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Orally administered bioactive compounds have to survive acidic environs (pH 1.2) of the stomach and reach the small intestine (pH 6.8-7.4), which is the main site of absorption in the gastrointestinal tract. Hence, it is desired to have a delivery system which can protect the active molecules from degradation in acidic pH but release them in the small intestine. This objective was achieved in the present work by formulating stable shellac colloidal particles that showed pH dependent release. Colloidal particles were prepared using a simple anti-solvent method, wherein shellac was precipitated spontaneously by adding ethanolic shellac solution to aqueous polymer (xanthan gum) solution, which acts as electrosteric stabiliser. The average particle size could be controlled from around 150 nm to 300 nm depending on the initial concentration of shellac in the stock solution. High negative surface charge (-64.8 to -81.7 mV) and spherical shape of the particles were confirmed using zeta-sizer and transmission electron microscopy. To evaluate the suitability of the colloidal particles for delivery of bioactive compounds, silibinin (a flavonolignan) was loaded up to 10% w/w into the shellac particles and characterised for pH stability and in vitro release. X-Ray diffraction studies indicated amorphous nature of the entrapped silibinin in the colloidal particles. The release of silibinin was followed under gastric (pH 1.2) and intestinal conditions (pH 7.4) and the amount was detected in terms of antioxidant activity (Ferric Reducing Antioxidant Power). Due to the pH dependent solubility of shellac, silibinin entrapped in the colloidal particles was found to be stable to acidic pH and showed more than 90% release in the intestinal pH

Title: Colloidal complexation of a macromolecule with a small molecular weight natural polyphenol: Implications in modulating polymer functionalitiesDescription: This work reports the use of a small molecular weight compound to alter the functionality of an industrially relevant polymer. Spontaneous interactions of tannic acid with methylcellulose resulted in the formation of colloidal particles which showed striking eff ect on the interfacial properties (enhanced oil-water and air-water interface stabilization) and the bulk property (loss of thermoreversible gelation).

We prepared dispersions from bacterial cellulose microfibrils (CMF) of a commercial Nata de Coco source. We used an ultra-high-energy mechanical deagglomeration process that is able to disperse the CMFs from the pellicle in which they are organized in an irregular network. Because of the strong attractions between the CMFs, the dispersion remained highly heterogeneous, consisting of fiber bundles, flocs, and voids spanning tens to hundreds of micrometers depending on concentration. The size of these flocs increased with CMF concentration, the size of the bundles stayed constant, and the size of the voids decreased. The observed percolation threshold in MFC dispersions is lower than the theoretical prediction, which is accounted for by the attractive interactions in the system. Because bacterial cellulose is chemically very pure, it can be used to study the interaction of attractive and highly shape-anisotropic, semiflexible fiberlike colloidal particles.

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