Influence of the Hydrophobicity of Polyelectrolytes on Polyelectrolyte Complex Formation and Complex Particle Structure and Shape

Mende, Mandy; Schwarz, Simona; Zschoche, Stefan; Petzold, Gudrun; Janke, Andreas

doi:10.3390/polym3031363

Cited by 13 publications

(18 citation statements)

References 18 publications

(21 reference statements)

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“…Interestingly, the mechanical properties were found to depend on overall water content within the PEC, which could be tuned via hydrophobicity and the nature of the salt. This swelling behavior has also been observed in a study by Mende et al [ 39 ], on strong polyelectrolytes based on alternating maleic anhydride copolymers, where the formation of less swollen particles with the more hydrophobic polyelectrolytes using atomic force microscopy was reported.…”

Section: Introductionsupporting

confidence: 82%

Engineering Peptide-Based Polyelectrolyte Complexes with Increased Hydrophobicity

2019

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Polyelectrolyte complexation is a versatile platform for the design of self-assembled materials. Here we use rational design to create ionic hydrophobically-patterned peptides that allow us to precisely explore the role of hydrophobicity on electrostatic self-assembly. Polycations and polyanions were designed and synthesized with an alternating sequence of d- and l-chiral patterns of lysine or glutamic acid with either glycine, alanine or leucine due to their increasing hydrophobicity index, respectively. Two motifs were considered for the oppositely charged patterned peptides; one with equal residues of charged and uncharged amino acids and the other with increased charge density. Mass spectroscopy, circular dichroism, H- and F-NMR spectroscopy were used to characterize the polypeptides. Polyelectrolyte complexes (PECs) formed using the sequences were characterized using turbidity measurements, optical microscopy and infrared spectroscopy. Our results show that the critical salt concentration, a key measure of PEC stability, increased with both increasing charge density as well as hydrophobicity. Furthermore, by increasing the hydrophobicity, the amount of PEC formed increased with temperature, contrary to purely ionic PECs. Lastly, we assessed the encapsulation behavior of these materials using a hydrophobic dye. Concluding that encapsulation efficiency increased with hydrophobic content of the complexes providing insight for future work on the application of these materials for drug delivery.

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Section: Introductionsupporting

confidence: 82%

Engineering Peptide-Based Polyelectrolyte Complexes with Increased Hydrophobicity

2019

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“…For N:P > 3, stable complexes of relatively small sizes were obtained. The evolution of the PSD with the N:P ratio was in agreement with a stabilization mechanism where the excess polyion, respectively the siRNA at N:P ≤ 1 and the COS-50 at N:P > 3, was located at the particle surface thereby preventing the aggregation of particles [49,50]. In most studies, N:P ratios ranging from 4 to 30 were used regardless the molar mass and DA of chitosan, thus emphasizing the limited stabilizing capacity of chitosan [3,14,51,52].…”

Section: Resultsmentioning

confidence: 62%

Effects of Chain Length of Chitosan Oligosaccharides on Solution Properties and Complexation with siRNA

et al. 2019

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In the context of gene delivery, chitosan has been widely used as a safe and effective polycation to complex DNA, RNA and more recently, siRNA. However, much less attention has been paid to chitosan oligosaccharides (COS) despite their biological properties. This study proposed to carry out a physicochemical study of COS varying in degree of polymerization (DP) from 5 to 50, both from the point of view of the solution properties and the complexing behavior with siRNA. The main parameters studied as a function of DP were the apparent pKa, the solubility versus pH, the binding affinity with siRNA and the colloidal properties of complexes. Some parameters, like the pKa or the binding enthalpy with siRNA, showed a marked transition from DP 5 to DP 13, suggesting that electrostatic properties of COS vary considerably in this range of DP. The colloidal properties of siRNA/COS complexes were affected in a different way by the COS chain length. In particular, COS of relatively high DP (≥50) were required to form small complex particles with good stability.

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“…Entropy gain from the release of adsorbed counterions and dehydration is believed to be the main driving force for complexation [ 4 , 5 , 6 , 7 , 8 , 9 ]. However, short-range forces such as hydrogen bonding and hydrophobic interactions can also be involved in the complex formation process [ 10 , 11 , 12 , 13 , 14 , 15 ]. Hydrogen bonding between the sequence pairs results in strong interactions and the formation of a compact structure.…”

Section: Introductionmentioning

confidence: 99%

Deciphering the Role of π-Interactions in Polyelectrolyte Complexes Using Rationally Designed Peptides

2021

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Electrostatic interactions, and specifically π-interactions play a significant role in the liquid-liquid phase separation of proteins and formation of membraneless organelles/or biological condensates. Sequence patterning of peptides allows creating protein-like structures and controlling the chemistry and interactions of the mimetic molecules. A library of oppositely charged polypeptides was designed and synthesized to investigate the role of π-interactions on phase separation and secondary structures of polyelectrolyte complexes. Phenylalanine was chosen as the π-containing residue and was used together with lysine or glutamic acid in the design of positively or negatively charged sequences. The effect of charge density and also the substitution of fluorine on the phenylalanine ring, known to disrupt π-interactions, were investigated. Characterization analysis using MALDI-TOF mass spectroscopy, H NMR, and circular dichroism (CD) confirmed the molecular structure and chiral pattern of peptide sequences. Despite an alternating sequence of chirality previously shown to promote liquid-liquid phase separation, complexes appeared as solid precipitates, suggesting strong interactions between the sequence pairs. The secondary structures of sequence pairs showed the formation of hydrogen-bonded structures with a β-sheet signal in FTIR spectroscopy. The presence of fluorine decreased hydrogen bonding due to its inhibitory effect on π-interactions. π-interactions resulted in enhanced stability of complexes against salt, and higher critical salt concentrations for complexes with more π-containing amino acids. Furthermore, UV-vis spectroscopy showed that sequences containing π-interactions and increased charge density encapsulated a small charged molecule with π-bonds with high efficiency. These findings highlight the interplay between ionic, hydrophobic, hydrogen bonding, and π-interactions in polyelectrolyte complex formation and enhance our understanding of phase separation phenomena in protein-like structures.

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Influence of the Hydrophobicity of Polyelectrolytes on Polyelectrolyte Complex Formation and Complex Particle Structure and Shape

Cited by 13 publications

References 18 publications

Engineering Peptide-Based Polyelectrolyte Complexes with Increased Hydrophobicity

Engineering Peptide-Based Polyelectrolyte Complexes with Increased Hydrophobicity

Effects of Chain Length of Chitosan Oligosaccharides on Solution Properties and Complexation with siRNA

Deciphering the Role of π-Interactions in Polyelectrolyte Complexes Using Rationally Designed Peptides

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