Preparation of Deproteinized Natural Rubber Latex and Properties of Films Formed by Itself and Several Adhesive Polymer Blends Wiwat Pichayakorn,* ,† Jirapornchai Suksaeree, † Prapaporn Boonme, † Wirach Taweepreda, ‡ and Garnpimol C. Ritthidej § † Department of Pharmaceutical Technology, Faculty of Pharmaceutical Sciences, and ‡ Department of Materials Science and Technology, Faculty of Science, Prince of Songkla University, Songkhla 90112, Thailand § Department of Pharmaceutics and Industrial Pharmacy, Faculty of Pharmaceutical Sciences, Chulalongkorn University, Bangkok 10330, Thailand ABSTRACT: This work aimed first to prepare deproteinized natural rubber latex (DNRL) and investigate the properties of films after it was blended with various adhesive polymers: hydroxypropylmethyl cellulose (HPMC), methyl cellulose (MC), sodium carboxymethyl cellulose (SCMC), poly(vinyl alcohol) (PVA), poloxamer 407, and sodium alginate. The second aim was to identify the films that would be the best for medical and pharmaceutical applications. Dibutyl phthalate (DBP), diethyl phthalate, dibutyl sebacate, triethyl citrate, and glycerin (GLY) were used as plasticizers to improve the elasticity and adhesiveness of the novel materials. DNRL was prepared by proteolytic alcalase enzyme treatment, followed by centrifugation. The DNRL was virtually free of protein, produced no significant reaction in the rabbit skin irritation test, and formed a good elastic film, but it had low skin adhesive properties. Blending DNRL with several polymers produced better films with different elastic and adhesive properties. Moisture uptake and swelling tests indicated that its films provided increasing hydrophilicity when blended with several polymers. SEM showed homogeneous films, and water hydraulic permeability tests indicated some porosity in matrix films. Blending DNRL with HPMC or PVA and DBP or GLY produced films with the best potential for novel materials. FT-IR, DSC, and XRD studies indicated the compatibility of the blended ingredients. In conclusion, DNRL blends could be used suitably for medical and pharmaceutical applications. 1. INTRODUCTION Natural rubber latex (NRL), the colloidal cis-1,4-polyisoprene polymer obtained from Hevea brasiliensis, is a white or slight yellow milky liquid that undergoes acid coagulation to an elastic solid in 4-6 h at room temperature. 1 Freshly tapped latex contains about 30% rubber fraction, 5% nonrubber, and other components which are dispersed in water, the serum com- ponent. The polymer from NRL has interesting physical prop- erties such as high tensile strength, high elongation at break, outstanding resilience, impermeability to gases and liquids, and easiness of forming films. 2 However, the surface of rubber particles is covered by a continuous monolayer of a negatively charged phospholipid-protein complex that provides colloidal stability. 3 There are 14 NRL proteins (Hev b1-14) recognized by the International Union of Immunological Societies (IUIS) as causative agents of NRL allergies. 4 Hev b1 and Hev b3 are two of the major allergenic proteins. Hev b1 is found mainly on large rubber particles, whereas Hev b3 is more abundant in smaller rubber particles. 1 Deproteinized NRL (DNRL) pre- pared by treatment with proteolytic enzymes that removed the allergenic protein from fresh NRL has been reported else- where. 5 However, there have been no reports about a specific DNRL preparation that can be used for medical and phar- maceutical skin applications, and for producing blends of DNRL with other substances for formation of nonallergenic films. Polymer patches are now effective alternative products for transdermal drug delivery systems to deliver small drug mole- cules into the systemic blood circulation. For the development of transdermal drug delivery systems, polymer selection and product design are important since they directly affect the physicochemical properties, adhesion-cohesion balance, com- patibility, and stability of the obtained products. 6 Many types of polymers such as cellulose derivatives, 7 poly(vinyl alcohol) (PVA), 8 chitosan, 9 and polyacrylate 10 are being used as mate- rials to apply to the skin as gelling agents, thickening agents, and film formers to control drug release. 6 However, there are only a few reports about using NRL as a material for medical and pharmaceutical skin applications. 11,12 Recently, applica- tions of DNRL and its polymer blends in transdermal drug delivery have been developed by our groups; 13-16 however, the details of DNRL preparations and characterization have not been given yet. This research is focused on the preparation of DNRL and the improvement of its properties by blending it with other bio- adhesive polymers and plasticizers. Hydroxypropylmethyl cellu- lose (HPMC), methyl cellulose (MC), sodium carboxymethyl cellulose (SCMC), PVA, poloxamer 407 (P407), or sodium algi- nate (SAG) was chosen to form blended polymers with DNRL. Dibutyl phthalate (DBP), diethyl phthalate (DEP), dibutyl seba- cate (DBS), triethyl citrate (TEC), and glycerin (GLY) were used as plasticizers. The mechanical and physicochemical properties of these polymers were investigated. Moreover, the feasibility of using Received: July 25, 2012 Revised: September 16, 2012 Accepted: September 20, 2012 Published: September 20, 2012 Article pubs.acs.org/IECR © 2012 American Chemical Society 13393 dx.doi.org/10.1021/ie301985y | Ind. Eng. Chem. Res. 2012, 51, 13393-13404