Water structure and improved mechanical properties of phospholipid polymer hydrogel with phosphorylcholine centered intermolecular cross-linker

Mechanistically Different Mechanochromophores Enable Calibration and Validation of Molecular Forces in Glassy Polymers and Elastomeric Networks

Sterically distorted donor-acceptor π-systems, termed DA springs, can be progressively planarized under mechanical load causing a bathochromic shift of the photoluminescence (PL) spectrum. By combining theory and experiment, we here use a simple linear force calibration for two different conformational mechanochromophores to determine molecular forces in polymers from the mechanochromic shift in PL wavelength during multiple uniaxial tensile tests. Two systems are used, i) a highly entangled linear glassy polyphenylene and ii) a covalent elastomeric polydimethylsiloxane network. The mean forces estimated by this method are validated using known threshold forces for the mechanochemical ring-opening reactions of two different spiropyran force probes. The agreement between both approaches underlines that these DA springs provide the unique opportunity for the online monitoring of local molecular forces present in diverse polymer matrices.

Recent progress and perspectives in applications of 2-methacryloyloxyethyl phosphorylcholine polymers in biodevices at small scales

Bioinspired materials have attracted attention in a wide range of fields. Among these materials, a polymer family containing 2-methacryloyloxyethyl phosphorylcholine (MPC), which has a zwitterionic phosphorylcholine headgroup inspired by the...

Effects of mixing, sheeting, and cooking on the starch, protein, and water structures of durum wheat semolina and chickpea flour pasta

The influence of the pasta preparation stages on starch, proteins, and water structures of semolina and chickpea pasta was studied. The hydrated starch structures (995/1022 FTIR ratio) increased in semolina and reduced in chickpea pasta. The processing stages in semolina pasta led to a significant increase of β-sheet structures (~50% to ~68%). The β-sheet structures content in chickpea pasta was lower (~52%), and was most affected by sheeting and cooking. The water structure was assessed by the analysis of the OH fingerprint FTIR region (3700-2800 cm^-1) and showing that water molecules (~90%) are strongly and moderately bound. The chickpea pasta displayed the highest content of strongly bonded water (about 55%) in contrast to the semolina pasta (~48%). A principal component analysis showed that the molecular organization of semolina pasta was mostly affected by dough formation and cooking; the molecular organization of chickpea pasta was determined by the cooking stage.

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.

Controlled release of antibiotics from photopolymerized hydrogels: Kinetics and microbiological studies

The development of convenient synthetic methods and improved materials for the production of high load-capacity and biocompatible drug delivery systems is a challenging task with important implications in health sciences. In this work, acrylamide/2-hydroxyethylmethacrylate and N-isopropylacrylamide/2-hydroxyethylmethacrylate hydrogels were synthesized by photopolymerization using energy-efficient green-LEDs. A functionalized silsesquioxane was used as both crosslinker and co-initiator for the photopolymerization. The hybrid organic-inorganic nature of the silsesquioxane improved the resulting hydrogels' properties increasing their swelling capacity and biocompatibility. Additionally, the mild conditions used during the photopolymerization allowed the synthesis of hydrogels in the presence of antibiotics yielding high load-capacity materials in which the drug preserves its molecular structure and antimicrobial activity (as confirmed by HPLC and microbiological assays). The materials were characterized by FTIR, DSC and SEM. Additionally, the kinetics of gels´ swelling and drug release were studied under physiological conditions (pH 7.4 and 37 °C). The results demonstrate how hydrogel composition affects the antibiotics-release kinetics. The final drug release percentage increased with increasing molar fraction of acrylamide or N-isopropylacrylamide and in most cases exceeded 85%. Finally, the antibacterial effect of loaded gels was characterized using a number of assays against Gram negative and Gram positive bacteria. The observed antibacterial effect correlated well with swelling and drug release results. Furthermore, gels are not toxic for isolated erythrocytes as demonstrated by haemolytic tests. Overall, our results indicate that the produced hydrogels are promising materials to develop controlled drug-delivery devices such as capsules, dermatological patches and others.

Sulfobetaines Meet Carboxybetaines: Modulation of Thermo- and Ion-Responsivity, Water Structure, Mechanical Properties, and Cell Adhesion

A procedure for the preparation of copolymers bearing sulfobetaine and carboxybetaine methacrylic-based monomers by free-radical polymerization is described and discussed. A combination of monomers affects the upper critical solution temperature (UCST) in water and in the presence of a simple NaCl electrolyte while retaining the zwitterionic character. In addition, hydrogel samples were prepared and showed tunable water structure and mechanical properties. The total nonfreezable water content decreases with the amount of carboxybetaine segment in the hydrogel feed and the compression moduli were in a range of 0.7-1.6 MPa. Responses to external conditions such as temperature and ion strength were investigated and a potential application such as modulated thermal detection is proposed. The presence of the carboxylate group in the carboxybetaine segment enables a small fluorescence probe and peptide bearing RDG motif to be attached to polymer and hydrogel samples, respectively. The hydrogel samples functionalized with the RGD motif exhibit controlled cell adhesion. Such synthetic strategy based on combination of different zwitterionic segments offers a simple pathway for the development of zwitterionic materials with programmable properties.

Molecularly Imprinted Nanocavities Capable of Ligand-Binding Domain and Size/Shape Recognition for Selective Discrimination of Vascular Endothelial Growth Factor Isoforms

Vascular endothelial growth factor 165 (VEGF165) is known to be predominantly expressed in the first stage of vascularization; therefore, the detection of VEGF165 is important in the stage diagnosis of cancers. Molecularly imprinted nanocavities, capable of the selective discrimination of VEGF165 from other VEGF isoforms, were prepared by surface-initiated atom transfer radical polymerization. VEGF165 was immobilized on a gold-coated glass substrate by anchored heparin moieties, where the immobilized heparin was able to capture VEGF165 by binding with the heparin-binding domain (HBD) on VEGF165. Molecular imprinting was conducted on the immobilized VEGF165 by using methacrylic acid (MAA) as a functional monomer to interact with basic amino acids outside of the HBD of VEGF165 by electrostatic interaction. After the removal of VEGF165 from the obtained polymer thin layer (ca. 7 nm), VEGF165-imprinted nanocavities remained, in which the heparin moiety and MAA residues were located in suitable positions for VEGF165 recognition. The molecularly imprinted polymer (MIP) thin layer showed a binding affinity for VEGF165 (dissociation constant: 3.4 nM) that was ten times higher than that of the substrate before polymerization (heparin-immobilized substrate). A much lower binding affinity for VEGF121, which contains no heparin-binding domain, was observed. Moreover, the MIP thin layer distinguished VEGF165 from VEGF189, which possesses a larger molecular size than VEGF165, an amino acid sequence homology of 87%, and contains HBDs, whereas the heparin-immobilized substrate showed almost no selectivity. These results suggested that the heparin moiety within the nanocavity provided HBD selectivity and the polymer matrix composed of the molecularly imprinted nanocavity provided size/shape selectivity, which resulted in the highly selective discrimination of VEGF isoforms.

Surface zwitterionization on versatile hydrophobic interfaces via a combined copolymerization/self-assembling process

A special surface modification for coating amphiphilic zwitterionic polymers in a single step for antifouling applications in complex media.

Epoxylated Zwitterionic Triblock Copolymers Grafted onto Metallic Surfaces for General Biofouling Mitigation

Titanium and stainless steel materials are widely used in numerous devices or in custom parts for their excellent mechanical properties. However, their lack of biocompatibility seriously limits their usage in the biomedical field. This study focuses on the grafting of triblock copolymers on titanium and stainless steel metal susbtrates for improving their general biofouling resistance. The series of copolymers that we designed is composed of two blocks of zwitterionic sulfobetaine (SBMA) monomers and one block of glycidyl methacrylate (GMA). The number of repeat units forming each block, n, was finely tuned and controlled to 25, 50, 75, or 100, permitting regulation of the grafting thickness, the morphology, and the dependent properties such as the surface hydrophilicity and biofouling resistance. It was shown that the copolymer possessing n = 50 repeat units in each block, corresponding to a molecular weight of about 15.2 kDa, led to the best nonfouling properties, assessed using plasma proteins, blood cells, fibroblasts cells, and various bacteria. This was explained by an optimized grafting degree and chain organization of the copolymer. Lower value (n = 25) and higher values (n = 75, 100) led to low surface coverage and the formation of aggregates, respectively. The best copolymer was grafted onto scalpels (steel) and dental roots (titanium), and antifouling properties demonstrated using Escherichia coli and HT1080 cells. Results of this work show that this unique triblock copolymer holds promise as a potential material for surface modification of biomedical metallic devices, provided a fine-tuning of the blocks organization and length.

Zwitterionic surface grafting of epoxylated sulfobetaine copolymers for the development of stealth biomaterial interfaces

Most biomaterials have a lack of a simple, efficient and robust antifouling modification approach that limits their potential for biomedical applications. The challenge is to develop a universal surface grafting solution to meet the antifouling requirement. In this work, a new formulation of zwitterionic sulfobetaine-based copolymer, ploy(glycidyl methacrylate-co-sulfobetaine methacrylate) (poly(GMA-co-SBMA)), is designed as a chemical for grafting onto material and is introduced for the surface zwitterionization of versatile biomaterials, including ceramic, metal, and plastics. The grafting principle used to stabilize the poly(GMA-co-SBMA) on the target surfaces is based the base-induced ring opening reaction between epoxied and hydroxyl groups. A universal surface modification procedure was developed and performed from an optimized sequence of ultra-violet ozone pretreatment and trimethylamine-catalyzed zwitterionization on a selective case of versatile surfaces including silicon wafer, ceramic glass, titanium, steel, and polystyrene. The prepared poly(GMA-co-SBMA) with an optimum PGMA/PSBMA ratio of 0.23 and a molecular weight of 25kDa exhibited the best resistance to fibrinogen adsorption with over 90% reduction as well as blood cell activation, tissue cell adhesion and bacterial attachment on the zwitterionic copolymer grafted surfaces. The developed antifouling grafting introduces a universal modification method to generate zwitterionic interfaces on versatile biomaterial substrates, providing great potential for application in medical device coating.

STATEMENT OF SIGNIFICANCE

A simple, efficient and robust antifouling modification approach is critical for many scientific interests and industrial applications. In current stage, the existing available zwitterionic modifications suffer from the lack of universal surface grafting solution to achieve the antifouling requirement on versatile biomaterial substrates. In this study, we synthesized and characterized a new zwitterionic sulfobetaine-based copolymer, ploy(glycidyl methacrylate-co-sulfobetaine methacrylate) (poly(GMA-co-SBMA)), which is designed as chemical grafting onto material and introduced for the surface zwitterionization of versatile biomaterials, including ceramic, metal, and plastics. This research have a promising opportunity for the application of stealth biomaterial interfaces on the next generation of medical devices.

Underwater Superoleophobic Surfaces Prepared from Polymer Zwitterion/Dopamine Composite Coatings

Hydration is central to mitigating surface fouling by oil and microorganisms. Immobilization of hydrophilic polymers on surfaces promotes retention of water and a reduction of direct interactions with potential foulants. While conventional surface modification techniques are surface-specific, mussel-inspired adhesives based on dopamine effectively coat many types of surfaces and thus hold potential as a universal solution to surface modification. Here, we describe a facile, one-step surface modification strategy that affords hydrophilic, and underwater superoleophobic, coatings by the simultaneous deposition of polydopamine (PDA) with poly(methacryloyloxyethyl phosphorylcholine) (polyMPC). The resultant composite coating features enhanced hydrophilicity (i.e., water contact angle of ~10° in air) and antifouling performance relative to PDA coatings. PolyMPC affords control over coating thickness and surface roughness, and results in a nearly 10 fold reduction in Escherichia coli adhesion relative to unmodified glass. The substrate-independent nature of PDA coatings further promotes facile surface modification without tedious surface pretreatment, and offers a robust template for codepositing polyMPC to enhance biocompatibility, hydrophilicity and fouling resistance.

Zwitterionic nanocomposite hydrogels as effective wound dressings

Zwitterionic poly(sulfobetaine acrylamide) (pSBAA) nanocomposite hydrogels were synthesized and implemented as effective chronic wound dressings.

Iron Oxide Nanoparticles Grafted with Sulfonated and Zwitterionic Polymers: High Stability and Low Adsorption in Extreme Aqueous Environments

A facile "grafting through" approach was developed to tether tunable quantities of poly(2-acrylamido-2-methylpropanesulfonic acid) (PAMPS) as well as zwitterionic poly([3-(methacryloylamino)propyl]dimethyl(3-sulfopropyl)ammonium hydroxide) (PMPDSA) homopolymer onto iron oxide (IO) nanoparticles (NPs). In this case, homopolymers may be grafted, unlike "grafting to" approaches that often require copolymers containing anchor groups. The polymer coating provided steric stabilization of the NP dispersions at high salinities and elevated temperature (90 °C) and almost completely prevented adsorption of the NPs on silica microparticles and crushed Berea sandstone. The adsorption of PAMPS IO NPs decreased with the polymer loading, whereby the magnitude of the particle-surface electrosteric repulsion increased. The zwitterionic PMPDSA IO NPs displayed 1 order of magnitude less adsorption onto crushed Berea sandstone relative to the anionic PAMPS IO NPs. The ability to design homopolymer coatings on nanoparticle surfaces by the "grafting through" technique is of broad interest for designing stable dispersions and modulating the interactions between nanoparticles and solid surfaces.