Self-association and microenvironment of random amphiphilic copolymers of sodium N-acryloyl-l-valinate and N-dodecylacrylamide in aqueous solution

Conformational Changes of Poly(Maleic Anhydride-alt-styrene) Modified with Amino Acids in an Aqueous Medium and Their Effect on Cytocompatibility and Hemolytic Response

The conformational changes of poly(maleic anhydride-alt-styrene) (PSMA) modified with different amino acids (PSMA-Aa) were studied in an aqueous medium as a function of ionic strength and pH. The specific viscosity of PSMA-Aa decreased with increasing salt concentration due to a more compact conformation. There was a decrease in surface tension with increasing concentrations of the modified polyelectrolyte having a greater effect for the PSMA modified with l-phenylalanine at pH 7.0, demonstrating a greater surface-active character. The conformational changes were also confirmed by molecular dynamics studies, indicating that PSMA-Aa exhibits a compact structure at pH 4.0 and a more extended structure at pH 7.0. On the other hand, the conformational changes of PSMA-Aa were related to its biological response, where the higher surface-active character of the PSMA modified with l-phenylalanine correlates very well with the higher hemolytic activity observed in red blood cells, in which the surface-active capacity supports lytic potency in erythrocytes. The cytocompatibility assays indicated that there were no significant cytotoxic effects of the PSMA-Aa. Additionally, in solvent-accessible surface area studies, it was shown that the carboxylate groups of the PSMA modified with l-phenylalanine are more exposed to the solvent at pH 7.0 and high salt concentrations, which correlates with lower fluorescence intensity, reflecting a loss of mitochondrial membrane potential. It is concluded that the study of the conformational changes in PE modified with amino acids is essential for their use as biomaterials and relevant to understanding the possible effects of PE modified with amino acids in biological systems.

Aqueous solution behaviour of novel water-soluble amphiphilic copolymers with elevated hydrophobic unit content

The synthesis and aqueous solution behaviour of water-soluble copolymers poly(OEGMA-stat-styrene)-b-PDMAPMA with a relatively high content of styrene units were explored.

Preparation, characterization, and biocompatibility evaluation of poly(Nɛ-acryloyl-L-lysine)/hyaluronic acid interpenetrating network hydrogels

In the present study, poly(Nɛ-acryloyl-L-lysine)/hyaluronic acid (pLysAAm/HA) interpenetrating network (IPN) hydrogels were successfully fabricated through the combination of hydrazone bond crosslinking and photo-crosslinking reactions. The HA hydrogel network was first synthesized from 3,3'-dithiodipropionate hydrazide-modified HA and polyethylene glycol dilevulinate by hydrazone bond crosslinking. The pLysAAm hydrogel network was prepared from Nɛ-acryloyl-L-lysine and N,N'-bis(acryloyl)-(L)-cystine by photo-crosslinking. The resultant pLysAAm/HA hydrogels had a good shape recovery property after loading and unloading for 1.5 cycles (up to 90%) and displayed a highly porous microstructure. Their compressive moduli were at least 5 times higher than that of HA hydrogels. The pLysAAm/HA hydrogels had an equilibrium swelling ratio of up to 37.9 and displayed a glutathione-responsive degradation behavior. The results from in vitro biocompatibility evaluation with pre-osteoblasts MC3T3-E1 cells revealed that the pLysAAm/HA hydrogels could support cell viability and proliferation. Hematoxylin and eosin staining indicated that the pLysAAm/HA hydrogels allowed cell and tissue infiltration, confirming their good in vivo biocompatibility. Therefore, the novel pLysAAm/HA IPN hydrogels have great potential for bone tissue engineering applications.

Structure and Properties of Lignosulfonate with Different Molecular Weight Isolated by Gel Column Chromatography

The characteristics of structural and properties of four sodium lignosulfonate (LS) fractions with narrow molecular weight (Mw) distribution isolated by gel column chromatography were investigated with infrared spectroscopy, elemental analysis, 13C NMR analysis, fluorescence spectroscopy and thermogravimetric analysis. LS with higher Mw possesses more aryl ring structural units and the side-chain of the structural unit is mostly composed of propanol rather than propane. With the increase of Mw of LS, the contents of sulfonic group and methoxy group decrease. The critical aggregation concentration (CAC) of LS aqueous solution was determined by fluorescence spectroscopy, which shows that the CAC of LS with higher Mw is lower, indicating that the LS molecule with low Mw is easier to aggregate. TGA results indicate that the weight loss of LS tends to be slow and the thermal stability enhances with the increase in Mw. The dispersive effect of LS with different Mw to dimethomorph suspension shows that the sediment layer thickness and index of dispersity and stability both decease with increasing Mw of LS, which indicates that LS with higher Mw has a better dispersion performance.

Non-surface activity and micellization behavior of cationic amphiphilic block copolymer synthesized by reversible addition-fragmentation chain transfer process

Cationic amphiphilic diblock copolymers of poly(n-butylacrylate)-b-poly(3-(methacryloylamino)propyl)trimethylammonium chloride) (PBA-b-PMAPTAC) with various hydrophobic and hydrophilic chain lengths were synthesized by a reversible addition-fragmentation chain transfer (RAFT) process. Their molecular characteristics such as surface activity/nonactivity were investigated by surface tension measurements and foam formation observation. Their micelle formation behavior and micelle structure were investigated by fluorescence probe technique, static and dynamic light scattering (SLS and DLS), etc., as a function of hydrophilic and hydrophobic chain lengths. The block copolymers were found to be non-surface active because the surface tension of the aqueous solutions did not change with increasing polymer concentration. Critical micelle concentration (cmc) of the polymers could be determined by fluorescence and SLS measurements, which means that these polymers form micelles in bulk solution, although they were non-surface active. Above the cmc, the large blue shift of the emission maximum of N-phenyl-1-naphthylamine (NPN) probe and the low micropolarity value of the pyrene probe in polymer solution indicate the core of the micelle is nonpolar in nature. Also, the high value of the relative intensity of the NPN probe and the fluorescence anisotropy of the 1,6-diphenyl-1,3,5-hexatriene (DPH) probe indicated that the core of the micelle is highly viscous in nature. DLS was used to measure the average hydrodynamic radii and size distribution of the copolymer micelles. The copolymer with the longest PBA block had the poorest water solubility and consequently formed micelles with larger size while having a lower cmc. The "non-surface activity" was confirmed for cationic amphiphilic diblock copolymers in addition to anionic ones studied previously, indicating the universality of non-surface activity nature.

Nanostructure formation in aqueous solution of amphiphilic copolymers of 2-(N,N-dimethylaminoethyl)methacrylate and alkylacrylate: Characterization, antimicrobial activity, DNA binding, and cytotoxicity studies

Three amphiphilic random copolymers poly(2-(dimethylaminoethyl)methacrylate-co-alkylacrylate) (where, alkyl = hexyl, octyl, dodecyl) with 16 mol% hydrophobic substitution were synthesized. Surface tension, viscosity, fluorescence probe, dynamic light scattering (DLS), as well as transmission electron microscopic (TEM) techniques were utilized to investigate self-assembly formation by the hydrophobically modified polymers (HMPs) in pH 5. Formation of hydrophobic domains through inter-polymer chain interaction of the copolymer in dilute solution was confirmed by fluorescence probe studies. Average hydrodynamic diameter of the copolymer aggregates at different polymer concentration was measured by DLS studies. The copolymer with shorter hydrophobic chain exhibits larger hydrodynamic diameter in dilute solution, which decreased with either increase of concentration or increase of hydrophobic chain length. TEM images of the dilute solutions of the copolymers with shorter as well as with longer hydrophobic chain exhibit spherical aggregates of different sizes. The antimicrobial activity of the copolymers was evaluated by measuring the minimum inhibitory concentration value against one Gram-positive bacterium Bacillus subtilis and one Gram-negative bacterium Escherichia coli. The copolymer with the octyl group as pendent hydrophobic chain was found to be more effective in killing these microorganisms. The interaction of the cationic copolymers with calf-thymus DNA was studied by fluorescence quenching method. The polymer-DNA binding was found to be purely electrostatic in nature. The hydrophobes on the polymer backbone were found to have a significant influence on the binding process. Biocompatibility studies of the copolymers in terms of cytotoxicity measurements were finally performed at different concentrations of the HMPs to evaluate their potential application in biomedical fields.