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

Kumar, Jatin; Pang, Victoria Y. T.; Aik, Shalen Xue Ling

doi:10.1039/c7tb01670k

Cited by 7 publications

(4 citation statements)

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“…TBA-alg was first esterified with bromoisobutyric acid and subsequently treated with polymethyl-metacrylate (PMMA) under SET-LRP conditions to produce self-aggregating micelles as potential smart drug delivery devices [63] that are suitable for post-functionalization on the free alg carboxylic groups. RAFT polymerization was used to produce copolymers of alg and poly(oligo ethylene glycol methacrylate) (POEGMA), which, in the presence of Ca 2+ ions, formed nanoparticle-based encapsulation materials for 4-n-butylresorcinol [64]. An alternative route to alg-POEGMA copolymers made use of the azide to alkyne click-reaction, followed by nanoparticles self-assembly in the presence of Ca 2+ ions, providing efficient encapsulation matrices for the chemotherapy drugs doxorubicin and paclitaxel [65].…”

Section: Synthesis Of Graft Copolymersmentioning

confidence: 99%

Strategies to Functionalize the Anionic Biopolymer Na-Alginate without Restricting Its Polyelectrolyte Properties

2020

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The natural anionic polyelectrolyte alginate and its derivatives are of particular interest for pharmaceutical and biomedical applications. Most interesting for such applications are alginate hydrogels, which can be processed into various shapes, self-standing or at surfaces. Increasing efforts are underway to functionalize the alginate macromolecules prior to hydrogel formation in order to overcome the shortcomings of purely ionically cross-linked alginate hydrogels that are hindering the progress of several sophisticated biomedical applications. Particularly promising are derivatives of alginate, which allow simultaneous ionic and covalent cross-linking to improve the physical properties and add biological activity to the hydrogel. This review will report recent progress in alginate modification and functionalization with special focus on synthesis procedures, which completely conserve the ionic functionality of the carboxyl groups along the backbone. Recent advances in analytical techniques and instrumentation supported the goal-directed modification and functionalization.Polymers 2020, 12, 919 2 of 23 Physicochemical and Polyelectrolyte Characteristics of AlginateThe composition, internal structure, and molar mass of the alg backbone govern the functional properties [9]. The solubility of alg in water depends on the pH value and the type of the counterions of the carboxyl groups. At pH < 3, both the M-and G-structures will precipitate as alginic acid. However, alternating M-and G-structures precipitate at lower pH values compared to the alg containing Polymers 2020, 12, 919 3 of 23 more homogeneous block structures. Neutralization of the alginic acid occurs at pH > 4, where it is converted into its corresponding salt [10]. Na-alg is an example of a water-soluble alg.Na-alg behaves in aqueous solution as a typical linear homogeneously charged polyelectrolyte. The chain conformation and consequently the solution viscosity strongly depend on the ionic strength, i.e., on both the alg concentration and the simultaneous presence of low molar mass salt. The intramolecular electrostatic repulsion between the neighboring negatively charged carboxyl groups of each monomer unit forces alg molecules into an extended random coil conformation in aqueous solution [11]. This results in highly viscous solutions even at relatively low alg concentration. The dynamic viscosity increases exponentially with the molar mass, while the intrinsic flexibility of the alg chains in solution increases in the order GG < MM < MG [12]. On the other hand, the selectivity for cation-binding and gel-forming properties strongly depends on the composition and sequence. Divalent cations preferably bind to the G-blocks. The ability to form ionotropic gels is based on this selective binding of cations. Mixing solutions of Na-alg with solutions of cationic polyelectrolytes yields precipitates of polyelectrolyte complexes.The rheological behavior of Na-alg solutions is important for a number of technologies and depends on both the concentration and th...

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Section: Synthesis Of Graft Copolymersmentioning

confidence: 99%

Strategies to Functionalize the Anionic Biopolymer Na-Alginate without Restricting Its Polyelectrolyte Properties

2020

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“…Alginate-based comb copolymers were synthesized by reversible addition–fragmentation chain transfer (RAFT) with poly(oligo ethylene glycol methacrylate). The resulting comb copolymers self-assembled into nanoparticles ranging between 100 and 500 nm when introducing calcium chloride . Kapishon et al developed poly(methyl methacrylate) grafted alginate by single electron-transfer living radical polymerization that also self-assembled into nanoparticles .…”

Section: Introductionmentioning

confidence: 99%

“…The resulting comb copolymers self-assembled into nanoparticles ranging between 100 and 500 nm when introducing calcium chloride. 21 Kapishon et al developed poly(methyl methacrylate) grafted alginate by single electron-transfer living radical polymerization that also self-assembled into nanoparticles. 22 While end modification of polysaccharides like alginate can be chemically challenging, recent reports have successfully developed methods that enable the covalent modification of the reducing end of alginate.…”

Section: ■ Introductionmentioning

confidence: 99%

Alginate-Based Amphiphilic Block Copolymers as a Drug Codelivery Platform

et al. 2021

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Structured nanoassemblies are biomimetic structures that are enabling applications from nanomedicine to catalysis. One approach to achieve these spatially organized architectures is utilizing amphiphilic diblock copolymers with one or two macromolecular backbones that self-assemble in solution. To date, the impact of alternating backbone architectures on self-assembly and drug delivery is still an area of active research limited by the strategies used to synthesize these multiblock polymers. Here, we report self-assembling ABC-type alginate-based triblock copolymers with the backbones of three distinct biomaterials utilizing a facile conjugation approach. This “polymer mosaic” was synthesized by the covalent attachment of alginate with a PLA/PEG diblock copolymer. The combination of alginate, PEG, and PLA domains resulted in an amphiphilic copolymer that self-assembles into nanoparticles with a unique morphology of alginate domain compartmentalization. These particles serve as a versatile platform for co-encapsulation of hydrophilic and hydrophobic small molecules, their spatiotemporal release, and show potential as a drug delivery system for combination therapy.

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“…[10][11][12][13][14][15] As many other polysaccharides like hyaluronic acid, dextran, carboxymethylcellulose or chitosan, alginates are also considered as an important polymeric platform for developing thermoresponsive assemblies that can be used on purpose for biomedical applications like drug delivery or tissue engineering. [16][17][18][19][20] For instance, alginates can be modified with polymer precursors characterized by a Lower Critical Solution Temperature (LCST) in water, like poly(ethylene oxide-co-propylene oxide), [21][22] poly(oligo ethylene glycol methacrylate), 23 poly (N-vinyl caprolactam), 24 or poly(N-isopropylacrylamide) [25][26][27] (PNIPAM) in order to design temperature responsive micelles or vesicles for controlled drug delivery or copolymer solutions with sol/gel properties paving the way to injectable hydrogels and 3D cell culture. Although ionotropic gels formed by the complexation of alginates with multivalent cations are almost temperature independent, we have recently shown that alginates having a high mannuronic content (high-M) can form thermotropic gels upon cooling when they were studied at high ionic strength in the presence of monovalent cations.…”

Section: Introductionmentioning

confidence: 99%

Cold and Hot Gelling of Alginate-graft-PNIPAM: a Schizophrenic Behavior Induced by Potassium Salts

et al. 2018

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Recently, alginates (ALG) characterized by high mannuronic content (M blocks) have been shown to undergo a reversible sol/gel transition during cooling in the presence of potassium salts. Cold gelling takes place at low temperatures, just below 0 °C for a KCl concentration of 0.3 mol/kg, but the aggregation process can be easily shifted to higher temperatures by increasing the salt concentration. In the present paper, we take advantage of this peculiar behavior to design a copolymer with schizophrenic gelling properties. For this purpose, side chains of poly(N-isopropylacrylamide) (PNIPAM), characterized by a Lower Critical Solution Temperature (LCST) in water, were grafted on the alginate backbone. Working in semidilute solutions, we show by coupling DSC and viscoelastic measurements that ALG-g-PNIPAM solutions are able to form gels either by cooling or heating depending on the ionic environment. As the aggregation process of ALG and PNIPAM depends mainly and respectively on the nature of the cations and anions, the choice of the salt is then critical to control the self-assembly behavior and the gel properties. Moreover, as the gelation process of alginates driven by the aggregation of mannuronic sequences is characterized by a large hysteresis of 20-30 °C between gelling and melting, both ALG and ALG-g-PNIPAM polymers offer a large versatility not only in terms of salt (nature and concentration) but also in preparation history as different states (sol or gel) can be obtained at room temperature.

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

Abstract: Self-assembly of alginate into nanoparticles was realized by grafting hydrophilic brushes via RAFT.

Cited by 7 publications

References 50 publications

Strategies to Functionalize the Anionic Biopolymer Na-Alginate without Restricting Its Polyelectrolyte Properties

Strategies to Functionalize the Anionic Biopolymer Na-Alginate without Restricting Its Polyelectrolyte Properties

Alginate-Based Amphiphilic Block Copolymers as a Drug Codelivery Platform

Cold and Hot Gelling of Alginate-graft-PNIPAM: a Schizophrenic Behavior Induced by Potassium Salts

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