Polylactic acid

Ciprofloxacin hydrochloride monohydrate (CPX) was obtained from Uquifa (Castellbisbal, Spain). Poly-ε-caprolactone (PCL, Mw 80000 Da) was supplied by Perstorp Caprolactones Ltd (Warrington, United Kingdom), and poly(lactic acid) (PLA viscosity midpoint 2.0 dL/g) was supplied by Natureworks® (Naarden, Netherlands). For the mucoadhesive layer, polyethylene oxide (PEO, Mw 200000 Da) was purchased from the Dow Chemical Company (Montomeryville, PA, USA), and Eudragit RS100 (PAC, copolymer of ethylacrylate, methyl methacrylate and trimethylammonioethyl meth-acrylate chloride) was purchased from Evonik Industries (Essen, Germany). Chloroform (ACS reagent, ≥99.8%) was supplied by Sigma-Aldrich (Madrid, Spain), whilst methanol (≥99%) was supplied by Panreac Química S.L.U. (Castellar del Vallès, Barcelona). The solvent 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) was supplied by Fluorochem (Hadfield, United Kingdom) and N,N,-dimethylformamide (DMF, ≥99.8%) was purchased from VWR Chemicals (Leuven, Belgium). All the polymers and reagents were used as received without further purification.

The intumescent formulation consisted of ammonium polyphosphate (APP), purchased from Clariant under the trade name Exolit AP 422, and alkaline lignin (Lig), supplied by Tokyo Chemical Industry (Tokyo, Japan) (product code L0082). Polylactic acid (PLA), supplied by NatureWorks (Minnetonka, MN, USA) under the trade name Ingeo™ Biopolymer 2003D, was used as the polymeric matrix. Raw, sodic montmorillonite (ANa) originated from Paraíba, Brazil, was submitted to an acidic activation with 4 mol L⁻¹ H₂SO₄ solution, for 2 and 5 h, at a concentration of 10% m/v mineral clay, to promote an increase in the concentration of the acidic sites, as described in a previous work [29 (link)]. The acidified clays were labelled as AH2 (for 2 h treatment) and AH5 (for 5 h treatment).

Poly (vinyl alcohol) (98% hydrolysis degree, M_w 13,000–23,000 g/mol) and methanol came from Sigma-Aldrich^®, St. Louis, MO, USA. Poly(lactic acid) (M_w 200,000 g/mol) was a donation from Natureworks, Minnetonka, MN, USA. Dimethylsulfoxide, glutaraldehyde (aqueous solution 25% (v/v)), sodium chloride (Pro Analyses), dibasic sodium phosphate (P.A.) and chloroform were purchased from Vetec^® Química Fina, Brazil. Potassium chloride (P.A.) was procured from Isofar, Brazil. Monobasic potassium phosphate (P.A.) was from Reagen, Brazil. Anforicin B (the amphotericin micellar system) was from Cristália (Itapira, São Paulo, Brazil), and amphotericin B drug powder (AmB) was purchased from Indofine Chemical Company, Inc. (Hillsborough, NJ, USA).

Ethylene vinyl acetate (vinyl acetate content = 26% (w/w), MFI = 5.5 g/min) was purchased from Asia Polymer Corporation (Taiwan). Poly (lactic acid) (Mw = 121.5 kDa, MFI = 6.09 g/10 min) was obtained from Nature Works (LLC, Minnetonka, MI, USA). The drug Aspirin (10 mg/tablet) was purchased from D. Watson (Islamabad, Pakistan). All of the chemicals used for the experimental work were of medical grades.