Lecture 3 (10/23/2011) Nano/Micro Encapsulation Technologies

Transcription

1 Lecture 3 (10/23/2011) Nano/Micro Encapsulation Technologies Qingrong Huang Department of Food Science Tel: qhuang@aesop.rutgers.edu

2 Food Delivery Systems Food Ingredients of Interest: - Food flavors, enzymes, nutraceuticals, and food colors. others: nutrients, food microbial, etc. Motivations: - Encapsulated materials can be protected from moisture, heat, oxidation, or other extreme conditions; - Enhance food stability and maintain viability; - Some bad odors or tastes can be masked, etc

3 Encapsulation Basics Encapsulation: a process by which one material or mixture of materials is coated or entrapped within another material or system. The material that is coated or entrapped can be a liquid, a solid particle, or gas, and is referred as core material (or fill, internal phase). The material that forms the coating is referred to as wall material (or carrier, shell, membrane, coating).

4 Common Encapsulation Methods 1. Spray Drying First, the carrier or wall material (such as maltodextrin, modified starch, gum, etc ) is hydrated. The flavor or ingredient to be encapsulated is added to the carrier and homogenized or thoroughly mixed into the system using a similar technique. Typical ratio of carrier:core materials is 4:1. The mixture is homogenized to create small droplets of flavor or ingredient within the carrier solution, and then fed into a spray dryer where it is atomized through a nozzle or spinning wheel. Hot air contacts the atomized particles and evaporates the water, producing a dried particle that is a starch or carrier matrix containing small droplets of flavor or core. The dried particles fall to the bottom of the dryer and are collected.

5 2,4-Decadienal Level (ppm) Common Encapsulation Methods 1. Spray Drying Spray Dried 2,4-Decadienal Encapsulated in Neobee; Shelf Life Study Days of Shelf Life 5 Degrees Celcius 25 Degrees Celcius 40 Degrees Celcius 60 Degrees Celcius 40 Degrees Celcius 60 Degrees Celcius

6 Common Hydrocolloids Natural Sulfated: Carrageenan, furcellaran, agar, iridophycan, fucoidan, hypnean Carboxylic Alginate, pectin, Arabic, tragacanth, karaya, ghatti, xanthan gum, quince seed, larch, psyllium seed gum, okra gum, gellan gum, flax seed gum Phosphorylated Phosphomannans Nonionic Dextran, starch and its fractions, locust beam gum, guar, tamarind seed gum, laminaran Semisynthetic Sulfated starch Carboxymethylcellulose, low methoxylpectin, propylene glycol alginate, triethanolamine alginate, carboxymethyl locust bean gum, carboxymethyl guar gum Starch phosphate Methylcellulose, hydroxypropylcellulose, hydroxyethylcellulose, hydroxypropylmethylcellulose, ethylhydroxyethylcellulose

7 SEM Images (a) (b)

8 Characterization of Capsules 50 μm Optical image AFM height image

9 Common Encapsulation Methods 1. Spray Drying Advantages: Most economical and widely used method of encapsulation; Equipment is readily available and production cost is low; Also a dehydration process and used in the preparation of dried materials such as powered milk; Disadvantages: Producing very fine powder which needs further processing such as agglomeration to instantized the dried material; Not good for heat sensitive materials.

10 Common Encapsulation Methods 2. Spray Cooling Similar to spray drying in that core material is dispersed in a liquified coating or wall material and atomized, but unlike spray drying, there is no water to be evaporated; The core and wall mixtures are atomized into cooled air which causes the wall (typically a vegetable oil, melting point C) to solidify around the core; this method is often used to encapsulate solid materials such as vitamins or minerals; With the ability to select the melting point of the wall, this method of encapsulation can be used for controlled release.

11 Common Encapsulation Methods 3. Media Milling (part 1) Media milling involves placing solid particles to be mechanically reduced to nano dimensions in a ball mill or milling unit that contains milling media beads. Dry and wet media milling procedures can be used. In a dry milling process, no solvent or liquid is added to the ball mill. In a wet milling process a liquid is present. It usually is water, but can be a food grade vegetable oil. In both dry and wet milling procedures, a dispersing agent is present. It may be a polymer or nonpolymeric surfactant. Once loaded, the milling unit is rotated or agitated in some manner. Impact and shearing forces between moving milling media beads reduce the suspended solid particles to nanoparticles. Stress intensity coupled with number of contact points with milling beads are primary factors that define final milled particle size

12 Common Encapsulation Methods 3. Media Milling (part 2) Stress intensity is influenced by kinetic energy transmitted to the grinding media through the agitator shaft within the machine s stator housing. The smaller the beads are, the smaller the nanoparticle produced, because the number of contacts increases as bead size decreases. The rule of thumb is that nanoparticle size equals 1/1000 the size of the grinding media; Milling media beads of µm yield a fine particle size distribution. Before wet-milled After wet-milled

13 Wet Milling System

14 Common Encapsulation Methods: 4. Emulsion encapsulation/entrapment Key step: Formation of a oil-in-water (o/w) emulsion: The active material to be encapsulated or entrapped is added to a hydrocolloid solution. A small volume of this aqueous phase is then added to a large volume of oil and the mixture is homogenized to form the emulsion. Once the O/W emulsion is formed, the water-soluble polymer must be insolubilized (cross-linked) to form tiny gels within the oil phase. The smaller the internal phase particle size of the emulsion, the smaller the final microparticles will be. Cross-linking method: e.g. alginate/ca ++.

15 Encapsulation of β-carotene using Polymer Micelles b-carotene: antioxidant character, anticancer activity, enhancement of the immune response, inhibition of mutagenesis, and blocking of free radical-mediated reactions The demand for b-carotene has increased

16 Background b-carotene: lipophilic unsaturated susceptible during storage In order to insert the lipophilic b-carotene into aqueous food systems and enhance its stability, different technologies are investigated

17 Background Nanotechnology serve as carriers for nutriceutical, effective vehicles for drug delivery and controlled release, and gene therapy. Encapsulation of b-carotene by nanotechnology Nanodispersion: protein, polymeric matrices - B. S. Chu et al. J. Sci Food Agric , S. C. Sutter et al. Interna. J. Pharmaceutics , C. P. Tan et al. J. Sci Food Agric , (0.024%) Nanoparticle: emulsion, amphiphilic polymer - M. Murakami et al. J. Chem Engin Japan , A. Hentschel et al. J. Food Sci , N1-N6. - X. Y. Pan et al. J. Colloid Interface Sci , J. P. Jee et al. Europ J Pharmac Biopharmac S. A. Desobry et al. J. Food Sci ,

18 Background Chitosan: is a cationic polysaccharide is a fully or partially N- deacetylated product of naturally abundant chitin biocompatible, biodegradable, low-toxic, bioadhesive attract increasing attention in the fields of food, textile, cosmetics, biomedical, pharmaceutical, and other industries

19 Background poor solubility in either water or organic solvents limited applications Modified Chitosan hydrophobic Simultaneous Modification scarce hydrophilic A number of publications show the suitability of selfassembled nanoparticles from modified chitosan for encapsulation of sensitive ingredients

20 Hypothesis and Objective Chitosan can be modified using acyl chloride as hydrophobic group and MPEG* as hydrophilic group, which could exhibit amphiphilic properties. A hypothetical scheme of micellization of modified chitosan Because b-carotene is very lipophilic, the modified chitosan nanoparticles can be used to encapsulate it, and to enhance its solubility and stability. * polyethylene glycol monomethyl ether

21 Synthetic scheme of modified chitosan amphiphile: acylchitosan acylchitompeg The Structure Fourier Transform Infrared Nuclear Magnetic Resonance

22 Characterization: Sample DS (Degree of Substitution) NH 2 NHAc NHR OR chitosan acylchitosan Sample DS R =DS(NHR+OR) DS R /DS M DS M acylchitompeg Molecular formula of acylchitompeg C 6 H 7 O 2 (OH) 1.08 (OR) 0.92 (NH 2 ) 0.23 (NHCOCH 3 ) 0.23 (NHR) 0.08 (NHCOCH 2 CH 2 COMPEG)

23 Solubility Test: Sample Milli-Q water Ethanol Acetone CH 2 Cl 2 CHCl 3 THF Dioxane Chitosan acylchitosan - acylchitompeg The improved solubility will make acylchitompeg be easily fabricated into various micro- and/or nanoparticles, which will extend the use of chitosan derivatives in biomedical applications

24 Intensity (a.u.) Self-assembly Properties: I 1 I 3 (a) (b) I 1 /I acylchitompeg Wavelength (nm) E Concentration (mg/ml) Critical Aggregation Concentration (CAC): mg/ml. CAC of chitosan: above 1 mg/ml. M. M. Amiji Carbohydr. Polym ,

25 Atomic Force Microscopy(AFM) Images: Surface morphology images of acylchitompeg. Left is height image and right is phase image

26 Particle Size: G (q,t) t ( s) Single stretched exponential fit by dynamic light scattering (DLS) sample Diameter (nm) by AFM by SEF acylchitompeg

27 P(r) (a.u.) I(Q) (cm -1 ) Structure by Synchrotron small-angle X-ray scattering (SAXS): acylchitompeg 20 mg/ml 10 mg/ml 5 mg/ml 2.5 mg/ml 1.25 mg/ml Slope: large scale agglomeration of associated particles x r (Å) Q (Å -1 ) The scattering profile 2 I(Q = 0)= c n Δb / M I - scattering intensity Q -scattering vector c -sample concentration n -association number b-scattering length difference of one molecule relative to the surrounding medium M -the molecular weight

28 Cytotoxicity Analysis: Relative Cell Viability (%) Concentration ( g/ml) Suggesting that it was well biocompatible and had the potential to be used in biomedical applications and encapsulation of active food ingredients

29 Picture of sample solutions encapsulating b-carotene: Concentration of sample in water: 10 mg/ml

30 ε-poly(lysine)-based Micelles ε-poly(lysine), or EPL, is generated naturally EPL is produced by bacterium Streptomyces albulus (35) lysine monomers. Mw Da

31 Food Applications of EPL 1. antimicrobial agent against both Gram(+) and Gram(-) bacteria because of its positive charge GRAS (2004), in cooked rice or sushi rice 2. dietary agent inhibit pancreatic lipase suppress dietary fat absorption

32 ε-poly(lysine)-based Micelles EPL + octenyl succinic anhydride (OSA) (J. Agr. Food Chem. 2010, 58, )

33 Physical Properties Samples Tg ( o C) EPL OSA-g- EPL OSA-g- EPL OSA-g- EPL OSA-g- EPL

34 Micelle Structure I(Q) a.u OSA103 OSA106 OSA110 OSA103 fit 10-3 OSA106 fit OSA110 fit Q (A -1 ) Small-angle x-ray scattering profiles Pair distribution function

35 Antimicrobial vs. Cytotoxicity Minimum Inhibition Concentration (MIC)=12.5 (μg/ml) Cytotoxicity in Hep G2 cells was found for OSA-g-EPL between μg/ml.

36 Three loading methods to compare the encapsulation capacity

37 Encapsulated curcumin showed increased cellular antioxidant activity **: P<0.01

38 Conclusions of micellar encapsulation experiments Curcumin was able to be solubilized in micelle solution, exampled by micelles formed by modified starch and newly synthesized modified epsilon polylysine. Upon encapsulation, in vitro bioactivity of curcumin was increased, suggesting that solubility limited the cellular absorption of curcumin.