pH-responsive hydrogels with dispersed hydrophobic nanoparticles for the oral delivery of chemotherapeutics

Abstract

Amphiphilic polymer carriers were formed by polymerizing a hydrophilic, pH-responsive hydrogel composed of poly(methacrylic-grafted-ethylene glycol) (P(MAA-g-EG)) in the presence of hydrophobic PMMA nanoparticles. These polymer carriers were varied in PMMA nanoparticle content to elicit a variety of physiochemical properties which would preferentially load doxorubicin, a hydrophobic chemotherapeutic, and release doxorubicin locally in the colon for the treatment of colon cancers. Loading levels ranged from 49% to 64% and increased with increasing nanoparticle content. Doxorubicin loaded polymers were released in a physiological model where low pH was used to simulate the stomach and then stepped to more neutral conditions to simulate the upper small intestine. P(MAA-g-EG) containing nanoparticles were less mucoadhesive as determined using a tensile tester, polymer samples, and fresh porcine small intestine. The cytocompatibility of the polymer materials were assessed using cell lines representing the GI tract and colon cancer and were noncytotoxic at varying concentrations and exposure times.

Figure 1. Doxorubicin release of P(MAA-g-EG) and P(MAA-g-EG) containing nanoparticles in neutral pH conditions

Doxorubicin loaded P(MAA-g-EG) (♦), P(MAA-g-EG)-1.0NP (), P(MAA-g-EG)-2.5NP (▲), and P(MAA-g-EG)-5.0NP (○) crushed particles (75 – 150 µm) were released in 1× PBS (pH 7.4) for 6 hr. Doxorubicin release is expressed as M_t/M_∞. Curves generated are n = 3 and error bars represent error propagation due to ratio of M_t/M_∞. M_∞ ranged was 42.5, 18.7, 29.4, and 33.7 µg/mL for P(MAA-g-EG), P(MAA-g-EG)-1.0NP, P(MAA-g-EG)-2.5NP, and P(MAA-g-EG)-5.0NP, respectively.

Figure 2. Doxorubicin release of P(MAA-g-EG) and P(MAA-g-EG) containing nanoparticles in two – step pH conditions

Doxorubicin loaded P(MAA-g-EG) (♦), P(MAA-g-EG)-1.0NP (), P(MAA-g-EG)-2.5NP (▲), and P(MAA-g-EG)-5.0NP (○) crushed particles (75 – 150 µm) were released in 1× PBS (pH 2.0) for 90 min. Then the pH was increased to 7.0 by adding 5 N NaOH and release continued for 6 hr. Doxorubicin release is expressed as M_t/M_∞. Curves generated are n = 3 and error bars represent error propagation due to ratio of M_t/M_∞. M_∞ ranged was 42.5, 18.7, 29.4, and 33.7 µg/mL for P(MAA-g-EG), P(MAA-g-EG)-1.0NP, P(MAA-g-EG)-2.5NP, and P(MAA-g-EG)-5.0NP, respectively.

Figure 3. Doxorubicin release of P(MAA-g-EG) and P(MAA-g-EG) containing nanoparticles in low pH conditions

Doxorubicin loaded P(MAA-g-EG) (♦) or P(MAA-g-EG)-5.0NP (○) crushed particles (75 – 150 µm) were released in 1× PBS (pH 2.0) for 120 min. Doxorubicin release is expressed as M_t/M_∞. Curves generated are n = 3 and error bars represent error propagation due to ratio of M_t/M_∞.

Figure 4. Effect of 2 hr P(MAA-g-EG) and P(MAA-g-EG) containing nanoparticles on Caco-2, HT29-MTX, and SW620 cell proliferation

P(MAA-g-EG) (■), P(MAA-g-EG)-1.0NP (□), P(MAA-g-EG)-2.5NP (), and P(MAA-g-EG)-5.0NP (■) microparticles (75 – 150 µm) were added to all cell lines and incubated for 2 hr. Error bars represent error propagated over control cells. n = 6 – 8.

Figure 5. Effect of 6, 12, or 24 hr P(MAA-g-EG) and P(MAA-g-EG) containing nanoparticles exposure on Caco-2, HT29-MTX, and SW620 cell proliferation

P(MAA-g-EG) (■) and P(MAA-g-EG)-5.0NP (□) microparticles (75 – 150 µm) were added to all cell lines and incubated for 6, 12, or 24 hr. Error bars represent error propagated over control cells. n = 6 – 8.

Figure 6. Mucoadhesion for P(MAA-g-EG) and P(MAA-g-EG)-5.0NP

P(MAA-g-EG) (■) and P(MAA-g-EG)-5.0NP (□) discs were brought into contact with fresh porcine small intestine for 5 min, retracted slowly, the force measured with a tensile tester, and the work of adhesion computed Results demonstrate statistical significance (p < .01). n = 3 – 4 ± SD.