Starch Pickering Emulsions - Release Mechanisms

Abstract

Background. Released mechanisms were investigated in Pickering emulsions stabilized by quinoa starch granules. Non-heat treated (NHT) and heat treated (HT) emulsions were studied for their stability and for their ability to efficiently encapsulate peptides and give controlled release after partially simulated in vitro intestinal digestion with release systems containing combinations of phosphate buffer, a-amylase, lipase and bile salts. Oil-in-water emulsions (O/W) encapsulating actives can be a promising candidate of drug delivery systems. Insulin was selected as the polypeptide to encapsulate since oral administration of insulin is of high technological importance with promising applications in pharmaceutical field. Methods. The project included a design and method development phase where a method to disperse insulin in oil (insulin-oil mix) and an analytical method to detect and quantify the amount of released drug were developed. Detection was done by a chromatographic HPLC method developed for this project. During this phase, placebo emulsions were characterized with physical observation, microscopically and for their particle size distribution. After method development was completed, a drug experiment was carried out including insulin-encapsulated emulsions preparation, heat-treatment of HT emulsions, incubation under release system presence, drug isolation and chromatographic detection. Results and Discussion. The combination of insulin-oil mix preferably used in the drug experiment contained acidic organic solvent of methanol 0.75%. The preferred temperature of emulsions heat-treatment was 60 oC for 10 min. Physical observation of incubated emulsions combined with microscopic images revealed that a-amylase could partially destruct emulsions, while merely presence of bile salts had only a slight effect. Nevertheless, combination of a-amylase with bile salts with or without lipase resulted in full emulsion digestion. HPLC results were not conclusive for the released amount of drug. However, it was found that more release-resistant emulsions had a detectable released insulin, whilst degraded emulsions had non-detectable released drug. Conclusion. Further investigation is required to determine the released mechanisms of Pickering emulsions and the potential interactions of released insulin.

Popular Abstract

Several products in food, pharmaceutical and cosmetics industry are systems of at least two immiscible phases where one is dispersed to another in the form of spherical droplets. These systems are called emulsions and common examples are butter, mayonnaise, ice cream and skin care products. Main types of emulsions are oil droplets-in-water (O/W) and water droplets-in-oil (W/O).
Since emulsions contain naturally immiscible phases, the addition of components called stabilizers is important. Traditionally, molecules called surfactants are used as stabilizers. However, due to health and environmental concerns there is a need for shifting to more natural, sustainable, biodegradable and of course inexpensive substances.
Recently, it was found out that solid particles can stabilize emulsions without the presence of molecular surfactants. Emulsions stabilized by solid particles so called Pickering emulsions have shown to have high stability over time. Starch is an example of alternative stabilizers since it is organized in solid particles called granules.
Since starch is a daily component of human diet it has been used widely in food products, but also in pharmaceutical and cosmetic formulations as well. It is generally considered safe as it is edible, is produced world widely and is inexpensive. Although, cereals are known for their starch content, starches from different botanical sources have recently attracted the interest of technologists. It has been found out that starch granules derived from seeds known as pseudo-cereal present special properties in terms of size, shape and composition. For instance, quinoa starch has a relatively small granular size allowing better oil droplet stabilization.
In addition to the properties of quinoa starch, the general complex structure of granules provides unique functional properties. Heating of starch in presence of water undertakes starch to a process called gelatinization associated with water uptake and granular swelling. During gelatinization, granules enlarge in size and this is advantageous when emulsions are stabilized by starch. The reason is that when granules swelling the space between them in the oil-water interface reduces and, thus, provides a barrier effect in the oil droplets. Hence, heat treatment of starch under certain conditions of temperature and time allows to design an appropriate barrier which can improve the stability of emulsions.
In the industry, it is often required that formulations should deliver bioactive components (actives) susceptible or reactive with other ingredients. It is essential that these formulations can enclose the actives so they are protected from external conditions, such as enzymes, pH change and oxidation. There are numerous applications such as functional food products enriched with vitamins and minerals (in food industry), pills delivering drug components (in pharmaceutical industry) and lotions with essential oils (in cosmetics). Thus, there is a technological need to develop delivery systems which encapsulate, protect and give controlled release of the actives.
One category of delivery systems capable to encapsulate actives is O/W emulsions. Since stability is an important aspect, O/W emulsions stabilized by quinoa starch granules are a promising candidate to effectively encapsulate actives. Moreover, heat treatment of starch-based emulsions could increase the encapsulation stability of actives.
When encapsulating actives, it is essential to consider the route it is introduced to the body such as through the skin (cutaneous) or by the mouth (oral). In the case of oral drug intake, the gastrointestinal tract (GIT) conditions (including enzymes and pH change) are factors which determine the mechanisms of controlled drug release from the formulations. Therefore, in the present study it was examined the drug release of O/W emulsions under conditions simulating partially the GIT environment. The release systems added to the emulsions were combinations of a component emulsifying immiscible oil molecules called bile salts, an enzyme catalyzing starch breakdown namely a-amylase and an enzyme reacting with lipids (oil phase) called lipase. In the GIT, there are more enzymes present which should be included in further investigation.
Among different potential candidates to encapsulate, insulin was selected to be investigated in this study. Chemically, insulin in a polypeptide (a small size protein) and, biologically, is a hormone important for blood sugar regulation to human body. Diabetes mellitus is a chronic disease associated with abnormalities in blood sugar levels. Worldwide, many patients with diabetes mellitus are struggling with their treatment which requires subcutaneous insulin injection often resulting to discomfort, pain, and low compliance. In contrast, oral administration of insulin seems promising as it will relief those patients. However, there are still several technological challenges to overcome. Two of the main challenges are how can we make insulin dispersible to the oil phase of the emulsions and how can we develop O/W emulsion systems able to effectively encapsulate insulin and release afterwards under GIT conditions. Nevertheless, consideration of controlled absorption of insulin in the epithelial cells of the small intestine should be also bear in mind in further investigations.

• author: Anastasiadis, Dimitrios
• supervisor: Marie Wahlgren
• organization: Food Technology and Nutrition (M.Sc.)
• course: KLGM01 20201
• year: 2020
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: Quinoa starch, Pickering emulsions, insulin, encapsulation, release, in vitro digestion, food technology, livsmedelsteknologi
• language: English
• id: 9029080
• date added to LUP: 2020-09-25 17:08:50
• date last changed: 2020-09-25 17:08:50