Data di Pubblicazione:
2017
Citazione:
Design of SEBS-based pressure-sensitive adhesives for medicated plasters preparation / G.M.G. Quaroni, C.G.M. Gennari, F. Cilurzo, G. Ducouret, C. Creton, P. Minghetti. ((Intervento presentato al 2. convegno European Conference on Pharmaceutics tenutosi a Krakov nel 2017.
Abstract:
INTRODUCTION
Styrene-block-(ethylene-co-butylene)-block-styrene (SEBS) copolymers are well known biocompatible elastomers with outstanding stability under physiological conditions1. It was also demonstrated that the compounding with paraffin oil and aliphatic resins (tackifier) allows to obtain a pressure sensitive adhesive (PSA) with a very high creep resistance2. These features make SEBS a potential candidate for the design of transdermal patches and/or medicated plasters. In this work the influence of SEBS molecular weight and tackifier type on the adhesive properties, mechanical characteristics and biopharmaceutical performances of medicated plasters containing S-ibuprofen (S-IB) were investigated.
EXPERIMENTAL METHODS
Materials
Three types of SEBS were kindly donated by Polimeri Europa (San Donato Milanese, Milan, Italy). They were SOL TH® 2311 (Mw = 45.61 kDa), SOL TH® 2312 (Mw = 64.23 kDa) and SOL TH® 2315 (Mw = 176.35 kDa). The aliphatic hydrocarbon resins Regalite R1100® and Eastotac H100W® were used as tackifiers and they were received as a gift from Eingemann & Veronelli Spa (Rho, Milan, Italy).
Mixtures preparation
To prepare the polymeric solution, all components were dissolved in toluene. The final composition of the placebo PSAs is illustrated in Table 1. For the preparation of the drug-loaded mixtures, S-IB was added at 10% (w/w).
Rheological characterization
The rheological properties were obtained by using a rotational rheometer (Discovery Hybrid Rheometer). A frequency-sweep deformation was applied into the samples and the response in terms of stress was measured.
Probe tack test
The adhesion and debonding mechanisms of the placebo PSAs on a stainless steel probe were determined by using a custom-designed probe tack tester. Tack experiments were performed at 25 °C and 32 °C with a compression force of 30 N; the contact time was set at 10 s and the debonding velocity was varied from 10 to 1000 μm/s. PSA thickness was about 200 ± 10 μm.
Drug release rate
S-IB plasters were prepared by using a LabCoater unit Mathis LTE-S(M). Final thickness of adhesive matrices was about 55 ± 5 μm. The S-IB release was carried out using a USP28 paddle dissolution apparatus (8.034 cm2; 300 mL; pH 7.4 phosphate buffer; 32 ± 1 °C; 25 rpm).
RESULTS AND DISCUSSION
Rheological characterization
In order to develop suitable medicated plasters, a balance between peel and creep is crucial3. Therefore, the PSA should have viscoelastic behaviour: in fact, as a viscous liquid it should be able to dissipate energy during the peel process (at high shear rate), while as a solid it should have a good resistance to shear over long time4.
The rheological measurements showed as the PSAs made with SEBS-low molecular weight behaved as viscoelastic fluids over the whole range of frequencies, while PSAs made with the intermediate and the high molecular weight polymers behaved more like moderately viscoelastic solids. As shown in Fig. 1, only for the formulation containing SOL THÒ 2311 (Form.1) the elastic modulus decreased strongly at low frequency, typical of a material with a pronounced viscoelastic character. No differences on the rheological pattern were observed by changing the tackifier.
The probe tack test is generally used to evaluate the instant adhesion properties of a PSA, but the debonding phase can be also studied to analyze the failure mechanism. Form. 1-6 showed a liquid-like behaviour at the lower debonding velocity with many digitations, because they have more time to relax (Fig. 2, black line). On the contrary, at the faster debonding velocity, they did not have time to relax: in these conditions, PSAs showed a more solid-like behavior and the formation of a high number of cavities was observed (Fig. 2, re
Tipologia IRIS:
14 - Intervento a convegno non pubblicato
Elenco autori:
G.M.G. Quaroni, C.G.M. Gennari, F. Cilurzo, G. Ducouret, C. Creton, P. Minghetti
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