Search results for "Biomaterials"

New Perspectives of HPMA-based Copolymers Derived by Post-Polymerization Modification

2014

Poly[N-(2-hydroxypropyl) methacrylamide] (HPMA) was one of the first polymers applied as polymer drug conjugate in the clinics. Since then many attempts have been made to expand the functionality of HPMA-based copolymers from advanced synthetic pathways to multiple biomedical applications. This Feature Article highlights multifunctional HPMA based copolymers prepared by controlled radical polymerization and subsequent post-polymerization modification of activated ester precursor polymers via aminolysis. This approach combines precise control of the polymer's microstructure (molecular weight, dispersity, block copolymer formation, end group functionalization) with an easy introduction of var…

pH-sensitive hydrogel based on a novel photocross-linkable copolymer.

2004

A pH sensitive hydrogel has been prepared by a UV irradiation technique. Starting polymer was the PHM (poly hydroxyethylaspartamide methacrylated) obtained from polyaspartamide (PHEA) partially derivatized with methacrylic anhydride (MA). This new copolymer has been further derivatized with succinic anhydride (SA) to obtain PHM-SA that has been cross-linked by UV irradiation to form a pH sensitive hydrogel. The network, recovered after washing as a powder, has been been characterized by FT-IR spectrophotometry and particle size distribution analysis. Moreover, to have information about water affinity of the prepared sample, swelling measurements have been carried out in aqueous media mimick…

Time-Resolved study of network self-organization from a biopolymeric solution

1991

Time-resolved studies of network self-organization from homogeneous solutions of the representative biostructural polymer agarose are presented. Solutions are temperature quenched and observed by several techniques. Consistent with previous suggestions by the authors, experiments at concentrations up to about 1.75% w/v provide direct kinetic evidence for the occurrence of at least two distinct processes, leading, in sequence, to self-assembly. These are as follows: (a) a liquid–liquid phase separation of the solution occurring via spinodal demixing and resulting in two sets of regions that have, respectively, higher and lower than average concentrations of random-coiled polymers; and (b) th…

Aggregation Processes and Formation of Silico-calco-alkaline Gels under High Ionic Strength

2002

This paper presents a systematic in situ study of the process of formation of silico-calco-alkaline gels starting from a liquid colloidal solution containing different alkaline ions and different calcium concentration until the final gel state. The combined use of X-ray and neutron small-angle scattering (SAS) and dynamical rheometry techniques lead to a consistent description of the structure of the aggregates and of the mechanisms of aggregation involved in gel formation. SAS results indicate that the aggregates are fractal objects, their structure strongly depending on calcium ion concentration. The differences in gelation kinetics for systems containing different alkaline ions were attr…

Introducing PeptoPlexes: Polylysine-block-Polysarcosine Based Polyplexes for Transfection of HEK 293T Cells

2014

A series of well-defined polypeptide-polypeptoid block copolymers based on the body's own amino acids sarcosine and lysine are prepared by ring opening polymerization of N-carboxyanhydrides. Block lengths were varied between 200-300 for the shielding polysarcosine block and 20-70 for the complexing polylysine block. Dispersity indexes ranged from 1.05 to 1.18. Polylysine is polymerized with benzyloxycarbonyl as well as trifluoroacetyl protecting groups at the ϵ-amine group and optimized deprotection protocols for both groups are reported. The obtained block ionomers are used to complex pDNA resulting in the formation of polyplexes (PeptoPlexes). The PeptoPlexes can be successfully applied i…

Conformational preferences of side-chain protected amino acid residues and their impact in peptide synthesis

1983

Using the host-guest technique, tentative scales for the helix-inducing power and the β-structure-forming potential of various side-chain protected amino acid residues in trifluoro-ethanol are established mainly by CD measurements. The generally lower tendency for β-structure formation of the host–guest peptides compared to that of the host peptide is discussed. The influence of these conformational features on the solubility of the peptides is also pointed out.

A High‐Capacity Negative Electrode for Asymmetric Supercapacitors Based on a PMo 12 Coordination Polymer with Novel Water‐Assisted Proton Channels

2020

The development of a negative electrode for supercapacitors is a critical challenge for the next-generation of energy-storage devices. Herein, two new electrodes formed by the coordination polymers [Ni(itmb)4 (HPMo12 O40 )]·2H2 O (1) and [Zn(itmb)3 (H2 O)(HPMo12 O40 )]·4H2 O (2) (itmb = 1-(imidazo-1-ly)-4-(1,2,4-triazol-1-ylmethyl)benzene), synthesized by a simple hydrothermal method, are described. Compounds 1 and 2 show high capacitances of 477.9 and 890.2 F g-1 , respectively. An asymmetric supercapacitor device assembled using 2 which has novel water-assisted proton channels as negative electrode and active carbon as positive electrode shows ultrahigh energy density and power density of…

Corrigendum to “Biomolecule-corona formation confers resistance of bacteria to nanoparticle-induced killing: Implications for the design of improved …

2020

Structural Investigation of Water/Lecithin/Cyclohexane Microemulsions by FT-IR Spectroscopy

1995

Abstract FT-IR spectra of water/lecithin/deuterated cyclohexane microemulsions as a function of water/lecithin molar ratio R ( R = [water]/[lecithin]) at various volume fractions ( O ) of the micellar phase have been recorded at 25°C. After elimination of the small spectral contributions due to deuterated cyclohexane and normalization, the shape of the C–H stretching band due to lecithin has been found dependent upon R and O whereas that of the O–H stretching band has been found dependent only upon R . The change in shape of the C–H band was interpreted in terms of a modification of the lecithin alkyl chain packing order. The analysis of the O–H band provides evidence that the hydroxylic gr…

Structural characterization of U(VI) surface complexes on kaolinite in the presence of humic acid using EXAFS spectroscopy.

2007

To determine the influence of humic acid (HA), pH, and presence of atmospheric CO2 on the sorption of U(VI) onto kaolinite, the structure of the surface complexes was studied by U L III-edge extended X-ray absorption fine structure (EXAFS) spectroscopy. The best fits to the experimental EXAFS data were obtained by including two uranium coordination shells with two axial (O ax) and five equatorial (O eq) oxygen atoms at 1.77+/-0.02 and 2.34+/-0.02 A, respectively, and two coordination shells with one Al/Si atom each at 3.1 and 3.3 A. As in the case of the binary system U(VI)-kaolinite, uranium forms inner-sphere surface complexes by edge sharing with aluminum octahedra and/or silicon tetrahe…