Purpose: The aim of this work was to evaluate, in the design of cutaneous patches containing ibuprofen (IB), the influence of styrene-block-(ethylene-co-butylene)-block-styrene (SEBS) molecular weight (Mw) and type of tackifier, added to obtain a pressure sensitive adhesive (PSA), on: i) rheological behaviour, ii) debonding mechanisms, iii) adhesive properties and iiii) in vitro drug release rate. Methods: Formulations differ for SEBS Mw (i.e. SOL TH®2311 - Mw = 45.61 kDa, SOL TH®2312 - Mw = 64.23 kDa and SOL TH®2315 - Mw = 176.35 kDa) and for the type of tackifier (i.e Regalite R1100® - C9 aliphatic resin and Eastotak H100W® - C5 aliphatic). For the preparation of the drug-loaded patches, IB was added at 10% (w/w). The rheological properties were obtained using a rotational rheometer, applying a frequency-sweep deformation. The debonding mechanisms on a stainless steel probe were determined by using a custom-designed probe tack tester. Patches were prepared by casting and their adhesive properties were evaluated in terms of shear adhesion and peel adhesion. The in vitro drug release rate was also determined using an adapted disk assembly method. Results: PSAs made with low Mw SEBS behaved as viscoelastic fluids over the whole range of frequencies. The viscoelasticity is required to achieve a balance between peel and creep, crucial properties in the development of a patch. As a viscous liquid it should be able to dissipate energy during the peel process; while as a solid it should have a good resistance to shear. The failure mechanisms during the debonding process revealed that the behavior of all the PSAs was related to the relaxation time. At the lower debonding velocity they showed a liquid-like behavior with many digitations. This mechanism is required to achieve an adhesive failure without residues after the debonding process. Aiming to rationalize the selection of suitable formulations for the development of cutaneous patches, the cohesive (shear adhesion) and adhesive (peel adhesion) properties were evaluated. The shear adhesion revealed that the polymer Mw influenced the cohesive strength: increasing SEBS-Mw, the shear adhesion values decreased. Moreover, IB caused a further reduction of the shear adhesion. However, all the patches showed an ideal cohesive strength and optimal peel adhesion, if compared to those available on market, suggesting that they will not ooze during application and could be detached without skin damage and pain upon removal. Finally, taken into consideration the biopharmaceutical performances, the percentage of IB released from the prepared patches was not influenced by SEBS-Mw and the profiles were superimposable. The drug release was completed within 24 hours according to the Higuchi pattern. Conclusions: The overall data demonstrated the feasibility to design cutaneous patches made of SEBS. The resin type used in the preparation of SEBS-based PSA did not influence the matrix behavior. Low Mw SEBS polymer worthy of consideration because of its favorable viscoelastic behavior.
On the characterization of Sebs pressure sensitive adhesives for the design of cutaneous patches / G.M.G. Quaroni. ((Intervento presentato al 11. convegno AItUN tenutosi a Padova nel 2017.
On the characterization of Sebs pressure sensitive adhesives for the design of cutaneous patches
G.M.G. Quaroni
2017
Abstract
Purpose: The aim of this work was to evaluate, in the design of cutaneous patches containing ibuprofen (IB), the influence of styrene-block-(ethylene-co-butylene)-block-styrene (SEBS) molecular weight (Mw) and type of tackifier, added to obtain a pressure sensitive adhesive (PSA), on: i) rheological behaviour, ii) debonding mechanisms, iii) adhesive properties and iiii) in vitro drug release rate. Methods: Formulations differ for SEBS Mw (i.e. SOL TH®2311 - Mw = 45.61 kDa, SOL TH®2312 - Mw = 64.23 kDa and SOL TH®2315 - Mw = 176.35 kDa) and for the type of tackifier (i.e Regalite R1100® - C9 aliphatic resin and Eastotak H100W® - C5 aliphatic). For the preparation of the drug-loaded patches, IB was added at 10% (w/w). The rheological properties were obtained using a rotational rheometer, applying a frequency-sweep deformation. The debonding mechanisms on a stainless steel probe were determined by using a custom-designed probe tack tester. Patches were prepared by casting and their adhesive properties were evaluated in terms of shear adhesion and peel adhesion. The in vitro drug release rate was also determined using an adapted disk assembly method. Results: PSAs made with low Mw SEBS behaved as viscoelastic fluids over the whole range of frequencies. The viscoelasticity is required to achieve a balance between peel and creep, crucial properties in the development of a patch. As a viscous liquid it should be able to dissipate energy during the peel process; while as a solid it should have a good resistance to shear. The failure mechanisms during the debonding process revealed that the behavior of all the PSAs was related to the relaxation time. At the lower debonding velocity they showed a liquid-like behavior with many digitations. This mechanism is required to achieve an adhesive failure without residues after the debonding process. Aiming to rationalize the selection of suitable formulations for the development of cutaneous patches, the cohesive (shear adhesion) and adhesive (peel adhesion) properties were evaluated. The shear adhesion revealed that the polymer Mw influenced the cohesive strength: increasing SEBS-Mw, the shear adhesion values decreased. Moreover, IB caused a further reduction of the shear adhesion. However, all the patches showed an ideal cohesive strength and optimal peel adhesion, if compared to those available on market, suggesting that they will not ooze during application and could be detached without skin damage and pain upon removal. Finally, taken into consideration the biopharmaceutical performances, the percentage of IB released from the prepared patches was not influenced by SEBS-Mw and the profiles were superimposable. The drug release was completed within 24 hours according to the Higuchi pattern. Conclusions: The overall data demonstrated the feasibility to design cutaneous patches made of SEBS. The resin type used in the preparation of SEBS-based PSA did not influence the matrix behavior. Low Mw SEBS polymer worthy of consideration because of its favorable viscoelastic behavior.
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