Issue link: http://www.e-digitaleditions.com/i/1199406
eye on excipients This edition of "Eye on Excipients" dis- cusses the pharmaceutical applications for zein in film coating and as an excipient. Pharmaceutical and nutraceuti- cal manufacturers are increasingly seeking natural materials to encap- sulate active ingredients. This effort is partly due to an industry trend to reduce the use of synthetics and chemicals and partly to a reevalua- tion by regulatory authorities in the EU, US, and elsewhere of the health and environmental impacts of mate- rials that pharmaceutical companies currently use for encapsulation. Natural polymers provide ver- satility as excipients, are renewable and biodegradable, and offer sev- eral advantages in the encapsulation of active ingredients. You can cre- ate capsules or films from natural polymers using several techniques, including spray dr ying; emulsion; coacervation (a chemical method for producing polymer droplets in sus- pension); and ionotropic gelation (a method of crosslinking oppositely charged ionic poly mer s). Nat u- ral polymers also exhibit attractive chemical properties such as: • the ability to form films; • good emulsification properties; • high resistance to the environ- ment of the gastrointestinal tract; • biodegradability; • low viscosity at high solids content; and • low hygroscopicity. Food and pharmaceutical compa- nies seeking a vegan alternative to shellac-based coating formulations have investigated the use of zein, a prolamin found in corn, as one such alternative, due to its reputation for being superior to other coatings in terms of resistance to heat, abrasion, and humidity. Zein demonstrates a wide spec- tr um of beneficial encapsulation properties while displaying negligi- ble interactions with active ingredi- ents. For encapsulated drug products, zein can provide a zero-order, con- trolled-release pattern, releasing a constant level of drug for an extended period of time, or a delayed-release pattern, in which a rapid release fol- lows an initial lag time. Recently, the industr y has also been evaluating zein as an excipi- ent in other drug delivery systems, including targeted or sustained drug delivery [1], transdermal patches [2], food-grade capsules [3], and tissue engineering [4]. Recent research has also shown that zein improves the absorption of essential nutri- ents, such as vitamins D and E and omega-3 fatty acids [5]. Zein as a delivery system Zein is one of the few hydropho- bic, water-insoluble biopolymers that the US FDA has approved for oral use. Because it's hydrophobic, zein can easily be transformed into colloidal particles by changing the solubilizing capacity of the primary solvent through dilution with a non- solvent [6]. This is due to the excel- lent miscibility of ethanol and water, whereas water isn't a good solvent for the dissolved zein. Zein micro- and nanoparticles also appear promising for drug delivery, especially for hydrophobic nutrients or drugs. Generally, you can dissolve hydrophobic bioactives together with zein in an aqueous, ethanol binary solvent and then mix the solution with an antisolvent, such as water, to coprecipitate the bioactives with zein. Zein can create a protective layer because of its extremely high surface area and trapping efficiency. It's also known for its resistance to digestive enzymes, resulting in slower diges- tion in the gastrointestinal tract, which you can exploit for the con- trolled release of functional compo- nents loaded in colloidal zein parti- cles. Taken together, these properties make it an attractive novel material in a wide range of applications for protecting bioactive components, such as polyphenols, vitamins, and omega-3 fatty acids [7]. Coating applications Manufacturers can easily produce zein films by solvent casting, extru- sion, and spin casting. An appro- priate polymer film for a coating application generally requires ideal mechanical and barrier properties, such as elongation, tensile strength, and water and gas per meabilit y. Manufacturers can tailor these film properties to both the formulation and the process of film formation. In some cases, manufacturers also use plasticization, chemical cross- Dan Rosen FloZein Products 42 January 2020 Tablets & Capsules