosan:polymer ratio on median dissolution time (MDT) and release efficiency (RE_8h).

Figure 7. In vitro release profiles of optimized sponge formulae (n = 3, Error bars indicate SD).

Table 3. Composition and evaluation of the optimized sponge formulae.

Formula	Anionic polymer type	Chitosan:polymer ratio	Optimizing additive	MDT (h)	RE8h (%)	Release mechanism	Desirability factor
F13	Carbopol®	3:1	1% HPMC	0.462 ± 0.041	28.8 ± 3.96	Fickian diffusion	0.786
F14	Carbopol®	3:1	2% HPMC	0.631 ± 0.028	36.1 ± 3.96	Fickian diffusion	0.834
F15	Carbopol®	3:1	1% Imwitor^®	0.551 ± 0.035	34.1 ± 3.96	Fickian diffusion	0.659
F16	Carbopol®	3:1	2% Imwitor^®	0.585 ± 0.034	26.7 ± 3.96	Fickian diffusion	0.869
F17	Xanthan gum	1:1	2% Imwitor^®	0.541 ± 0.050	44.9 ± 3.96	Fickian diffusion	0.359
F18	Polycarbophil	3:1	2% Imwitor^®	0.478 ± 0.039	50.6 ± 3.96	Fickian diffusion	0.199
F19	Na alginate	3:1	2% Imwitor^®	0.446 ± 0.036	57.5 ± 3.96	Fickian diffusion	0.543

All values are mean of three readings ± SD.

Equations for the desirability function of the maximized response (MDT) are:

Equations for the desirability function of the minimized response (RE_8h) are:

Equation for the overall desirability values is: the following equation: ^1/2, where d_1–2 is the individual desirability factors of each response and Y_i is the experimental result.

Figure 8. Photographs of treated rat femur treated with formula F16 showing osteoblasts (→) and remodeling (m) phase of bone healing at magnifications of (a) 16×, (b) 40× and (c) 64×.

Figure 9. Photographs of control rat femur showing empty lacunae (→), collagen fibers (c), osteoclasts (cl) and fibroblasts (f) in area of healing at magnifications of (a) 16×, (b) 40×, (c) 64× and (d) 160×.