Electrified Interactions of Polyzwitterions with Charged Surfaces: Role of Dipole Orientation and Surface Potentials

The zwitterionic groups possess strong dipole moments, leading to inter- or intrachain interactions among zwitterionic polymers. This study aims to demonstrate the interaction of polyzwitterions poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC), and poly(carboxybetaine methacrylate) (PCBMA) with electrified surfaces, despite their electrically neutral nature. We studied the adsorption of polyzwitterions and their monomers on electrified surfaces by using an electrochemical quartz crystal microbalance with dissipation (EQCM-D). The interaction between zwitterionic molecules and charged surfaces is explored by adjusting the surface potentials. Interestingly, the adsorption of polyzwitterions can be influenced by external potential, primarily due to the formation of polyzwitterions restricting the mobility of zwitterionic groups, affecting the adsorption behavior of polyzwitterions based on the surface potential. The impact is determined by the arrangement of positive and negative ions within the zwitterionic groups, which are the dipole orientation. Additionally, surface potentials determine the adsorption rate, amount, and chain conformation of the adsorbed thin polyzwitterion layers. The effect of ionic strength was investigated by introducing electrolytes into the aqueous solutions to assess the range of influenced surface potentials.

Poly(dehydroalanine)-Based Hydrogels as Efficient Soft Matter Matrices for Light-Driven Catalysis

Soft matter integration of photosensitizers and catalysts provides promising solutions to developing sustainable materials for energy conversion. Particularly, hydrogels bring unique benefits, such as spatial control and 3D-accessibility of molecular units, as well as recyclability. Herein, the preparation of polyampholyte hydrogels based on poly(dehydroalanine) (PDha) is reported. Chemically crosslinked PDha with bis-epoxy poly(ethylene glycol) leads to a transparent, self-supporting hydrogel. Due to the ionizable groups on PDha, this 3D polymeric matrix can be anionic, cationic, or zwitterionic depending on the pH value, and its high density of dynamic charges has a potential for electrostatic attachment of charged molecules. The integration of the cationic molecular photosensitizer [Ru(bpy)3 ]2+ (bpy = 2,2'-bipyridine) is realized, which is a reversible process controlled by pH, leading to light harvesting hydrogels. They are further combined with either a thiomolybdate catalyst ([Mo3 S13 ]2- ) for hydrogen evolution reaction (HER) or a cobalt polyoxometalate catalyst (Co4 POM = [Co4 (H2 O)2 (PW9 O34 )2 ]10- ) for oxygen evolution reaction (OER). Under the optimized condition, the resulting hydrogels show catalytic activity in both cases upon visible light irradiation. In the case of OER, higher photosensitizer stability is observed compared to homogeneous systems, as the polymer environment seems to influence decomposition pathways.

Amphiphilic Polyampholytes for Fouling-Resistant and Easily Tunable Membranes

The versatility of membranes is limited by the narrow range of material chemistries on the market, which cannot address many relevant separations. Expanding their use requires new membrane materials that can be tuned to address separations by providing the desired selectivity and robustness. Self-assembly is a versatile and scalable approach to create tunable membranes with a narrow pore size distribution. This study reports the first examples of a new class of membrane materials that derives state-of-the-art permeability, selectivity, and fouling resistance from the self-assembly of random polyampholyte amphiphilic copolymers. These membranes feature a network of ionic nanodomains that serve as nanochannels for water permeation, framed by hydrophobic nanodomains that preserve their structural integrity. This copolymer design approach enables precise selectivity control. For example, sodium sulfate rejections can be tuned from 5% to 93% with no significant change in the pore size or fouling resistance. Membranes developed here have potential applications in wastewater treatment and chemical separations.

Cell-repellent polyampholyte for conformal coating on microstructures

Repellent coatings are critical for the development of biomedical and analytical devices to prevent nonspecific protein and cell adhesion. In this study, prevelex (polyampholytes containing phosphate and amine units) was synthesized for the fine coating of microdevices for cell culture. The dip-coating of the prevelex on hydrophobic substrates altered their surfaces to be highly hydrophilic and electrically neutral. The range of prebake temperature (50–150 °C) after dip-coating was moderate and within a preferable range to treat typical materials for cell culture such as polystyrene and polydimethylsiloxane. Scanning electron microscopy revealed a conformal and ultra-thin film coating on the micro/nano structures. When compared with poly(2-hydroxyethyl methacrylate) and poly(2-methacryloyloxyethyl phosphorylcholine), prevelex exhibited better characteristics for coating on microwell array devices, thereby facilitating the formation of spheroids with uniform diameters using various cell types. Furthermore, to examine cellular functionalities, mouse embryonic epithelial and mesenchymal cells were seeded in a prevelex-coated microwell array device. The two types of cells formed hair follicle germ-like aggregates in the device. The aggregates were then transplanted to generate de novo hair follicles in nude mice. The coating material provided a robust and fine coating approach for the preparation of non-fouling surfaces for tissue engineering and biomedical applications.

Highly Tough, Stretchable and Self-Healing Polyampholyte Elastomers with Dual Adhesiveness

A new type of polyampholyte with unique viscoelastic properties can be easily synthesized by the copolymerization of butyl acrylate with dimethylaminoethyl methacrylate and acid acrylate in one pot. The elastic modulus of the as-prepared polyampholyte can be easily tuned by adjusting the ratio between the butyl acrylate and ionic monomers. The polyampholyte synthesized by a low proportion of ionic monomer showed low tensile strength and high stretchability, resulting in good conformal compliance with the biological tissues and potent energy dissipation. Due to the existence of high-intensity reversible ionic bonds in the polymer matrix, excellent self-recovery and self-healing properties were achieved on the as-prepared polyampholytes. By combining the high Coulombic interaction and interfacial energy dissipation, tough adhesiveness was obtained for the polyampholyte on various substrates. This new type of polyampholyte may have important applications in adhesives, packaging and tissue engineering.

Pseudo Polyampholytes with Sensitively Ion-Responsive Conformational Transition Based on Positively Charged Host-Guest Complexes

Biological polyampholytes are ubiquitous in living organisms with primary functions including that serving as transporters for moving chemical molecular species across the cell membranes. Synthetic amphoteric macromolecules that can change their phase states depending on the environment to simulate some properties of natural polyampholytes are of great interests. Here, we explore implementation of synthetic pseudo polymeric ampholytes with ion-recognition-triggered conformational change. The phase transition behaviors of the ion-recognition-creative polyampholytes that containing deprotonated carboxylic acid groups as negative charges and 18-crown-6 units for forming positively charged host-guest complexes are systematically investigated. The ion-recognition-triggered phase transition behaviors of pseudo polyampholytes are significantly dependent on cation species and concentrations. Only those specific ions like K⁺ , Ba²⁺ , Sr²⁺ and Pb²⁺ ions that can form 1:1 host-guest complexes with 18-crown-6 units in polymers enable to control over the conformational change like that of the traditional pH-dependent polyampholytes. By regulating the content of the carboxylic acid groups to match the content of the ion-recognized positive charges provided by the host-guest complexes, the pseudo polyampholytes are more sensitive to the recognizable cations. Such ion-recognition-triggered amphoteric characteristics make the pseudo polyampholytes acting like biological proteins, nucleic acids and enzymes as molecular transporters, genetic code storage and biocatalysts in artificial systems. This article is protected by copyright. All rights reserved.

Macromolecular cryoprotectants for the preservation of mammalian cell culture: lessons from crowding, overview and perspectives

Cryopreservation is a process used for the storage of mammalian cells at a very low temperature, in a state of 'suspended animation.' Highly effective and safe macromolecular cryoprotectants (CPAs) have gained significant attention as they obviate the toxicity of conventional CPAs like dimethyl sulfoxide (DMSO) and reduce the risks involved in the storage of cultures at liquid nitrogen temperatures. These agents provide cryoprotection through multiple mechanisms, involving extracellular and intracellular macromolecular crowding, thereby impacting the biophysical and biochemical dynamics of the freezing medium and the cryopreserved cells. These CPAs vary in their structures and physicochemical properties, which influence their cryoprotective activities. Moreover, the introduction of polymeric crowders in the cryopreservation media enables serum-free storage at low-DMSO concentrations and high-temperature vitrification of frozen cultures (-80 °C). This review highlights the need for macromolecular CPAs and describes their mechanisms of cryopreservation, by elucidating the role of crowding effects. It also classifies the macromolecules based on their chemistry and their structure-activity relationships. Furthermore, this article provides perspectives on the factors that may influence the outcomes of the cell freezing process or may help in designing and evaluating prospective macromolecules. This manuscript also includes case studies about cellular investigations that have been conducted to demonstrate the cryoprotective potential of macromolecular CPAs. Ultimately, this review provides essential directives that will further improve the cell cryopreservation process and may encourage the use of macromolecular CPAs to fortify basic, applied, and translational research.

Peptide Design and Self-assembly into Targeted Nanostructure and Functional Materials

Peptides have been extensively utilized to construct nanomaterials that display targeted structure through hierarchical assembly. The self-assembly of both rationally designed peptides derived from naturally occurring domains in proteins as well as intuitively or computationally designed peptides that form β-sheets and helical secondary structures have been widely successful in constructing nanoscale morphologies with well-defined 1-d, 2-d, and 3-d architectures. In this review, we discuss these successes of peptide self-assembly, especially in the context of designing hierarchical materials. In particular, we emphasize the differences in the level of peptide design as an indicator of complexity within the targeted self-assembled materials and highlight future avenues for scientific and technological advances in this field.

Synthesis of a zwitterionic N-Ser-Ser-C dimethacrylate cross-linker and evaluation in polyampholyte hydrogels

Polyampholyte hydrogels are attractive materials for tissue engineering scaffolds as they offer a wide variety of features including nonfouling, selective protein delivery, and tunable physical characteristics. However, to improve the potential performance of these materials for in vivo applications, there is a need for a higher diversity of zwitterionic cross-linker species to replace commonly used ethylene glycol (EG) based chemistries. Towards this end, the synthesis of a dipeptide based zwitterionic cross-linker, N-Ser-Ser-C dimethacrylate (S-S) from N-Boc-l-serine is presented. The strategy utilized a convergent coupling of methacrylated serine partners followed by careful global deprotection to yield the zwitterionic cross-linker with good overall yields. This novel cross-linker was incorporated into a polyampholyte hydrogel and its physical properties and biocompatibility were compared against a polyampholyte hydrogel synthesized with an EG-based cross-linker. The S-S cross-linked hydrogel demonstrated excellent nonfouling performance, while promoting enhanced cellular adhesion to fibrinogen delivered from the hydrogel. Therefore, the results suggest that the S-S cross-linker will demonstrate superior future performance for in vivo applications.

Development of Nonfouling Zwitterionic Copolymerized Peptides Based on Glutamic Acid and Lysine Dimers for Adjustable Enzymatic Degradation

Nonspecific protein adsorption-resistant materials, the so-called nonfouling materials, are crucial biomaterials in biomedical applications. Up-to-date, little attention was paid to the biodegradability of these materials. In this work, nonfouling zwitterionic copolymerized peptides composed of the N-l-glumatyl-l-lysine dimer (EK) and δ-l-lysinyl-l-glutamic acid dimer (E-K, glutamic acid with the lysine side chain) at various ratios were synthesized to investigate the enzymatic degradation rate. Two types of proteases (trypsin and alkaline protease), which represent a site-specific and less site-specific cleavage protease, respectively, were used to demonstrate the adjustable degradability by tracking the molecular weight (M_w) at different digestion times. Results showed that higher compositions of the E-K dimer lead to slower degradation rates by both proteases and larger fragments after 120 min digestion. With the composition of the E-K dimer over 50%, the degradation of copolymerized peptides by both proteases becomes very slow. This indicated that the bulky lysinyl side chain on E-K can alter the enzymolysis process for adjusting the enzymatic degradability of the newly synthesized zwitterionic copolymerized peptides, which could be promising candidates for biomedical applications in vivo.

Sequence-defined oligoampholytes using hydrolytically stable vinyl sulfonamides: design and UCST behaviour

Water soluble sequence-defined oligoampholytes with precisely positioned charges were synthesised via an iterative solid-phase synthesis protocol using vinyl sulfonamide and acrylate building blocks.

Self-Healable Porous Polyampholyte Hydrogels with Higher Water Content as Cell Culture Scaffolds for Tissue Engineering Applications

In this paper, we first demonstrate the control of the film pore size using neutral hydrophilic 2-hydroxyethyl methacrylate (HEMA) content. To improve the mechanical properties of a polyampholyte (PA), both HEMA and the cross-linker N,N'-methylenebisacrylamide (Bis-Am) were introduced into the PA chain. The predesigned copolymers showed great mechanical properties and optical behavior. The introduction of HEMA significantly increased the water content of the polymer, leading to the formation of porous structures in xerogels. The dynamic interaction between the positive and negative termini of the PA endowed the hydrogels with self-healing ability. The synthesized chemically cross-linked PA gels showed high stability in saline solution. The biocompatibility of the PA gels was confirmed using a cytotoxicity test of cells attached to the synthesized PA-X-2 and PA/HEMA-90/10-X-0.5. The results of this investigation indicate that the synthesized PA gels are applicable as a polymeric scaffold for cell culture.

Enhanced Biocompatibility of Polyampholyte Hydrogels

Tissue-engineered scaffolds encounter many challenges including poor integration with native tissue. Nonspecific protein adsorption can trigger the foreign body response leading to encapsulation and isolation from the native injured tissue. This concern is mitigated with nonfouling polymer scaffolds. This study investigates the long-term biocompatibility of a nonfouling polyampholyte system composed of positively charged [2-(acryloyloxy)ethyl]trimethylammonium chloride monomers and negatively charged 2-carboxyethyl acrylate monomers, cross-linked with triethylene glycol dimethacrylate. This system has previously shown resistance to nonspecific protein adsorption and short-term cell attachment via conjugated proteins. However, longer-term cell survival has not been evaluated with this system. First, the environmental pH was monitored with varying amounts of counter ions present in the hydrogel synthesis buffer. The lowest level (3 M NaOH) and the level that resulted in pH values closest to physiological conditions (6.7 M NaOH) were chosen for further investigation. These two formulations were then compared in terms of their contact angle, qualitative protein adsorption and conjugation capacity, and quantitative cell adhesion, proliferation, and viability. The 3 M NaOH formulation showed higher initial protein conjugation and cell adhesion compared to the 6.7 M NaOH formulation. However, the 3 M NaOH hydrogels had low cell viability after 24 h due to the acidic component release into the culture environment. The 6.7 M NaOH formulation showed a lower initial conjugation and cell adhesion but overcame this limitation by providing a stable environment that maintained cell viability for over 5 days. The 6.7 M NaOH polyampholyte hydrogel formulation shows increased biocompatibility, while maintaining resistance to nonspecific protein adsorption, as demonstrated by the targeted cell adhesion and proliferation. Therefore, this polyampholyte formulation demonstrates strong potential as a tissue-engineered scaffold.

A comprehensive review of the structures and properties of ionic polymeric materials

This review focuses on the mechanistic approach, the structure–property relationship and applications of ionic polymeric materials.

The structure and Hirshfeld surface analysis of the salt 3-methacryl-amido-N,N,N-tri-methyl-propan-1-aminium 2-acryl-amido-2-methyl-propane-1-sulfonate

The title salt, C10H21N2O+·C7H12NO4S-, comprises a 3-methacryl-amido-N,N,N-tri-methyl-propan-1-aminium cation and a 2-acryl-amido-2-methyl-propane-1-sulfonate anion. The salt crystallizes with two unique cation-anion pairs in the asymmetric unit of the ortho-rhom-bic unit cell. The crystal studied was an inversion twin with a 0.52 (4):0.48 (4) domain ratio. In the crystal, the cations and anions stack along the b-axis direction and are linked by an extensive series of N-H⋯O and C-H⋯O hydrogen bonds, forming a three-dimensional network. Hirshfeld surface analysis was carried out on both the asymmetric unit and the two individual salts. The contribution of inter-atomic contacts to the surfaces of the individual cations and anions are also compared.

Structure and Hirshfeld surface analysis of the salt N,N,N-trimethyl-1-(4-vinyl-phen-yl)methanaminium 4-vinyl-benzene-sulfonate

In the title compound, the asymmetric unit comprises an N,N,N-trimethyl-1-(4-vinyl-phen-yl)methanaminium cation and a 4-vinyl-benzene-sulfonate anion, C12H18N+·C8H7O3S-. The salt has a polymerizable vinyl group attached to both the cation and the anion. The methanaminium and vinyl substituents on the benzene ring of the cation subtend angles of 86.6 (3) and 10.5 (9)° to the ring plane, while the anion is planar excluding the sulfonate O atoms. The vinyl substituent on the benzene ring of the cation is disordered over two sites with a refined occupancy ratio of 0.542 (11):0.458 (11). In the crystal, C-H⋯O hydrogen bonds dominate the packing and combine with a C-H⋯π(ring) contact to stack the cations and anions along the a-axis direction. Hirshfeld surface analysis of the salt and of the individual cation and anion components is also reported.

Reversible Addition?Fragmentation Chain-Transfer Polymerization of Amphiphilic Polycarboxybetaines and Their Molecular Interactions

In this work, we report the first molecular weight-controlled amphiphilic polybetaine synthesis using various hydrocarbons via reversible addition?fragmentation chain-transfer (RAFT) polymerization. The experimental separation of the alkyl aminocrotonate tautomers, which has been the subject of debate, was completed for the first time. The enamine form of these tautomers was further used as a monomer for the RAFT polymerization of amphiphilic polycarboxybetaines. Self-assembly of the amphiphilic polycarboxybetaines showed micelle structures from spherical, rod-like to fractal in the aqueous media due to the competition between both electrostatic and hydrophobic forces. Hydrophobically dominant interactions among amphiphilic polycarboxybetaines and long-chain hydrocarbon alkane molecules were investigated to understand long-chain hydrocarbon alkane crystallization using alkane crystal deposition and viscosity experiments. Strong hydrophobic forces between poly(hexadecyl-grafted aminocrotonate?methacrylic acid) and long-chain hydrocarbon alkane molecules changed the surface properties of the long-chain hydrocarbon alkane nucleus and inhibited the growth of paraffin crystals.

Physicochemical, Complexation and Catalytic Properties of Polyampholyte Cryogels

Polyampholyte cryogels are a less considered subject in comparison with cryogels based on nonionic, anionic and cationic precursors. This review is devoted to physicochemical behavior, complexation ability and catalytic properties of cryogels based on amphoteric macromolecules. Polyampholyte cryogels are able to exhibit the stimuli-responsive behavior and change the structure and morphology in response to temperature, pH of the medium, ionic strength and water–organic solvents. Moreover, they can uptake transition metal ions, anionic and cationic dyes, ionic surfactants, polyelectrolytes, proteins, and enzymes through formation of coordination bonds, hydrogen bonds, and electrostatic forces. The catalytic properties of polyampholyte cryogels themselves and with immobilized metal nanoparticles suspended are outlined following hydrolysis, transesterification, hydrogenation and oxidation reactions of various substrates. Application of polyampholyte cryogels as a protein-imprinted matrix for separation and purification of biomacromolecules and for sustained release of proteins is demonstrated. Comparative analysis of the behavior of polyampholyte cryogels with nonionic, anionic and cationic precursors is given together with concluding remarks.

Hydrophobic Polyampholytes and Nonfreezing Cold Temperature Stimulate Internalization of Au Nanoparticles to Zwitterionic Liposomes

Nanomedicine relies on the effective internalization of nanoparticles combined with polymeric nanocarriers into living cells. Thus, exploration of internalization is essential for improving the efficacy of nanoparticle-based strategies in clinical practice. Here, we investigated the physicochemical internalization of gold nanoparticles (AuNPs) conjugated with hydrophobic polyampholytes into cell-sized liposomes at a low but nonfrozen temperature. The hydrophobic polyampholytes localized in the disordered phase of the membrane, and internalization of AuNPs was enhanced in the presence of hydrophobic polyampholytes together with incubation at -3 °C as compared to 25 °C. These results contribute toward a mechanistic understanding for developing a model nanomaterials-driven delivery system based on hydrophobic polyampholytes and low temperature.

Synthetic Polyampholytes as Macromolecular Cryoprotective Agents

A series of polyampholytes based on different molar ratios on N, N-dimethylaminopropyl methacrylamide (DMAPMA), acrylic acid (AA), and optionally, N- tert-butylacrylamide ( t-BuAAm), were prepared by free radical copolymerization, and tested as DMSO-free cryoprotective agents for 3T3 fibroblast cells by using a standard freeze-rethaw protocol. Polybetaines prepared by reaction of DMAPMA homo and copolymers with 1,3-propane sultone were used as additional controls. Results showed strong effects of copolymer composition, molecular weight, polymer and NaCl concentrations, on post-thaw cell viability. Binary (DMAPMA/AA) copolymers showed best post-thaw cell viability of 70% at a 30/70 mol % ratio of DMAPMA/AA, which increased to 90% upon introduction of 9 mol % t-BuAAm while maintaining the 30/70 mol % cation/anion ratio. The use of acrylamide linkages in DMAPMA ensures absence of hydrolytic loss of cationic side chains. These polyampholytes were found to decrease ice crystal size and to form a polymer-rich, ice-free layer around cells, reducing damage from intercellular ice crystals during both freezing and thawing steps. These polyampholytes also dehydrate cells during freezing, which helps protect cells from intracellular ice damage. While cell viability immediately after thawing was high, subsequent culturing revealed poor attachment and long-term viability, which is attributed to residual cell damage from intracellular ice formation. Addition of 2 wt % DMSO or 1% BSA to the polymer-based freeze medium was found to mitigate this damage and result in post-thaw viabilities matching those achieved with 10 wt % DMSO.

Hydrophobically Modified Polycarboxybetaine: From Living Radical Polymerization to Self-Assembly

Polybetaines have received widespread attention due to their smart response properties and structures which resemble biological polymers like peptides and DNA. However, few studies have focused on the controlled synthesis and self-assembly of hydrophobically modified polybetaines due to the difficulty of synthesizing these materials. We report the first molecular weight-controlled synthesis of hydrophobically modified polycarboxybetaines (HMPCB). Poly(dodecyl grafted aminocrotonate -methacrylic acid) (P(DACRO-MAA)) was synthesized via the reversible addition-fragmentation chain-transfer (RAFT) polymerization approach. The two different tautomers of the monomer were also successfully identified and separated via thin layer chromatography (TLC) and column chromatography, making it possible to obtain pure polycarboxybetaine via RAFT synthesis. Both the successfully separated enamine form of the monomer and the resulting polycarboxybetaine were confirmed via FTIR and NMR. The polycarboxybetaine was found to have a low polydispersity (PDI) of 1.214, and its molecular weight was determined as 70590 g/mol via gel permeation chromatography (GPC) measurements. Spherical, rodlike, and fractal assembled structures for the P(DACRO-MAA) were observed with pH change using TEM, zeta sizer, and dynamic light scattering (DLS). The unique self-assembled structures of HMPCB synthesized via RAFT provide an opportunity to understand fundamental polymer science and can be engineered for broad applications.

RAFT copolymerization of oppositely charged monomers and its use to tailor the composition of nonfouling polyampholytes with an UCST behaviour

The RAFT copolymerization of oppositely-charged monomers is studied to optimize the composition of polyampholytes with an UCST behaviour and nonfouling properties.

Amino acid-derived alternating polyampholyte luminogens

A unique polyampholyte luminogen comprised of alternatively placed oppositely charged moieties onto the poly(styrene-alt-maleimide) skeleton was synthesized, and used for the specific detection of carbon disulfide (CS₂) in both solution and vapor phases.

Polyampholytic graft copolymers based on polydehydroalanine (PDha) – synthesis, solution behavior and application as dispersants for carbon nanotubes

We herein introduce a versatile platform of graft copolymers featuring a polyampholytic backbone and side chains of varying length and polarity using post-polymerization modification of polydehydroalanine (PDha).

Synthesis of Diblock Polyampholyte PAMPS-b-PMAPTAC and Its Adsorption on Bentonite

To study the adsorption of polyampholyte on bentonite (Bent), a block polyampholyte, PAMPS-b-PMAPTAC, comprised of 2-Acrylamido-2-Methylpropane Sulfonic Acid (AMPS) units and Methacrylamido Propyl Trimethyl Ammonium Chloride (MAPTAC) units, was synthesized using reversible addition-fragmentation chain transfer polymerization (RAFT) method. The block polyampholyte samples were characterized by FTIR, ¹H NMR and Gel Permeation Chromatography (GPC). The microstructure of block polyampholyte and random polyampholyte in deionized water indicated that uneven distribution of charged groups increased the entanglement of polymer chains. Addition of salt weakened the electrostatic interactions among charged groups, and, therefore, increased the zeta potential of polyampholyte in aqueous solutions. The adsorptive behaviors of PAMPS-b-PMAPTAC on Bent were studied using elemental analysis, and the effects of external factors were considered. The adsorption equilibrium of polymers on Bent was reached after 12 h. Increased temperature and increased salinity exerted a positive and negative effect on the adsorption of polyampholyte, respectively. The molecular weight played as the decisive factor for the adsorption of polyampholyte in the absence of NaCl, while the content of cationic groups acted as the main factor in the presence of NaCl. Block polyampholyte exhibited higher adsorption than random polyampholyte in the absence of salt. XRD results also indicated that block polyampholyte had a better intercalation effect than random polyampholyte.

Intra- and Interpolyelectrolyte Complexes of Polyampholytes

At present, a large amount of research from experimental and theoretical points of view has been done on interpolyelectrolyte complexes formed by electrostatic attractive forces and/or interpolymer complexes stabilized by hydrogen bonds. By contrast, relatively less attention has been given to polymer⁻polymer complex formation with synthetic polyampholytes (PA). In this review the complexation of polyampholytes with polyelectrolytes (PE) is considered from theoretical and application points of view. Formation of intra- and interpolyelectrolyte complexes of random, regular, block, dendritic polyampholytes are outlined. A separate subsection is devoted to amphoteric behavior of interpolyelectrolyte complexes. The realization of the so-called "isoelectric effect" for interpolyelectrolyte complexes of water-soluble polyampholytes, amphoteric hydrogels and cryogels with respect to surfactants, dye molecules, polyelectrolytes and proteins is demonstrated.

Polyampholyte Hydrogels in Biomedical Applications

Polyampholytes are a class of polymers made up of positively and negatively charged monomer subunits. Polyampholytes offer a unique tunable set of properties driven by the interactions between the charged monomer subunits. Some tunable properties of polyampholytes include mechanical properties, nonfouling characteristics, swelling due to changes in pH or salt concentration, and drug delivery capability. These characteristics lend themselves to multiple biomedical applications, and this review paper will summarize applications of polyampholyte polymers demonstrated over the last five years in tissue engineering, cryopreservation and drug delivery.

pH Responsiveness of hydrogels formed by telechelic polyampholytes

We investigate the influence of pH on the rheological and structural properties of hydrogels formed by hydrophobic association of the sticky ends of the triblock terpolymer poly(methyl methacrylate)-b-poly(2-(diethylamino)ethyl methacrylate-co-methacrylic acid)-b-poly(methyl methacrylate) (PMMA-b-P(DEA-co-MAA)-b-PMMA). The middle block is a weak polyampholyte having a pH dependent charge density and sign, which enables tuning of the rheological and structural properties by pH variation. Small-angle neutron scattering (SANS) studies of solutions in D₂O at 0.05 wt% and pH 3.0 reveal clusters of interconnected spherical micelles having PMMA cores, stabilized by repulsive ionic interactions in the middle polyampholyte block. With increasing pH, the degree of ionization of the DEA units decreases, whereas the one of the MAA units increases, resulting in a complete loss of the correlation between these micelles. At a concentration of 3 wt% at low pH values, the system forms a gel with charged fuzzy spheres from PMMA interacting via a screened Coulomb potential. With increasing pH, the gel disintegrates due to the decrease in the effective charge on the micelles. At both concentrations, the hydrophobic aggregation of micelles is observed near the isoelectric point. At pH 3.0-7.4, the autocorrelation functions measured by rotational dynamic light scattering at 3 wt% exhibit a decay steeper than single exponential, which confirms that the gels are frozen, presumably due to the glassy PMMA cores and hydrophobic interpolyelectrolyte complexes. At pH 11, the diffusion of single micelles is observed in addition to the frozen dynamics.

Precisely Alternating Functionalized Polyampholytes Prepared in a Single Pot from Sustainable Thiolactone Building Blocks

Polyampholytes with precisely alternating cationic and anionic functional groups were prepared using sustainable thiolactone building blocks in a simple one-pot procedure at room temperature and in water. Ring opening of the N-maleamic acid-functionalized homocysteine thiolactone monomer enabled the introduction of different functional groups into the polymer chain, which contributed to both ionic and hydrogen bonding interactions. The resulting polyampholytes exhibited various isoelectric points while maintaining high solubility in water under different pH and ionic strengths, which expands their potential applications. Finally, it is shown that the upper critical solution temperature (UCST) of these alternating polyampholytes in water/ethanol (30/70% vol) solutions can be tuned as a function of the content of ionic and hydroxyl groups.

Design of a C-b-(A-co-B)-b-C telechelic polyampholyte pH-responsive gelator

We report the synthesis and the pH dependent structural and rheological properties of a telechelic polyampholyte associative polymer, composed of a random polyampholyte central block, end-capped by shorter hydrophobic blocks [C-b-(A-co-B)-b-C block/random terpolymer type].

Preparation and study of multi-responsive polyampholyte copolymers of N-(3-aminopropyl)methacrylamide hydrochloride and acrylic acid

Multi-responsive polyampholytes show LCST and UCST behaviour at different pH values, based on electrostatic and hydrogen bonding interactions.

Characterizing Drug Release from Nonfouling Polyampholyte Hydrogels

Controlled delivery of bioactive signaling molecules and drugs is essential for the development of the next generation of tissue regeneration scaffolds. However, these molecules must be delivered from a nonfouling platform, so that the therapeutic role is not masked by the naturally occurring foreign body response. Therefore, the purpose of this study is to characterize the release profiles of three pseudodrug molecules from a nonfouling polyampholyte hydrogel to gain insight into the potential for this platform to serve as a tissue regeneration scaffold. Hydrogels composed of equimolar concentrations of [2-(acryloyloxy)ethyl] trimethylammonium chloride (TMA) and 2-carboxyethyl acrylate (CAA) monomers were synthesized in the presence of caffeine, methylene blue, or metanil yellow. Then the release of these three molecules was tracked as a function of the hydrogel cross-linker density, the solution pH, and the solution ionic strength. The results suggest that the release of the neutral caffeine molecule is dictated by diffusion alone, while the release of the two charged pseudodrug molecules are controlled by their interactions with the charged regions of the TMA and CAA monomer subunits. These interactions are clearly impacted by solution pH and ionic strength leading to clear changes in the rate of release and extent of release for metanil yellow and methylene blue. Additionally, an enzyme-linked immunosorbent assay was used to confirm that the TMA:CAA hydrogels retain their nonfouling characteristics following the release of the pseudodrug molecules. When these results are combined with the literature related to TMA:CAA hydrogels, it is concluded that this system represents a promising multifunctional platform for both short-term and long-term delivery of bioactive molecules for tissue regeneration.