Self-assembly Of Alginate Research Articles

Calcium triggered self-assembly of alginate-graft-POEGMA via RAFT for the encapsulation of lipophillic actives.

Alginate based comb copolymers were synthesized by reversible addition-fragmentation chain transfer (RAFT). Alginate was used both in its supplied (213 kDa) and depolymerized (73 kDa) forms and prepared into a macroRAFT agent by solubility modification with tetrabutyl ammonium ions and functionalization with a RAFT agent on its hydroxyl moieties. Poly(oligo ethylene glycol methacrylate) (POEGMA) was then polymerized from the macroRAFT agents in organic solvent demonstrating pseudo first-order kinetics. The copolymers dissolved well in a range of organic solvents and demonstrated self-assembly into nanoparticles upon the introduction of calcium chloride in both aqueous and methanolic solutions with particle sizes ranging between 100 and 500 nm. Remarkable encapsulation efficiencies of 4-n-butylresorcinol, a lipophillic active pharmaceutical ingredient, were demonstrated in methanol, and a sustained release profile was observed over 6 hours in aqueous acidic media. These new materials complement a growing library of biodegradable and sustainable polymers that show notable potential for the use in encapsulation and drug delivery.

Multilayered vitamin C nanoliposomes by self-assembly of alginate and chitosan: Long-term stability and feasibility application in mandarin juice

A polyelectrolyte delivery system for vitamin C, achieved by sequential deposition of positive chitosan (CH) and negative sodium alginate (AL) onto the surface of anionic nanoliposomes (NLs), was investigated. Compared with uncoated NLs, AL and CH coated NLs (ALCHNLs) displayed more significant changes in average diameter, zeta potential, pH and morphology, with lower lipid peroxidation and vitamin C release after 90 days of storage at 4 °C, suggesting that the shell (AL-CH) altered the surface properties of ALCHNLs and protected the core (NLs) structure from oxidation and hydrolysis. Further food matrices protection studies implied that mandarin juice fortified with ALCHNLs had less changes in organoleptic characteristics (pH, total acidity and color difference) and showed higher microbiological stability than naked NLs and vitamin C solution. Present results indicated that the biopolymers played a key role on the liposomal membrane structure stability and sustained release of entrapped molecules by a steric barrier on the surface. It provided a potential platform for tailored design of carriers for nutrients or preservatives to enhance both the shelf-life and safety of food matrices.

Preparation of Superparamagnetic Fe3O4@Alginate/Chitosan Nanospheres for Candida rugosa lipase Immobilization and Utilization of Layer-by-Layer Assembly to Enhance the Stability of Immobilized Lipase

Superparamagnetic alginate nanospheres with diameter of 50 nm were prepared by self-assembly of alginate in the Ca(2+) solution; and then superparamagnetic alginate/chitosan nanospheres, which have positive charge and could adsorb lipase directly, were obtained with a following assembly of chitosan based on the electrostatic interaction between alginate and chitosan. Subsequently, oxidic poly (ethylene glycol) was used to functionalize the magnetic alginate/chitosan nanospheres. Thus, the magnetic nanospheres with aldehyde groups and a brushlike structure were formed. With various characterizations, it was verified that the magnetic alginate/chitosan nanospheres held small diameters (around 60 nm) and displayed superparamagnetism with high saturation magnetization. The Candida rugosa lipase (CRL), meanwhile, was immobilized onto the magnetic alginate/chitosan nanospheres by electrostatic adsorption and covalent bonding, respectively. Afterward, a layer-by-layer (LBL) assembly process was utilized to coat the immobilized CRL (ICRL) with covering layers made up of alginate and chitosan. After studying the properties of ICRL such as activity, kinetic behaviors, stability and reusability, it was proved that the ICRL prepared with two methods displayed more excellent properties than that prepared with electrostatic adsorption only. Additionally, coating ICRL with covering layers showed good effect on improving the stability of ICRL.

Effect of Ions on the Aggregation Behavior of Natural Polymer Alginate

The effect of the presence of ions on the aggregation behavior of natural polymer alginate in aqueous media was investigated. Through self-assembly of alginate in aqueous solutions containing Ca2+ and CO(3)(2-) ions under very mild conditions, nanosized aggregates with four different morphologies, i.e., nanosphere, vesicle, nanoparticle, and nanorod, could be obtained under different ion concentrations. This study provides a simple approach to prepare organic/inorganic (O/I) hybrid natural polymer based aggregates with different morphologies.

Fabrication of Nanospheres and Vesicles as Drug Carriers by Self-Assembly of Alginate

A new method was developed to fabricate nanospheres and vesicles as drug carriers. The drug-loaded nanospheres and vesicles were prepared by self-assembly of alginate in aqueous media containing Ca2+ and CO32− ions under very mild conditions. The preparation method did not involve any organic solvent and surfactant and could offer good control over the morphology and the size of self-assemblies. Through adjusting the preparation conditions, nanosized drug-delivery systems with different shapes, that is, nanospheres and vesicles, could be obtained. The morphologies of the drug-delivery systems were observed by transmission electron microscopy (TEM). 5-Fluorouracil (5-FU), an anticancer drug, was encapsulated in the nanospheres and vesicles, and in vitro drug release behavior was investigated. The effect of drug-loading content on the release was studied. The release of 5-FU could be effectively sustained from both drug-loaded nanospheres and vesicles because the presence of CaCO3 in the nanospheres/vesicles could reduce the permeability of the entrapped drug for the alginate-based self-assemblies.